Date   
Re: Where can I buy floater balloon?

J68HZ
 

Some science here.

 

Balloons lift (are buoyant) on the basis of Archimedes principle (cite: https://en.wikipedia.org/wiki/Archimedes%27_principle) which has the corollary that less dense material will rise above more dense material.  It’s the same principle that causes oil to float on water… and with gases, it causes the lightest one (less dense gas) to rise above a heavier gas.  Even hot air will rise above ambient air just because the density of the air in the balloon is less than that of ambient air.

 

In the buoyancy calculation, the force of lift is proportional to the relative differences between the densities of the gases… and in this case, that would be H2 (or whatever the lift gas is) and air.  Now, the density of a gas can be calculated from the ideal gas law… P*V=n*R*T, or rewriting, P=p*R*T/Mw where “p” is the gas density and “Mw” is the molecular weight of the gas.  The ratio for lift is then [P1*Mw1/T1]/[P2*Mw2/T2].  Plug in the numbers and you can determine where the lift will cease.  Of course you need to do a force balance for the real lift and include the weight of the payload and the balloon.

 

The point here is that the buoyancy can vary based on the ambient temperature and pressure… even of the temperature and pressure of the gas in the balloon stays constant.

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Mikael Dagman
Sent: Sunday, May 26, 2019 1:28 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Where can I buy floater balloon?

 

The balloon was filled and stored in the same room in the house.

There is some unknown factors in play here, probably the material change characteristics at altitude, be it temperature, pressure, lack of moisture and that the He have expanded and is now filling the whole envelope and just not concentrated to the top part of the balloon as it is a ground level.

So anyway, if you going to fly fill just before lauch and not a day or two before.

/Mikael


Virus-free. www.avg.com

#pa #u3s Extreme power curve across the bands. #pa #u3s

Nik
 

I've been using my U3S for the last month or so, with the bifilar inductor installed, and 1 to 3 BC170's.  The rf output curve appears to be very fierce.  I get max power at 7MHz, but at 14MHz it has sloped away to less than 20mW.  I've now installed the 5W PA module, and replaced the winding on the toroid with the 25 turn option.

With both the U3S and the PA zero biased, and the Shaping option set to 20 140 (using a 13.8V supply), power is around 6W on 7MHz but only 200mW on 14MHz.

Is this normal, and if so is there any mod I can perform to change the output curve to something a little more even?

All input appreciated!

Nik M1DOX

Re: Where can I buy floater balloon?

Braden Glett
 

OH THE HUMANITY!!

Re: #pa #u3s Extreme power curve across the bands. #pa #u3s

ajparent1/KB1GMX
 

What low pass filter are you useing for 7mhz and what low pass filter for 14mhz?

I ask that as the detail level is very low and if you not changing the low pass filter 
decaying output power with frequency is to be expected as the filter is doing its job
of attenuating harmonics.

Allison

Re: Is the CLK0 pin of si5361a supposedly up to driving an HEF4013 direct?

ajparent1/KB1GMX
 

BS170 and 2n7000 are not identical.  

While the 2n7000 can handle a bit more power it has higher capacitances
and one has to watch the gate threshold.

For class D and E one has to hit the gate hard as in 5-6V to insure the device
is turned on hard (acts like a switch) and turned off hard.

As to the HEF4013 you need the correct drive voltage to get the logic to switch.
Generally using 3 or 3.3V logic (SI5351) to drive 5V CMOS is bad practice
(also unreliable) and you need a level converter to go from 3V to 5V levels.

Going down in frequency its generally easier to drive power MOSFETS
so doing class D or E at 630m or 2200m is switch mode power technology.
There are low cost parts that can easily hit KW power levels at 630M.
You still need the right drive levels.

Allison

Re: LightAPRS Tracker

J68HZ
 

I bought one of these things… programmed it (listened for it on my 2 meter radio), and tried using it at Dayton.  I even used a 4’ car top mount antenna with it and it has never once registered on APRS running all over the USA for a week.  I have an arrow antenna and will try the thing this afternoon but so far not impressed with this $100 item.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Mustafa Tan
Sent: Saturday, May 25, 2019 7:12 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] LightAPRS Tracker

 

Hi Leigh,

 

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?

 

On startup, GPS needs at least 2-3 minutes to fix 4 satellites. Since GPS antenna is passive, it can not fix very quick. After first gps fix and first beacon, default code sleeps GPS module (and also RF module)  until next beacon but gps backup pin is still powered so it wakes up quick.

 

2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?

 

You can modify LibAPRS preamble and tail parameters as follows: (we use default values)

 

  // You can define preamble and tail like this:

  // APRS_setPreamble(350);

  // APRS_setTail(50);

 

but not volume level via software 

 

3. Is there a schematic?  For example, see next question.

 

Unfortunately not :(

 

4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?

 

We did not use LED to save power. But we are using TX Led port (MigthyCore Atmega1284 Port 1 -> LibAPRS PB1 port ) to configure PTT duration of DRA818V.

 

5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

 

  RfON; -> Wake up RF (DRA818V) module

  delay(2000); -> DRA818V needs at least 2 seconds to wake up 

  RfPttON; -> PTT on

  delay(1000); -> DRA818V need at least 1 second to gain max power

 

Also you can modify these parameters above but we found out these values after many tests.

 

I hope my answers help, please do not hesitate to ask any other questions if you need.

 

TA2MUN

 

On Sat, May 25, 2019 at 2:13 AM Leigh L Klotz, Jr. <leigh@...> wrote:

This looks great!  Thanks Mustafa and Hans!  I received mine and used Arduino IDE to program it and am getting mixed results, so I'm looking for debugging guidance. 

I will take a look at the audio spectrum on the receive side soon, to see if all looks OK, but in the meantime I have a few questions:

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?
2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?
3. Is there a schematic?  For example, see next question.
4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?
5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

73 es MNY TNX,
Leigh/WA5ZNU


 

--


Virus-free. www.avg.com

Re: LightAPRS Tracker

 

Once I put in my call and changed the startup freq to 154.39 mine worked.



On Sun, May 26, 2019, 10:44 J68HZ <bill@...> wrote:

I bought one of these things… programmed it (listened for it on my 2 meter radio), and tried using it at Dayton.  I even used a 4’ car top mount antenna with it and it has never once registered on APRS running all over the USA for a week.  I have an arrow antenna and will try the thing this afternoon but so far not impressed with this $100 item.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook!

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Mustafa Tan
Sent: Saturday, May 25, 2019 7:12 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] LightAPRS Tracker

 

Hi Leigh,

 

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?

 

On startup, GPS needs at least 2-3 minutes to fix 4 satellites. Since GPS antenna is passive, it can not fix very quick. After first gps fix and first beacon, default code sleeps GPS module (and also RF module)  until next beacon but gps backup pin is still powered so it wakes up quick.

 

2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?

 

You can modify LibAPRS preamble and tail parameters as follows: (we use default values)

 

  // You can define preamble and tail like this:

  // APRS_setPreamble(350);

  // APRS_setTail(50);

 

but not volume level via software 

 

3. Is there a schematic?  For example, see next question.

 

Unfortunately not :(

 

4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?

 

We did not use LED to save power. But we are using TX Led port (MigthyCore Atmega1284 Port 1 -> LibAPRS PB1 port ) to configure PTT duration of DRA818V.

 

5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

 

  RfON; -> Wake up RF (DRA818V) module

  delay(2000); -> DRA818V needs at least 2 seconds to wake up 

  RfPttON; -> PTT on

  delay(1000); -> DRA818V need at least 1 second to gain max power

 

Also you can modify these parameters above but we found out these values after many tests.

 

I hope my answers help, please do not hesitate to ask any other questions if you need.

 

TA2MUN

 

On Sat, May 25, 2019 at 2:13 AM Leigh L Klotz, Jr. <leigh@...> wrote:

This looks great!  Thanks Mustafa and Hans!  I received mine and used Arduino IDE to program it and am getting mixed results, so I'm looking for debugging guidance. 

I will take a look at the audio spectrum on the receive side soon, to see if all looks OK, but in the meantime I have a few questions:

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?
2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?
3. Is there a schematic?  For example, see next question.
4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?
5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

73 es MNY TNX,
Leigh/WA5ZNU


 

--


Virus-free. www.avg.com

Re: LightAPRS Tracker

Joe WB9SBD
 

What unit are we talking about here?

Joe WB9SBD

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 5/26/2019 10:06 AM, Frank W1FRA wrote:
Once I put in my call and changed the startup freq to 154.39 mine worked.



On Sun, May 26, 2019, 10:44 J68HZ <bill@...> wrote:

I bought one of these things… programmed it (listened for it on my 2 meter radio), and tried using it at Dayton.  I even used a 4’ car top mount antenna with it and it has never once registered on APRS running all over the USA for a week.  I have an arrow antenna and will try the thing this afternoon but so far not impressed with this $100 item.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook!

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Mustafa Tan
Sent: Saturday, May 25, 2019 7:12 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] LightAPRS Tracker

 

Hi Leigh,

 

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?

 

On startup, GPS needs at least 2-3 minutes to fix 4 satellites. Since GPS antenna is passive, it can not fix very quick. After first gps fix and first beacon, default code sleeps GPS module (and also RF module)  until next beacon but gps backup pin is still powered so it wakes up quick.

 

2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?

 

You can modify LibAPRS preamble and tail parameters as follows: (we use default values)

 

  // You can define preamble and tail like this:

  // APRS_setPreamble(350);

  // APRS_setTail(50);

 

but not volume level via software 

 

3. Is there a schematic?  For example, see next question.

 

Unfortunately not :(

 

4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?

 

We did not use LED to save power. But we are using TX Led port (MigthyCore Atmega1284 Port 1 -> LibAPRS PB1 port ) to configure PTT duration of DRA818V.

 

5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

 

  RfON; -> Wake up RF (DRA818V) module

  delay(2000); -> DRA818V needs at least 2 seconds to wake up 

  RfPttON; -> PTT on

  delay(1000); -> DRA818V need at least 1 second to gain max power

 

Also you can modify these parameters above but we found out these values after many tests.

 

I hope my answers help, please do not hesitate to ask any other questions if you need.

 

TA2MUN

 

On Sat, May 25, 2019 at 2:13 AM Leigh L Klotz, Jr. <leigh@...> wrote:

This looks great!  Thanks Mustafa and Hans!  I received mine and used Arduino IDE to program it and am getting mixed results, so I'm looking for debugging guidance. 

I will take a look at the audio spectrum on the receive side soon, to see if all looks OK, but in the meantime I have a few questions:

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?
2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?
3. Is there a schematic?  For example, see next question.
4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?
5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

73 es MNY TNX,
Leigh/WA5ZNU


 

--


Virus-free. www.avg.com

Re: LightAPRS Tracker

Mustafa Tan
 

Hi William,

We are testing every unit. If it's still a hardware problem, we can send you a new one. Ca you send uploaded source code to support@...

Thanks

TA2MUN


On Sun, May 26, 2019 at 5:44 PM J68HZ <bill@...> wrote:

I bought one of these things… programmed it (listened for it on my 2 meter radio), and tried using it at Dayton.  I even used a 4’ car top mount antenna with it and it has never once registered on APRS running all over the USA for a week.  I have an arrow antenna and will try the thing this afternoon but so far not impressed with this $100 item.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Mustafa Tan
Sent: Saturday, May 25, 2019 7:12 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] LightAPRS Tracker

 

Hi Leigh,

 

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?

 

On startup, GPS needs at least 2-3 minutes to fix 4 satellites. Since GPS antenna is passive, it can not fix very quick. After first gps fix and first beacon, default code sleeps GPS module (and also RF module)  until next beacon but gps backup pin is still powered so it wakes up quick.

 

2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?

 

You can modify LibAPRS preamble and tail parameters as follows: (we use default values)

 

  // You can define preamble and tail like this:

  // APRS_setPreamble(350);

  // APRS_setTail(50);

 

but not volume level via software 

 

3. Is there a schematic?  For example, see next question.

 

Unfortunately not :(

 

4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?

 

We did not use LED to save power. But we are using TX Led port (MigthyCore Atmega1284 Port 1 -> LibAPRS PB1 port ) to configure PTT duration of DRA818V.

 

5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

 

  RfON; -> Wake up RF (DRA818V) module

  delay(2000); -> DRA818V needs at least 2 seconds to wake up 

  RfPttON; -> PTT on

  delay(1000); -> DRA818V need at least 1 second to gain max power

 

Also you can modify these parameters above but we found out these values after many tests.

 

I hope my answers help, please do not hesitate to ask any other questions if you need.

 

TA2MUN

 

On Sat, May 25, 2019 at 2:13 AM Leigh L Klotz, Jr. <leigh@...> wrote:

This looks great!  Thanks Mustafa and Hans!  I received mine and used Arduino IDE to program it and am getting mixed results, so I'm looking for debugging guidance. 

I will take a look at the audio spectrum on the receive side soon, to see if all looks OK, but in the meantime I have a few questions:

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?
2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?
3. Is there a schematic?  For example, see next question.
4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?
5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

73 es MNY TNX,
Leigh/WA5ZNU


 

--


Virus-free. www.avg.com



Re: LightAPRS Tracker

J68HZ
 

154.39 ?

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Frank W1FRA
Sent: Sunday, May 26, 2019 10:06 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] LightAPRS Tracker

 

Once I put in my call and changed the startup freq to 154.39 mine worked.

 

 

 

On Sun, May 26, 2019, 10:44 J68HZ <bill@...> wrote:

I bought one of these things… programmed it (listened for it on my 2 meter radio), and tried using it at Dayton.  I even used a 4’ car top mount antenna with it and it has never once registered on APRS running all over the USA for a week.  I have an arrow antenna and will try the thing this afternoon but so far not impressed with this $100 item.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook!

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Mustafa Tan
Sent: Saturday, May 25, 2019 7:12 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] LightAPRS Tracker

 

Hi Leigh,

 

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?

 

On startup, GPS needs at least 2-3 minutes to fix 4 satellites. Since GPS antenna is passive, it can not fix very quick. After first gps fix and first beacon, default code sleeps GPS module (and also RF module)  until next beacon but gps backup pin is still powered so it wakes up quick.

 

2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?

 

You can modify LibAPRS preamble and tail parameters as follows: (we use default values)

 

  // You can define preamble and tail like this:

  // APRS_setPreamble(350);

  // APRS_setTail(50);

 

but not volume level via software 

 

3. Is there a schematic?  For example, see next question.

 

Unfortunately not :(

 

4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?

 

We did not use LED to save power. But we are using TX Led port (MigthyCore Atmega1284 Port 1 -> LibAPRS PB1 port ) to configure PTT duration of DRA818V.

 

5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

 

  RfON; -> Wake up RF (DRA818V) module

  delay(2000); -> DRA818V needs at least 2 seconds to wake up 

  RfPttON; -> PTT on

  delay(1000); -> DRA818V need at least 1 second to gain max power

 

Also you can modify these parameters above but we found out these values after many tests.

 

I hope my answers help, please do not hesitate to ask any other questions if you need.

 

TA2MUN

 

On Sat, May 25, 2019 at 2:13 AM Leigh L Klotz, Jr. <leigh@...> wrote:

This looks great!  Thanks Mustafa and Hans!  I received mine and used Arduino IDE to program it and am getting mixed results, so I'm looking for debugging guidance. 

I will take a look at the audio spectrum on the receive side soon, to see if all looks OK, but in the meantime I have a few questions:

1. GPS appears to take a long time start, 0 sats for a minute or two before hitting 3 and 4.  Is there a warm start option, or is the board missing some kind of battery backup necessary for that feature?
2. It sounds like the audio isn't 100% gain at the beginning of transmission; after the 1s silent delay, the audio starts, then seems to get louder.  Any parameters to tune here?
3. Is there a schematic?  For example, see next question.
4. in LightAprs-*.ino, it does "digitalRead(1)" and says "LibAprs TX Led pin PB1"... I don't see any LED onboard, and this is a read, so I'm a little confused.  Is this a status from the Dra818?
5. sendLocation has "RfON;, delay(2000); RfPttON; delay(1000);" before the APRS data is sent.  What does the first 2000ms delay do?  Allow the RF chip to boot?  What is the second delay for?  Can it be reduced, for urban use?  What is the minimum?

73 es MNY TNX,
Leigh/WA5ZNU


 

--

 

Virus-free. www.avg.com

Re: Where can I buy floater balloon?

Jerry Gaffke
 

Bill,

In post 34692 Mikael said:

> If I fill a foil balloon (like the one linked to first in this thread) with helium with 6gram of lift, seal it and let it sit inside it have lost its 6 gram of lift within a week and fall to the > floor but when used as a balloon for a radio tracker at +10000m its fine for several month, I had a tracker up for 64 days last year before a storm toke it down and Dave > > have a balloon released in February with this (2) balloon stil flying, whats happening at altitude that prevents the gas from leaking out as it does at ground level?

In post 34705 he states that this is repeatable, so I assume he did not happen to have a leak
in the balloons that remained in the house.

Is there something about mylar that makes it more impermeable to helium at -50C
(as found at 10,000 meters) vs room temperature of 20C?


I don't see PV=nRT     https://en.wikipedia.org/wiki/Ideal_gas_law
causing the reported behavior.
Here is my reasoning, a first attempt at thinking this through:

Let's assume the balloon has "just enough" helium to fill it out at 10,000 meters,
so the pressure inside the balloon is always equal to the ambient pressure,
whether it is at sea level or at 10,000 meters.
At 10,000 meters the air is roughly four times less dense, so the balloon
will be 4 times larger than at sea level.  But at sea level, the air that the balloon displaces
will have 4 times the density, so the lift of the helium is the same as at 10,000 meters.
(The lift is equal to the weight of the air displaced by the balloon minus the weight of the helium.)
Likewise, the temperature change affects the density of helium and air in equal measure.
(Assume the helium eventually reaches the same temperature as the ambient air.)

If the mylar balloon has more helium than needed at 10,000 meters (but does not pop),
then the pressure of the helium at altitude will be greater than the "just enough" case
and thus it is more dense.  The lift will be less at altitude than it is at sea level. 
The balloon will rise to that altitude at which the lift is equal to the weight of the payload.

When Mikael's balloon left behind in the house sinks to the floor after a week, it has
less helium remaining in the balloon than the one that is floating at 10,000 meters.
Even though the balloon at altitude is likely overfilled, with the helium pressing on the mylar walls.

But somehow the balloon leaks less at altitude?  Curious.

Jerry, KE7ER
 


On Sun, May 26, 2019 at 12:21 AM, J68HZ wrote:

Some science here.

 

Balloons lift (are buoyant) on the basis of Archimedes principle (cite: https://en.wikipedia.org/wiki/Archimedes%27_principle) which has the corollary that less dense material will rise above more dense material.  It’s the same principle that causes oil to float on water… and with gases, it causes the lightest one (less dense gas) to rise above a heavier gas.  Even hot air will rise above ambient air just because the density of the air in the balloon is less than that of ambient air.

 

In the buoyancy calculation, the force of lift is proportional to the relative differences between the densities of the gases… and in this case, that would be H2 (or whatever the lift gas is) and air.  Now, the density of a gas can be calculated from the ideal gas law… P*V=n*R*T, or rewriting, P=p*R*T/Mw where “p” is the gas density and “Mw” is the molecular weight of the gas.  The ratio for lift is then [P1*Mw1/T1]/[P2*Mw2/T2].  Plug in the numbers and you can determine where the lift will cease.  Of course you need to do a force balance for the real lift and include the weight of the payload and the balloon.

 

The point here is that the buoyancy can vary based on the ambient temperature and pressure… even of the temperature and pressure of the gas in the balloon stays constant.

Re: Where can I buy floater balloon?

J68HZ
 

The balloon leaks less at altitude because the pressure on the inside and the outside come to equilibrium by diffusion.  The contents will leak until equilibrium is reached (if that is, in fact what is happening).  At that point then, the buoyancy balance is reduces like this:  [Pgas*Mwgas/Tgas]/[Pair*Mwair/Tair]… but now Pgas=pair… so the buoyancy ratio is [Mwgas*Tair]/[Mwair*Tgas].  And futher, for the most part, the temperature of the lift gas is approximately the same as that of the air… give or take… of course, this can change in the daytime when the sun warms the balloon and causes the lift gas to get warmer… but at night, the buoyancy equation reduces to Mwgas/Mwair… (2/16) meaning you will always have lift.  Again you need to do the real force balance to determine if there is enough lift gas quantity for the balloon to rise or fall… but what it does shows is the limiting case where the balloon will eventually reach a maximum and minimum buoyancy (day/night) and I think we see this in the altitude data that gets reported.

 

The balloon would actually leak MORE at altitude because the ambient pressure at altitude is lower.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Sunday, May 26, 2019 11:19 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Where can I buy floater balloon?

 

Bill,

In post 34692 Mikael said:

> If I fill a foil balloon (like the one linked to first in this thread) with helium with 6gram of lift, seal it and let it sit inside it have lost its 6 gram of lift within a week and fall to the > floor but when used as a balloon for a radio tracker at +10000m its fine for several month, I had a tracker up for 64 days last year before a storm toke it down and Dave > > have a balloon released in February with this (2) balloon stil flying, whats happening at altitude that prevents the gas from leaking out as it does at ground level?

In post 34705 he states that this is repeatable, so I assume he did not happen to have a leak
in the balloons that remained in the house.

Is there something about mylar that makes it more impermeable to helium at -50C
(as found at 10,000 meters) vs room temperature of 20C?


I don't see PV=nRT     https://en.wikipedia.org/wiki/Ideal_gas_law
causing the reported behavior.
Here is my reasoning, a first attempt at thinking this through:

Let's assume the balloon has "just enough" helium to fill it out at 10,000 meters,
so the pressure inside the balloon is always equal to the ambient pressure,
whether it is at sea level or at 10,000 meters.
At 10,000 meters the air is roughly four times less dense, so the balloon
will be 4 times larger than at sea level.  But at sea level, the air that the balloon displaces
will have 4 times the density, so the lift of the helium is the same as at 10,000 meters.
(The lift is equal to the weight of the air displaced by the balloon minus the weight of the helium.)
Likewise, the temperature change affects the density of helium and air in equal measure.
(Assume the helium eventually reaches the same temperature as the ambient air.)

If the mylar balloon has more helium than needed at 10,000 meters (but does not pop),
then the pressure of the helium at altitude will be greater than the "just enough" case
and thus it is more dense.  The lift will be less at altitude than it is at sea level. 
The balloon will rise to that altitude at which the lift is equal to the weight of the payload.

When Mikael's balloon left behind in the house sinks to the floor after a week, it has
less helium remaining in the balloon than the one that is floating at 10,000 meters.
Even though the balloon at altitude is likely overfilled, with the helium pressing on the mylar walls.

But somehow the balloon leaks less at altitude?  Curious.

Jerry, KE7ER
 

On Sun, May 26, 2019 at 12:21 AM, J68HZ wrote:

Some science here.

 

Balloons lift (are buoyant) on the basis of Archimedes principle (cite: https://en.wikipedia.org/wiki/Archimedes%27_principle) which has the corollary that less dense material will rise above more dense material.  It’s the same principle that causes oil to float on water… and with gases, it causes the lightest one (less dense gas) to rise above a heavier gas.  Even hot air will rise above ambient air just because the density of the air in the balloon is less than that of ambient air.

 

In the buoyancy calculation, the force of lift is proportional to the relative differences between the densities of the gases… and in this case, that would be H2 (or whatever the lift gas is) and air.  Now, the density of a gas can be calculated from the ideal gas law… P*V=n*R*T, or rewriting, P=p*R*T/Mw where “p” is the gas density and “Mw” is the molecular weight of the gas.  The ratio for lift is then [P1*Mw1/T1]/[P2*Mw2/T2].  Plug in the numbers and you can determine where the lift will cease.  Of course you need to do a force balance for the real lift and include the weight of the payload and the balloon.

 

The point here is that the buoyancy can vary based on the ambient temperature and pressure… even of the temperature and pressure of the gas in the balloon stays constant.


Virus-free. www.avg.com

Re: #pa #u3s Extreme power curve across the bands. #pa #u3s

Nik
 

Hi Allison,

I'm using the 40m lpf and the 20m lpf (positions 5 and 3 respectively).  Although, I've double checked the values and the windings on the 40m filter, I've not checked the 20m one!  Think I'd better take them all out and have a check, then test with just the 2 in place. (I've 80m in slot 0, 40m in 5, 30 in 4, 20 in  3, 17 in 2 and 15 in 1).

In fact I think I'll put a signal through them and have a look on the scope.

Thank you.  It's nice to have someone else's thoughts.

Nik.

Re: Where can I buy floater balloon?

Stephen Farthing G0XAR JO92ON97
 

Gerry, 

I’m wondering what you mean by four times larger? Do you mean four times the volume? Or four times the surface area? 

It’s not a trick question. I’m just trying to follow your argument. It’s 50 years since I did any academic physics so I’m a bit rusty. 

Warm regards from a rainy England, 

Steve G0XAR 

Re: Where can I buy floater balloon?

Joe Street
 

K9HZ wrote:
"The balloon leaks less at altitude because the pressure on the inside and the outside come to equilibrium by diffusion."

One has to consider the partial pressure of gasses.  There is still a huge difference in partial pressure of He between inside and outside regardless of altitude so the balloon should continue to leak at altitude all other things being equal.  My guess is that it is what was conjectured previously (sorry I can't remember who wrote it) something happens to mylar at cold temperatures which densifies it at a molecular level thereby lowering the diffusion through the material.


Joe


On Sun, May 26, 2019 at 12:47 PM J68HZ <bill@...> wrote:

The balloon leaks less at altitude because the pressure on the inside and the outside come to equilibrium by diffusion.  The contents will leak until equilibrium is reached (if that is, in fact what is happening).  At that point then, the buoyancy balance is reduces like this:  [Pgas*Mwgas/Tgas]/[Pair*Mwair/Tair]… but now Pgas=pair… so the buoyancy ratio is [Mwgas*Tair]/[Mwair*Tgas].  And futher, for the most part, the temperature of the lift gas is approximately the same as that of the air… give or take… of course, this can change in the daytime when the sun warms the balloon and causes the lift gas to get warmer… but at night, the buoyancy equation reduces to Mwgas/Mwair… (2/16) meaning you will always have lift.  Again you need to do the real force balance to determine if there is enough lift gas quantity for the balloon to rise or fall… but what it does shows is the limiting case where the balloon will eventually reach a maximum and minimum buoyancy (day/night) and I think we see this in the altitude data that gets reported.

 

The balloon would actually leak MORE at altitude because the ambient pressure at altitude is lower.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Sunday, May 26, 2019 11:19 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Where can I buy floater balloon?

 

Bill,

In post 34692 Mikael said:

> If I fill a foil balloon (like the one linked to first in this thread) with helium with 6gram of lift, seal it and let it sit inside it have lost its 6 gram of lift within a week and fall to the > floor but when used as a balloon for a radio tracker at +10000m its fine for several month, I had a tracker up for 64 days last year before a storm toke it down and Dave > > have a balloon released in February with this (2) balloon stil flying, whats happening at altitude that prevents the gas from leaking out as it does at ground level?

In post 34705 he states that this is repeatable, so I assume he did not happen to have a leak
in the balloons that remained in the house.

Is there something about mylar that makes it more impermeable to helium at -50C
(as found at 10,000 meters) vs room temperature of 20C?


I don't see PV=nRT     https://en.wikipedia.org/wiki/Ideal_gas_law
causing the reported behavior.
Here is my reasoning, a first attempt at thinking this through:

Let's assume the balloon has "just enough" helium to fill it out at 10,000 meters,
so the pressure inside the balloon is always equal to the ambient pressure,
whether it is at sea level or at 10,000 meters.
At 10,000 meters the air is roughly four times less dense, so the balloon
will be 4 times larger than at sea level.  But at sea level, the air that the balloon displaces
will have 4 times the density, so the lift of the helium is the same as at 10,000 meters.
(The lift is equal to the weight of the air displaced by the balloon minus the weight of the helium.)
Likewise, the temperature change affects the density of helium and air in equal measure.
(Assume the helium eventually reaches the same temperature as the ambient air.)

If the mylar balloon has more helium than needed at 10,000 meters (but does not pop),
then the pressure of the helium at altitude will be greater than the "just enough" case
and thus it is more dense.  The lift will be less at altitude than it is at sea level. 
The balloon will rise to that altitude at which the lift is equal to the weight of the payload.

When Mikael's balloon left behind in the house sinks to the floor after a week, it has
less helium remaining in the balloon than the one that is floating at 10,000 meters.
Even though the balloon at altitude is likely overfilled, with the helium pressing on the mylar walls.

But somehow the balloon leaks less at altitude?  Curious.

Jerry, KE7ER
 

On Sun, May 26, 2019 at 12:21 AM, J68HZ wrote:

Some science here.

 

Balloons lift (are buoyant) on the basis of Archimedes principle (cite: https://en.wikipedia.org/wiki/Archimedes%27_principle) which has the corollary that less dense material will rise above more dense material.  It’s the same principle that causes oil to float on water… and with gases, it causes the lightest one (less dense gas) to rise above a heavier gas.  Even hot air will rise above ambient air just because the density of the air in the balloon is less than that of ambient air.

 

In the buoyancy calculation, the force of lift is proportional to the relative differences between the densities of the gases… and in this case, that would be H2 (or whatever the lift gas is) and air.  Now, the density of a gas can be calculated from the ideal gas law… P*V=n*R*T, or rewriting, P=p*R*T/Mw where “p” is the gas density and “Mw” is the molecular weight of the gas.  The ratio for lift is then [P1*Mw1/T1]/[P2*Mw2/T2].  Plug in the numbers and you can determine where the lift will cease.  Of course you need to do a force balance for the real lift and include the weight of the payload and the balloon.

 

The point here is that the buoyancy can vary based on the ambient temperature and pressure… even of the temperature and pressure of the gas in the balloon stays constant.


Virus-free. www.avg.com

Re: Where can I buy floater balloon?

Joe WB9SBD
 

In actuality, this is Backwards of what is happening with these small floaters.

They are in fact miniature small "Superpressure" Balloons.

When they float it is because there is it lifting gas that has lost it's lifting power because it has become more dense that is was at low altitudes because it is now under pressure. There is a much larger pressure differential inside vs outside of the balloon envelope when at float than there is when at lower altitudes.

so the thought that at float, if it is going to leak it has less chance is 100% totally backwards.

Joe WB9SBD

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 5/26/2019 2:30 PM, Joe Street wrote:
K9HZ wrote:
"The balloon leaks less at altitude because the pressure on the inside and the outside come to equilibrium by diffusion."

One has to consider the partial pressure of gasses.  There is still a huge difference in partial pressure of He between inside and outside regardless of altitude so the balloon should continue to leak at altitude all other things being equal.  My guess is that it is what was conjectured previously (sorry I can't remember who wrote it) something happens to mylar at cold temperatures which densifies it at a molecular level thereby lowering the diffusion through the material.


Joe

On Sun, May 26, 2019 at 12:47 PM J68HZ <bill@...> wrote:

The balloon leaks less at altitude because the pressure on the inside and the outside come to equilibrium by diffusion.  The contents will leak until equilibrium is reached (if that is, in fact what is happening).  At that point then, the buoyancy balance is reduces like this:  [Pgas*Mwgas/Tgas]/[Pair*Mwair/Tair]… but now Pgas=pair… so the buoyancy ratio is [Mwgas*Tair]/[Mwair*Tgas].  And futher, for the most part, the temperature of the lift gas is approximately the same as that of the air… give or take… of course, this can change in the daytime when the sun warms the balloon and causes the lift gas to get warmer… but at night, the buoyancy equation reduces to Mwgas/Mwair… (2/16) meaning you will always have lift.  Again you need to do the real force balance to determine if there is enough lift gas quantity for the balloon to rise or fall… but what it does shows is the limiting case where the balloon will eventually reach a maximum and minimum buoyancy (day/night) and I think we see this in the altitude data that gets reported.

 

The balloon would actually leak MORE at altitude because the ambient pressure at altitude is lower.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Sunday, May 26, 2019 11:19 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Where can I buy floater balloon?

 

Bill,

In post 34692 Mikael said:

> If I fill a foil balloon (like the one linked to first in this thread) with helium with 6gram of lift, seal it and let it sit inside it have lost its 6 gram of lift within a week and fall to the > floor but when used as a balloon for a radio tracker at +10000m its fine for several month, I had a tracker up for 64 days last year before a storm toke it down and Dave > > have a balloon released in February with this (2) balloon stil flying, whats happening at altitude that prevents the gas from leaking out as it does at ground level?

In post 34705 he states that this is repeatable, so I assume he did not happen to have a leak
in the balloons that remained in the house.

Is there something about mylar that makes it more impermeable to helium at -50C
(as found at 10,000 meters) vs room temperature of 20C?


I don't see PV=nRT     https://en.wikipedia.org/wiki/Ideal_gas_law
causing the reported behavior.
Here is my reasoning, a first attempt at thinking this through:

Let's assume the balloon has "just enough" helium to fill it out at 10,000 meters,
so the pressure inside the balloon is always equal to the ambient pressure,
whether it is at sea level or at 10,000 meters.
At 10,000 meters the air is roughly four times less dense, so the balloon
will be 4 times larger than at sea level.  But at sea level, the air that the balloon displaces
will have 4 times the density, so the lift of the helium is the same as at 10,000 meters.
(The lift is equal to the weight of the air displaced by the balloon minus the weight of the helium.)
Likewise, the temperature change affects the density of helium and air in equal measure.
(Assume the helium eventually reaches the same temperature as the ambient air.)

If the mylar balloon has more helium than needed at 10,000 meters (but does not pop),
then the pressure of the helium at altitude will be greater than the "just enough" case
and thus it is more dense.  The lift will be less at altitude than it is at sea level. 
The balloon will rise to that altitude at which the lift is equal to the weight of the payload.

When Mikael's balloon left behind in the house sinks to the floor after a week, it has
less helium remaining in the balloon than the one that is floating at 10,000 meters.
Even though the balloon at altitude is likely overfilled, with the helium pressing on the mylar walls.

But somehow the balloon leaks less at altitude?  Curious.

Jerry, KE7ER
 

On Sun, May 26, 2019 at 12:21 AM, J68HZ wrote:

Some science here.

 

Balloons lift (are buoyant) on the basis of Archimedes principle (cite: https://en.wikipedia.org/wiki/Archimedes%27_principle) which has the corollary that less dense material will rise above more dense material.  It’s the same principle that causes oil to float on water… and with gases, it causes the lightest one (less dense gas) to rise above a heavier gas.  Even hot air will rise above ambient air just because the density of the air in the balloon is less than that of ambient air.

 

In the buoyancy calculation, the force of lift is proportional to the relative differences between the densities of the gases… and in this case, that would be H2 (or whatever the lift gas is) and air.  Now, the density of a gas can be calculated from the ideal gas law… P*V=n*R*T, or rewriting, P=p*R*T/Mw where “p” is the gas density and “Mw” is the molecular weight of the gas.  The ratio for lift is then [P1*Mw1/T1]/[P2*Mw2/T2].  Plug in the numbers and you can determine where the lift will cease.  Of course you need to do a force balance for the real lift and include the weight of the payload and the balloon.

 

The point here is that the buoyancy can vary based on the ambient temperature and pressure… even of the temperature and pressure of the gas in the balloon stays constant.


Virus-free. www.avg.com

Re: LightAPRS Tracker

 

Obviously I meant 144.390  !

Re: Where can I buy floater balloon?

J68HZ
 

Here’s the math.   Again, excuse the bandwidth and delete this straight away if you have no interest.  This will be my last post on the subject because it’s getting old.

 

There is no reason to really talk in terms of partial pressures of gas on the balloon side.  It’s a pure gas for all intent.  Oh the other side, air is a mix and I suppose you could add the force from the partial pressures of N2 + O2, but they are so similar in molecular weight, size, and behavior that they can be treated as the same (or just use the reference below which gives the density of air at various temperatures, pressures, altitudes.)

 

In general a volume V of material of density ρ immersed in a fluid of density ρf experiences a buoyant force of

 

Fb= ρfgV

and a weight of

W=−gVρ.

so the available lifting force is

Fl=gV(ρfρ).

 

Where the object is floating at the surface of a liquid the buoyant force is modified to reflect the volume of liquid displaced Fb=gVdρf  where Vd is enough to cover the weight of the floating object.

 

Similarly, buoyant force on a submerged object (e.g. a balloon submerged/ floating in air) is equal to the weight of the displaced fluid,

Fb=ρfgV

The physical origin of this force is actually the pressure difference between the top and bottom surfaces of the floating object. Pressure in a fluid at a certain height is related to the depth of the fluid above that height by

P(height2)−P(height1)=ρfg(height2−height1),

 

that is, density of fluid times gravitational acceleration times height difference. If you have an object whose top and bottom surfaces are parallel, then it's pretty easy to calculate the buoyant force as the pressure differential times the area of those surfaces,

Fb=(ΔP)(A)=ρfg*Δheight*A=ρfgV

 

For an irregular shape like a baloon, you'll have to do some integration (a sphere for a balloon is a good approximation). You can also take into account variations in density (or gravitational acceleration) over the size of the balloon by doing some additional calculus. But, according to the US standard atmosphere model, the density of the atmosphere takes about 12 miles to drop off to near zero, which corresponds to a fraction of a percent change over the height of a typical hot air balloon (a few tens of meters). That fraction of a percent is negligible, so you're pretty safe just using a single value for the density.  However, you can't neglect differences in density between vastly different altitudes. Remember that the buoyant force on the balloon is equal to the weight of the amount of fluid displaced. As you go higher, the density of the air drops, which means the balloon displaces a lower mass of air. Therefore, as the balloon rises, the buoyant force drops. Eventually it reaches a height at which the buoyant force exactly balances out the weight of the balloon (and payload), and the balloon levitates at that level.  For a controlled balloon, you can adjust the level by either heating the gas inside the balloon (thus making it expand and displace more air) or by letting some gas out (thus making the balloon contract and displace less air).

 

 

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Joe WB9SBD
Sent: Sunday, May 26, 2019 2:37 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Where can I buy floater balloon?

 

In actuality, this is Backwards of what is happening with these small floaters.

They are in fact miniature small "Superpressure" Balloons.

When they float it is because there is it lifting gas that has lost it's lifting power because it has become more dense that is was at low altitudes because it is now under pressure. There is a much larger pressure differential inside vs outside of the balloon envelope when at float than there is when at lower altitudes.

so the thought that at float, if it is going to leak it has less chance is 100% totally backwards.

Joe WB9SBD


The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 5/26/2019 2:30 PM, Joe Street wrote:

K9HZ wrote:

"The balloon leaks less at altitude because the pressure on the inside and the outside come to equilibrium by diffusion."

 

One has to consider the partial pressure of gasses.  There is still a huge difference in partial pressure of He between inside and outside regardless of altitude so the balloon should continue to leak at altitude all other things being equal.  My guess is that it is what was conjectured previously (sorry I can't remember who wrote it) something happens to mylar at cold temperatures which densifies it at a molecular level thereby lowering the diffusion through the material.

 

 

Joe

 

On Sun, May 26, 2019 at 12:47 PM J68HZ <bill@...> wrote:

The balloon leaks less at altitude because the pressure on the inside and the outside come to equilibrium by diffusion.  The contents will leak until equilibrium is reached (if that is, in fact what is happening).  At that point then, the buoyancy balance is reduces like this:  [Pgas*Mwgas/Tgas]/[Pair*Mwair/Tair]… but now Pgas=pair… so the buoyancy ratio is [Mwgas*Tair]/[Mwair*Tgas].  And futher, for the most part, the temperature of the lift gas is approximately the same as that of the air… give or take… of course, this can change in the daytime when the sun warms the balloon and causes the lift gas to get warmer… but at night, the buoyancy equation reduces to Mwgas/Mwair… (2/16) meaning you will always have lift.  Again you need to do the real force balance to determine if there is enough lift gas quantity for the balloon to rise or fall… but what it does shows is the limiting case where the balloon will eventually reach a maximum and minimum buoyancy (day/night) and I think we see this in the altitude data that gets reported.

 

The balloon would actually leak MORE at altitude because the ambient pressure at altitude is lower.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

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From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Sunday, May 26, 2019 11:19 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Where can I buy floater balloon?

 

Bill,

In post 34692 Mikael said:

> If I fill a foil balloon (like the one linked to first in this thread) with helium with 6gram of lift, seal it and let it sit inside it have lost its 6 gram of lift within a week and fall to the > floor but when used as a balloon for a radio tracker at +10000m its fine for several month, I had a tracker up for 64 days last year before a storm toke it down and Dave > > have a balloon released in February with this (2) balloon stil flying, whats happening at altitude that prevents the gas from leaking out as it does at ground level?

In post 34705 he states that this is repeatable, so I assume he did not happen to have a leak
in the balloons that remained in the house.

Is there something about mylar that makes it more impermeable to helium at -50C
(as found at 10,000 meters) vs room temperature of 20C?


I don't see PV=nRT     https://en.wikipedia.org/wiki/Ideal_gas_law
causing the reported behavior.
Here is my reasoning, a first attempt at thinking this through:

Let's assume the balloon has "just enough" helium to fill it out at 10,000 meters,
so the pressure inside the balloon is always equal to the ambient pressure,
whether it is at sea level or at 10,000 meters.
At 10,000 meters the air is roughly four times less dense, so the balloon
will be 4 times larger than at sea level.  But at sea level, the air that the balloon displaces
will have 4 times the density, so the lift of the helium is the same as at 10,000 meters.
(The lift is equal to the weight of the air displaced by the balloon minus the weight of the helium.)
Likewise, the temperature change affects the density of helium and air in equal measure.
(Assume the helium eventually reaches the same temperature as the ambient air.)

If the mylar balloon has more helium than needed at 10,000 meters (but does not pop),
then the pressure of the helium at altitude will be greater than the "just enough" case
and thus it is more dense.  The lift will be less at altitude than it is at sea level. 
The balloon will rise to that altitude at which the lift is equal to the weight of the payload.

When Mikael's balloon left behind in the house sinks to the floor after a week, it has
less helium remaining in the balloon than the one that is floating at 10,000 meters.
Even though the balloon at altitude is likely overfilled, with the helium pressing on the mylar walls.

But somehow the balloon leaks less at altitude?  Curious.

Jerry, KE7ER
 

On Sun, May 26, 2019 at 12:21 AM, J68HZ wrote:

Some science here.

 

Balloons lift (are buoyant) on the basis of Archimedes principle (cite: https://en.wikipedia.org/wiki/Archimedes%27_principle) which has the corollary that less dense material will rise above more dense material.  It’s the same principle that causes oil to float on water… and with gases, it causes the lightest one (less dense gas) to rise above a heavier gas.  Even hot air will rise above ambient air just because the density of the air in the balloon is less than that of ambient air.

 

In the buoyancy calculation, the force of lift is proportional to the relative differences between the densities of the gases… and in this case, that would be H2 (or whatever the lift gas is) and air.  Now, the density of a gas can be calculated from the ideal gas law… P*V=n*R*T, or rewriting, P=p*R*T/Mw where “p” is the gas density and “Mw” is the molecular weight of the gas.  The ratio for lift is then [P1*Mw1/T1]/[P2*Mw2/T2].  Plug in the numbers and you can determine where the lift will cease.  Of course you need to do a force balance for the real lift and include the weight of the payload and the balloon.

 

The point here is that the buoyancy can vary based on the ambient temperature and pressure… even of the temperature and pressure of the gas in the balloon stays constant.

 

Virus-free. www.avg.com

 

QCX party on Monday 27th May #qcx #qrp-dx

Peter GM0EUL
 

Good evening everyone

Remember its the last Monday tomorrow so its the QCX party.  Fun for all and conditions seem reasonable today so fingers crossed it will stay good.  Hope to catch some of you on the air and if you haven't tried it yet please do, its great fun and a good opportunity to get some qcx/qcx contacts.  

Don't worry if you are a beginner at cw or don't consider yourself a contester.  Its not a contest and everyone is very friendly and accommodating.

Rules and info here https://www.qrp-labs.com/party.html

73
Peter GM0EUL

Re: Where can I buy floater balloon?

Joe WB9SBD
 


On 5/26/2019 4:26 PM, J68HZ wrote:

For an irregular shape like a baloon, you'll have to do some integration (a sphere for a balloon is a good approximation). You can also take into account variations in density (or gravitational acceleration) over the size of the balloon by doing some additional calculus. But, according to the US standard atmosphere model, the density of the atmosphere takes about 12 miles to drop off to near zero, which corresponds to a fraction of a percent change over the height of a typical hot air balloon (a few tens of meters). That fraction of a percent is negligible, so you're pretty safe just using a single value for the density.  However, you can't neglect differences in density between vastly different altitudes. Remember that the buoyant force on the balloon is equal to the weight of the amount of fluid displaced. As you go higher, the density of the air drops, which means the balloon displaces a lower mass of air. Therefore, as the balloon rises, the buoyant force drops. Eventually it reaches a height at which the buoyant force exactly balances out the weight of the balloon (and payload), and the balloon levitates at that level.  For a controlled balloon, you can adjust the level by either heating the gas inside the balloon (thus making it expand and displace more air) or by letting some gas out (thus making the balloon contract and displace less air).


You are forgetting, that the gas in the balloon is also getting less dense per unit of volume as it rises due to expansion.

The Balloon expands to equalize the pressure internally vs externally.


Until the balloon stops expanding, the buoyancy amount does not change from 10 feet above sea level to 150,000 feet above sea level NO DIFFERENCE!


Joe WB9SBD

 

 

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Joe WB9SBD
Sent: Sunday, May 26, 2019 2:37 PM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Where can I buy floater balloon?

 

In actuality, this is Backwards of what is happening with these small floaters.

They are in fact miniature small "Superpressure" Balloons.

When they float it is because there is it lifting gas that has lost it's lifting power because it has become more dense that is was at low altitudes because it is now under pressure. There is a much larger pressure differential inside vs outside of the balloon envelope when at float than there is when at lower altitudes.

so the thought that at float, if it is going to leak it has less chance is 100% totally backwards.

Joe WB9SBD


The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 5/26/2019 2:30 PM, Joe Street wrote:

K9HZ wrote:

"The balloon leaks less at altitude because the pressure on the inside and the outside come to equilibrium by diffusion."

 

One has to consider the partial pressure of gasses.  There is still a huge difference in partial pressure of He between inside and outside regardless of altitude so the balloon should continue to leak at altitude all other things being equal.  My guess is that it is what was conjectured previously (sorry I can't remember who wrote it) something happens to mylar at cold temperatures which densifies it at a molecular level thereby lowering the diffusion through the material.

 

 

Joe

 

On Sun, May 26, 2019 at 12:47 PM J68HZ <bill@...> wrote:

The balloon leaks less at altitude because the pressure on the inside and the outside come to equilibrium by diffusion.  The contents will leak until equilibrium is reached (if that is, in fact what is happening).  At that point then, the buoyancy balance is reduces like this:  [Pgas*Mwgas/Tgas]/[Pair*Mwair/Tair]… but now Pgas=pair… so the buoyancy ratio is [Mwgas*Tair]/[Mwair*Tgas].  And futher, for the most part, the temperature of the lift gas is approximately the same as that of the air… give or take… of course, this can change in the daytime when the sun warms the balloon and causes the lift gas to get warmer… but at night, the buoyancy equation reduces to Mwgas/Mwair… (2/16) meaning you will always have lift.  Again you need to do the real force balance to determine if there is enough lift gas quantity for the balloon to rise or fall… but what it does shows is the limiting case where the balloon will eventually reach a maximum and minimum buoyancy (day/night) and I think we see this in the altitude data that gets reported.

 

The balloon would actually leak MORE at altitude because the ambient pressure at altitude is lower.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

From: QRPLabs@groups.io [mailto:QRPLabs@groups.io] On Behalf Of Jerry Gaffke via Groups.Io
Sent: Sunday, May 26, 2019 11:19 AM
To: QRPLabs@groups.io
Subject: Re: [QRPLabs] Where can I buy floater balloon?

 

Bill,

In post 34692 Mikael said:

> If I fill a foil balloon (like the one linked to first in this thread) with helium with 6gram of lift, seal it and let it sit inside it have lost its 6 gram of lift within a week and fall to the > floor but when used as a balloon for a radio tracker at +10000m its fine for several month, I had a tracker up for 64 days last year before a storm toke it down and Dave > > have a balloon released in February with this (2) balloon stil flying, whats happening at altitude that prevents the gas from leaking out as it does at ground level?

In post 34705 he states that this is repeatable, so I assume he did not happen to have a leak
in the balloons that remained in the house.

Is there something about mylar that makes it more impermeable to helium at -50C
(as found at 10,000 meters) vs room temperature of 20C?


I don't see PV=nRT     https://en.wikipedia.org/wiki/Ideal_gas_law
causing the reported behavior.
Here is my reasoning, a first attempt at thinking this through:

Let's assume the balloon has "just enough" helium to fill it out at 10,000 meters,
so the pressure inside the balloon is always equal to the ambient pressure,
whether it is at sea level or at 10,000 meters.
At 10,000 meters the air is roughly four times less dense, so the balloon
will be 4 times larger than at sea level.  But at sea level, the air that the balloon displaces
will have 4 times the density, so the lift of the helium is the same as at 10,000 meters.
(The lift is equal to the weight of the air displaced by the balloon minus the weight of the helium.)
Likewise, the temperature change affects the density of helium and air in equal measure.
(Assume the helium eventually reaches the same temperature as the ambient air.)

If the mylar balloon has more helium than needed at 10,000 meters (but does not pop),
then the pressure of the helium at altitude will be greater than the "just enough" case
and thus it is more dense.  The lift will be less at altitude than it is at sea level. 
The balloon will rise to that altitude at which the lift is equal to the weight of the payload.

When Mikael's balloon left behind in the house sinks to the floor after a week, it has
less helium remaining in the balloon than the one that is floating at 10,000 meters.
Even though the balloon at altitude is likely overfilled, with the helium pressing on the mylar walls.

But somehow the balloon leaks less at altitude?  Curious.

Jerry, KE7ER
 

On Sun, May 26, 2019 at 12:21 AM, J68HZ wrote:

Some science here.

 

Balloons lift (are buoyant) on the basis of Archimedes principle (cite: https://en.wikipedia.org/wiki/Archimedes%27_principle) which has the corollary that less dense material will rise above more dense material.  It’s the same principle that causes oil to float on water… and with gases, it causes the lightest one (less dense gas) to rise above a heavier gas.  Even hot air will rise above ambient air just because the density of the air in the balloon is less than that of ambient air.

 

In the buoyancy calculation, the force of lift is proportional to the relative differences between the densities of the gases… and in this case, that would be H2 (or whatever the lift gas is) and air.  Now, the density of a gas can be calculated from the ideal gas law… P*V=n*R*T, or rewriting, P=p*R*T/Mw where “p” is the gas density and “Mw” is the molecular weight of the gas.  The ratio for lift is then [P1*Mw1/T1]/[P2*Mw2/T2].  Plug in the numbers and you can determine where the lift will cease.  Of course you need to do a force balance for the real lift and include the weight of the payload and the balloon.

 

The point here is that the buoyancy can vary based on the ambient temperature and pressure… even of the temperature and pressure of the gas in the balloon stays constant.

 

Virus-free. www.avg.com