Date   

Re: Decoupling a GPIO pin for WSPR

Sam KJ4VPI
 

Bob,
Yep. You know what I'm trying to do!
Very comprehensive post.
Sent you email to the address on QRZ.
Thx.
73 KJ4VPI, Sam


Re: Looking for a good power supply that will handle a load

Perry Ogletree
 

Marlin P Jones Electronics (MPJA.com) has a 4 amp wall wart that comes with several USB adapters for different micro boards (including the RPi 3B+) for around $10. They also offer USPS flat rate shipping for $7. I've been a satisfied purchaser for many years.

Perry K4PWO


Re: Decoupling a GPIO pin for WSPR

w9ran <w9ran@...>
 

On 3/24/2020 6:32 AM, Sam KJ4VPI wrote:

What sort of capacitor should I use to de-couple the GPIO pin from DC so as not to short anything?
I was an early user of the Raspberry Pi (model 1) as a wspr transmitter and if you've read cautionary notes about isolating the GPIO4 pin as well as filtering the output, that's because of me.   I initially just coupled the pin through a filter to an antenna but after transmitting on a different radio and antenna found that sufficient voltage had been induced via the antenn onto the GPIO4 pin to damage the Pi.    So there are two concerns that have been addressed in my "transmitter" board:

1.   Low pass (or bandpass) filtering to remove harmonics.   (On some frequencies there are subharmonics that will go right through a LPF, requiring a PBF to ensure a clean output).

2.  A means of isolating the GPIO pins of the Pi from the RF world.  I suggest capacitively coupling the GPIO4 pin through a 100nF to a TTL gate - I use several sections of the 74HCT04 wired in parallel, and then to a low pass filter.    Suitable filter designs can be found at: http://www.gqrp.com/technical2.htm (Thank you G3RJV, SK)   (Bear in mind that the GPIO4 signal is a square wave that is rich with harmonics clear up to the VHF range, so the LPF is necessary to filter that into a nice legal single-frequency sine wave).

The WsprryPi software is the only way to go: https://github.com/JamesP6000/WsprryPi       The ability to synch to NNTP time servers makes a  Pi-based wspr transmitter more accurate than virtually any commercial radio used for wspr and I also find the random transmit option greatly increases the number of spots.

There's still no guarantee but if you do have induced or otherwise excessive voltage present it means you'll be replacing a 35 cent IC instead of a 35 dollar Raspberry Pi.   Using a good quality (preferably linear) power supply is recommended and a battery backup or UPS will help prevent data corruption if you have a loss of power while the software is running.

The direct 16dBm output of my Pi has been spotted all over the world (>14,000 km) with a good antenna, and you'll get spots with even a poor antenna with that power level on 20 and 17 meters, and even on the lower bands when propagation is favorable.    But you'll want to scale it up to the 100mW to 2 watt range to really get out more on 30 meters and below. Anything more than that is QRO on HF wspr!

73, Bob W9RAN


Re: Decoupling a GPIO pin for WSPR

David Ranch
 

Hello Sam,

Just managed to acquire a Pi 3 and want to try WSPR with it after I get it set up and running.

Ok, sounds good.  Just to be clear, are you going to be running WSTJ-X or some other program that implements the WSPR protocol?


What sort of capacitor should I use to de-couple the GPIO pin from DC so as not to short anything?

I'm not what you mean here.  It seems you're intending to use one of the GPIO pins as the actual transmitter.  Correct?  If so, you *must* use a proper LPF to block out all the sidebands coming off the GPIO pin.  No other caps will be required here.


Also, if I want to adjust the output before running the input into an amp and LPF, would a simple potentiometer between 3.3V and GND aft of the capacitor suffice? I mean is there a recommended circuit to use downstream of the GPIO pin to ultimately feed an antenna?

I don't know if I've heard of anyone trying to feed an amp with a modulated GPIO pin.  Regardless, WSPR is not about RF power and if anything less, it's about the LACK of power.  I'm unclear about your desire to attenuate the power level out of the GPIO but here is one kit that takes the output up to about 100mw:

   https://www.ke6mt.us/2019/06/new-equipment-qrpguys-ez-wspr-pi/

--David
KI6ZHD


Re: Looking for a good power supply that will handle a load

John Tetreault (WA1OKB)
 

It seems to handle my 45w radios, plus the case cooling fans, plus the raspberry pi repeater controller just fine...    

I had initially looked at actual repeater cases, like the CDR700 case... Until I saw the outrageous price they get for them, even ordering from china they're outrageously expensive for what they are....  That's when it occured to me that it really just looks like a PC tower case... And so I dug out one of my old dead mini tower PC's (I told the wife it wasn't junk haha) and the rest is history.

On Tue, Mar 24, 2020, 10:41 AM BruceN <k4tql@...> wrote:
John,
I asked the question because the discussion seemed to revolve around using those wall wart supplies all of whom seem to have limited capacity.  I was just trying to suggest using something heftier.

BTW, that re-purposed PC case is a great idea.  And I can use it here to service my APRS and Weather Station nodes.  Keeps everything in one place neat and tidy.  Now I know what to do with those cases I have that have been robbed of their power supplies.

The breakout board looks to be a good device but I'm afraid that the full capacity of the power supply might not be available.  The main power conductors on the ATX connector are just two, three, or four 22 gauge conductors.  Good for several amps but not enough for a high power radio (50 watts or so).  I will stand corrected if I'm wrong.

BruceN / K4TQL
On Mon, Mar 23, 2020 at 07:40 PM, John Tetreault (WA1OKB) wrote:
Of course someone has thought of repurposing a PC power supply.... I actually repurposed an entire mini tower case and power supply for my repeater build... The 5 1/4" drive bays fit two mobile radios quite nicely.
 
Then just used one of these to breakout 12v for the radios, and 5v to power a raspberry pi repeater controller
 
 

 
 

 


Re: Looking for a good power supply that will handle a load

BruceN
 

John,
I asked the question because the discussion seemed to revolve around using those wall wart supplies all of whom seem to have limited capacity.  I was just trying to suggest using something heftier.

BTW, that re-purposed PC case is a great idea.  And I can use it here to service my APRS and Weather Station nodes.  Keeps everything in one place neat and tidy.  Now I know what to do with those cases I have that have been robbed of their power supplies.

The breakout board looks to be a good device but I'm afraid that the full capacity of the power supply might not be available.  The main power conductors on the ATX connector are just two, three, or four 22 gauge conductors.  Good for several amps but not enough for a high power radio (50 watts or so).  I will stand corrected if I'm wrong.

BruceN / K4TQL

On Mon, Mar 23, 2020 at 07:40 PM, John Tetreault (WA1OKB) wrote:
Of course someone has thought of repurposing a PC power supply.... I actually repurposed an entire mini tower case and power supply for my repeater build... The 5 1/4" drive bays fit two mobile radios quite nicely.
 
Then just used one of these to breakout 12v for the radios, and 5v to power a raspberry pi repeater controller
 
 

 
 

 


Decoupling a GPIO pin for WSPR

Sam KJ4VPI
 

Hello,
Just managed to acquire a Pi 3 and want to try WSPR with it after I get it set up and running. 

What sort of capacitor should I use to de-couple the GPIO pin from DC so as not to short anything? Also, if I want to adjust the output before running the input into an amp and LPF, would a simple potentiometer between 3.3V and GND aft of the capacitor suffice? I mean is there a recommended circuit to use downstream of the GPIO pin to ultimately feed an antenna?

Thanks,
KJ4VPI, Sam


Re: pitnc_get params gives me "Bad file descriptor

Gary B
 

I for one am thankful for some of the information posted here and at least I don't have the arrogance to denigrate those who are attempting to assist. James, maybe you need to self isolate yourself from any type of humanity long enough to realise there is no need to live life as a complete arsehole.


On Tue., 24 Mar. 2020, 09:43 james, <jmsrandazzo@...> wrote:

who gives  rat ass

On 3/23/2020 4:41 PM, John Tetreault (WA1OKB) wrote:
Unless you're running modified version of Raspbian, such as Pi-Star, which doesn't have the config program.

On Mon, Mar 23, 2020, 6:31 PM <list-raspberry_pi_4-ham_radio@...> wrote:
raspi-config is just a shell script. One way to see what is does is to
read it:

   more /usr/bin/rapsi-config


Max via Groups.Io wrote on 2020-03-23 6:56 a.m.:
> Personally, I like to know what changes raspi-config makes to the OS. In
> the early days of the PI, raspi-config either didn't exist, or didn't
> have all the options it does now. Maybe not so important now, but I
> still want to know.
>
> Max KG4PID




Re: pitnc_get params gives me "Bad file descriptor

james <jmsrandazzo@...>
 

who gives  rat ass

On 3/23/2020 4:41 PM, John Tetreault (WA1OKB) wrote:
Unless you're running modified version of Raspbian, such as Pi-Star, which doesn't have the config program.

On Mon, Mar 23, 2020, 6:31 PM <list-raspberry_pi_4-ham_radio@...> wrote:
raspi-config is just a shell script. One way to see what is does is to
read it:

   more /usr/bin/rapsi-config


Max via Groups.Io wrote on 2020-03-23 6:56 a.m.:
> Personally, I like to know what changes raspi-config makes to the OS. In
> the early days of the PI, raspi-config either didn't exist, or didn't
> have all the options it does now. Maybe not so important now, but I
> still want to know.
>
> Max KG4PID




Re: pitnc_get params gives me "Bad file descriptor

John Tetreault (WA1OKB)
 

Unless you're running modified version of Raspbian, such as Pi-Star, which doesn't have the config program.


On Mon, Mar 23, 2020, 6:31 PM <list-raspberry_pi_4-ham_radio@...> wrote:
raspi-config is just a shell script. One way to see what is does is to
read it:

   more /usr/bin/rapsi-config


Max via Groups.Io wrote on 2020-03-23 6:56 a.m.:
> Personally, I like to know what changes raspi-config makes to the OS. In
> the early days of the PI, raspi-config either didn't exist, or didn't
> have all the options it does now. Maybe not so important now, but I
> still want to know.
>
> Max KG4PID




Re: Looking for a good power supply that will handle a load

John Tetreault (WA1OKB)
 

Of course someone has thought of repurposing a PC power supply.... I actually repurposed an entire mini tower case and power supply for my repeater build... The 5 1/4" drive bays fit two mobile radios quite nicely.

Then just used one of these to breakout 12v for the radios, and 5v to power a raspberry pi repeater controller




On Mon, Mar 23, 2020, 8:31 AM BruceN <k4tql@...> wrote:
Has no one thought of using a repurposed PC power supply?  I took an old PC supply, removed most of the inside wires and replaced them with 10/12 gauge conductors.  Put banana jacks or Graypole connectors on the case for 12 VDC, 5 VDC and 3 VDC.  Made up a small distribution board using USB A receptacles for 5 VDC and then use good quality USB A to micro A cables for 5 V.  Got plenty of power (many amps) and service several Pi's or other boards.  Cost: about $40 if you bought new.  0 if you scarfed the supply from an old PC.

I haven't had any issues with noise because I try to use only heavy duty power supplies.  Believe it or no,, you can tell by weight.  If it's light, it will be noisy.  BTW, I use these supplies on a couple of radios, too.  So far, so good.

If you do a web search, you'll find several sources with information on how to re-purpose the supplies.  There is even one which shows how to change the 12 VDC to 13.6 VDC more suitable for most radio equipment.

My only gripe and frustration is how to find heavy duty USB cables.  And price doesn't mean a thing.  I've paid a pretty penny for "heavy duty" cables only to find that they are crap for DC.  I'm considering adding a good coaxial connect to the Pi for DC.  A little less handy but it will eliminate low voltage issues.

BruceN / K4TQL


Re: pitnc_get params gives me "Bad file descriptor

list-raspberry_pi_4-ham_radio@...
 

raspi-config is just a shell script. One way to see what is does is to read it:

more /usr/bin/rapsi-config


Max via Groups.Io wrote on 2020-03-23 6:56 a.m.:

Personally, I like to know what changes raspi-config makes to the OS. In the early days of the PI, raspi-config either didn't exist, or didn't have all the options it does now. Maybe not so important now, but I still want to know.
Max KG4PID


Re: Looking for a good power supply that will handle a load

Ray Wells
 

Who died and left you in charge?

Most people are sensible enough to realise that sometimes a simplistic question doesn't get the best answers and, as many people here know, a lot of RPi problems can't be solved by using "a good power supply", per se. The original question invited OT answers to ensure the OP was on the right track, and fragmenting such answers to a new topic destroys the flow of valid and valuable closely related, as in joined at the hip, information, especially for newbies who already find it difficult enough to wade through the available information, and who don't know WHICH questions to ask to get answers. If somebody suspected a voltage related SD Card failure, then that too is related to the power supply and voltage drop, making it very much ON topic.

This is a forum to help RPi users resolve problems, not a place where individuals are afraid to post for fear of someone jumping on them.

You don't intimidate me, bullies never do. Lighten up.

Ray vk2tv

On 24/3/20 8:28 am, chuck gelm wrote:
On 3/22/20 2:46 PM, Mark Griffith via Groups.Io wrote:
Eh, I've been using the same PNC 32GB Class 10 SD card for more than 4 years. This card started life on an old Pi 2, then to a Pi 3 and now to a Pi 4. I have re-imaged it many times, installed and uninstalled many many software packages on it, and done all the PiGate development work on this same card with absolutely zero problems.  It sits here sending and receiving email messages all day and night, and is always available when I try to login. Total reliability for more then 4 years.

One day, just like a hard disk, it will fail.  But I have backups.

I'd say, from my experience, don't waste your money on "premiere" cards.  Just make sure it is a Class 10 card.

My 2 cents.

Mark
KD0QYN
Hijacked topic.


Re: Looking for a good power supply that will handle a load

chuck gelm <rpi4ham@...>
 

On 3/23/20 12:06 PM, Allen wrote:
Bruce,
If you want some good Cat6 cable use Ubiquity Tough Cable. It is double shielded and has a drain wire. You just need your ends. Yes I wondering  if you should just use 50 ohm or consider using 70 ohm. 70 ohm is great for video and audio which is digital. In my past business we used only 70 ohm for video and audio with the police vests and dog vests. In your case you do not need to worry about connectors in the RF world as they have special 70 ohm connectors for that. In you case they are USB3 or 2 and micro USB.
Allen Higgins
KE8KZO
_.
hijacked topic.


Re: Raspberry Pi3+b With 4 relay Plate

chuck gelm <rpi4ham@...>
 

On 3/23/20 12:51 AM, Allen wrote:
Type in terminal http://wiki.52pi.com/index.php?title=4 Channel_Relay_Hat_Board_For_Raspberry_Pi_SKU:_EP-0099
"http://wiki.52pi.com/index.php?title=4 Channel_Relay_Hat_Board_For_Raspberry_Pi_SKU:_EP-0099"

looks like a URL for a 'web resource'.

It seems to me this is not something that would be 'Type in terminal'.
:-|


Re: Looking for a good power supply that will handle a load

chuck gelm <rpi4ham@...>
 

On 3/22/20 5:17 PM, Ray Wells wrote:
I think that's an unnecessary expense, and the hundreds of thousands of RPi's using Class 10 (even worse) consumer grade cards speaks highly of the reliability of those cards, especially if recommended methods to reduce write cycles is followed. Failures are a very low count overall, and their use extends well beyond just the RPi.
Again, topic was hijacked.


Re: Looking for a good power supply that will handle a load

chuck gelm <rpi4ham@...>
 

On 3/22/20 2:46 PM, Mark Griffith via Groups.Io wrote:
Eh, I've been using the same PNC 32GB Class 10 SD card for more than 4 years. This card started life on an old Pi 2, then to a Pi 3 and now to a Pi 4. I have re-imaged it many times, installed and uninstalled many many software packages on it, and done all the PiGate development work on this same card with absolutely zero problems.  It sits here sending and receiving email messages all day and night, and is always available when I try to login. Total reliability for more then 4 years.

One day, just like a hard disk, it will fail.  But I have backups.

I'd say, from my experience, don't waste your money on "premiere" cards.  Just make sure it is a Class 10 card.

My 2 cents.

Mark
KD0QYN
Hijacked topic.


Re: Looking for a good power supply that will handle a load

chuck gelm <rpi4ham@...>
 

On 3/22/20 8:30 AM, Sam KJ4VPI wrote:
many times we experience voltage deviations.
A typical 120vac to 5vdc power supply accepts 100 to 240 vac.
Do your AC mains fluctuate out side of those limits?


Re: Looking for a good power supply that will handle a load

Teton Amateur Radio Repeater Association (TARRA)
 

If you use some type over regulating system to drop it down to 5V, keep your 5V lead length as short as you can. I think mine are about three inches long.

Mick - W7CAT

----- Original Message -----
From: Ray Wells
To: RaspberryPi-4-HamRadio@groups.io
Sent: Monday, March 23, 2020 03:06:15 PM
Subject: Re: [RaspberryPi-4-HamRadio] Looking for a good power supply that will handle a load

>
> +1 on the power supply socket and its related problems. I still haven't
> overlooked employing a dangling lead with a coaxial line socket for each
> of my RPi's. Then I ca be absolutely certain the power lead has adequate
> conductor size.
>
> Ray vk2tv
>
> On 24/3/20 1:22 am, Max via Groups.Io wrote:
> > I agree with the problem of finding heavy duty USB cables. I wish the
> > pi had an on-board regulator that would accept 8 to 18 volts or so
> > along with a coaxial power connection. That would have eliminated most
> > if not all of the power problems that users have had over the years.
> >
> > I keep looking for a USB power cable much like what you would have if
> > you were to cut off the cable of a Pi4 power supply. Just a USB-C
> > connector on a 20awg two-wire cable. Then I could use a single power
> > supply and distribute the power to multiple Pi's.
> >
> > Max KG4PID
> >
> > On Monday, March 23, 2020, 07:31:34 AM CDT, BruceN
> > wrote:
> >
> >
> > Has no one thought of using a repurposed PC power supply?  I took an
> > old PC supply, removed most of the inside wires and replaced them with
> > 10/12 gauge conductors.  Put banana jacks or Graypole connectors on
> > the case for 12 VDC, 5 VDC and 3 VDC.  Made up a small distribution
> > board using USB A receptacles for 5 VDC and then use good quality USB
> > A to micro A cables for 5 V. Got plenty of power (many amps) and
> > service several Pi's or other boards.  Cost: about $40 if you bought
> > new.  0 if you scarfed the supply from an old PC.
> >
> > I haven't had any issues with noise because I try to use only heavy
> > duty power supplies.  Believe it or no,, you can tell by weight.  If
> > it's light, it will be noisy. BTW, I use these supplies on a couple of
> > radios, too. So far, so good.
> >
> > If you do a web search, you'll find several sources with information
> > on how to re-purpose the supplies.  There is even one which shows how
> > to change the 12 VDC to 13.6 VDC more suitable for most radio equipment.
> >
> > My only gripe and frustration is how to find heavy duty USB cables. 
> > And price doesn't mean a thing.  I've paid a pretty penny for "heavy
> > duty" cables only to find that they are crap for DC.  I'm considering
> > adding a good coaxial connect to the Pi for DC.  A little less handy
> > but it will eliminate low voltage issues.
> >
> > BruceN / K4TQL
> >
>
>
>
>
>
--

 

0


Re: Looking for a good power supply that will handle a load

Ray Wells
 

+1 on the power supply socket and its related problems. I still haven't overlooked employing a dangling lead with a coaxial line socket for each of my RPi's. Then I ca be absolutely certain the power lead has adequate conductor size.

Ray vk2tv

On 24/3/20 1:22 am, Max via Groups.Io wrote:
I agree with the problem of finding heavy duty USB cables. I wish the pi had an on-board regulator that would accept 8 to 18 volts or so along with a coaxial power connection. That would have eliminated most if not all of the power problems that users have had over the years.

I keep looking for a USB power cable much like what you would have if you were to cut off the cable of a Pi4 power supply. Just a USB-C connector on a 20awg two-wire cable. Then I could use a single power supply and distribute the power to multiple Pi's.

Max KG4PID

On Monday, March 23, 2020, 07:31:34 AM CDT, BruceN <k4tql@dts-ga.com> wrote:


Has no one thought of using a repurposed PC power supply?  I took an old PC supply, removed most of the inside wires and replaced them with 10/12 gauge conductors.  Put banana jacks or Graypole connectors on the case for 12 VDC, 5 VDC and 3 VDC.  Made up a small distribution board using USB A receptacles for 5 VDC and then use good quality USB A to micro A cables for 5 V. Got plenty of power (many amps) and service several Pi's or other boards.  Cost: about $40 if you bought new.  0 if you scarfed the supply from an old PC.

I haven't had any issues with noise because I try to use only heavy duty power supplies.  Believe it or no,, you can tell by weight.  If it's light, it will be noisy. BTW, I use these supplies on a couple of radios, too. So far, so good.

If you do a web search, you'll find several sources with information on how to re-purpose the supplies.  There is even one which shows how to change the 12 VDC to 13.6 VDC more suitable for most radio equipment.

My only gripe and frustration is how to find heavy duty USB cables.  And price doesn't mean a thing.  I've paid a pretty penny for "heavy duty" cables only to find that they are crap for DC.  I'm considering adding a good coaxial connect to the Pi for DC.  A little less handy but it will eliminate low voltage issues.

BruceN / K4TQL

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