Date   
Re: Adding uv meter .board and leads to ubitx

Bob Lunsford <nocrud222@...>
 

Good idea. Those amps are usually pretty small. Most
I have seen are on a board about 2-in square.

Bob — KK5R

--------------------------------------------

On Sun, 1/20/19, d balfour <davesters@...> wrote:

Subject: Re: [BITX20] Adding uv meter .board and leads to ubitx
To: BITX20@groups.io
Date: Sunday, January 20, 2019, 8:32 AM

I took a used computer speaker
apart and removed the amplifier. Stripped off the switch,
volume control, and plug in ports. Mounted it in the case
with a couple of standoffs and bolts.Ran the output of the
v4 into the input of the amp. I bought the v4 used with an
indian case. The volume control was biased with equal 4.7 k
resisters The power comes from the main switch of the
radio.

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Curt
 

Dave

I suggest keeping this surgery within your comfort zone.  Nothing sacred about surface mount parts, but at 45 MHz keep connections short.  I am not yet considering this particular mod - but you could consider using a small daughter board connected with leads to main board.  At the moment with lower bands doing the best - I suggest the LPF filter relay issue is a bigger deal.  Here in our club build we are adding 3 relays on a daughter board. 

I have been trying the approach of using an added xtal filter at C22 - while it corrects spurious we find it inhibits CW transmit power on 40m. 

I suggest insuring your work can be reversed if correction is found not to work well enough - been there, doing that. 

73 Curt

Re: CW operation on microBITX

Curt
 

Geoff

fantastic to have you aboard ! 

for CW - there isn't a specific mode.  for 40m - note rig will say LSB.  then press the key - display should read CW and you should hear sidetone.  if you got rig doing this - I would observe on your power meter if you have transmitted power. 

that 4.7k resistor must be in place.  what happens is the controller reads the voltage across this resistor - and knows to do CW.  this only works with a straight key.  with a paddle there is need to externally add 2 resistors - I can talk you through this as required. 

that thing you found is a menu setting -- yes speed and I forget what else.  honestly the most important menu operation here is to press the button - see BAND SELECT - press again without turning knob - and you can QSY between bands by turning the knob. 

this rig has its own coolness - be patient and enjoy the ride.  I can discuss via email - see qrz.com.  when I get this rig sufficiently worked - I may need your help when I build a valve rig. 

Curt WB8YYY

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Dave Space
 

Yep good ideas.  I'm also considering the daughter card filtering option.  Unfortunately I tried to buy from QRP labs but it didn't like my credit card for some reason.  Luckily they give instructions on most of it so I bought some of the parts from other places to try to assemble some variation of my own.

Checking with just an RTL-SDR transmitting at 7.15 MHZ I saw a harmonic at about 21 MHZ range that was at the same power as my transmit frequency.  Plus I presume lots of IMD / spurs around 0.75MHZ up and down away from the main transmit frequency at only about -30db.

So definitely need to do something to be able to use it.


On Sun, Jan 20, 2019 at 05:31 PM, Curt wrote:
Dave

I suggest keeping this surgery within your comfort zone.  Nothing sacred about surface mount parts, but at 45 MHz keep connections short.  I am not yet considering this particular mod - but you could consider using a small daughter board connected with leads to main board.  At the moment with lower bands doing the best - I suggest the LPF filter relay issue is a bigger deal.  Here in our club build we are adding 3 relays on a daughter board. 

I have been trying the approach of using an added xtal filter at C22 - while it corrects spurious we find it inhibits CW transmit power on 40m. 

I suggest insuring your work can be reversed if correction is found not to work well enough - been there, doing that. 

73 Curt

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Curt
 

Dave

There are more affordable options for the low pass filter mod, much less than the nice qrp labs relay board. Our club is using a board layed out by Gordon G. I would stand by until someone offers a kit.

Most spurs below 18 MHz haven't been that horrific,  no not 0 dB down. I can share measurements on my rig later this week, but several examples are around. Many of us are using the rig on lower bands while a solution emerges. I would stay barefoot with the rig, and avoid operating above 20m. The types of antennas you use also impacts degree of caution. These spurs were be addressed with affordable solutions in time.

Curt

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Jerry Gaffke
 

Agreed, spurs on 80m-20m are not a big issue with a stock uBitx.
Harmonics on a stock rig are 30dB down or more, so down in power by a factor of 1000.
Should be better, but I doubt anybody will ever get into trouble using a stock rig on the air. 

But do avoid the use of an external linear amp.
Avoid using any scheme to goose the mike gain unless you can take some measurements of spurs,
since increasing mike audio above that given with the stock mike will disproportionately increase the spurs.
 
I would tend to question what that RTL-SDR was telling you.
For one, it's only got an 8 bit ADC, so dynamic range is limited to 40dB or so (theoretical max of 48dB).
You would have to carefully adjust the power into the RTL-SDR using a step attenuator such that your 
carrier uses up most but not all of those 8 bits if you want to see spurs or harmonics that are 40dB down.
My guess is that you overloaded the RTL-SDR.

Jerry, KE7ER


On Sun, Jan 20, 2019 at 07:40 PM, Curt wrote:
Most spurs below 18 MHz haven't been that horrific,  no not 0 dB down. I can share measurements on my rig later this week, but several examples are around. Many of us are using the rig on lower bands while a solution emerges. I would stay barefoot with the rig, and avoid operating above 20m. The types of antennas you use also impacts degree of caution. These spurs were be addressed with affordable solutions in time.

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Dave Space
 

Possibly.  I'm using a -40db attenuation.  Think it needs more attenuation than that for RTL-SDR?


On Sun, Jan 20, 2019 at 08:43 PM, Jerry Gaffke wrote:
Agreed, spurs on 80m-20m are not a big issue with a stock uBitx.
Harmonics on a stock rig are 30dB down or more, so down in power by a factor of 1000.
Should be better, but I doubt anybody will ever get into trouble using a stock rig on the air. 

But do avoid the use of an external linear amp.
Avoid using any scheme to goose the mike gain unless you can take some measurements of spurs,
since increasing mike audio above that given with the stock mike will disproportionately increase the spurs.
 
I would tend to question what that RTL-SDR was telling you.
For one, it's only got an 8 bit ADC, so dynamic range is limited to 40dB or so (theoretical max of 48dB).
You would have to carefully adjust the power into the RTL-SDR using a step attenuator such that your 
carrier uses up most but not all of those 8 bits if you want to see spurs or harmonics that are 40dB down.
My guess is that you overloaded the RTL-SDR.

Jerry, KE7ER


On Sun, Jan 20, 2019 at 07:40 PM, Curt wrote:
Most spurs below 18 MHz haven't been that horrific,  no not 0 dB down. I can share measurements on my rig later this week, but several examples are around. Many of us are using the rig on lower bands while a solution emerges. I would stay barefoot with the rig, and avoid operating above 20m. The types of antennas you use also impacts degree of caution. These spurs were be addressed with affordable solutions in time.

ubitx or bitx 40

Dave Dixon
 

Hi,
      Looking for a ubitx or bitx 40 contact me daveg0ayd@...
i am located in the uk. Dave G0AYD. CW OPS 2159 FISTS 15892.            

Re: CW operation on microBITX

geoffg3wzp@...
 

Curt
thanks for reply .....I will have another look today when I have finished getting the mic attached to check out SSB first ..if that all works then back to the key ...CW is my preferred mode goes back to days of no money as a teenager when I got licence in 1967 couldnt afford an AM modulator so all rigs were CW only !
Urban QRM here is S8 so hoping to use the MbitX on holidays now I am retired !
73

Re: Good mic for Ubitx and Bitx40

Paul Dobosz
 

Almost all of the land mobile (Motorola & Harris/GE/Ericsson/MaCom) are dynamic mics that have an internal preamp.  I've had an excellent experience using them in applications that were designed for Electret mics.  They are plentiful and relatively inexpensive in both NOS and used condition on the usual online sites  and are built extremely solidly..  The mobile mics tend to be quite heavy with most having a large piece of heavy steel inside for no other reason than to give them "heft".  I generally remove the weight as I wire the mic up for the radio I'm using it on.

73 - Paul - K8PD

Re: Good mic for Ubitx and Bitx40

iz oos
 

I believe the stock element is fine. I have tried other electrets elements and all delivered less output. I did change I believe R63 to have higher output. Some suggested to use very sensitive elements (-24db/pa). Mouser and others have them. However upon a suggestion here in this forum I opted using a dynamic element and a Plessey SL6270C, which is not just a preamplifier, it is a compressor. So it delivers about 90mv whatever you shout or you whisper. Average power drastically increased. I have a mil manpack, which I love (my first solid state transceiver) that exactly use this type of Plessey Vogad compressor. My point is that with QRPs a compressor, not a preamplifier or equalizer, is what is really needed.


Il 21/gen/2019 13:53, "Paul Dobosz" <pjdobosz@...> ha scritto:
Almost all of the land mobile (Motorola & Harris/GE/Ericsson/MaCom) are dynamic mics that have an internal preamp.  I've had an excellent experience using them in applications that were designed for Electret mics.  They are plentiful and relatively inexpensive in both NOS and used condition on the usual online sites  and are built extremely solidly..  The mobile mics tend to be quite heavy with most having a large piece of heavy steel inside for no other reason than to give them "heft".  I generally remove the weight as I wire the mic up for the radio I'm using it on.

73 - Paul - K8PD

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Bill Cromwell
 

Hi,

I agree with Jerry. I have an RTL-SDR here. It's a fun toy. Signals from off the air overload it regularly. Never mind about being in the same room with a transmitter. It is not good for that kind of work.

Sorry to say but you are fooling yourself.

73,

Bill KU8H

On 1/21/19 12:11 AM, Dave Space wrote:
Possibly.  I'm using a -40db attenuation.  Think it needs more attenuation than that for RTL-SDR?
On Sun, Jan 20, 2019 at 08:43 PM, Jerry Gaffke wrote:
Agreed, spurs on 80m-20m are not a big issue with a stock uBitx.
Harmonics on a stock rig are 30dB down or more, so down in power by
a factor of 1000.
Should be better, but I doubt anybody will ever get into trouble
using a stock rig on the air.
But do avoid the use of an external linear amp.
Avoid using any scheme to goose the mike gain unless you can take
some measurements of spurs,
since increasing mike audio above that given with the stock mike
will disproportionately increase the spurs.
I would tend to question what that RTL-SDR was telling you.
For one, it's only got an 8 bit ADC, so dynamic range is limited to
40dB or so (theoretical max of 48dB).
You would have to carefully adjust the power into the RTL-SDR using
a step attenuator such that your
carrier uses up most but not all of those 8 bits if you want to see
spurs or harmonics that are 40dB down.
My guess is that you overloaded the RTL-SDR.
Jerry, KE7ER
On Sun, Jan 20, 2019 at 07:40 PM, Curt wrote:
Most spurs below 18 MHz haven't been that horrific,  no not 0 dB
down. I can share measurements on my rig later this week, but
several examples are around. Many of us are using the rig on
lower bands while a solution emerges. I would stay barefoot with
the rig, and avoid operating above 20m. The types of antennas
you use also impacts degree of caution. These spurs were be
addressed with affordable solutions in time.
--
bark less - wag more

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Dave Space
 

On Mon, Jan 21, 2019 at 05:38 AM, Bill Cromwell wrote:
Hi,

I agree with Jerry. I have an RTL-SDR here. It's a fun toy. Signals from
off the air overload it regularly. Never mind about being in the same
room with a transmitter. It is not good for that kind of work.

Sorry to say but you are fooling yourself.

73,

Bill KU8H

On 1/21/19 12:11 AM, Dave Space wrote:
Possibly.  I'm using a -40db attenuation.  Think it needs more
attenuation than that for RTL-SDR?


On Sun, Jan 20, 2019 at 08:43 PM, Jerry Gaffke wrote:

Agreed, spurs on 80m-20m are not a big issue with a stock uBitx.
Harmonics on a stock rig are 30dB down or more, so down in power by
a factor of 1000.
Should be better, but I doubt anybody will ever get into trouble
using a stock rig on the air.

But do avoid the use of an external linear amp.
Avoid using any scheme to goose the mike gain unless you can take
some measurements of spurs,
since increasing mike audio above that given with the stock mike
will disproportionately increase the spurs.

I would tend to question what that RTL-SDR was telling you.
For one, it's only got an 8 bit ADC, so dynamic range is limited to
40dB or so (theoretical max of 48dB).
You would have to carefully adjust the power into the RTL-SDR using
a step attenuator such that your
carrier uses up most but not all of those 8 bits if you want to see
spurs or harmonics that are 40dB down.
My guess is that you overloaded the RTL-SDR.

Jerry, KE7ER


On Sun, Jan 20, 2019 at 07:40 PM, Curt wrote:

Most spurs below 18 MHz haven't been that horrific,  no not 0 dB
down. I can share measurements on my rig later this week, but
several examples are around. Many of us are using the rig on
lower bands while a solution emerges. I would stay barefoot with
the rig, and avoid operating above 20m. The types of antennas
you use also impacts degree of caution. These spurs were be
addressed with affordable solutions in time.

--
bark less - wag more

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Evan Hand
 

From my personal experience the RF Explorer seems to be good at the harmonics.  I have measured the 3rd harmonic at the same levels as reported by others (between 35 and 40 DB down), which gives me confidence on that front.  I have not been able to measure the reported spurs on bands above 20 meters.  Makes me question the usefulness for that measurement.

The minimum bandwidth setting is 112khz, which is broken into 112 segments so that each segment is 1khz wide.  That is then measuring only 112khz of the spectrum.  If you open the bandwidth to cover more, the resolution goes down.  So that for a 1.12mhz bandwidth, the resolution is 10khz, and so on.  What ever is displayed can only be divided into 112 discrete measurement intervals.  Based on that spec, it should work.  I just have not been able to see the spur.  More likely an error on the operators part.

Overall I am not disappointed with the device, it is 1/8 to 1/10 the cost of a Siglent or Rigol.  It is also portable (the main selling point) so that you can use it in the field.  However, If you are going to get really serious on RF measurements, then it may not be enough.

Above is my opinion/experience.  Yours may vary.

73
Evan
AC9TU

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Bill Cromwell
 

Hi Evan, Dave,

I looked at the 'specs' as shown on the Amazon page Dave referenced. It didn't include information that Evan has given. The big deal about a spectrum analyzer is a requirement to display very weak signals that live right next to very strong signals. Good shielding is also required. There is nothing in those specs I saw to give clues about those requirements for the measurements we want to make. Maybe the RF Explorer can do the harmonics as Evan says. Maybe others can report their results.

We can get at least some usable information from just about any 'spectrum analyzer' system including the RTL-SDR dongle and our computer sound cards. Evan an old fashioned 'wobbulator' But maybe not good enough for the kind of "measurements" we want to make here. It could be better than nothing at all. Or it could even be worse than nothing at all. Worst case is they can say "something is there". Determining just what and how much may be out of reach. Let's see what others have to say about that RF Explorer. I just ordered some 'toys' from Amazon and that RF Explorer caught my attention. I took a pass on that.

73,

Bill KU8H

On 1/21/19 9:55 AM, Evan Hand wrote:
>From my personal experience the RF Explorer seems to be good at the
harmonics.  I have measured the 3rd harmonic at the same levels as reported by others (between 35 and 40 DB down), which gives me confidence on that front.  I have not been able to measure the reported spurs on bands above 20 meters.  Makes me question the usefulness for that measurement.
The minimum bandwidth setting is 112khz, which is broken into 112 segments so that each segment is 1khz wide.  That is then measuring only 112khz of the spectrum.  If you open the bandwidth to cover more, the resolution goes down.  So that for a 1.12mhz bandwidth, the resolution is 10khz, and so on.  What ever is displayed can only be divided into 112 discrete measurement intervals.  Based on that spec, it should work.  I just have not been able to see the spur.  More likely an error on the operators part.
Overall I am not disappointed with the device, it is 1/8 to 1/10 the cost of a Siglent or Rigol.  It is also portable (the main selling point) so that you can use it in the field.  However, If you are going to get really serious on RF measurements, then it may not be enough.
Above is my opinion/experience.  Yours may vary.
73
Evan
AC9TU
--
bark less - wag more

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Dave Space
 

On Mon, Jan 21, 2019 at 06:55 AM, Evan Hand wrote:
From my personal experience the RF Explorer seems to be good at the harmonics.  I have measured the 3rd harmonic at the same levels as reported by others (between 35 and 40 DB down), which gives me confidence on that front.  I have not been able to measure the reported spurs on bands above 20 meters.  Makes me question the usefulness for that measurement.

The minimum bandwidth setting is 112khz, which is broken into 112 segments so that each segment is 1khz wide.  That is then measuring only 112khz of the spectrum.  If you open the bandwidth to cover more, the resolution goes down.  So that for a 1.12mhz bandwidth, the resolution is 10khz, and so on.  What ever is displayed can only be divided into 112 discrete measurement intervals.  Based on that spec, it should work.  I just have not been able to see the spur.  More likely an error on the operators part.

Overall I am not disappointed with the device, it is 1/8 to 1/10 the cost of a Siglent or Rigol.  It is also portable (the main selling point) so that you can use it in the field.  However, If you are going to get really serious on RF measurements, then it may not be enough.

Above is my opinion/experience.  Yours may vary.

73
Evan
AC9TU

Thanks interesting.  I wonder how much of a limitation that is... I wonder if running at 10khz it will pick up spikes at 1khz so you can zoom in later.. doing wide bandwidth first and then zoom in.. otherwise would have to scan up and down the band to cover it completely I guess.

Another more expensive item I saw was this but no tracking generator but seems like one of the most reasonably priced new ones I've seen...  Don't think I'm ready to spend this kind of money though still.

https://www.amazon.com/Rigol-DSA705-Spectrum-Analyser-500MHz/dp/B06XTB7JGQ/ref=sr_1_6?keywords=spectrum+analyzer+rigol&qid=1548084044&sr=8-6

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Evan Hand
 

I too looked at that Rigol.  My perspective is if I am going to spend that much, I might as well go all in and get the units that include the tracking generator.  Depends on how you will be using it.  Just to check for spurious emissions, or want to look at filter responses, detailed design analysis, etc....  There is a reason for the tracking generators.

The unit you listed would handle the uBitx emissions testing.

More on the RF Explorer:
If you connect to a computer and use the software, it is really easy to shift scanned start and stop frequencies.  I will look again later this week (I am traveling on business and will not be able to "play") and let you know if I learn any more.  Will also try to take some pictures of the software to show you how it works.

Maybe we need to take this off of the reflector and do it with private emails.

My opinions only

73
Evan
AC9TU

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Jerry Gaffke
 

If you want to pursue this, what you really need next is a step attenuator:
Kees is on the forum, he has a nice one here, kit #13 for $15:  https://www.qsl.net/k5bcq/Kits/Kits.html
And a whole bunch of other stuff you could spend that $165 on.

The RTL-SDR will be fine to learn with, a much better choice if you plan to
burn out the front end with that transmitter.  (I assume you also have an up-converter,
since those DVB-T dongles only down to around 30mhz.)
If you wind up with a $2000 spectrum analyzer someday, you will still need the step attenuator.

Yup, red flag that they say nothing about dynamic range on the RF Explorer, that's pretty basic info.
Manual is under Documents here, describes a bunch of different versions of the RF Explorer:
    https://www.seeedstudio.com/RF-Explorer-WSUB1-p-2986.html
Page 46 of the manual has a table showing "Measurable Input Range" when using various
external attenuators, the figures they give are consistent with an 8 bit ADC (a 40dB dynamic range).
  https://www.seeedstudio.com/RF-Explorer-WSUB1-p-2986.html
Get the vague impression elsewhere that it can see stuff between roughly -115dBm and 0dBm,
but that could be done with an 8 bit ADC and a variable gain amp.
So a very red flag.
But I could be wrong in this, look forward to hearing further from those that have one.

Jerry, KE7ER

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Bill Cromwell
 

Hi,

Radios and projects like this one seem to want something to use for spectrum examination. Don't take it off list and hide it from the rest of us.

73,

Bill KU8H

On 1/21/19 10:42 AM, Evan Hand wrote:
I too looked at that Rigol.  My perspective is if I am going to spend that much, I might as well go all in and get the units that include the tracking generator.  Depends on how you will be using it.  Just to check for spurious emissions, or want to look at filter responses, detailed design analysis, etc....  There is a reason for the tracking generators.
The unit you listed would handle the uBitx emissions testing.
More on the RF Explorer:
If you connect to a computer and use the software, it is really easy to shift scanned start and stop frequencies.  I will look again later this week (I am traveling on business and will not be able to "play") and let you know if I learn any more.  Will also try to take some pictures of the software to show you how it works.
Maybe we need to take this off of the reflector and do it with private emails.
My opinions only
73
Evan
AC9TU
--
bark less - wag more

Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Bill Cromwell
 

Hi Jerry,

I read something in an ARRL publication about getting around that 40 dB dynamic range problem. Maybe by W7ZOI or W1FB. But it almost wants a spectrum analyzer to set it up. So it's a circular solution. Circular means chasing your own tail :) If you have a spectrum analyzer to set it up why do you need the toy analyzer?

It might be doable without a second SA.

73,

Bill KU8H

On 1/21/19 10:53 AM, Jerry Gaffke via Groups.Io wrote:
If you want to pursue this, what you really need next is a step attenuator:
Kees is on the forum, he has a nice one here, kit #13 for $15: https://www.qsl.net/k5bcq/Kits/Kits.html
And a whole bunch of other stuff you could spend that $165 on.
The RTL-SDR will be fine to learn with, a much better choice if you plan to
burn out the front end with that transmitter.  (I assume you also have an up-converter,
since those DVB-T dongles only down to around 30mhz.)
If you wind up with a $2000 spectrum analyzer someday, you will still need the step attenuator.
Yup, red flag that they say nothing about dynamic range on the RF Explorer, that's pretty basic info.
Manual is under Documents here, describes a bunch of different versions of the RF Explorer:
https://www.seeedstudio.com/RF-Explorer-WSUB1-p-2986.html
Page 46 of the manual has a table showing "Measurable Input Range" when using various
external attenuators, the figures they give are consistent with an 8 bit ADC (a 40dB dynamic range).
  https://www.seeedstudio.com/RF-Explorer-WSUB1-p-2986.html
Get the vague impression elsewhere that it can see stuff between roughly -115dBm and 0dBm,
but that could be done with an 8 bit ADC and a variable gain amp.
So a very red flag.
But I could be wrong in this, look forward to hearing further from those that have one.
Jerry, KE7ER
--
bark less - wag more