Peaberry TX not working as should

General discussion and support for the Peaberry SDR V1.

Re: Peaberry TX not working as should

Postby AE9RB » Mon May 20, 2013 4:25 pm

The SPKR jack is designed for powered speakers. If it produces a clean sound then I'd guess the TX amplifiers are somehow picking up the 1kHz from the USB cable. I've never seen this happen so don't have a specific solution but there are some things you can try.

Put a ferrite choke on the USB cable or find a USB cable that has one. Check for ground loops. Make sure you power supply is floating and doesn't have its negative tied to ground. Cut the USB_SHIELD jumper and replace it with any of the leaded capacitors you have left over from the kit. Rebuild the three transformers in the transmitter. And, as Rainer said, check the power supply voltage while transmitting to make sure the voltage doesn't drop.
73 David AE9RB
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Re: Peaberry TX not working as should

Postby CT1IQI » Mon May 20, 2013 10:39 pm

tnx for suggesions & help.
It is not the power supply; that is 20 A capable and stabilized. Would like to take a more systematic approach to finding the cause of the problem.
Is there a 48 kHz IQ test file somewhere that simulates a clean CW carrier and that I could send to the Peaberry to look with the oscilloscope to the signals?
I assume this must produce two sine waves 90 degrees out of phase on VoutL & R.
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Re: Peaberry TX not working as should

Postby DJ&OA » Tue May 21, 2013 12:15 am

Have a look at http://dl6iak.etonlein.de/projects/projects.htm. There are IQ Double Tone and Double Tone generators for Windows which you should download.

Run the Double Tone Generator (only one tone thereof first, both is only of interest for intermodulation tests) on one computer and connect the audio output thereof to the mic input of the Peaberry and you may follow the whole signal path up to the TX output. Please be aware that the audio output (even the line output) of the computer running the Double Tone Generator may be quite high so that at least a 10:1 attenuator is advisable since otherwise the volume slider of the program is quite difficult to adjust. The mic input of the Peaberry is quite sensitive and may readily overdriven, but you will see that on the oscilloscope and correct it.

The IQ Double Tone Generator is only of interest if you use a separate sound card for mic play, With Peaberry, for an IQ signal, you would need symmetric signals at the inputs of U7 A/B and U7 C/D, possibly by means of transformers, and would have to interrupt the audio chain which is not justified.

Good luck!

73, Rainer
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Re: Peaberry TX not working as should

Postby AE9RB » Tue May 21, 2013 12:25 am

If you want something you can script with Linux into a test harness, use the "tune" function of twadio.rb to transmit a tone of any length.
https://github.com/WardCunningham/Small ... /twadio.rb

I use the CW or AM mode of an app to generate a tone for tracing the TX signal path.
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Re: Peaberry TX not working as should

Postby hansvi » Tue May 21, 2013 12:31 pm

Or if you have gnuradio installed, use the grc file I used for this experiment. (has a slider to control the volume).
73,
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Re: Peaberry TX not working as should

Postby CT1IQI » Tue May 21, 2013 1:00 pm

@AE9RB
tnx. Got the ruby script starting on Ubuntu 12.04 after
sudo apt-get install ruby1.9.1
sudo apt-get install ruby1.9.1-dev
sudo gem install ffi
sudo gem install ffi-portaudio
sudo gem install libusb

but doing a command like
ruby ./twadio.rb tune 7.020000 0 1 0.5 600
I get
ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5)
ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5)
ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5)
ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5)
ALSA lib pcm_dmix.c:957:(snd_pcm_dmix_open) The dmix plugin supports only playback stream
Signal: 7.020000 MHz
LO: 7.025000 MHz
Image: 7.030000 MHz

and my Peaberry transmits absolutely nothing. On my PC the Peaberry is forced to be enumerated as alsa card # 1.
Strange as the script does not throw an error for not finding the Peaberry. It does when I disconnect Peaberry's USB, so the board is found.
Yet Peaberry seems not being controlled and/or reached by an IQ stream from twadio.rb.
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Re: Peaberry TX not working as should

Postby CT1IQI » Tue May 21, 2013 1:41 pm

with twadio.rb active in tune mode, and using usbsoftrock to issue ptt on/off the Peaberry can produce a carrier.
Sometimes the carrier is fairly clean, probably the wanted state with just some weak spurious sidebands, sometimes it starts with the dirty 1 kHz modulation, and sometimes the 1 kHz is intermittently there.
Have tried whether this can be influenced by 'hand effect' but the instability seems to be happening entirely in the digital domain. I can touch and manipulate on the board whatever, it does not change this behaviour.
Also the usb shield or cable have no effect on this. It is as if something that should have been initialised is in a floating in-between state, causing havoc at random to the transmit signal.
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Re: Peaberry TX not working as should

Postby hansvi » Tue May 21, 2013 3:29 pm

I don't see how a digital signal could generate harmonics or something like that. Especially if it is intermittent.If the speaker signal is clear, the main suspect is the RF part. Just take the block schematic and check everything from USB to speakers as "tested and working". The problem then must lie in one of the other blocks. (Or you tested the speaker at a moment when the signal was clean; that's the most frustrating part of troubleshooting something that "sometimes works").

Hans.
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Re: Peaberry TX not working as should

Postby hansvi » Tue May 21, 2013 3:50 pm

Maybe you could give my gnuradio test program a try. just do "aptitude install gnuradio" and then you can run my test program with "gnuradio-companion test_peaberry_audio.grc".
Execute the flowgraph and you'll get a window with a slider to control the volume on the fly. This way you can test if the amplitude changes something. (You'll need to turn on/off the PTT with usbsoftrock).
If you want to be able to change the frequency too, that's easily added (and a good hello-world-type introduction to the wonderful world of gnuradio).
73,
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Re: Peaberry TX not working as should

Postby AE9RB » Tue May 21, 2013 9:27 pm

The audio clock on the Peaberry is phase locked with the 1kHz clock on your USB bus. Perhaps your USB bus is dirtier than ones I've tested or your test equipment is more sensitive than mine. How much dB lower than the carrier are your spurs?
73 David AE9RB
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