Receiving Ghost Signals

General discussion and support for the Peaberry SDR V2.

Receiving Ghost Signals

Postby KC8UD » Sun Jan 11, 2015 5:06 pm

Just recently something started happening that causes interference in receiving once in a while. I've figured out that I'm hearing moderately strong signals from 12 KHz above and/or below my TUNE frequency. These signals are loud and clear but do not show up in the spectral display or the waterfall at the TUNE frequency when using HDSDR. The display may show total silence at my tune frequency but I can clearly hear conversations and can correlate the audio with what I see either 12 KHz below or above. I can change my tune frequency to the 12 KHz freq above or below and hear the conversation just as clear while seeing it on the display, so I can tune in those stations at two places. This seems to have nothing to do with where the LO frequency is set. What is magic about 12 KHz? Any help to narrow this problem down and resolve it will be appreciated. I've been dabbling with this issue for a week or so testing for solder breaks on the board but not certain if this is hardware or software related. As luck would have it I can't always make it happen.

EDIT:
I can now confirm that I see this issue while using MultiPSK software as well. Its like seeing/hearing both sidebands.
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Re: Receiving Ghost Signals

Postby W4MMP » Sun Jan 11, 2015 6:47 pm

Hi,
Please make a recording with HDSDR when the issue occurs. Configure HDSDR to record all three (RF,IF and AF). I don't think the files may be attached to a post so perhaps you can upload recordings to dropbox or something along that line. I would like to take a look with HDSDR.
73
Ron / W4MMP
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Re: Receiving Ghost Signals

Postby Jtrenalone » Sun Jan 11, 2015 7:17 pm

I have been having e same issues lately, although I have not measured he exact frequancy offset. I'd be curious what you find out,
Joel
KD6AGW
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Re: Receiving Ghost Signals

Postby KC8UD » Tue Jan 20, 2015 2:23 am

OK Ron,

I've had a hard time to make this happen and catch it in the act but it just happened a moment ago and I was finally able to snatch a recording. The links to each file take you to my Google Drive. This recording is on 20 meters late in the evening and the band is almost shut down so the signals are weak. The most prominent occurrence of ghosting is from a signal on 14.273 MHz USB. If you tune 12 KHz higher to 14.285 MHz you will hear the same signal again but notice it does not show up on the spectrum or the waterfall. Another occurrence is from a signal on 14.340 MHz USB. If you tune 12 KHz down to to 14.328 MHz or tune 12 KHz up to 14.352 MHz you will hear the same signal. And again the signal does not show in the spectrum or waterfall. Just to note, when I tried to tune the signals + and - 12 Khz of 14.340 Mhz while playing back the recording i could not notice the ghosting so much. But it is still quite prominent 12 KHz above the signal at 14.273 Mhz.

RF file
https://drive.google.com/file/d/0B9ArRH ... sp=sharing


AF file
https://drive.google.com/file/d/0B9ArRH ... sp=sharing


IF file
https://drive.google.com/file/d/0B9ArRH ... sp=sharing


Thanks for giving this a try. Another thing I've noticed that is strange sometimes, when I first initialize the software and begin receiving, the TUNE frequency and spectrum will indicate that I'm tuned to the phone portion of 20 meters while I'm clearly hearing and seeing digital mode signals and CW. Something is certainly confused and if I use the Freq manger menu to change frequencies then it seems to shake it up a bit and set it straight. The ghosting issue is not just an issue with HDSDR as it also occurs while using MultiPSK software.

73 Gary
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Re: Receiving Ghost Signals

Postby W4MMP » Tue Jan 20, 2015 2:44 am

Hi,
Sure wish it was not Spanish :) I'm listening now.

Another thing I've noticed that is strange sometimes, when I first initialize the software and begin receiving, the TUNE frequency and spectrum will indicate that I'm tuned to the phone portion of 20 meters while I'm clearly hearing and seeing digital mode signals and CW. Something is certainly confused and if I use the Freq manger menu to change frequencies then it seems to shake it up a bit and set it straight.


HDSDR does not send an initialization frequency to the rig when HDSDR is started. I have not really examined the Peaberry initialization procedures in the firmware and not really sure how or what frequency is chosen when the Peaberry powers up. The bottom line is there is a good probability there is a mismatch between what HDSDR thinks the operating frequency is and the Peaberrys operating frequency when the station is brought up.
73
Ron / W4MMP
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Re: Receiving Ghost Signals

Postby AE9RB » Wed Jan 21, 2015 12:12 am

I don't understand the problem description. However, the RF recording looks good so the problem isn't a faulty build. Have you tried a different computer?
73 David AE9RB
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Re: Receiving Ghost Signals

Postby Jtrenalone » Fri Jan 23, 2015 11:48 pm

Well, I am not sure if this is the same issue that the others have been having, but I did catch the problem on video.

I'm fairly sure it is an HDSDR issue.
Here is a link to the video on youtube:

http://youtu.be/8A4ovnCpq2M

You can see that the tuned frequency shows nothing on the large waterfall, but it clearly shows on the zoomed waterfall display. The audio is clear and loud, but it is from a signal about 12k down (you can see it on the display). When I start and stop it it goes away.

Let me know if anyone has any clues,
Thanks,
Joel
KD6AGW
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Re: Receiving Ghost Signals

Postby AE9RB » Sat Jan 24, 2015 1:46 am

Good video. Can say it's definitely not hardware. Maybe try a newer/older version of HDSDR.
73 David AE9RB
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