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Author Topic: Intermixing of SW and headphones  (Read 429 times)

Offline bandarr3000

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Intermixing of SW and headphones
« on: March 30, 2018, 1336 UTC »
Hope this is the right forum.  When I crank up the gain on my SDR, I'm picking up audio from my son's USB headphones from his PC about 10 feet away.  It only happens near very strong SWBC signals.  It doesn't happen when I disconnect the antenna.  I wrapped the headphone cable around a snap on ferrite a few times.  No change.  Thoughts?  Bad headphones? Intermixing?  I am befuddled.  Thanks.
Yaesu FTDX3000D
SDRPlay RSP1A
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Grand Rapids, MI

Offline MDK2

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Re: Intermixing of SW and headphones
« Reply #1 on: March 30, 2018, 1358 UTC »
Hi Bandarr3000. That's interesting that it happen just near strong signals. I can't really advise on why that is. But as a fellow RSP2 user, I can say that in general I don't find cranking the RF gain to be a lot of help. It could be because of my urban surroundings, which I'm starting to really realize is full of strong broadcast signals that are likely affecting things. I'm not sure that the RSP2pro, the metal cased version which I have, is actually that good at front end interference rejection. I have tons of MW images in the 2-3 MHz range despite the use of a 2 MHz high pass filter, and even if I'm using one of the SMA connections instead of the High Z port. It could be my coax (LMR400) and it could be that I should try to bury it instead of hanging it, but it could be that the SDRplay RSPs, nice as they are, are still limited in some features as you might expect for a product that's as inexpensive as it is. Personally, I would like to see what things for me would be like if I plugged in a higher end SDR but left everything else as is.

Anyway, boosting the RF gain tends to make little difference to increasing the signal, at least to my ears or to the posted SNR, while making unwanted noise slightly worse. So I usually use it only when I'm tuned to a weak signal that can benefit from it, or one of my usually fruitless attempts to decode a DRM signal. I never use it on good signals. So if you're experiencing this ONLY when you boost the RF gain, my suggestion would be to keep it lower, or halfway up at the most.

Good luck!
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Offline bandarr3000

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Re: Intermixing of SW and headphones
« Reply #2 on: April 12, 2018, 0052 UTC »
Thanks MDK2.  Per your suggestion I've set the RF gain in the middle of the slider and left it, using an MFJ-956 to try to pull up weak signals.  My goal someday is to have a Yaesu FT-DX3000 of my very own for ham and listening.  I'd get a good used rig but I'm concerned that the ones that are < $500 on ebay require a lot of maintenance and upkeep, filters, etc. that the cost of getting them into shape would cost me as much as a new good rig. 
Yaesu FTDX3000D
SDRPlay RSP1A
RadioWavz G5RV Jr.
Grand Rapids, MI

Offline pinto vortando

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Re: Intermixing of SW and headphones
« Reply #3 on: April 13, 2018, 1257 UTC »
Distance is your friend, move the SDR and PC as far apart as possible.
Otherwise, have used a MFJ 956 with the RSP1 with some success in receiving weak sigs and cutting down the spurs.
Das Radiobunker somewhere in Michigan