Re: [TenTec] Argo RF In to computer Speakers..

[Ken Brown <ken.d.brown@verizon.net>]

I use an Argo V into a TT Tuner and 450 0hm feed. There is nothing else in line.,  What do I need to do keep hearing myself in the external computer speakers? If I use the tiny internal computer speaker, No problem..

Hi Larry,

Most external computer speakers plug into the headphone jack on the 
computer and have built in audio amps in one of the speakers, and an 
external "wall wart" power supply. So there are three possible paths for 
RF into the audio amp in the external speaker 1) the stereo audio input 
cable from the computer, 2) the audio output to the second speaker, 3) 
the DC power input cord. (or some combination of those)

The DC power input connects to a much larger antenna system, the AC 
power system in your house and the whole power grid. So it might be the 
most likely line to bring in the most RF. I would try the standard 
methods of RFI elimination on this line first, and if that doesn't fix 
it, move on to the other lines. By standard methods I mean wrapping the 
cable through ferrite cores, adding bypass capacitors, possibly 
sheilding the cable. ARRL Radio Amateur's Handbooks have information on 
these methods, as well a their RFI Handbook.

You may want to try a few tests that could help figure out if the 
problem is from RF radiated by your antenna, or your feeline, or 
something else going on. Does varying the RF output power from the rig 
change the intensity or character of the noise in the speakers? What if 
you feed your TX to a dummy load instead of the tuner and antenna? Does 
the problem completely go away, or is it just reduced? How about a test 
load at the antenna end of the feedline instead of the antenna? Does 
that make the problem go away? Is it the same on every band? Does the 
volume control on the external speaker system effect the noise, or is it 
the same even turned all the way down? How about if the speaker system 
has no audio input (not plugged into the computer) and still connected 
to power?

What have you tried already? Do you know anybody in the commercial 
broadcast industry that has ever worked on an RFI problem that could 
give you some tips?

DE N6KB

> .................................................................................................As a side note: I have access, through my work with the commercial broadcast industry, to heavy duty audio software which I have adapted to communications.  I can go into a crowed band. graphically express 3 signals on the monitor and have the come out in 3 positions in my shack, while completely eliminating a fourth. Larry GreenbergN5BEA
>
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