[1000mp] speaker RF

[Rob Atkinson]

my experience has been that most of the unwanted stray rf making its 
way back to a transceiver arrives via the outside surface of the 
feedline shield, and the ground strap.
I have never run a rig with a computer connected to it so i don't know 
about that.  But other lines such as amp keying, headphones, speaker, 
power supply, key and mic lines have not been big problems.   most hams 
in some way or other, have their shack rf ground system tied to house 
wiring safety ground, perhaps via equipment cabinets.   this can 
function as a big antenna picking up your transmitted rf and bringing 
it back to the rig.  the solution isn't to separate the wiring safety 
ground from the rf ground, but rather, if the operation of the rig is 
okay doing this, to simply undo the strap bolted to the rear panel lug 
for the rf ground and remove it.   i operate a ts870 in this fashion 
and it works fine (better actually) ungrounded.   For the feedline you 
can make an effective common mode choke, (a.k.a. line isolator or 1:1 
unun) by winding around 50 feet of 58U or 8X coax on a plastic paint 
pail around 5 or 6  inches (15 cm) diameter.  it's okay if the sides of 
the pail slant a little bit.  connect this to the rig right behind it 
and hook the antenna feed to the other end with a barrel connector.  
you can do the same thing with about 18 inches of coax and 40 or 50 
small ferrite beads on it.  material 31 probably works well at HF.    
material 31 beads are available from mouser,   www.mouser.com.

rob / k5uj

On Friday, October 21, 2005, at 06:36 AM, ROBERT SCOTT wrote:

> Hi Mike and everyone who has sent messages to try and
> help me with this problem.
>                          I have put a ferrite on the
> speaker cable and wound it on and shortened the cable
> as short as I could and it has cured the problem at
> least 75% at 100watts I haven't put my amplifier on
> yet I will let you know what happens when I hookup my
> amp again.
> And I have had the radio in other rooms in my house
> and have had the same problem, my antenna is at least
> 70 to 80 feet away from my shack I also use a extended
> zepplin and was getting the same problem.
> It doesn't matter what beam heading I used I was still
> getting the same problem with the beam.
> But as I said I have wound the lead around a ferrite
> until I just had enough to get from the speaker to the
> rig and it has cured the RF at least 75%, but I will
> keep you posted on what happens when I use my
> amplifier.
> I would like to thank everybody for helping me with
> this problem and with anymore help in the future.
>                Thanks
>                    73's good DX Robin (MI5RJS)
>
>
>
> Robert J Scott
>
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