[1000mp] coax line isolators or chokes

[Pete Smith]

At 05:26 PM 3/7/03 -0500, you wrote:
>Has anyone ever opened one of the Radio Works coax line isolators?
>http://www.radioworks.com/clitop.html
>What is inside? Is it like the choke in ARRL Handbooks with steel wool 
>inside a tube?
>
>I have what seems like a similar product CF5KV "High-Q Common Mode Choke" 
>from rf inquiry of Japan. http://www.rfinq.com/
>
>It seems to have helped rfi problems here, MarkV and 91-beta amp. They 
>claim to have sold 20,000 to the Japanese market but don't mention sales 
>numbers in USA. They give some interesting measurements on the web site 
>which I had not seen before. Since it was kind of expensive I haven't 
>opened it either. I hope it is full of ferrite washers and not steel wool!
>
>ron w8gus.

These things are grotesquely expensive, particularly the oddly-named 
Japanese unit.  Anyone can make up a common mode choke that is just as 
effective with 50-100 ferrite beads from Fair-Rite or Palomar and a length 
of teflon-jacketed coax.  The only trick is choosing the right ferrite mix, 
and then putting the choke in the right place on the line.  I have never 
mastered the latter trick, so I tend to overdo it and put them at a couple 
of different places.  For example, I have choke baluns at the feedpoints of 
all my balanced antennas, a feedline choke at the entrance to the shack, 
and another between my transceiver and amplifier.  Seems to work, but then 
I haven't seen any tigers in the neighborhood either, and I don't know if 
that's because of anything I've done....

73, Pete N4ZR
The World HF Contest Station Database was updated 23 Feb 03.
Are you current? www.pvrc.org/wcsd/wcsdsearch.htm