[Elecraft] Telephone RFI

[Jim Wiley]

Terry -


You could try going back to wired phones.  In every case I have tried, 
wrapping 20 - 30 turns of  telephone cord around an old transistor radio 
ferrite loopstick core (with the original antenna wire stripped off) has 
been effective.  I simply get a 15-20 foot extension cord (pre-made with 
plugs on each end), wrap it around the core, put some heat-shrink tubing 
(or plastic electrical tape) over the whole thing to hold the turns in 
place.  Plug it into the phone as near the phone (not the wall) as 
possible.  Usually, I try to arrange things so as to have a  pigtail 
about 3" long at the phone end, and 3 or 4 feet (or whatever is 
appropriate) for the link to the wall outlet.   It really doesn't matter 
how long the cord on the "wall" side of the filter is, as long as lead 
on the "phone" side is short. 


Zap - no RFI, even from my KW, running into a  220'  open-wire fed 
doublet on 160-20 meters.  


BTW - Multiple layers of phone cord are fine.  I usually start with one 
of the cores that are about 4 or 5 inches long, rather flat in shape, 
and about 3 or 4 times as wide as they are thick.  They look like a flat 
bar of ferrite.  I have also been able to use round cores of the same 
type, but the flat bars have more ferrite per inch than the round models.  


Every time I have tried wireless phones, on the other hand, there has 
been some failing or another that has made me go back to hard wired 
sets.  I even have my DSL connection routed  through one of these 
things, and it runs just fine.


Good luck!


Jim, KL7CC



Wingkeel at aol.com wrote:

>Hi everyone,
>
>     I have two antennas...an unmatched longwire and a vertical.  The 
>unmatched longwire interferes with our two line 900MHz phone system a little bit but 
>the vertical almost destroys audible altogether.  While transmitting CW on the 
>vertical, there is a loud clicking sound on both the receiving AND 
>transmitting telephone, even though one or the other could be removed by several miles.
>
>The phone line within the building is all CAT-5 with the exception of the 
>last 15' of the base station telephone.  I've tried 10 turns of flat 4-conductor 
>telephone cord through a toroid...no difference, (however, I don't know what 
>the toroid is made of).  I've tried one of the clamp on decouplers with no 
>change.  I can't put a coupling capacitor on the line because of our high speed 
>DSL.
>
>It only happens on 40 and 80 meters.  There is no interference at 20 meters.  
>Does anyone know who builds telephone RFI filters for this frequency range?  
>I called the local phone company and they said that they don't have anything 
>to do with aircraft frequencies (????).  I figured it would be fruitless to 
>pursue this avenue of approach!
>
>If I don't get this fixed pretty soon, one of three things will happen:
>             1. Discontinue use of my K2 between the hours of 0600-2300.
>             2. Find a solution to this dilemma.
>             3. Become a priest, because I'll be celibate after this anyway.
>
>                                Thanks in advance
>
>                               Terry de KC0QZX
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