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Re: [Amps] Antenna traps

To: "Vic K2VCO" <>,"Amps reflector" <>
Subject: Re: [Amps] Antenna traps
From: "Gene Bigham" <>
Date: Tue, 13 Dec 2005 16:47:52 -0600
List-post: <>
Tried the coaxial ones and indeed they are heavy, also got hot and burned up 
using RG8 foam coax, suppose I should try some with solid dielectric 
These Unadilla's are supposed to be good for 2kw PEP but when I tried to pin 
the maker down to what that meant, I got a song and a dance.  I am taking up 
this new set with him and see what he says.  In the mean time I would like 
to have a set of 40 traps to put in the antenna instead of it just being 80 
meter and 160, I have a set of 40 traps for A3S beam that might work but 
have to dig them out, I know they will take the power.
Thanks for the reply.

----- Original Message ----- 
From: "Vic K2VCO" <>
To: "Gene Bigham" <>; "Amps reflector" 
Sent: Tuesday, December 13, 2005 4:29 PM
Subject: Re: [Amps] Antenna traps

> Gene Bigham wrote:
>> I know this is not about amplifiers, except for being able to use one on 
>> a trapped antenna, but has anyone found a set of traps for 40 and 80 that 
>> can handle a legal amplifier output?
> You have two problems in making traps: current and voltage.
> I made some using 5KV doorknobs (for 160/80) and exploded the doorknobs at 
> less than legal power.  This was a result of heating as a result of 
> inadequate current capacity.  They also drifted a bit before blowing up. 
> Now I have one made of a 6 KV mica capacitor that is about 3" x 4" x 3" 
> which worked fine at QRO.
> The trick with traps is to make sure they are NOT resonant at a frequency 
> that you will operate on!  The voltage across a parallel resonant circuit 
> increases enormously as you get close to resonance. For example, my 160/80 
> meter inverted L (used for CW only) trap is resonant at about 3480 KHz. 
> The impedance in the lower part of the band is still high enough to 
> isolate the 160 M section, but the voltage isn't astronomical.
> You can make traps out of coax which will handle the power.  Just google 
> 'coax traps' and you'll find some information.  They are heavy, though.
> -- 
> 73,
> Vic, K2VCO
> Fresno CA

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