[Amps] Antenna traps

[Vic K2VCO]

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
http://www.qsl.net/k2vco