Topband: 40/80/160 Meter Antenna

Tom Rauch W8JI@contesting.com
Fri, 15 Nov 2002 20:38:02 -0500


> I am curious about your statement regarding additional loss as a
> result of using a low Q trap. You stated that the loss at the
> non-trapped frequency, in this case 160 meters would be insignificant
> regardless of the trap type used. So I am assuming that the loss that
> you are referring to is the loss in effective gain at the trapped
> frequency compared to a 1/4wl vertical operating against the same
> ground at the trapped frequency. Is this correct?

That's correct, and of course this also applies to trapped dipoles 
and yagis as well as low band antennas.

The exception would be "traps" using very low C and high inductive 
reactance, which may have significant loss at the pass frequency. 
This type of "trap" would be the high inductance coils used to 
isolate antenna sections while substantially reducing length. Those 
"traps" or isolators can seriously degrade the "pass" frequency 
performance, and people building 160/80 antennas should keep in mind 
the 160 performance can be seriously degraded by using very large 
inductors as "traps".

Of course any antenna is better than no antenna, so these are just 
guidelines to shoot for.73, Tom W8JI
W8JI@contesting.com