On 10/23/2021 4:56 AM, Mark - N5OT wrote:
I hope to make a trap vertical that works on 80 and 160.
First question is, why a trap? If it's not height, consider a fan.
Second, there's a design for 2-band 2nd harmonic dipoles where there's a
loading coil (NOT a trap) near what would be the quarter-wave point of
the lower frequency band, with a relatively short wire beyond it. That
design has relatively narrow SWR bandwidth on the lower frequency band,
but bandwidth comparable to dipole on the higher band.
This design works quite well, and there have been several successful
commercial implementations of it. Hypower Antenna Company (tiny ad in
QST) sells them, and may sell the loading coils separately. I measured
their coils for the 160/80 and 80/40 designs many years ago, and can
probably find the data. But it's a fairly easy design to do in NEC, and
I recently did one for a 40/20 dipole made from Al tubing for use on CQP
county expeditions.
73, Jim K9YC
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|