I have never seen a design for a trap diople or similar dual band antenna
for 20M and 30M although my modelling shows it should just about work
although the end section after the trap is very short. Commercial antennas
are all either the normal bands or the WARC bands but not both with the
exception of lossy resistively loaded wide band antennas or rhombics. Has
anyone tried this combination?
Dick

Richard Ferryman wrote:
I have never seen a design for a trap diople or similar dual band antenna
for 20M and 30M although my modelling shows it should just about work
although the end section after the trap is very short. Commercial antennas
are all either the normal bands or the WARC bands but not both with the
exception of lossy resistively loaded wide band antennas or rhombics. Has
anyone tried this combination?
Dick

Trap antennas where the traps are close in frequency do not work very well.

In the notes for Unadilla traps they say to NOT use the combinations of
10/12, 12/15, 15/17, 17/20.

20M and 30M are far enough apart it should work though it may be a little
touchy to tune up.

My guess is there are not a lot of people that interested in having a 30/20
dual bander.



--
Jim Pennino

On Monday, March 17, 2014 4:56:43 PM UTC-4, Richard Ferryman wrote:
I have never seen a design for a trap diople or similar dual band antenna

for 20M and 30M although my modelling shows it should just about work

although the end section after the trap is very short. Commercial antennas

are all either the normal bands or the WARC bands but not both with the

exception of lossy resistively loaded wide band antennas or rhombics. Has

anyone tried this combination?

Dick

Add a parasitic 20 meter element to a 30 meter dipole. Works for me.

I have never seen a design for a trap diople or similar dual band antenna
for 20M and 30M although my modelling shows it should just about work
although the end section after the trap is very short. Commercial antennas
are all either the normal bands or the WARC bands but not both with the
exception of lossy resistively loaded wide band antennas or rhombics. Has
anyone tried this combination?

It sounds worth trying.

With realistic estimates for the impedance and Q of the trap, what
does your model show about the effective 20-meter SWR bandwidth of the
antenna, compared to an ordinary 20-meter dipole?

Another option to consider might be a 30-meter dipole, with some
single-wire stubs dropped down from it partway along to provide a
20-meter resonance.

30 meters is not a harmonic of 20....

WARC - added some bands to the American Band Plan that were odd harmonic's. It was easier to sell a antenna that only did WARC then to make one that did everything.

10 meters difference between 20 and 30 isn't all that much in the grand scheme of things.

The offcenter fed dipole I use for Field Days will not operate on 15 meters, nor will it work on 30 - although I never really tried to use it on 30.
It is only marginal on 12 and 17.

My Solorcon A99 seems to work well on everything from 10 to 17 meters - although if the band is not open, it doesn't perform as well as other antenna designs.

The comment that no antenna is designed for use on both 20 and 30 is a misnomer.. The Barker & Williamson BWD 90 will work on everything from 10 - 80 meters. Regardless of what anyone's opinion about it is!

The bottom line is - traps are very inefficient and unreliable - not the best antenna in the world to use on a long term basis.

On Monday, March 17, 2014 3:56:43 PM UTC-5, Richard Ferryman wrote:
I have never seen a design for a ... dual band antenna for 20M and 30M

A 102 ft dipole fed with ~63.5 ft of VF=0.9 ladder-line through a 1:1 choke will be resonant on both 30m and 20m.
--
73, Cecil, w5dxp.com