Topband: front to back?

[David Sinclair]

From:           	"Barry " <w2up at mindspring.com>
To:             	FlagandPennantAntennas at yahoogroups.com, topband at contesting.com
Date sent:      	Sun, 25 May 2003 13:39:09 -0000
Priority:       	normal
Subject:        	Topband: front to back?
Send reply to:  	w2up at mindspring.com
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> Hi all,
> Just finished installing a rotatable delta-shaped "pennant" a la 
> K6SE's QST article. (18:1 K1FZ xfmr, 948 ohm termination, horiz 
> portion about 10 ft above ground). The loop is about 150 ft from any 
> other metal. 
> I was playing with it last night, and noted the following:
> 1.6 MHz BC AM signal (no sigs on 160 at the time) F/B 10-15 db
> 80 CW F/B ~15 db
> 40 CW F/B 15-20 db
> 
> I didn't notice any significant F/S until at least 90 degrees from 
> the heading. I've heard others talk about 30-40 db F/B, but this is 
> nowhere close. I'd like to hear others' experiences.
> Tnx,
> Barry--
> Barry Kutner, W2UP

Hi, Barry-

I don't think you can expect any significant F/S from a
single Flag/Pennant/Delta. You would see some if you
had the room to run an array of two of them, with some
pretty generous spacings of around 200-400ft. or so.

As I understand it, the difference between getting only
15-20dB of F/B versus 30-40dB depends very much
on whether you go to the trouble of designing in a
remotely variable termination. Some have used not
only a remotely controlled variable resistance, but
also variable inductance and/or capacitance. When
tuned (terminated) very carefully with just the right
constants, you may see the greater F/B, and you may
also notice that varying the termination remotely allows
you to steer tha precise compass direction of greatest
F/B, and also to some extent the peak angle for max
F/B. A number of others have reported on this,
especially WA1ION who has done extensive BCB
DXing with them as well.  73, David K3KY