TopBand: Shunt fed tower with wide band width

[leewells@lexmark.com]

I decided to take down my inv-L that was hanging beside my 72 ft Trylon tower
and try to gamma feed the tower.  (The L also interfered with a sidemounted
antenna!).  To keep the L out of the path of the sidemounted antenna, I tried
moving the L closer to the tower (it was about 5 ft away).  But as I got closer
the real part of the impedance went upwards of 100 ohms (according to my MFJ-259B).

I got the gamma feed working last night, but I'm surprised at the bandwidth.  Its around
260 kHz!!!  I was expecting something much sharper.

----- DETAILS -----
Gamma wire:  #14 stranded copper.  4ft spacing.  48ft tall.
Feed:        235pf series cap (2 470's in series)
Tower:       72 ft self supporting   -  face width:  4ft at base - 18" at top
Antennas:    5el 10m beam at 50ft. 24 ft boom.  grounded elements.
	     F-12 20/40m beam at 73 ft.  30 ft boom.  insulated elements.
	     F-12 15m beam at 84 ft.  24 ft boom.  insulated elements.
Ground:      45 radials ranging from 20 to 130 ft.
Feedlines:   Attach to tower at 30ft level, then slopes off to house 30 ft away.


I added a horizontal wire (50 ft long over to a tree in the yard) to the top of the 
tower (70 ft level) so that I would have some high angle radiation like the L.

SWR dips at about 1.1:1 at 1900.  2:1 at 2000 & 1740.

Without the horizontal wire, the SWR still dipped at about 1900, but with a 1.4:1
match.

I was able to work HI8 last night with 100 watts and a few calls.  I heard a few US
stations working into Europe, but I couldn't hear the EU stations.

So what do you think???  Is the antenna really that broad, or do I have a lot of loss
in the ground system (I'm planning on adding more radials anyway).

Are conditions on 160 much worse than last year???  Last year I was able to work into
EU fairly easily with the inv-L and 4 elevated radials.

Any other ideas for improving the system????

73
--Lee - KT4ZX

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