[TowerTalk] 80M Inverted L using 43 foot vertical ?

[bills stuff]

One 80 m Inv L Experience

Loosely based on ANTENNA BOOK information, I put up an Inv L for 80 
using 46 ft of 6 ft Al tubing (43+3 from junk box) commonly available, 
starting at 2.125inch OD going down to 1.25 inch .  One set of guys was 
put at 30 ft. The top wire is 55 ft of zip line pair (again junk box) 
sloping down to 20 ft at the end.  Radial system consists of 6 elevated 
(~ 8 ft high typical) radials of 57 ft (insensitive to exact length).  
My soil appears to be very poor, which motivated the elevation (this is 
subject to much discussion).  The system is resonant at about 3 MHz 
(X=0) with smallish R.  At 3.55 MHz it has a R of about 50 and a 
significant inductive reactance that can be cancelled by a simple series 
air variable capacitor adjusted to about 150 mfd at the base.  It is fed 
by RG8 with a current choke.  So this longer-than-resonance antenna has 
the charm of needing only a very simple matching network (1 series cap) 
and it can be adjusted within the band by shortening the top section and 
retuning the capacitor.  Around the chosen resonant frequency, a 
bandwidth for 2:1 SWR is about 150 kHz.  A compromise length of top 
section can allow switching between CW and SSB bands with only a change 
in the capacitor setting, albeit with some modest suffering of SWR 
increase in both bands, but still under 2:1 over a useful range.  It was 
put up to finish off 80 m DXCC this season and has allowed working 90 
countries in 4 months running about 600 watts, mostly CW.  I think this 
is a good antenna, but not necessarily a great antenna. 

As a final bonus, if you simply tack on about 65 ft of additional top 
wire, it can be tuned to 160 meters using just the same 25-500 mfd 
variable capacitor.  However you will have to play with the length of 
the top section and will also have a rather more modest bandwidth.  This 
will probably no longer be called a good antenna.

Bill, N6MW

robertsmg at aol.com wrote:
> Hello, All:
>
> I've been thinking about ways to improve my signal on 80 meters from my .3 acre suburban lot.? Have a SteppIR yagi with the 40/30 kit so those bands are well covered.? ? I'm contemplating using my existing 43 foot vertical as the vertical portion of an inverted L for 80 meters, and then running a wire over to my tower for the horizontal component.?There is already a passable radial system under the 43 footer.? The inspiration for this came from the ON4UN chapter on Inverted L antennas, where there is a diagram of such an antenna using a 1.6 inch diameter 39 foot vertical pole and a 40 foot 12 AWG horizontal wire.? Has anyone done anything similar using?one of the commercially available 43 foot vertical models?? I don't have?experience with modeling software, and am wondering how long the wire should be for resonance around 3.600 MHz.? What would be the best method to feed it?? Any and all comments welcome.? 73 de
> .? 
>
> Gavin W9EYE
>
>
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