[Top] [All Lists]

[Towertalk] Inverted L update

To: <>
Subject: [Towertalk] Inverted L update
From: (
Date: Tue, 20 Aug 2002 18:13:42 -0400
Very straightforward.

160:  Grounding is very poor for the needs and the ground connection is 
providing a very lossy unvarying addition to the probable natural 25 ohm 
impedance of the L. Low band shortened/bent vertical against ground antennas 
with low, broad SWR's are heating up the grass with a large percentage of the 
applied power. Using the back yard as a partial dummy load. Dummy loads have 
flat wide SWR's.

HOWEVER, you will be able to work people on 160. (By the way, just about zilch 
SS activity on 160. But plenty on 75/80)

80: This is a high impedance feed, possibly as high as 1000 ohms or more. You 
will need a tuned network to get power into it. BUT, once you do, you will find 
that the ground system you describe is "good enough" and you will do nicely on 
75/80m, particularly for SS, and do more than you would expect with DX. I have 
used antenna's of this sort on 75/80 since the 50's with excellent results

There are several ways to feed this. SOME ready built tuners will match this.

Rolling your own, get a coil and a cap, put them in parallel. One end to the 
wire, the other to ground. Run the coax shield from SWR bridge to the ground, 
run the center conductor to an alligator clip. Start with the clip on the coil 
about 1/5 up from ground end on the coil. Tune cap for min SWR. Move clip up or 
down for min SWR. Repeat this sequence until best match. If the match is not 
all that good and overly broad, esp if the cap is fully meshed, add more coil 
to the assembly. If the match is very narrow and overly sharp, remove some coil.

Since the coax is only 6 feet to the antenna, you can get away with the network 
being on the transmitter end of the antenna coax.

This is a voltage point. You will need a capacitor with some spacing between 
the plates, depending on your power level. 

There are other equally good ways of dealing with this that will allow you to 
use a typical tuner. 

This antenna will also work well on 40 and 30 meters.

> From: "FireBrick" <>
To: <>
> Date: 2002/08/20 Tue AM 11:28:39 EDT
> To: "TowerTalk List" <>
> Subject: [Towertalk] Inverted L update
> Subsequent to my previous post. I just for grins hooked a piece of coax to
> the inverted L with the braid going to the ground that all (don't laugh, 4
> radials) is attached to.
> I'm seeing
> 1801 1.2 to 1
> 1902 1.2 to 1
> 1950 1.35 to 1
> 1997 1.5 to 1
> This is too good to be true.
> So why the good readings?
> BTW: no match at all on 80
> And I forgot to say that I had a Sommer 15 foot boom multiband on top of the
> tower.
> -----------------------------------------------------
> Anything worth fighting for is worth fighting dirty for.
> -----------------------------------------------------
> Bill H. in Chicagoland
> _______________________________________________
> Self Supporting Towers, Wireless Weather Stations, see web site: 
> Call 888-333-9041 to place your order, mention you saw this ad and take an 
> additional 5 percent off
> any weather station price.
> _______________________________________________
> Towertalk mailing list

<Prev in Thread] Current Thread [Next in Thread>