[Towertalk] Inverted L update

[olinger@bellsouth.net]

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" <w9ol@billnjudy.com>
> Date: 2002/08/20 Tue AM 11:28:39 EDT
> To: "TowerTalk List" <towertalk@contesting.com>
> 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
> w9ol@billnjudy.com
> www.billnjudy.com
> http://files.billnjudy.com
> 
> 
> 
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