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TopBand: 160/80 shunt fed tower?

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Subject: TopBand: 160/80 shunt fed tower?
From: gtaft@voyager.net (gtaft@voyager.net)
Date: Tue, 26 Nov 1996 23:50:59 -0500 (EST)
Jim

I have used my 78ft tower for years as a 160M shunt fed vertical.  It has
plenty of top loading - 5 el 20M KLM yagi and a Mosley 2 el 40.  Works great
on top band.  

I decided to try it for 80 and put another gamma rod on the side opposite
the 160 M gamma.  Using an omega match shorter than the other, I was able to
easily match it to 1:1 SWR but it just didn't play.  We concluded that it
was substantial taller than a quarter wave on 80 and probably approached a
half wave.  I finally tied the two gammas together for 160 to increase the
bandwidth.

Suspect u have the same "too tall problem" as we calculated with the top
loading u and I have on the towers, u'd need only abt 30 ft of tower to
reach an electrical quarter wave on 80 M.  Make sense??

73  George  
W8UVZ




>Hello Topbanders,
>
>I have a 65 ft tower with a TH7 and 40-2CD on top and 16 radials from 
>1/8 to 1/4 wavelength long.  I have shunt fed it for 160m with a 
>jumper across the 18 inch spaced shunt at abt 50 ft.  It seems to
> work pretty good.  The SWR is almost flat across the entire 160m band.
>  Is that typical?
>
>I also tried to add an 80 meter shunt on the opposite side of the 
>tower.  I havn't been able to find an optimum jumper point on the 
>shunt.  The lowest SWR has been 2:1 and the bandwith is quite narrow 
>(which is OK).  The performance has been poor.  I probably just need
> more time to refine it.  My question regards interaction between the 
>two shunts.  It appears that the 160m performance has decreased since
> I added the 80 m shunt.  Could this be true or is it just my biased
> judgement or band conditions?
>
>Have any of you had success with a combo 160/80 m shunt fed tower?  
>Any guess where the 80 m jumper would be with 18 inch spacing?
>
>Thanks for reading my questions and for your response if you can 
>help.
>
>73,
>
>Jim Hood, K5TT
>President, Oklahoma DX Association
>wv5s@icon.net
>Past operations: KC6SS, V63SH, /XE, /WH6, /NH7, /KP2
>Previous calls: WV5S, W0PUD, W7KDH, K5TWD
>USA-CA # 432
>
>--
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>
>
                                        73
                                           George  W8UVZ

                                                    


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