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
>
>--
>FAQ on WWW: http://www.contesting.com/topband.html
>Submissions: topband@contesting.com
>Administrative requests: topband-REQUEST@contesting.com
>Sponsored by Akorn Access, Inc & KM9P
>
>
73
George W8UVZ
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Sponsored by Akorn Access, Inc & KM9P
|