I found the same problem with a 100' tower and a 10/15/20 Xmas tree 10
years ago. Could never get the 80 to really play. I then grid dipped the
tower and found it was 1/4 wave reasonant on 1450KHz!
Im wondering now if anyone has tried moving the 80M feed up the tower and
use isolated elevated radials?
Havent tried to model this one....dont know if its even possible.
73..........Carl
On Tue, 26 Nov 1996 23:50:59 -0500 (EST) gtaft@voyager.net writes:
>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
>
--
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
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