[TowerTalk] Shunt Feeding, Can this be?

[Pete Smith]

Hi Pat - Lynn told me you called, I'd guess about this.  My shunt feed is similarly flat across much of 160.  Tom W8JI says that does not reflect high losses, but I'm reasonably sure that losses account for a lot of it.  Anyway, as you said it does appear to work.

I'm surprised that you were able to cover both 80 and 160 just with adjustment of the series capacitor.  I would have thought that the tap point on the tower would be a considerably different impedance on 80 than on 160, and you wouldn't have been able to tune that out with the series capacitor.

73, Pete

At 05:55 PM 11/15/2005, Pat Chiles wrote:
>Gene, you obviously do not have my black cloud.  My surprise is more a 
>result of it working on the first try than anything else.  This can't be! 
>Was my original reaction.  I will accept you suggestion because it makes 
>sense and is going to save me putting up another 160m antenna to make 
>comparisons with.
>
>Bill,  I don't have a 1000 watts for 160M.  Just 100 watts for . First the 
>antenna then the amplifier.  I did put 400 watts into it on 80M with my 
>SB220 and a G3 told me that my signal was "crushing".  Once again, I knew he 
>couldn't be talking about my signal because of my black cloud so I went 
>looking for a problem.
>
>Thanks for the responses.  I will just enjoy it and not ask questions.
>
>Pat, K8PC
>----- Original Message ----- 
>From: <ersmar at comcast.net>
>To: "Pat Chiles" <chilesp at adelphia.net>; <towertalk at contesting.com>
>Sent: Tuesday, November 15, 2005 4:13 PM
>Subject: Re: [TowerTalk] Shunt Feeding, Can this be?
>
>
>> Pat:
>>
>>     I just checked the SWR on my 160M shunt-fed tower from the shack and 
>> it's 2:1 or lower from 1.8 - 1.9+ MHz.  I don't ask questions.
>>
>> 73 de
>> Gene Smar  AD3F
>>
>>
>>
>>>
>>> I now have 30 radials installed on my tower and am shunt-feeding it 
>>> through new
>>> coax, an antenna switch, and a vacuum variable.  The coax run is 30ft. 
>>> The
>>> tower is a 55ft crank-up with 20 ft of mast out the top and a TH7 at 56ft 
>>> and a
>>> XM240 at 69ft.  The shunt wire is 30 inches away from the tower and is #6
>>> stranded.  I am able to get 1:1 on both 80M and 160M with my motor driven
>>> variable in a Gamma match configuration.
>>>
>>> The 1:1 reading is absolutely flat for about 60-70Khz.  It is the same on 
>>> both
>>> bands in as far as being flat and wide.  I thought I might have a poor 
>>> ground,
>>> but I have double checked all connections and resoldered everything that 
>>> looks
>>> even remotely bad.  I also have 15 ground rods connected to the tower on 
>>> three
>>> legs besides the radials.  This is my first attempt at shunt feeding a 
>>> tower and
>>> my question is if it is possible to have such a flat SWR on a shunt fed 
>>> tower?
>>> My numbers are with the MFJ are:
>>> 1830Khz  R=24    X=167 SWR>25  397pf on the vacuum             variable 
>>> for a
>>> 1:1 reading
>>>
>>> 3500Khz  R=24    X=295  SWR>25  157pf on the vacuum variable for a 1:1 
>>> reading
>>> _______________________________________________
>>>
>>> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
>>> Weather
>>> Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any 
>>> questions
>>> and ask for Sherman, W2FLA.
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>> _______________________________________________
>>
>> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
>> Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with 
>> any questions and ask for Sherman, W2FLA.
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>> 
>
>
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
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