[Elecraft] Strange Vertical - need help

[David Gilbert]

Correct.   They're using the 100 feet of coax to add enough loss to 
swamp out the native feed impedance.  Note that they specify it as a 
minimum length, not some particular length that might provide some kind 
of transformation.  If you use enough coax with enough loss you can get 
almost a perfect 50 ohm match at the transmitter with an open circuit on 
the far end.  It becomes just a long dummy load.

KC6CNN could improve his match by simply exchanging the low loss LMR400 
for RG-8X.   ;)

But he wouldn't get any more power to the antenna.

73,
Dave   AB7E



On 3/11/2012 10:06 AM, Joe Subich, W4TV wrote:
> The Zero-Five web site specifies 100 feet of feedline and a "wide range
> antenna tuner" for that antenna.  The SWR readings you report are about
> what I would expect for an untuned antenna of its type.
>
> The Zero-Five GP40-10 is essentially a 20 meter half wave (26 feet
> vertical, 8.25 feet horizontal) fed 25% from one end ... a classic
> OCF design.  The claims of operation on 40 (and 30 meters) bother me
> since the antenna is far too short for effective 40 meter operation.
> I suspect the feedline is part of the antenna on 40 meters.
>
> Since the antenna manufacturer specifies a minimum feedline length
> of 100 feet, they're obviously using the feedline to moderate the
> native feed impedance so the tuner can handle it.
>
> 73,
>
>      ... Joe, W4TV
>
>
> On 3/11/2012 11:48 AM, KC6CNN wrote:
>> I installed a vertical with ground radial kit up 20 feet.
>> The antenna mast and negative sheild connector is grounded to a ground rod.
>> The antenna covers 10 to 40 meters.
>> I can tune 10 meters fine, and fourty meters fine, but 12,15,17,20,and 30
>> will not tune and SWR are high.
>> here are the SWR reading taken on AM running 25 watts.
>>
>> 10 meter
>>
>> 2804550 is 2 to 1 SWR
>>
>> 2882000 is 1.5  to 1 SWR
>>
>>
>> 12 meter
>>
>> 2490000 is 3 to 1 SWR
>>
>> 24990 is 3 to 1 SWR
>>
>>
>> 15 meter
>>
>> 2103900 is 4 to 1 SWR
>>
>> top porting is 3 to 1 SWR
>>
>>
>> 17 meter
>>
>> 1809000 is 3 to 1 SWR
>>
>> 1817000 is 2 to 1 SWR
>>
>>
>> 20 meter
>>
>> 1402800 is 2 to 1 SWR
>>
>> 1430000 is 2 to 1 SWR
>>
>>
>> 30 meter
>>
>> 1010500 is 4 to 1 SWR
>>
>> 1014000 is 4 to 1 SWR
>>
>>
>> 40 meter
>>
>> 7026 is 2 to 1 SWR
>>
>> 7290 is 1.5 to 1 SWR
>>
>> Any help or suggestions would be greatly appreciated. I will be receiving my
>> K3 on Tuesday and am trying to get this antenna sorted out before then.
>> Oh yea the rig I'm using right now is a Kenwood 570, the Coax is LMR400 with
>> a 100' run. the Antenna is a ZeroFive GP10-40.
>>
>> Thank you
>> Gerald Manthey
>> KC6CNN
>>
>>
>> --
>> View this message in context: http://elecraft.365791.n2.nabble.com/Strange-Vertical-need-help-tp7363205p7363205.html
>> Sent from the Elecraft mailing list archive at Nabble.com.
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>