Thanks for the response Herb. I can obtain a good match using the 65 ft tap
point, but my question is why my analyzer is measuring a change in the
feedpoint resistance (real component of R + jX).
Regards,
Marty
> On Oct 15, 2019, at 3:19 PM, Herbert Schoenbohm
> <herbert.schoenbohm@gmail.com> wrote:
>
> Best to use a 3 or 4 wire cage feed and you will find the match easier. You
> should tap the tower at 50 feet and work down till you find the sweet spot.
> A 500 to 750 vac variable will take care of any measure inductive component.
>
> Herb, KV4FZ
>
>> On Tue, Oct 15, 2019 at 3:10 PM Marty Ray <dxcc1@comcast.net> wrote:
>> I am shunt feeding a 70 ft Trylon tower with a Tennadyne T12.10-30HD LPDA at
>> 70 ft and a full size 40m rotatable dipole at 79 ft, (the top of the mast is
>> ~85 ft). Both antennas have relays that electrically bond them to the tower
>> when the shunt feed is in use.
>>
>> I have tried two shunt tap points, one at 65 feet and another at 45 feet.
>> Using a Rig Expert AA-55 Zoom, the Rs measured a little over 100 ohms on the
>> 65 foot version and 49 ohms on the 45 foot version. In both cases, adding
>> the shunt capacitor caused Rs to drop by approximately 50 percent, (to
>> around 60 ohms and 23 ohms respectively).
>>
>> I expected Rs to not change much, if any. I tried a vacuum variable, an air
>> variable and a silver mica. Same result.
>>
>> Has anyone seen this happen before?
>>
>> Regards,
>> Marty N9SE
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