Just a comment that may be obvious to most but 23 feet is not the
correct length for all types of coax. It depends on the velocity factor
- 23 feet is the length for Belden 8237 but, for example, if you use
LMR400 it is 29.4 feet at 7.1 mHz. For Belden RG8x (Belden 9258) it is
27.7 feet. A nice little program to calculate these is TLW which comes
with the ARRL Antenna Book. If you really want to be accurate or are not
sure of the velocity factor of your coax use an antenna analyzer that
measures impedance. You want to cut it so the reactive component of the
open coax is zero at the frequency of interest.
Marv N5AW
On 9/10/2015 11:00 AM, cq-contest-request@contesting.com wrote:
Ok.
Now that you have put a 23' shorted stub on 40, put a 23' open
stub on 20. This will reject any 40 meter energy that shows up
on your 20 meter feedline, and it will pass 20 just fine.
Dave Hachadorian, K6LL
Yuma, AZ
--
Marvin Bloomquist
Burnet, TX
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