> I've looked at dozens of meters and NEVER found one with response to
common
> mode current levels found in worse case conditions. I have seen common
mode
> impedances change feedpoint impedances in specific cases. But the biggest
and
> most common problem I've found when SWR changes with line length has
always
> been when line Zo and meter Zo are dissimilar.
>
> Most 50 ohm cables I see range from 48 to 55 ohms. Toss that in with a
meter
> that might be set at 55 ohms, or 45 ohms, and it's no wonder SWR readings
> change when the meter is moved.
If I may kibbitz ...
I intend to run 75 ohm catv cable from the foundation of the house to the
tower base and up to near tower-top. The cable will terminate at an
Ameritron remote switch at the tower. Then I will use short runs of
flexible cable (probably 50 ohm) to connect to the two beam and two wire
antennas (I also intend to do the same at the shack at the other end).
What matching and/or misreading issues might I face, if any? Should I run
75 ohm flexible cable at both extremes?
I have been told that most beams are designed closer to 65 ohms than 50
ohms since the 50 ohm standard is not an international standard and that
other countries use 60, 65, 70, and 75 ohms. This would make 75 ohm cable
no greater issue for matching than 50.
Also, which device might best handle this situation as I make adjustments,
the new MFJ-259B or the new AEA-CIA (I am leaning towards the new MFJ-259B
since it is 1/2 the price of the AEA-CIA -- will a lighter duty user like
me really miss the features of the AEA-CIA?).
73, DavidC AA1FA
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