Hi Terry, see page 16 of this site
https://www.rigexpert.com/files/manuals/aa170/aa-170-manual.pdf
when looking for a 1/4 wave, leave the far end of the coax under test open.
when looking for a 1/2 wave, short the far end of the coax under test.
Your 57'7" pc of would be 1/4 wave at 3750 if the vf is 87.77
at vf .76 = 49.85 ft
at vf .80 = 52.48 ft
at vf .84 = 55.10 ft
Set your rig expert on freq 3750 and have it in the RX mode and you
should see something that makes sense.
Good Luck
Ed
KG4W
On 6/9/2018 3:55 PM, terry burge wrote:
Hi guys and gals,
I have got DX Engineering 75 ohm foam coax to make the stubs/feeders for my
Comtek 80 meter 4-Square and am finding some difficulty. Neither my MFJ-259B
nor my Rig Experts AA-170 seem to indicate a 1/2 WL at 7500 KHz or a 1/4 WL at
3750 KHz? Or any frequency up or down from there. Seems to me the last time I
did this a few years ago I didn't have a problem getting a 1/2 WL dip
indicating a resonance location. But now I just don't get any indication of a
resonance.
DX Engineering said they had got some 75 ohm foam coax that instead of 0.84 VF
was more like 0.80 down to 0.76 VF. But checking all the way down to 6000 KHz
on 40 meters or 2500 KHz on 80 meters fails.
My test is to use either antenna analyzer with a PL-259 installed at one end and
an open or a short at the other. I started with 57'7" of coax. Tried both with
the coax in a roll and strung out. What am I doing wrong?
Terry
KI7M
😞
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