Topband: cutting coax stubs for 80 meter 4-square

[Richard (Rick) Karlquist]

As a sanity check, terminate the coax with a 50 ohm resistor and verify
that you have good coax.  Flat line at 1:1 SWR, etc.

Rick N6RK

On 6/9/2018 4:57 PM, terry burge wrote:
> I don't know what is wrong here but I keep getting in this situation where my typing starts running back over my writing. I will try again to reply.
> 
> 
> Joel,
> 
> I have tried all that the manual says without success. All I see is the horizontal solid and dashed lines of R and X. No indication of a resonance point anywhere from 1880 KHz up to 10,500 KHz. Go figure? At least my mfj-259b is working old as it may be. Rig Experts is going to get a nasty note I think. Disappointing, huh?
> 
> 
> Terry
> 
> KI7M
> 
> 
>> On June 9, 2018 at 2:54 PM Joel Harrison wrote:
>>
>>
>>      Hi Terry,
>>
>>      I replaced the 1/4 lines on my 80 meter 4 square this past fall and used
>>      my AA-170 to set the length with no problem.
>>
>>      Just select "all" for the mode and set the freq you're aiming for and then
>>      trim the line until X equals zero with the far end open. Should work fine.
>>      I always calculate the length x VF then add a few feet to start.
>>
>>      73 Joel W5ZN
>>
>>          > > 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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