Topband: cutting coax stubs for 80 meter 4-square

[Wes Stewart]

Since he said the coax was 75-ohm, a 75-ohm termination would be better.


On 6/9/2018 5:07 PM, Richard (Rick) Karlquist wrote:
> 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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>>>>      >
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