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HF6V matching stub


Seli TF3AO
 

Hi all,
Was wondering if there is a way to check the 75ohm stub on my HF6V. About 1,5-2 years ago I replaced the stub and bought a new one from DX engineering. 
Recently, the SWR went up on 20m and when checked with an analyzer, other bands were not good also. 
It could be the corrosion from seasalt as I live not so far from the ocean and the winter gales have been strong.
But at first I want to check the stub if possible.
And BTW I see on DX engineering web page that the connection for the stub has been altered now.
73 Seli TF3AO


Siegfried Jackstien
 

if you have an analyzer you have a way to check that stub ... not tooo difficult and not that much things needed

analyzer

t connector

dummy load

your stub to be measured

connect t connector to analyzer and one port to 50 ohms dummy and the other to the stub

now make two sweeps (one open and one closed stub)

you sure find a defective stub that way (and can also measure if its resonance is ok)

maybe make a few sweeps and "wiggle" a bit the cable ... check connectors for corrosion (or just clean them all)

greetz sigi dg9bfc

Am 24.04.2020 um 18:21 schrieb Seli TF3AO:

Hi all,
Was wondering if there is a way to check the 75ohm stub on my HF6V. About 1,5-2 years ago I replaced the stub and bought a new one from DX engineering. 
Recently, the SWR went up on 20m and when checked with an analyzer, other bands were not good also. 
It could be the corrosion from seasalt as I live not so far from the ocean and the winter gales have been strong.
But at first I want to check the stub if possible.
And BTW I see on DX engineering web page that the connection for the stub has been altered now.
73 Seli TF3AO


 

Seli,
The stub length is only in effect on 20 meters.  On the other bands it looks just like transmission line.  You should be able to bypass the stub and check operation on other bands to see if there is still a problem.  An antenna analyzer would give an idea of the problem and where it is located as well.  The MFJ can help make that determination for both and open or shorted line.  If you have one, you can also walk it out to the base of the antenna and check there too.
Al
WB9UVJ


Seli TF3AO
 

Took another turn on this. Antenna went down and I took it all a part and lubricated all connection. 
Went up again, last evening and bingo all works fine. Must have isolated someplace.
Thanks for advise on testing the stub, will come handy later.
73 Seli TF3O


 

Seli,
That is good news.  I have replaced all the original hardware at the joints as the screws consistently loosened in the wind over time.  I use stainless steel hardware everywhere when I replace anything on the antenna.  I also use Burndy Penetrox when I reassemble.  I think I got the Penetrox from DX engineering or from some other ham supplier.
Al
WB9UVJ


n5pg@...
 

Stub is pretty  broad. After 30+ years of mine fighting weed-eaters, sundry rodents etc and remaking the end for attaching to the feedpoint several times mine showed X=0 at 14.95 MHz.
I made a new one but can't say I see much difference in operation.

You can get Penetrox and the like at auto parts stores or even Amazon.