[amsat-bb] M2 Leopack 2Meter swr

Mark L. Hammond marklhammond at gmail.com
Mon Jun 17 19:06:59 UTC 2019


While not the exact same antenna, I had an SWR problem on an M2 antenna (7
elements vertical yagi)  once that drove me nuts until I figured out the
problem.  This may help you (or others down the road...)  The observation
was the SWR was high (sometimes it was intermittent, but mostly it was
high).   The culprit?  It was a poor electrical connection between the
driven element and the boom!   There was "gunk" or corrosion of a type
under the aluminum "block" of the driven element that is screwed to the
main boom via the stainless steel screw.   Using a scratchy Scotchbrite pad
on both the block and the main boom, I was able to clean it up and fix the
SWR issue.

It took me months to determine the cause--I replaced the coax from antenna
to preamp, the preamp itself, swapped coax feedlines; I opened up the
original driven element, just SURE there had to be a break in the internal
wire(s).  Nope! I eventually bought another new antenna just like it to
swap out the driven element, and finally then did I see what was the
apparent cause.

It's a case of having to see it myself, to believe it...

Rafael, if I was you, I'd at least check the connection of both driven
elements to the boom---clean it up well, and see if that fixes it. If not,
no harm done...but this is a place that would NEVER have occurred to me

Please let us know what fixes your issue!


On Mon, Jun 17, 2019 at 1:09 PM Rafael Pena via AMSAT-BB <amsat-bb at amsat.org>

> Recently, I had my roof done and had to remove the M2 Leopack from the
> mast together with the G-5500 Az/El.   I sat it on the roof floor next to
> my house.   Now that I place it back, the 2M SWR is way high off the sat or
> regular 2m frequencies 440 is as expected.
> It is not coax since I tested it with a short piece and analyzer with same
> results.   I had not check the coax stubs yet and thought to write hear
> first.   Any hints will be appreciated.
> M2 website has a "Blog" which contains only info on Ohm meter testing.
> Rafael / NN3RP
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Mark L. Hammond [N8MH]

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