[amsat-bb] M2 LEOpack tuning

Mark D. Johns mjohns+K0JM at luther.edu
Wed Apr 8 19:42:12 UTC 2020

Just to follow up on this, I pretty much took the antenna apart --
removed all of the phasing harnesses to make sure the connectors were
clean, dry, and free of corrosion. I also removed the aluminum
"blocks" and made sure the boom was clean underneath them, per the
suggestions here. When I replaced the harnesses, I was very careful to
arrange them precisely as shown in the assembly instructions (I had a
couple of them not quite right). Then, I put the antenna analyzer on
and messed with the matching sliders until I got the SWR down to 1.2:1
at 145.9 MHz. Quite an improvement!

Thank you for all of the suggestions -- especially regarding the dress
of the harnesses. I think that was the big one.

Unfortunately, when I put the antenna back on the roof, it still
receives like a dummy load. I think I must have a bad piece of coax.
That will be the next project.

See you on the birds (eventually).
Mark D. Johns, KØJM
AMSAT Ambassador & News Service Editor
Brooklyn Park, MN USA   EN35hd
"Heaven goes by favor; if it went by merit,
   you would stay out and your dog would go in."
    ---Mark Twain

On Sun, Apr 5, 2020 at 7:57 AM Mark D. Johns <mjohns+K0JM at luther.edu> wrote:
> I’ve had my LEOpack antennas about 8 years, but over the winter my station became almost totally deaf on 2 meters. I took the 2 meter beam down and cleaned up a bunch of corrosion around the coax connector, and that seems to have helped the situation, but...
> I checked the antenna with my MFJ Antenna Analyzer (which I did not have back when I first assembled these antennas) and find that the 2 meter beam is resonant at about 143.95 MHz — just below the 2 meter ham band. Up at 145.9, where I would LIKE it to be resonant, my SWR is about 2.5:1. Pretty high.
> Messing with the tuning sliders only made things worse (these adjust impedance and not necessarily resonance), so I’m wondering, has anyone else found it necessary to trim the elements on these?
> My calculations are that about 1/8” off each end of the DEs would bring it up the 2 MHz needed. Opinions?
> --
> ***Sent from Gmail on iPhone***
> Mark D. Johns, Ph.D. K0JM
> Professor Emeritus of Communication Studies at
> Luther College, Decorah, Iowa USA
> Now residing in Minneapolis, Minn.
> ------------------------------------------------
> "Get the facts first. You can distort them later."
> ---Mark Twain

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