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?
Hi Mark,
Experience with these antennas at the demo station at Dayton, confirmed by Robert with M2 who fixed the issue, suggests that you may want to look at the routing and placement of the phasing cables. They are very sensitive on placement, and the issues we had were fixed by Robert rerouting them to be identical with the diagrams in the instructions. Good luck.
73, Drew KO4MA
-----Original Message----- From: AMSAT-BB amsat-bb-bounces@amsat.org On Behalf Of Mark D. Johns via AMSAT-BB Sent: Sunday, April 05, 2020 8:58 AM To: AMSAT amsat-bb@amsat.org Subject: [amsat-bb] M2 LEOpack tuning
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 _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
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@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
On 04/08/20 14:42, Mark D. Johns via AMSAT-BB wrote:
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.
Have you looked into something like the the NanoVNA as a diagnostic tool?
https://www.rtl-sdr.com/calculating-coax-length-by-using-a-nanovna-as-a-time...
Very handy for only $50!
--- Zach N0ZGO
participants (3)
-
Andrew Glasbrenner -
Mark D. Johns -
Zach Metzinger