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Old 11-21-2018, 10:40 AM
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Default 772 Mhz Moxon antenna project.

I was introduced to the Moxon antenna at an amateur radio club recently. Since I had been looking around for an easy to build directional antenna to monitor the local 770 MHz P25 system I decided to run the numbers for 772Mhz and see how big the antenna would be. It turned out to be small enough to sit on my desktop at about 3x7 inches. There are two nice calculators on the web.
Moxon Calculator
W4/VP9KF - Online Moxon calculator
===================
I built the antenna in the attached images using some plastic cardboard material like the political yard signs are made of. A block of wood with a slot cut in it serves as the base. The elements are made from a length of #12 copper wire (2.05 mm diameter) connected to an F type chassis mount coax connector. The wire is held in place with hot glue.

I have no equipment to test this antenna for SWR at this frequency so my performance report is anecdotal to be honest. I can say that it works better than I expected and gives me a better signal according to DSD+ sitting indoors on my desk than does my outdoor folded dipole cut for the same frequency. It is directional but not a sharp beam so aiming isn't critical. I use a TV splitter to send the signal to two SDR dongles.

Anyway so I offer it here for those of you who like to experiment. It is a quick and easy project that exceeded my expectations. If you are looking for an indoor or outdoor homebrew antenna this might be an option. I like it because I recently had lightning damage a computer with SDR dongles connected to an outdoor antenna. This one sits on the desk with a short connection to the dongles.
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Old 11-21-2018, 12:35 PM
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That looks cool. I gots to find some wire and try that out. I might try it on plexiglass...
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Old 11-21-2018, 2:23 PM
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That looks cool. I gots to find some wire and try that out. I might try it on plexiglass...
Plexiglass would be great and would probably hold the F connector a little better. I made a 3/8" loop out of some small gauge wire wrapped around the connector under the nut to solder the #12 wire on the ground side. A 3/8" lug would probably be the "right" way but no big deal.
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Old 11-21-2018, 4:13 PM
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Plexiglass would be great and would probably hold the F connector a little better. I made a 3/8" loop out of some small gauge wire wrapped around the connector under the nut to solder the #12 wire on the ground side. A 3/8" lug would probably be the "right" way but no big deal.
I just found to 14 inch lengths of #12. Now to find an f or bnc in my stash
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Old 11-22-2018, 2:54 PM
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How should that be oriented? Seen a few pics of them both vertical and horizontal.
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Old 11-22-2018, 4:20 PM
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How should that be oriented? Seen a few pics of them both vertical and horizontal.
Vertical. Most 2-way radio (VHF or higher) is vertically polarized. The antenna is directional. Point the feedpoint toward the tower.
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Old 11-26-2018, 10:24 PM
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I have to say, I am not seeing much in regards to directional. I rotate it 360 and do not see much of an increase or decrease in signal. Both with unitrunkers visual display and the level meter plug in in sdr# But it is picking up much better on a 700 mhz system I was having some trouble with..
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Old 11-27-2018, 12:50 AM
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I have to say, I am not seeing much in regards to directional. I rotate it 360 and do not see much of an increase or decrease in signal. Both with unitrunkers visual display and the level meter plug in in sdr# But it is picking up much better on a 700 mhz system I was having some trouble with..
It isn't a beam but the non feedline side is a reflector. Glad you got one going!
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Old 11-27-2018, 12:52 AM
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Then you're not getting a good null. Could be multipath or multiple transmitters or construction error (like not isolating the coax from the antenna)
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Old 12-06-2018, 5:39 PM
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Its properly built as per the old volt meter. It is a simulcast system. It does receive better than the rs 800 and the nmo 800 I have.


Have a bunch of sheets of copper clad, and gonna try one of these for fun

https://www.amazon.com/MOXON-Antenna.../dp/B07BRMKCNH
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Old 12-07-2018, 6:51 AM
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That is nice but I often wonder how some of these merchants sell anything. No description or dimensions? I tried looking up his callsign on Google to see if I could find out more information without success. Kinda high priced for a pcb board isn't it...
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Old 12-07-2018, 7:26 AM
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That is nice but I often wonder how some of these merchants sell anything. No description or dimensions? I tried looking up his callsign on Google to see if I could find out more information without success. Kinda high priced for a pcb board isn't it...
Especially since he didn't post anything about what frequency these were designed for, other than "UHF" which is a pretty broad brush.
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