Seeking MILAIR (225-400) Ground Plane Antenna Options

MDScanFan

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Before I go build something I am investigating my options for an off the shelf milair (225-400) omni antenna. Something like a simple fat ground plane antenna or fat dipole would work. Aside from some surplus antennas that pop up now and then I can’t find anything. I could have sworn I saw a Sirio fat ground plane antenna that would work (like photo below for 380-480), but I can’t find it anymore so maybe I am misremembering. Looking to stay under $150. I am already aware of the OmniX and discones. Anything come to mind that I should look into? Thanks.

8DA9D1C0-A7CF-46C4-BDD4-09D8834922FE.jpeg
 

prcguy

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The Sirio UHF ground plane would not be very useful for the 225-400MHz range. The Sirio VHF ground plane covers the entire VHF air band but its designed for that.

Although expensive surplus, the AT-197/GR Discone is a really good performer for 225-400MHz as it was specifically made for that. There are some surplus airport fat dipole antennas that come up on Ebay now and then but I don't see anything listed this week. There is also a common military fat dipole that mounts to comm shelters and Navy ships with a ground plane adapter. Here is the rare complete ground plane but the fat element shows up on Ebay all the time and you can easily fabricate a ground plane. AS-390A/SRC - Shipboard Communication Antenna - RAMI

Otherwise a typical good quality scanner Discone is hard to beat for 225-400MHz, something like a Diamond D130 series or even an Radio Shack version and throw away the top whip.


Before I go build something I am investigating my options for an off the shelf milair (225-400) omni antenna. Something like a simple fat ground plane antenna or fat dipole would work. Aside from some surplus antennas that pop up now and then I can’t find anything. I could have sworn I saw a Sirio fat ground plane antenna that would work (like photo below for 380-480), but I can’t find it anymore so maybe I am misremembering. Looking to stay under $150. I am already aware of the OmniX and discones. Anything come to mind that I should look into? Thanks.

View attachment 94452
 

ka3jjz

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I'd hesitate about removing the whip. If there is any activity in the VHF lo band (some National Guard and/or base ops) it would be more useful to keep it. Fort Belvoir in Virginia is such an example....Mike
 

iMONITOR

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Before I go build something I am investigating my options for an off the shelf milair (225-400) omni antenna. Something like a simple fat ground plane antenna or fat dipole would work. Aside from some surplus antennas that pop up now and then I can’t find anything. I could have sworn I saw a Sirio fat ground plane antenna that would work (like photo below for 380-480), but I can’t find it anymore so maybe I am misremembering. Looking to stay under $150. I am already aware of the OmniX and discones. Anything come to mind that I should look into? Thanks.

View attachment 94452
That is the:

Sirio GP 430 LB/N 380 - 480 MHz UHF Base Ant

I had one of those and wanted it to work for Mil-Air due to it's compact and bomb proof design. It worked pretty good for me even though it was not tuned for it. Probably because I'm only 10 mile from Selfridge ANGB in Michigan. There is some military land mobile use within that 380-480MHz band. 70cm amateur radio falls within that ranges as well.
 

MDScanFan

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Correct. That antenna is the one I reference in my post above. I included it simply because I thought I saw a 225-400 variant that looked like that from Sirio or some other company. Maybe I envisioned it in a dream. In my situation I would be giving up too much insertion loss if I tried to use that particular model directly.

That is the:

Sirio GP 430 LB/N 380 - 480 MHz UHF Base Ant

I had one of those and wanted it to work for Mil-Air due to it's compact and bomb proof design. It worked pretty good for me even though it was not tuned for it. Probably because I'm only 10 mile from Selfridge ANGB in Michigan. There is some military land mobile use within that 380-480MHz band. 70cm amateur radio falls within that ranges as well.
 

ka3jjz

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Wanna go back a few years? I'm pretty sure this is the same - or it's darn close - to the NilJon antenna that was fairly popular some years ago.


Interestingly the website says it doesn't have any reviews on it. Perhaps they should do some more homework....Mike
 

prcguy

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Are you comparing to the Bicone in the post above? There is no comparison, the Bicones are very, very good, I have two of them. I also have the Super M Ultra Base, or 08-ANT-0861 and its not anything to get excited about. Not much different than a Radio Shack Discone from my testing and its aluminum top hub will corrode to pieces if your near the beach and the top section has an NMO mount that mates it to the ground radials. Way too expensive for the performance and weatherproofing headaches.

Wanna go back a few years? I'm pretty sure this is the same - or it's darn close - to the NilJon antenna that was fairly popular some years ago.


Interestingly the website says it doesn't have any reviews on it. Perhaps they should do some more homework....Mike
 

vagrant

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That AT-141A/ARC looks like it would work well enough...at a significant elevation above the earth.

Oh good gosh, here is an AT-197/GR having a really bad day. See if you can spot the problem.

Before I had an AT-197/GR I used a discone for Mil Air. What helped the discone is a PAR 225-400 MHz pass filter that was around $70. With all the noise I have, it also helps with the AT-197 too.
 
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batdude

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Before I go build something I am investigating my options for an off the shelf milair (225-400) omni antenna.

i think you will be extremely happy with this antenna - I am.

 

digitalanalog

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That AT-141A/ARC looks like it would work well enough...at a significant elevation above the earth.
I disagree
Why do you say that?
Marine antennas only work on boats?

I had a private conversation with someone back in 2014 on this exact subject.
Here is what that person said. (edited out unrelated information)

"I have similar and probably better/cheaper aircraft antennas for mil air monitoring. They will need a ground plane around 2ft or larger in diameter for UHF and at least 3ft dia for VHF and when done the performance would be similar to a R/S Discone but with much less BW.

I have an AT-256A/ARC 225-400MHz, which is fairly standard UHF version and used on portable base stations where they put an aircraft radio in a box with power supply and this antenna on top of the box.. I also have a dual band 116-152MHz and 225-400MHz AT-1108/ARC.

Again, at best they will work about like a Discone with proper ground plane for home use but for mobile they would be hard to beat."


We all know and respect this persons knowledge and expertise on antennas and related subjects.
 

iMONITOR

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If larger elements such as the diameter of some antennas contribute to wider bandwidth why don't more antenna manufactures make them, and when does it become less effective to do so?
 

vagrant

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I would not argue against their point and agree that a ground plane is needed. Do others know that is needed though, especially the diameter in order to be effective? You easily spotted the issue with the AT/197, but you know what is missing. I was negligent that I did not consider your mention of a steel plate to be large enough as a ground plane, but just a method to secure it. Considering the size and shape, it would be a very interesting antenna if mounted top dead center of a vehicle roof, great for airport service work but peculiar on everyday vehicles.
 
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mancow

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I use a surplus military TACO fat dipole type monipole thing. It works great. They can be found on surplus sites at times.
 

cmdrwill

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If larger elements such as the diameter of some antennas contribute to wider bandwidth why don't more antenna manufactures make them,
Cost of the materials to make the antenna.

And the 'Com blade' antenna reminds me of when I worked for an aircraft antenna mfgr and spent time on the
antenna range.
 

MDScanFan

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Thanks for the suggestions. I searched a bit more and did not find anything that caught my eye with a decent price. I ended up buying a Tram 1410 that I will trim to cover 200 MHz and above.

In my searching I came across this listing on eBay. It looks like a ~4’ fiberglass antenna. With the limited details I am dubious of the claim that it covers 200-400 MHz. What do you guys think?

686CECB9-372D-4153-A4F4-1EA7116A5D3B.jpeg
 
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