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CAP Talk  |  Operations  |  Tools of the trade  |  Topic: Air-band Antenna Recommendations?
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Author Topic: Air-band Antenna Recommendations?  (Read 1006 times)
dmandrell
Newbie

Posts: 3
Unit: PCR-OR-065

« on: December 13, 2017, 07:59:45 PM »

I am interested in what other people are using for an air-band base radio antennas.  I am limited to mounting it in an attic, so size is a factor (and ground plane rods are a pain).  I really like the J-Pole antennas from Arrow Antennas (http://www.arrowantennas.com/sub/jpole.html).  I was going to email them and see what making one for 118-137 Mhz would cost, but also wanted to check for advice on here.

Thanks in advance for any advice!
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SarDragon
Global Moderator

Posts: 10,259
Unit: NAVAIRPAC

« Reply #1 on: December 13, 2017, 09:54:15 PM »

J-poles aren't really a good way to go. They are pretty inefficient for base station use.

I have a 5/8-wave mag mount that sits on a 2' circle of thin steel, and it works great. I used a 2 meter antenna base, and cut my own whip out of the right size stainless steel wire.

I know other folks who use pizza plates or cookie sheets, and get decent coverage and SWR.
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Dave Bowles
Maj, CAP
AT1, USN Retired
Mitchell Award (unnumbered)
C/WO, CAP, Ret
EMT-83
Salty & Seasoned Contributor

Posts: 1,845

« Reply #2 on: December 13, 2017, 11:16:50 PM »

A 1/4 wave mobile antenna mounted in the center of a cookie sheet or old road sign will work well, probably better than a gain antenna. Sounds backwards, but antenna performance isn't just about gain. The antenna pattern is just as important.

A 1/4 wave antenna has very good omnidirectional coverage. A gain antenna has significant signal nulls, particularly in regards to elevation. If your interest is in stations much higher than your elevation (such as airplanes), those nulls will be an issue.
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radioguy
Recruit

Posts: 24
Unit: MER-NC-019

« Reply #3 on: December 13, 2017, 11:40:50 PM »

I really like the J-Pole antennas from Arrow Antennas (http://www.arrowantennas.com/sub/jpole.html).  I was going to email them and see what making one for 118-137 Mhz would cost, but also wanted to check for advice on here.

If I recall correctly, you can call Arrow to find out the cost of a custom model OSJ for the aircraft band.  They also have two different ground plane models intended for the aircraft band.

DPD productions also offers several base antennas specifically for the aircraft band.
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dmandrell
Newbie

Posts: 3
Unit: PCR-OR-065

« Reply #4 on: December 14, 2017, 02:04:00 PM »

SarDragon - How did you confirm your antenna tuning, or did you just do the math and trim to the theoretical length?

EMT-83 - I have done this with other antennas, but had not thought about trimming a 2M down as SarDragon suggested.  I know the J-Pole has a pretty large low sensitivity zone overhead, but I assumed that aircraft relatively overhead would also have the most signal strength reaching the antennas vs. aircraft low/distant on the horizon.  I don't have a lot of experience with this, so the dead zone may be a bigger issue than I recognize.  I did not see their ground plane models, so I will have to go back and take a look at those too.

radioguy - I stumbled upon DPD's site, but could not tell if their antennas were designed for transmit capability.  Most of the text seemed to imply they were for scanners/listening, but it wasn't very clear to me.  One of their omni's mentioned transmitting, but it had to be tuned for the single frequency it would be used on.
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SarDragon
Global Moderator

Posts: 10,259
Unit: NAVAIRPAC

« Reply #5 on: December 14, 2017, 09:45:17 PM »

SarDragon - How did you confirm your antenna tuning, or did you just do the math and trim to the theoretical length?

Well, since air band is a lower freq than 2 meters, the antenna is longer, hence the need for a new whip. I initially did the math, cut it long, then used an antenna analyzer to trim it to the center of the band. Works great, and I also use it as an external antenna for my sticks receiver.
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Dave Bowles
Maj, CAP
AT1, USN Retired
Mitchell Award (unnumbered)
C/WO, CAP, Ret
dmandrell
Newbie

Posts: 3
Unit: PCR-OR-065

« Reply #6 on: December 15, 2017, 11:13:33 AM »

Thanks SarDragon!  I will look into the mag-mount approach first.  I like that it could be taken to the car if needed (although retrieving it from the attic would be a chore).  I'll have to track down someone locally with an antenna analyzer and maybe some more experience building antennas than I have to supervise :D
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SarDragon
Global Moderator

Posts: 10,259
Unit: NAVAIRPAC

« Reply #7 on: December 15, 2017, 05:50:15 PM »

They are cheap enough that you can buy two, and spend around $100. Check out your local ham radio shop (Ham Radio Outlet, in Portland) for the mag mounts, and get the whip material at an industrial supply store. Actually, I think I got the mag mount at Fry's (there's one in the Portland area).
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Dave Bowles
Maj, CAP
AT1, USN Retired
Mitchell Award (unnumbered)
C/WO, CAP, Ret
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CAP Talk  |  Operations  |  Tools of the trade  |  Topic: Air-band Antenna Recommendations?
 


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