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Airband - Ham Dual Band Antenna?

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KR7CQ

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This is a question for those who understand antenna design, and any help would be appreciated.

I am putting together a temporary setup for airband scanning, and I only have limited money and parts available at the present time. I know that the two antennas I am going to ask about are not ideal for airband monitoring, and I will be replacing them eventually with a real dedicated airband antenna. However, for the moment (this weekend) I have two choices of antenna available to use, and I wanted to see which would be likely to work better for what I am wanting to do, on a temporary basis until I get that airband antenna.

For air band scanning, my first priority is the 118-124 MHz range, and the second priority would be the 270-370 MHz range.

The first is a Diamond X30A, which is basically a half wave on 2 meters, and (2) 5/8 wave elements on 70 cm.

The second is a Diamond X50A which is (3) 1/4 wave elements on 2 meters, and (3) 5/8 wave elements on 70 cm.

Given the fact that I have to choose from one of these two for now, which one would you choose and why?
 

lotsofradios

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Diamond X50A, I actually have 1 in the attic and have used it for VHF air scanning with excellent results. Neither antenna will work that great for the UHF MilAir band because your 70cm portion is just too far away from the 300 MHz region. But it will do better than nothing. I don't know the type of MilAir traffic you have in your area that you will be listening too, but if you have a lot of high altitude MilAir traffic you'll do ok. Here in Florida we have a ton of MilAir traffic, can receive stuff just on rubber ducky at times.

If you want to use a ham antenna for the VHF and UHF air bands my suggestion is a tri-band antenna that covers 144, 220, and 440 MHz. You have that 220 active part of the antenna that will help in the lower areas of the UHF MilAir band. The guy who runs the Military Comms Monitoring MilAir Frequencies HF VHF UHF website had told me this and he uses the Nil-Jon Super M Antenna for mobile MilAir Its now discontinued but I found a used 1 and he was right, it has worked excellent for me mobile, almost as good as my outdoor discone up 25'. I was surprised..
 

LtDoc

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Don't put a lot of faith in this, but here's something to think about.
Neither antenna is 'optimized' for the frequencies you want to cover, so, while I think either of them would work okay, you just can't expect any huge performance from them. You're already aware of that anyway. Of the two, I think maybe the 1/2 wave on 2 meters may come closer to working than the 'vertical array' antenna (X50A). Most arrays have a lower elevation pattern where a typical 1/2's pattern has more of the higher elevations in it's pattern. Since most aircraft are going to higher than the antenna, being able to 'look' up would be desirable, right?
If you have both antennas then I would have to say to try both of them and see which works best for your situation. If you are going to have to beg/borrow/buy one or the other, make it cheap on yourself.
As for the 250 - 350 Mhz ranges I think that 1/2 wave would work out better than the other antenna, deals with that 'array' thingy an out of band usage, sort of. No ideas about that at all.
good luck.
- 'Doc

And as with any VHF/UHF antenna, the higher the better!
 

majoco

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N9JCQ

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As an aside, the Niljon SUper M is a mobile antenna that I use for both tri-band ham (2M, 220, and 440Mhz) and well as MIlair and Civil Air scanning. It works great. Niljon was rebranded to MP Antennas. Here is the Super-M for sale at Universal Radio:MP Antenna Super-M Classic Mobile Antenna.

I also use this Anli tri-band antenna for Ham/Scanning while mobile and it works about as well as the Super-M and I get far less stares and pointing :) Amazon.com : ANLI DC-124H TriBand 2M-222-440Mhz NMO Mobile Ham Radio Antenna : Electronics I can say I wanted to do the same as you are trying to do. K7KOA.

By the way, MP makes a home version of the Super-M and I replaced my discone with it and I am quite pleased with it's performance. I am using a YAesu Ft-7800 for Mobile as well as base Ham work and a Uniden 396T, Yupiteru 7100, or RS Pro-43 HH scanners for mobile milair and civil air work.
 

KR7CQ

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Thanks for all the responses. I have been looking at both the Niljon and the DPD, and would love to have both eventually, and know they would be far better than a ham antenna. I think I might purchase both eventually.

But for now I am just doing a temporary setup with parts I already have available, so I am stuck choosing either the X50A or the X30A. I used an antenna calculator and neither the 1/2 wave or a 1/4 wave on 2 meters corresponds to anything good in the air band, but I will have to pick between the two.
 
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