Antenna for MilAir in the attic suggestions?

[ka3jjz]

Larry Van Horn and others have written about the 380-400 mhz area; in fact there remains holes where milair remains active in this region of the band. Not every frequency slot in that range is being used in every area, so it's worthwhile to check these 'holes' to see what shows up. If you start hearing what sounds like a control channel, tho, time to take that one off the list.
I can't put my finger on it at the moment, but Larry had quite a list of these 'holes' in one of his columns....and I know he reads this forum - NavAirBoss, a hand please?

73s Mike

[edit] I'll answer my own question - it's in the August 2006 MT. the Milcom column page 52. You can order a reprint from Grove rather inexpensively, I might add, and probably quite easy, as it's a recent issue.

 

[K2GOG]

I am going to dedicate my 996T for MilAir. (225-400) I am going to run a Antenna in the attic. What would be my best choice for mounting a Antenna in my attic tuned for MilAir, also which cable would you run?
If I had to guess I would say the mounted antenna in the attic would be 15-17 feet off the ground. Better than a ducky!

Thanks for your input!

I made a 1/4 wave multi element ground plance out of a PL-259 and a S0-239. The attacehd picture shoudl provide enough clarity as to what is involved becaseu I dont have the time to type a thousand words. T eh PL-259 screws right into the bilkhead. I ran a piece of coax up a PVC pipe that I hose clamped the bulkhead to and mounted the PVC to one of the rafters in the attic.

The center element I started with was 22 inches and the two side elements were 10 and 9 inches. I trimmed them all down to get good SWR on 2m, 1.25m, and 70cm so I can use this as a backup transmit antenna. Since milair is VHF and UHF, this provided a good 2 band antenna for my milair monitoring efforts hidden in my attic. The radials were 22 inches.

the rod was old copper coat hangers that I stripped the enamel from as to get a good electrical contact.

 

[whooey]

Thanks for your help guys.

 

[whooey]

I got this off of E-bay: AT-197A/GR Portable (Quick Assembly) UHF Air to Ground Antenna

 

[whooey]

What kind of connector is this?

And how do I hook it up to my BNC jack on my scanner? I hope I havent screwed up!

 

[prcguy]

That is probably the best Discone for mil-air you can buy. The connector is an "HN", last one I bought cost around $15 new but I see current Amphenol prices start around $40. Surplus connectors and adaptors to BNC can be had cheap.
prcguy

What kind of connector is this?

And how do I hook it up to my BNC jack on my scanner? I hope I havent screwed up!

 

[whooey]

That is probably the best Discone for mil-air you can buy. The connector is an "HN", last one I bought cost around $15 new but I see current Amphenol prices start around $40. Surplus connectors and adaptors to BNC can be had cheap.
prcguy

Thanks for your input! Can anyone point me in the right direction of where to buy the best cable and connectors/adapters for this antenna to a BCD996T?? I need anywhere from 50-100 of cable.

Wow, you guys have been a tremendous help. I hope this thing works good in the attic!

 

[zonian149]

Would it be possible for you to post lots of dimensions on the antenna so some of us could maybe try building one. I was watching it on ebay also and was going to bid 150 on it but I am trying to save for a bcd996t scanner. Maybe there will be another on sometime, but I would sure like to try to duplicate it.--Gary

 

[prcguy]

Here is a company that has used HN connectors and adaptors cheap. http://www.mgs4u.com/HN-adapters.htm
I like to use at least LMR-400 for situations like this and lots of people have reported good things about this company for LMR-400 with connectors installed. Just measure the exact length you need and they will take care of the rest.
http://www.jefatech.com/category/d100.wbc400/
I suppose a good quality CATV RG-11 would do nearly as well at much less $, but if you’re going to have a nice antenna, why go cheap on the accessories? If you live in a rural area with no radio towers nearby and the attic location is away from RFI sources in the house you might consider a pre amp right at the antenna. This will also allow you to use cheaper coax to the radio as the performance of the whole system will be set at the antenna and pre amp.
I posted dimensions of the AT-197 Discone about a month ago, use the RR search and you should find it. They show up here and there for about $75 in nice shape, $150 is a bit much.
prcguy

 

[whooey]

PrcGuy, PM sent.

 

[whooey]

Ok, now I'm getting somewhere. How about this for a cable in this link:
Low Loss 400 Jumper Cable.

I can have them make it with a BNC for the 996T end, but only a Regular N connector on the other side. Will the N fit the HN correctly. I tried to do some research, the only difference I could find between HN and N is the HN is made for higher voltage. Am I correct here, the N male should fit the HN female just fine right?

 

[iMONITOR]

Ok, now I'm getting somewhere. How about this for a cable in this link:
Low Loss 400 Jumper Cable.

I can have them make it with a BNC for the 996T end, but only a Regular N connector on the other side. Will the N fit the HN correctly. I tried to do some research, the only difference I could find between HN and N is the HN is made for higher voltage. Am I correct here, the N male should fit the HN female just fine right?

It "looks" like it should work, but ask the people making the cable to be sure. They should know.

 

[prcguy]

The HN connector is like a giant N, they are not compatible!

Ok, now I'm getting somewhere. How about this for a cable in this link:
Low Loss 400 Jumper Cable.

I can have them make it with a BNC for the 996T end, but only a Regular N connector on the other side. Will the N fit the HN correctly. I tried to do some research, the only difference I could find between HN and N is the HN is made for higher voltage. Am I correct here, the N male should fit the HN female just fine right?

 

[whooey]

The HN connector is like a giant N, they are not compatible!

Thanks. I will order a BNC to BNC and go with a BNC female/ HN male adapter.