Military Air Base discone from Ebay

[TeRayCodA]

A while back ago,I ran across this discone part removed from a Military Air Base on ebay from FRS co.(sold as antenna parts, discone)

The plate reads:

Antenna,UHF Discone
Made for
Federal Aviation Administration
Type FA-7845
Contract FA67WA-1823
Serial No.1125
Antenna Products Co.
Mineral Wells,Texas

It did not have the skirt elements,and the disc was one round sheet of aluminum(10"dia).It was tuned to 225-400Mhz,but I needed it to go lower(118-150Mhz)for the other AM civilian/military aircraft,ATC.

So...I cut the disc down to 6"dia. added some 3/8"alum rod,added the proper length skirt elements(32")out of the rod stock.

This antenna came with a military type N connector,that would not mate with a generic type N connector -time for surgery!

I had to completely disassemble the antenna,and install a regular type N connector(chassis mount)

What I ended up with is a very rugged discone!(this thing has O rings too!)
I removed this one from the tower temporary to test my new 16 element discone.
The results were outstanding!
These do sometimes pop up on ebay!I only paid $20.00 for this one.(be on the look out!)
I had a lot of the 3/8" round alum stock also,so,this one was done pretty cheap!

 

[PointMan]

Wow that sounds like quite a deal, not only do you have a good preformer, but you can tell your scanning buddies "Oh I got a Govt Approved Mil Air band antenna." :wink:

Just out of curiosity, what are the element lengths for the stock 225-400 MHz antenna? Id like to make something for just Mil Air, and that brings me to my second question:

How does the Mil Air Discone preform compared to say a Rad Shack Discone or the Diamond discone? I have both, and I was wondering if there is any gain improvement between the 50-1300MHz type discone and the 225-400MHz discone? I know alot of people will start posting "ALL DISCONES ARE 0db GAIN!!!" Now let me type quick because the short bus is waiting for me, along with my fat pencils, but Id think there would be better preformance for soemthing designed for a narrower bandwidth right?

I gota say, thats some impressive antenna stuff you got going on there.

 

[N5TWB]

PointMan said: Now let me type quick because the short bus is waiting for me, along with my fat pencils,

made me LOL, gotta remember that one!

Back on topic, I think I will add this item to my eBay wish list - looks quite stout and a fun upgrade project.

 

[DaveH]

This antenna came with a military type N connector,that would not mate with a generic type N connector -time for surgery!

I had to completely disassemble the antenna,and install a regular type N connector(chassis mount)

There's a variant called the high-voltage N (HN) connector. That could be it. Another military-type RF connector is the C connector, which looks like a large BNC (but may have 3 posts on the female versus 2).

Dave

 

[TeRayCodA]

No,this connector is definitely some type of exotic "N"connector.No bayonet posts.

As a matter of fact I just saw another one of these up for auction on e-bay the other night,from the FRS Co.

Please keep in mind,that these have been stripped of the cone elements.
They have 1/2"threaded holes for the cone elements,and I had to use some brass shimstock to keep the 3/8"elements in place,also with the use of some S/S 1/4X20 socket head set screws.As I stated,I did have to disassemble the disc plate from the apex,(there is a brass rod spot welded to a smaller copper disc,that in turn is welded to the center of the connector).-It will pop right off.

The disc is about 12" in diameter,as you can see,I really modified mine to go lower frequencies.

All-in all you will have a very rugged antenna buit for MIL specs.

 

[TeRayCodA]

Also, I never tried it for use in the 225-400Mhz,as I wanted something to go lower for 118-136Mhz,and a portion of the 138-150Mhz military A.M. Air National Guard frequencies.
The cone now is 22" in diameter,and skirt elements are 32".

You probably would want the skirt elements to be about 18"I think?
There is a discone calculator or formula I saw somewhere,and if I find it,I'll post the link to it.

 

[merlin-7]

Nice!!!!