What's under the shark fin?

I'm going to use a lip mount on drivers side hood. Had it that way on my FJ and it worked great. Also installing a VHF/UHF ham radio.

 

True...but being that close to the other hole, I wonder if you would run into the outside diameter of the bulkhead? You're gonna want that thing flush against the roof

 

Sense you are expecting to be in the VHF/UHF bands I would recommend you look for an aircraft antenna that you like the the style of and then work to mount it. I think an IFF transponder antenna may suit your needs and would be small enough physically to not look out of place.

 

You're right I'm going to have to get a smaller antenna. I just got my 1/2 wave diamond and it's huge! So I decided to mount it on the bumper.



I think what I want to add to the roof is something like this if I can find a dual band. I can only find them in VHF or UHF only.


http://www.theantennafarm.com/catalog/laird-tech-trabt1420-780.html

That way I can still scan or do some short range TX if I have the front antenna folded or removed.

 

Again, many aircraft designed and marketed antennas are built to be able to be used across the UHF/VHF spectrum. I did avionics on Naval aircraft for 20 years.

 

Could you help a brother out then? I looked up IFF transponders came up with military equipment.

 

They are Military equipment. They are also civilian equipment. Let me see what I can come up with... If I had the specific frequency you intend to transmit it would help. I know that CB's are in the HF band around 27 MHZ If I remember correctly IFF is in the UHF around 1090 MHZ. The reason I like that antenna as an option for you is ours were smaller and would not look that out of place. If you know your freq.'s I'll give it my best if not tell me what you know and let me see what I can come up with. Feel free to PM me if you want...
Jared

 

Thanks PM'd!

 

Wrong frequency they will not work.

 

I PM'd Jared to see what's out there, but I could not find a dual band one.

Those stubbies are really fine tuned for with 2m or 7cm, and commercial or amateur, not any combination of the 4.

I need basically 144-470.

 

It will work but do not expect much your batter off with a rubber duck. They are also only 1 meg wide when tuned meaning you can not cover the ham VHF from bottom to top with out re tuning, the ham VHF covers 144 to 148 that's 4 megs.

 

Yeah I was afraid of that. I know there's a reason you don't see very many stubbies around.

The more I read I think the most versatile mobile setup is with a Yaesu 857D with a ATAS-120A antenna.

 

Correct the IFF transponder antenna is not the right antenna application. However there are several VHF/UHF blade antennas designed to function in these specific frequencies for this purpose. I have literally installed thousands of these over the years. One thing to consider as you move forward is do you want to operate multiple radios with one antenna or one radio with a wide bandwidth? The answer will effect the antenna and or hardware required to get it configured.

 

Iggy, I found options but will need insight to the above to be able to give you my advice. I am NOT a ham operator but recently was asked to consider it... I may stick my toe in the water in the future therefore I am not concerned with spending too much time on this. I am happy to help any way I can!

 

I plan on operating 1 radio with either one or multiple antennas. If what Tim says is true, then I would use a stubby for scanning and a longer antenna for transmitting.

 

The air craft antennas will work for receive most anything will if it's close but it will not work well for TX and will produce high VSWR. The stubby antenna frankly will not function great for anything. If you are in a city chances are you'll pick up PS stuff OK and transmit a couple of miles OK and the radio will be happy about the match to some extent but the capture area is just not there. The stubby antennas you see on vehicles are for stuff like GPS frequencies and microwave they work fine in those bands because the wave length is very short that is also why the shark fin antennas work. They make a little stubby antenna for HT's great for a ham fests and a gathering it's not in the way and does well for that kind of thing but don't expect to access the repeater 15 miles away. Here is a standard formula for a ½ wave antenna 468/ frequency in MHZ= feet so if you have a tiny antenna you still have to produce that length in some way usually done by wrapping the wire around something inside instead of vertically.

 

I am running the Larsen thru-the-glass dual-band antenna. It is working great and does not ground against the garage door when I pull in.

 

Well Tim, I don't know about the radios you are using or Iggy plans to use but I do know these antennas are designed for these frequencies and will work well for both for TX and RCV. Yes the electrical leingth of the antenna needs to be as close to a multiple of the desired wavelength as possible for the best performance and lowest VSWR. None of that explains why the aircraft antenna won't function and can't be matched for use in a transmitt mode. I would suggest contacting the manufactures of a couple of antennas and explain what you are trying to accomplish and the frequencies that you plan to use and see what they suggest.

 

I just pulled up the unclassified specs on one of the radios we used in the aircraft I maintained to see what our output power was. I don't remember everything as accurately as I once did... The AN/ARC-182 radio puts out in the 10-15 watts range minimum. It is possible that the higher power you intend to transmit could be an issue to discuss with the manufactures as well.