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FM radio Aerial

Posted: 30 Apr 2016 22:46
by HelloSailor
Hi All , Can someone advise me as to whether or not it is Ok to cut the aerial wire, and insert a male/female plug . This is on a 36Mhz Futaba Transmitter . This is so that the superstructure can be removed off the deck without any interference of having the aerial wire restricting how far it can be located from the hull.
Cheers, Jim.
PS : NO , its not my system :no: :no:

Re: FM radio Aerial

Posted: 01 May 2016 12:21
by RussF172
Hi Jim, I've done it and it seems to fine with no loss of signal as far as I can tell. An electronics expert might say otherwise.

Re: FM radio Aerial

Posted: 01 May 2016 21:36
by SlatsSSN
So long as you preserve the original antenna length that connects with your plug you should be fine. Also make sure you have a good clean electrical connection with the aerial wire to the plug.

We sub guys do it all the time. i.e. With the RX inside the water tight cylinder, the shortened aerial is soldered to a lug nut that fits over a bolt that runs through a bulkhead in the water tight cylinder and is secured by a locking nut. The bolt runs through the bulkhead of the water tight cylinder with the remaining aerial wire connected to the wet side of the bolt.

The bigger question in skimmers (surface ships) is why would you want to?
I'd be more concerned about mounting the RX and aerial in 2.4GHZ high in the model than I would 36 MHZ.

Whilst the rule of thumb we all hear is the higher you can mount a FM RX aerial the better, how much better is moot. 36MHZ RXs aerials do not need to be mounted in air or for that matter high. Case in point my subs maximum operating range on 36MHZ at 100m horizontal distance where I can't see it - is 5m vertical distance underwater. This is where the aerial is!! (Range test done at Central Coast Sub regatta with assistance from others).

So as far as I'm concerned mounting the RX high in the model for FM frequency is pure myth. I think you'd have to be pushing extreme ranges beyond the safe point of navigating your model for it to make any difference.

So 36MHZ works fine simply mounted high in the hull with the RX aerial strung out below deck level. FM doesn't have the same line of sight problems that 2.4GHZ has.



Re: FM radio Aerial

Posted: 03 May 2016 06:56
by kimwhite
I would agree with John on this. I was originally going to mount my aerial for Invincible actually high up between the masts, like on the full size ship. After taking some advice on this I decided to leave the RX in the bilges, and the aerial is simply stretched out to its full length and duct taped to a thin strip of wood, and laid flat along the inside of the hull at about waterline level.
When Invincible had her first sail last weekend she was operating about 200 metres out into the Lake and still in radio contact, so obviously the aerial setup is fine.
As John says, if a model submarine can still pick up signal underwater us surface operators should be able to get away with anything as long as we leave the aerial at its original length.

Re: FM radio Aerial

Posted: 03 May 2016 07:46
by HelloSailor
Hi John & Kim , Thanks for your input. As I mentioned , it is not my vessel , but for a gentleman I met last week who is building a 1/128
" Bismark " & was concerned about the aerial wire up into the mast restricting the distance when removing the superstructure. In Mighty Mo , I have done almost what you have done Kim , & run it along the inside of my combing for my superstructure & don't have any issues with signal loss . I mentioned this to the person concerned & I think he will go this way.
Cheers, Jim