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[red110kev]

Evening chaps.


I've trawled the forum for previous threads and t'interweb but not got any solid answers to my problem so I'm turning to you guys for help.



I have an old Club 500 that is now speed restricted so Joe Public's kiddies can have a go, and I'm currently using an old 2 channel 27MHz set (cos I don't want to risk the little darlings dropping one of my 2.4GHz sets)!


I've done the usual covering the end of the Tx aerial with some foam for safety, but I wondered if anyone has any experience of shortening the Tx aerial length to say 9- 12" BUT keeping the original length of the aerial by wrapping the equivalent length of copper wire around some dowel (or similar) to make a helical antenna? (Sorry if this is not a very good description).


If you have, was it successful?  Was there any loss in range? (I know the antenna will need to be angled so that it is as vertical as possible).


Cheers in advance.


Kev.

[C-3PO]

Could try this type of thing

https://www.thunderpole.co.uk/handheld-cb-antennas/midland-bnc-rubber-duck-antenna.html

C-3PO

[roycv]

Hi I had a Fleet 40 Mhtz set with a short rubber aerial as sold by Fleet and it had a range of about 12 foot 6 inches.  I now have a telescopic one now, works nicely.

Regards
Roy

[Colin Bishop]

I think that may work but the range will be significantly reduced which may or may not be a problem.


Colin

[malcolmfrary]

Trying to recall the unused theory from 50 odd years ago, the loading coil matches the aerial impedance to what the output stages are happy with, but you still have just a very short transmitting element which will work better than a "raw" aerial, but nothng like as well as the real thing.  The coil does almost as much cancelling as transmitting.  The formulas involved fluttered away shortly after the exam.
For the blob on the end, a kinder egg shell works well.  A cork from a wine bottle also does a good job.  Slit part way through lengthwise then a crosswise channel half way up to accept the aerials finial.  Careful removal of the foil from the bottle allows it to be re-used to keep the cork in place.  Practice makes perfect, and can be enjoyable.

[red110kev]

Thanks for all the info guys..... much appreciated.
It looks like the range would suffer so I don't think it's worth hacking the 27 Meg set.

However.... turn of events!....

Went in to my local model shop this lunchtime and there in the display case was a 2 channel 2.4GHZ radio and receiver they found in the basement, and I got it for £20!!!

Problem solved. 

[dreadnought72]

Might still be worth putting Malcolm's idea of a cork on the tx aerial, though ... That way you get a bottle of wine to go with it! 


Andy

[roycv]

Hi did anyone consider having the aerial only extended halfway?Roy

[C-3PO]

Extending the antenna half way is not desirable as this would definitely affect the resonant frequency and is likely to affect the match (VSWR) of the transmitter output to the antenna making it significantly less effective

C-3PO
 

[malcolmfrary]

A shorter aerial than designed for will reduce range.  On some sets, it might also cause the output transistors to go out of parameters and die.  Not immediately, but it can happen if it is habitually run with a collapsed aerial.
It is as well to remember that it is a radio, not a rifle.  The signal comes out sideways, the pointy end gives the absolute minimum signal, so it is no good pointing it at the model.

[roycv]

Hi Malcolm I always use the pointy end when I have lost the signal!regards Roy

[nemesis]

We always held the radio with the aerial, pointing to the sky as high as possible. It seems to work when the signal was poor. Dim and distant past with 40mgs and 2.4. nemesis

[Colin Bishop]

Vertical was always the 'approved' position and the signal then radiates out horizontally. But of course you also need to take into account the orientation of the receiver aerial which should also ideally be vertical but this was not always possible on a scale model so common practice was to run a length of aerial up the mast or to the masthead from the deck and then distribute the rest of the length inside the superstructure. So this probably matched the TX aerial being at a bit of an angle.

Decent kit would have sufficient signal strength even in this situation for normal model boating use if there was no external interference.

Colin

[Subculture]

Used a rubber duck aerial on my Robbe FC16 set without range issues. Usually used with submarines and in chlorinated pools, so a more challenging environment than most model boats present. However with the low cost of radio kit, I would be inclined to consider a basic 2.4ghz set.