Radio Frequencies

[mikew8760]

Hi,
Slowly working toward the Krick Type VIIb; at least when finished I should be able to re-write the abysmal instructions that come with the kit. But one aspect that must be shared by all subs is that of choice of radio frequency.
I intend to use 27MHz AM, as I have a load of stuff left over from model aircraft. I believe that 2.4GHz is practically useless in this application, especially if diving is intended, but can find nothing definitive. 35MHz would be illegal here in UK; 40MHz could be used, but it seems to be province of racing cars. What else is OK in UK?
Also, despite trawling the 'net, I have not found any guidelines on receiver installation, particularly regarding the disposition of the antenna - which for 27MHz is just a length of wire.

Any observations from those with practical experience would be most welcome.

[Guest]

Re: Radio Frequencies

You will get best reception with the antenna in the wet, however most of us just run it inside the pressure hull with no ill effects. It's always a bit of problem routing the aerial in the tight confines of a submarine, try and keep it in the largest loop possible.

I would make sure any pumps and motors are well surpressed, as 27mhz AM is more prone to interference from brush noise than 40mhz FM. three ceramic caps from each leg to the can, and one across the terminals is adequate protection. Make sure the speed controller has a failsafe either built in or add one.

[Wheelerdealer]

Re: Radio Frequencies

If your buying new radio gear, 40mhz is the way to go with subs.

[mikew8760]

Re: Radio Frequencies

Thanks for your responses; sounds like a "non-problem" really, but nice to be reassured. For now I shall persevere with 27MHz, but might consider modifying a transmitter to FM, or even some form of pcm.

Not at all sure what is meant by a "fail-safe" on the motor controller? What situations might arise where the motors need to be protected? I shall be using a decoder/pwm speed controller for the motors of my own design, which will stop them if, for example, the r/c signal is lost. This is intended to prevent the sub powering on deeper on a journey of no return; more clarification welcome.

[Guest]

Re: Radio Frequencies

You've kind of answered your own question.

As your controllers have failsafe built in on signal loss, you won't need an additional device. Some controllers have a failsafe built in, but some don't, and as you correctly pointed out, if radio is lost, without a failsafe, the throttle can get stuck on.

I've seen it happen, a chap came to a pool run organised and it took a full half an hour to spot the boat, that was in perfectly clear water. It was eventually spotted charging around in circles at the bottom. Imagine trying to find it in a murky pond!

[mikew8760]

Re: Radio Frequencies

Hi,
Thanks for the reassurance. Now you've got me wondering what is the best strategy to adopt if the failsafe has to kick in? I'm thinking along the lines of: operate dive pump to purge flood tank, (this assumes that with the design of this model the "schnorkel" is still in clear air), set dive planes to 'up-bubble', run motors at slow speed. Still leaves steering, set to mid-ships or a slight circle? Any recommendations?

Regards,
MikeW

[Guest]

Re: Radio Frequencies

Best failsaf settings- chop throttle, dive planes up. Blow ballast? Fine if the system allows it.