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 35mhz or 40mhz

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goldslinger
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PostSubject: 35mhz or 40mhz   Fri Sep 23, 2016 11:08 pm

hi all i am thinking of building an under water rov which of the above frequencies has the better water penetration
i can find lots of second hand 35mhz but 40mhz are like hens teeth
i am in the UK so i am limited to these frequencies
look forward to your replies
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barriew
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PostSubject: Re: 35mhz or 40mhz   Sat Sep 24, 2016 6:23 am

You don't actually have a choice! 35mHz is reserved for model aircraft in the UK. You could use 27mHz which may be easier to find.

Barrie
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Windy
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PostSubject: Re: 35mhz or 40mhz   Sat Sep 24, 2016 8:45 am

As Barrie says, 35Mhz is solely for aircraft use & is illegal to use for surface models http://www.ukrcc.org/index.html


Mark..
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goldslinger
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PostSubject: Re: 35mhz or 40mhz   Sat Sep 24, 2016 9:02 am

thanks for the link
i know the old 27mhz was some times used but that was also used for C.B radio
which makes that definitely out
which means it has got to be the 40mhz
the search will have to go on for a multi channel
there are some car hand grip ones but i think they only have 2  channels
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barriew
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PostSubject: Re: 35mhz or 40mhz   Sat Sep 24, 2016 9:07 am

We still have a number of members using 27 Mhz without any interference from CB Radio.

Here's a 40 Mhz set on ebay.

http://www.ebay.co.uk/itm/Futaba-3GR-40MHz-Synthesised-Radio-Control-Equipment-/112143202831

Barrie
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goldslinger
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PostSubject: Re: 35mhz or 40mhz   Sat Sep 24, 2016 10:02 am

thanks for that
do you know which has the better water depth penetration 27mhz or 40mhz
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barriew
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PostSubject: Re: 35mhz or 40mhz   Sat Sep 24, 2016 1:27 pm

goldslinger wrote:
thanks for that
do you know which has the better water depth penetration 27mhz or 40mhz
Not really, but based on the fact that 40 Mhz does penetrate water, but 2. 4Ghz does not, then I deduce that lower frequencies penetrate better - but I could be totally wrong lol!

Barrie
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Roadrunner
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PostSubject: Re: 35mhz or 40mhz   Sat Sep 24, 2016 2:01 pm

Underwater control usually works best with a crystal controlled frequency, 27mhz being the easiest and cheapest, but usually limit controllers to 2-3 channels which for machines requiring more ghannels such s an underwater rov is useless, 40mhz is your best bet, as they go from basic 2 channels up to 12! Price wise tho your looking to pay a hearty bill, however for control ability it's flawless, you can of corse try to locate a F14 controller.

2.4 MHz is useless when it comes to water surface penetration, it can be used so don't think it can't but it has seriouse limits when submerged.

As for 35mhz.... yes it's primiarly used for aircraft, that said most aircrafts are now in 2.4ghz to reduce signal loss also 2.4 offers longer ranges....making it almost a redundant frequency.

There is no law forbidding you to use 35mhz in a boat but it's not recommended, that said if it's you on your Tod in the middle of no where running a boat then 35mhz can be used with some caution ( just look up, no model aircraft around you, your good)

Their are also dedicated systems designed for u dewater use and those are using the 2.5ghz band which can also off a cam link back to shore for live streaming of your camera (fpv) those sets will run you up a much larger cost but they are great systems.

My honest advice Is to try to sorce a 40mhz system for your needs before getting a 35 set, this is just to reduce the hobby police getting annoyed, but if you can find a 35 set that meets your needs then there is no reason why you can't use it providing your sensible!

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goldslinger
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PostSubject: Re: 35mhz or 40mhz   Sun Sep 25, 2016 10:43 am

all sounds good i will start with to 40 and see how things go from there Very Happy Very Happy
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Hellmut1956
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PostSubject: A different view of your question!   Tue Oct 23, 2018 3:51 pm

Underwater communication requires to use frequencies as low as possible. So your guess that MHz systems could work and that equipment in the GHz part not is correct. But what about having a device floating on the surface of the water so that cheap and feature rich GHz systems could be used. It could be possible eventually to have the unit floating on the water surface following your unit below?
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dimtim
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PostSubject: Re: 35mhz or 40mhz   Thu Oct 25, 2018 7:43 pm

I used 40megs for my subs. But 27 will work.

people are using 433mhz but not 100% on these at the moment.
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Fred 1948
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PostSubject: Sub   Fri Oct 26, 2018 1:25 pm

Hi Goldslinger

Have a look at this forum http://www.theassociationofmodelsubmariners.com (outer sub forums are available)  it should help you with most of your questions with regards to model submarines, if not just ask and some one will come up with an answer,

I have just started using 433mhz for more info ask David F or Merriman as they are more up to speed on it than I am.

Fred
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