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    Another what radio

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    Polycell
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    Another what radio

    Post  Polycell on Mon Apr 14, 2014 8:17 am

    What radios are you chaps using for your boats 40Mhz?
    Are there any preferences does any get better response than others ?
    I guess 40Mhz would be optimum
    Fred
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    david f
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    Re: Another what radio

    Post  david f on Mon Apr 14, 2014 10:54 am

    (I am not sure which country you are from, so I will assume the UK.)

    So 40Mhz and 27Mhz are the only legal choices. 2.4Ghz is no good for submarines.

    27Mhz - should have a technical edge (transmitting through water) but you will probably not be able to get equipment with enough channels.

    So, sadly, we are now boxed into second hand 40Mhz equipment - a problem for our hobby.

    My personal favourites are Futaba transmitters and Schultze (good if you can get them) or Futaba dual conversion receivers.

    I know that others have their own preferences so over to them!

    David

    Polycell
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    Re: Another what radio

    Post  Polycell on Wed Apr 16, 2014 10:09 am

    david f wrote:(I am not sure which country you are from, so I will assume the UK.)

    So 40Mhz and 27Mhz are the only legal choices. 2.4Ghz is no good for submarines.

    27Mhz - should have a technical edge (transmitting through water) but you will probably not be able to get equipment with enough channels.

    So, sadly, we are now boxed into second hand 40Mhz equipment - a problem for our hobby.

    My personal favourites are Futaba transmitters and Schultze (good if you can get them) or Futaba dual conversion receivers.

    I know that others have their own preferences so over to them!

    David
    Seen loads of 35 Mhz radios about whats the verdict on these
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    Hermann
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    Re: Another what radio

    Post  Hermann on Wed Apr 16, 2014 6:13 pm

    Hello Fred,
    like David I don't know where you are living so I don't know whether RC-sets on 35MHz are legal for ship (and submarine) models in your country. I am living in Germany and here 35MHz is only permitted for use of model aeroplanes (and helicopters). This is primary for safety reasons so model pilotes need not to fear interference from other modellers (RC-car drivers or RC-ship captains) in their neigbourhood. In other words: 35MHz is not allowed for other use than RC-planes.
    By the general movement to 2.4GHz in the flight, car and ship model Scene you can find more and more advertisements of 35MHz RC-sets from private ownwers but we are not allowed to use them for our submarines (although it would fit from the technical point of view).

    As David has already written 2.4GHz is not suitable for model submarine application, the attenuation of the electromagnetic waves in water is too high so you will loose control just after less than half a metre depth. Consider that a microwave oven operates on 2.4GHz also and you will get a feeling about the absorption of electromagnetic field energy when you cook your meal inside this oven (it's the water that heats up).

    Kind regards
    Hermann

    Polycell
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    Re: Another what radio

    Post  Polycell on Wed Apr 16, 2014 6:16 pm

    Thanks I knew that 35Mhz were not allowed but didn't know why.
    I live in the UK
    Fred

    willte
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    Re: Another what radio

    Post  willte on Thu Apr 17, 2014 8:55 am

    Polycell wrote:Thanks I knew that 35Mhz were not allowed but didn't know why.
    I live in the UK
    Fred

    SAFTY 35mhz is for aircraft only and 40 MHz for land or water only you would not like to fly an air craft and some one sailing a boat with the same MHz if the air craft went out of control it can cause damage or death where the boat cant

    Polycell
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    Re: Another what radio

    Post  Polycell on Thu Apr 17, 2014 11:04 am

    willte wrote:
    Polycell wrote:Thanks I knew that 35Mhz were not allowed but didn't know why.
    I live in the UK
    Fred

    SAFTY 35mhz is for aircraft only and 40 MHz for land or water only  you would not like to fly an air craft and some one sailing a boat with the same MHz if the air craft went out of control it can cause damage or death where the boat cant
    Yes thanks I realised that!
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    david f
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    Re: Another what radio

    Post  david f on Fri Apr 18, 2014 12:32 pm

    Yes there are a lot of 35Mhz receivers around at the moment. I have actually bought quite a few, cheaply on ebay, in the expectation of being able to tweak them to work on 40Mhz. I must add that I don't quite know how to do it yet! It has been reported that you can get reasonable range by just putting 40Mhz crystals into a 35Mhz set. Though again I have not tried this apart from quick bench experiments. (It worked fine.)

    And this modification would of course be legal. (It is transmitting that is subject to the law.)

    A further problem seems to be a shortage of 40Mhz crystals. So stock up now!

    So the death or dearth of 40 Mhz gear is a real problem for the hobby. All we can hope for will be small, niche suppliers doing 40Mhz gear just for submarines. (Probably at a price.)

    David
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    Hermann
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    Re: Another what radio

    Post  Hermann on Fri Apr 18, 2014 9:05 pm

    A normal 35MHz receiver should be able to work on 40MHz when equipped with a 40MHz receiver crystal, although sensitivity will be somewhat lower, resulting in a lower receiving range, if the bandpass filter at the receiver input is not adjusted/ tuned to 40MHz. Our receivers are so called superheterodyne receivers that mix the incoming transmitter signal with a local oscillator signal that is generated within the Receiver and that is a portion lower than the transmitter frequency (normally about 455kHz lower for single conversion receivers). The differential frequency between transmitter frequency and local oscillator frequency, the so called intermediate frequency (here 455kHz) is filtered out, amplified and demodulated to restore the servo control signals.
    You can see that the frequency determinating item of the receiver is in fact the local oscillator frequency that is determinated by the receiver crystal. However, for broadband preselection the receivers have an input bandpass filter that is tuned to the intended frequency band (27MHz, 35MHz or 40MHz). In principle it should be possible to trim the centre frequency of the input filter to another frequency, however the trimming range (when turning the ferrite core of the filter inductor) of some receivers may be less than the required plus 5MHz for the migration from 35MHz to 40MHz. It might even be possible that the local oscillator of some 35MHz receivers won't oscillate with a 40MHz crystal without adjustment measures.

    I agree with David about the upcoming Problems with 40MHz gears. I even fear another problem that might occur in future: When the majority of RC modellers has changed to 2.4GHz the authorities might withdraw the licenses for RC Operation on 40MHz so that other telecommunication services could uses that band for other purposes. This would be a real disaster for us. Hopefully this will not happen too soon....
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    david f
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    Re: Another what radio

    Post  david f on Sat Apr 19, 2014 9:27 am

    Yes, I'm hoping that Futaba receivers were designed for both 35MHz and 40 Mhz without any component changes. (Nigel says that this is true.) So my hope is to locate the input filter and "tweak" that. The problem is that Futaba do not provide circuit diagrams - for obvious reasons!

    Our AMS expert member is Paul B who is a "Ham". I'm hoping to see him at Norwich, if not before.

    Yes, Hermann the risk that our Government will auction off the frequencies is ever present. Lets hope it goes to the European Government so it will take some time!

    Nigel thinks that the best option would be to offer the 35Mhz frequency to all r/c modellers.

    David




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    Re: Another what radio

    Post  timgarrod on Sat Apr 19, 2014 3:08 pm

    I might be worng. but I heard a few monthes ago that they where thinking of using/selling 27mhz band for the use of wireless internet and was being tested in scottland.
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    Hermann
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    Re: Another what radio

    Post  Hermann on Sun Apr 20, 2014 9:45 pm

    Hello,
    just this evening I had a telephone call with a dear submarine modeller friend from Cologne who forwarded me an information about the classic Radio Control frequencies. He had got this information from the magazine (issue February 2013) of the Nauticus (that is the main association of German ship modeller Clubs).
    According to this article the German authority for telecommunication has prolonged the existing allocation of RC-frequencies (including 27MHz, 35MHz and 40MHz) up to 31st December 2022.
    As the allocation of frequencies for various services (broadcast, TV, mobile phones etc.) base normally on international conventions, I suppose and hope that also in other countries (including the UK) the 27MHz and 40MHz will be available for us submarine modellers for at least the next eight years...
    We must wait and see what will happen then.

    Kind regards and happy Easter
    Hermann
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    david f
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    Re: Another what radio

    Post  david f on Mon Apr 21, 2014 9:28 am

    Let's hope so, Hermann.

    I did also see a scary report somewhere that Microsoft were busy lobbbying Governments to allocate "unused" frequencies to frequency hopping long range wifi systems! (Sounds like the thing that Tim is referring to.)

    Have a good Easter anyway!

    David


    Last edited by david f on Wed Apr 23, 2014 8:57 am; edited 1 time in total

    timgarrod
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    Re: Another what radio

    Post  timgarrod on Mon Apr 21, 2014 10:23 am

    cheers both, that was it Dave. was beening tested in Glasgow but think the Ham radio people kicked up fuzz's and didn't heard any thing else. Thats good new that we've got till 2022.
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    david f
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    Re: Another what radio

    Post  david f on Wed Apr 23, 2014 8:56 am

    Yes let's hope that Microsoft went away! (The "blue screen of death" brought to radio control modelling!)

    David

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