David

It's the crystals which dictate the frequency. They come in pairs; one each for the receiver and transmitter. This means that you don't have to specify a frequency when you buy the receiver. If you have two receiver crystals on the same frequency as the transmitter then you can use the transmitter with either model without changing the Tx crystal.

Now comes the more technical stuff; there are TWO different types of 40mHZ radios; AM (Amplitude Modulation) and FM (Frequency Modulation). They are NOT mutually compatible. You have to have FM transmitter, FM receiver and FM crystals (or all AM). You can't, for example, use an AM crystal in the receiver and an FM one in the transmitter.

It's also far safer to buy branded crystals to suit your make of radio e.g. if your radio is a Futaba then buy Futaba crystals. In general most types are interchangeable but there are exceptions.

Ref the speed controller, I'd suggest that you find out what type was originally fitted and see if you can buy one the same. I would say it needs to be at least 15A continuous current capacity and fitted with Battery Eliminator Circuitry. MTroniks' Viper15A is a popular unit.

You will find out a lot more by reading the article here **LINK**

Dave M

DM. I didnt know you were french ! Do you wear a beret as well??

David. Where abouts are you ??? a plea for redundant 27m or 40m sets may be the way to go. A lot of people have gone over to 2.4 now and all those old sets are laying around unloved in the corner.

2.4 may be cheaper in the long run even so,it is ever so convenient simply switching on the transmitter, then the boat, and sailing away without worrying about crystals…as a bonus the Planet sets only use 4x AA batts!

Ashley

As Dave says, if buying extra crystals, stick to the same manufacturer to ensure that it will all work. You can have as many receivers as you like with the same crystal, the transmitter knows no better. The downside is that they are usually supplied as a transmitter and receiver pair. The transmitter one is invariably labelled with the frequency it will cause to be transmitted to air. The receiver one, because of the way radios work will have been cut to work at an offset frequency. It might be labelled with either that frequency, or the frequency that it receives from air, usually with an "R" involved to avoid (?) confusion. There is the "normal" offset, then some manufacturers like to be a bit different, then there is a different one for FM, then, to put a top hat on it, there is something called a "double conversion" receiver, which is different again.

As Ashley says, brand new 2.4 GHz outfits are relatively cheap. What was not mentioned was that if you get lucky and pick the right one, compatible extra receivers are actually cheaper to buy than a pair of 40MHz crystals. Just the minor minefield of finding a good, but low cost transmitter that has cheap compatible receivers available.

While I can picture DM in a beret and trench coat, I'm not sure about the high heels and stockings…….

DM

For high heels and stockings to fit your manly girth there is a place in Sheffield or if you prefer French Sheffeeled

Enough,enough, I’m feeling queezy.

David. The crystal thing is simple. Please do not take offence at this easy explanation.

The set operates at 40Mhz. In order to focus the Hertz`s into channels (within the broad 40Hz spectrum), tuning crystals are used; they come in various frequencies (giving the channels) as marked on the things, You have to have one in the Tx and one in the Rx, obviously they need to match..ie be the same frequency) in order that the tx and rx operate as one. I hope thats explained it. Sometimes we take these things for granted.

For instance 40.685 is one channel, 40.695 is another and so on.

If you have two boats, you only need the pair of crystals, the tx marked one stays in the Transmitter and the Rx one can be moved to the reciever units in either boat….OR you get two pairs (of the same frequency)…and use one each Rx crystal in each boat (to save swapping about) and the one Tx crystal in the Tx unit.

Assuming yours is an FM set then the crystals spotted will be ok BUT the Tx one is in a little holder and the holder needs to fit your handset of you is in trouble. I have two makes of 27M sets and they had holders (long gone now) but the crystals simply plug straight in the little hole.

The 2.4Ghz sets do away with the crystals by using different technology, and all you need then is a transmitter and the corresponding manufacturers reciever, the pair are "bonded" electronically. This is what makes it easy, there is no need to have loads of crystals, any new recievers you buy are simply bonded to your personal transmitter and thats that.

Please be aware the only correct use for stockings is to cover boat hulls in prior to applying fibreglass/epoxy resin.. Wellies are the recommended footwear at the pond, at least, our pond..but customs vary, and we are down south…..

Ashley

Is there nobody on this forum that can give a simple answer to a simple question.

Just for a fleeting second back there I actually believed that I had……………………but it appears not.

(Back to the Cumulo-Nimbus and Alto-Stratus for me, then.)

DM

David,

You can purchase the appropriate receiver crystal here. If you have two 40 MHz AM Futaba receivers you will need two receiver crystals (one for each receiver) – otherwise buy one crystal and swap the crystal between the receivers.

**LINK**

Ian

So……………

David
Two new Futaba 40mHZ AM receivers at £18 each and two receiver crystals at £10 each comes to £56 (Hobby Store).

New Planet T5 Tx and Rx £45.50 plus spare receiver £15 = £60.50 (Howes). That's for a FIVE channel radio and no frequency worries. For an extra four quid. That's just enough to buy a pint of lager south of Potter's Bar. Do they drink bitter south of Potter's Bar anyway?

I know which choice I'd go for (and it ain't the lager, dude).

Paul
You are indeed a very strange man. My advice would be to avoid tight clothing and eating cheese before bed-time, and to put more whisky in your water.

Dave M