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Author Topic: 35Mhtz to 40mhtz  (Read 360 times)

roycv

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35Mhtz to 40mhtz
« on: January 12, 2021, 03:15:30 pm »

Hi all at the risk of sticking my head over the parapit again here goes.
Just bought a 2nd. hand Futaba 35Mhtz FF6 RC set.  Intention was to plug in some 40Mhtz crystals.  I looked at what I had bought and the rather daunting manual and saw that the receiver was a dual conversion one.  After charging all batteries I did a test to see all was working on 35Mhtz and all OK with servos plugged in etc.  I put 40Mhtz crystals into both with little expectation and nothing happened.

I have a lot of 3 to 5 ch. 40Mhtz receivers, at least a dozen, so I connected a replacement 40Mhtz rx. and all worked nicely, not much of a range check but the aerial was fully down.

So dual conversion 35Mhtz has to stay at 35Mhtz.  If anyone wants (free) this 7 ch rx with a pair of crystals send me a PM.

For boaters the Tx is a bit over the top but the manual turned out to be simple enough as I only needed to know ch reversing and ATV control.

I have another ex 35Mhtz rx. 7ch 'normal' rx. and that with a 40Mhtz crystal in works fine from this Tx.  It is just the dual conversion rx's that do not convert for use at 40Mhtz.

So why did I expect this to happen?  I have a Fleet 40 Mhtz RC set bought direct from the shop in Fleet and the Transmitter is marked 35Mhtz underneath, but was sold to me as a 'Plainsman' with 40Mhtz crystals in place.

I hope this will save a few 35Mhtz Tx's and rx's from being binned.  40 Mhtz crystals are easily available on-line.

 I know many modellers have gone over to 2.4Ghtz but I have 20+ RC sets and see no need to transfer.

Best regards
Roy




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JimG

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Re: 35Mhtz to 40mhtz
« Reply #1 on: January 12, 2021, 07:56:18 pm »

While 35MHz radios can be used as 40MHz by using different crystals they should really be retuned as they will be on the edge of their setup. However when using double conversion you really need to use the crystals from that manufacturer. Different manufacturers used different intermediate frequencies so even with 35MHz using non Futaba crystals wouldn't work. You didn't say who's crystals you were using but if you can get Futaba 40MHz double conversion crystals they might work.
Jim
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roycv

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Re: 35Mhtz to 40mhtz
« Reply #2 on: January 12, 2021, 08:21:52 pm »

Hi Jim thanks for that information, always good to know.  I remember when I was putting an RF circuit together rather a long while ago now there was just a small capacitor in the oscillator cct. that needed changing to alter to the other frequency.
No name on the 40Mhtz crystals I bought them on-line a while back.

I have been using my Fleet for years and that is a 35Mhtz set as I said above.  I would expect to have occasional hic cups in the esc (old type) and have the electric motor 'cough' with a possible drift in frequency.  These days my range needed is 40/50 metres at most.

What do you reckon?

Regards
Roy
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JimG

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Re: 35Mhtz to 40mhtz
« Reply #3 on: January 13, 2021, 12:56:16 pm »



I have been using my Fleet for years and that is a 35Mhtz set as I said above.  I would expect to have occasional hic cups in the esc (old type) and have the electric motor 'cough' with a possible drift in frequency.  These days my range needed is 40/50 metres at most.

What do you reckon?

Regards
Roy
Easy to do a range check with these older transmitters, you should get at least 30 metres with the transmitter aerial down. If range is a bit low with the aerial down then just recheck with the aerial up.
Jim
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roycv

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Re: 35Mhtz to 40mhtz
« Reply #4 on: January 13, 2021, 01:00:45 pm »

Hi Jim, my decision was based on looking out of the window and the weather got a thumbs down!  Been playing with RC for over 60 years now, I was naughty at the beginning as I never purchased a license, shame really as it would have been a nice memento to have.

best regards
Roy
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nemesis

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Re: 35Mhtz to 40mhtz
« Reply #5 on: January 13, 2021, 01:16:40 pm »

Still got my Licence somewhere, as you say , they should be framed. I suppose you reversed the x tals on your 27 meg set to give more slots. In those days everybody wanted to be on the water at the same time. nemesis
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roycv

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Re: 35Mhtz to 40mhtz
« Reply #6 on: January 13, 2021, 01:35:09 pm »

Hi Nemesis I remember switching the black one over which is fine until you find someone who has also done it!

Roy
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Big Ada

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Re: 35Mhtz to 40mhtz
« Reply #7 on: January 13, 2021, 04:05:08 pm »

Still got my Licence somewhere, as you say , they should be framed. I suppose you reversed the x tals on your 27 meg set to give more slots. In those days everybody wanted to be on the water at the same time. nemesis
Do you mean swopping the TX crystal for the RX one?

Len.
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roycv

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Re: 35Mhtz to 40mhtz
« Reply #8 on: January 13, 2021, 04:45:00 pm »

Yes
Roy
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spearfish99

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Re: 35Mhtz to 40mhtz
« Reply #9 on: January 13, 2021, 08:03:20 pm »


I have been using my Fleet for years and that is a 35Mhtz set as I said above. 



  I loved the Fleet gear when it came out in the 80's. I have two unused 40mhz sets still tucked away. While the cells in them never leaked, they both suffered from "black wire" syndrome . I keep looking at rewiring them and refitting new nimh's. Also have a 35mhz Tx that I was going to install one of the Frsky hack units in.  Having gone over to 2.4ghz in all my yachts , they probably won't get done any time soon.  shame really.


Think that using 2.4ghz has made us lazy with no crystal changes . I have a couple of Futaba Skysport sets and a T6ex on 40mhz languishing in the spare room .  Remember the days of 40mhz with the big old aeriels with the practice golf ball on the end to stop taking people's eyes out on! ;)



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roycv

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Re: 35Mhtz to 40mhtz
« Reply #10 on: January 13, 2021, 10:16:21 pm »

Hi Spearfish I keep my Fleet rx's and servos very separate in a box just in case I match them with standard connection servos and receivers.  I did it just once, I was in a hurry and wrote off a 35 rx.
The tx's have that timeless design a lot like the aluminium cased Futaba M series sets.  I have a Futaba M series 27Mhtz FM but found the matching rx's not much good and I made a couple of Micron rx 27 FM rx's up and they still work very nicely. 

A few years ago when my eye sight was better I replaced the old socket type connector strip for a modern type one.  I made a 6 ch Micron Tx as well very nice but it has a fault which has put it to one side for many years now.  You could do all sorts of things inside the Tx with mixing and servo ATV just plug and play.
Those were the days!
Roy


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spearfish99

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Re: 35Mhtz to 40mhtz
« Reply #11 on: January 15, 2021, 12:53:19 pm »

Hi Spearfish I keep my Fleet rx's and servos very separate in a box just in case I match them with standard connection servos and receivers.  I did it just once, I was in a hurry and wrote off a 35 rx.
The tx's have that timeless design a lot like the aluminium cased Futaba M series sets.  I have a Futaba M series 27Mhtz FM but found the matching rx's not much good and I made a couple of Micron rx 27 FM rx's up and they still work very nicely. 




I believe that Fleet used a different polarity than most makers and that you can get away with swapping the red and black leads around on other makes servos to use them.  I bought some loose Fleet leads off of Ebay a while ago with their strange plugs, so that I could make some crossover leads for futaba style servos, although I haven't tried it yet. 


Amongst my stuff, I also have a Fleet speed controller and an Astec one supplied to work on Fleet stuff. Both of these are for brushed motors.  LIke you say , the tx's are a beautiful piece of work. I also have a Futaba M series set that still works, bought to fit a 2.4ghz hack unit in but too good to mess about with given my level of electronic skills.  I did fit a hack unit to one of the 35mhz Graupner tray style transmitters which works well with one of Frsky's rx's, but the way the Graupner was made meant that the fitting was literally plug and play except for having to strip so much out to fit the aeriel where it needed to go then refitting everything.


On the subject of Tx cases, I still have my Flight Link Duette  27mhz 2 channel set which has a welded steel case which was then stove enamelled. Weighs a ton but still just about works although, again, needing fresh cells.


Since I have pretty much much gone over to 2.4ghz for simple convenience, not sure any of the old stuff will ever actually get used again, which is a shame.



 
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roycv

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Re: 35Mhtz to 40mhtz
« Reply #12 on: January 15, 2021, 01:11:15 pm »

Hi Spearfish, yes they have the little blue servo connectors.  I have spare connectors on servo wire with bare ends I bought at the time.  Let me know if you want more.
I have changed over most Fleet servos esc's etc over to the current connectors.  Still have the Rx battery with again his own special lead on.   When it comes to charging the Fleet transmitter I used the Din plug but cut off the charger and connected to my "all purpose, you name it" adapters which have a modern charger they plug into.

I have found that a modern charger is not always able to start a charge in a battery if it has not been used for a while.  This is where I connect a Lead acid type charger to the battery for half an hour which just blasts in a charge, then go back to the modern NiMh charger, seems to work fine.

 I also have some round Deac cells that still work!  Always looked nice in their translucent blue wrapping, must be at least 35 years old!
OK so I am hoarder, but if it works why bin it?
Regards
Roy


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