459 MHz TX & RX Chat

[Lima Hotel Foxtrot]

I don't know if this is just a vintage paperweight, but I'm sure a collector or technical wizz could make something of it. 

There doesn't seem to be an aerial, and I have no idea of the functionality of the rest.

The box is a Royal Mail medium package and weighs 2070 g.

Make an offer if you're interested because otherwise it's going in the electronics recycling bin at the tip.

[Paul De Tourtoulon]

I have never head of that one,,,

[Alan Gorham_]

Note that only the speed controller, charger and NiCd are Futaba. The radio is a Reftec item. As far as I'm aware Futaba never offered UHF radios.

[Andy Stephenson]

UHF was popular when CB started to interfere with 27MHz, although it was never very reliable for flying. I used a 2 channel set marketed under the name Vendene but made by Reftec. The receiver was manufactured in typical 80s style with components crammed onto the circuit board, some hanging off because it wouldn't all fit. They had some clever system that allowed the receiver to track the drift in frequency of the transmitter. Due to some restrictions on the 459MHz band where it was shared with industrial comms the receiver came with an earplug to listen in to the channel to check it was clear before switching on the Tx. Needless to say mine had this appendage removed.

[Lima Hotel Foxtrot]

SOLD.

[Phil Green]

2 hours ago, Andy Stephenson said:

...UHF was popular when CB started to interfere with 27MHz, although it was never very reliable for flying.

IMHO thats a unfair generalisation Andy based it seems on experience of whats generally accepted to be the least reliable UHF system of the time (which BTW was nothing to do with Futaba)

The quality of UHF sets varied, some were poor in stability but not all should be dismissed, for example in several of the Ponty S/C & Retro R/C event videos Pete Christy can be seen flying his UHF Talisman, four decades on  👍

Cheers

Phil

Edited August 24, 2022 by Phil Green

[Peter Christy]

Thanks for the comment, Phil!

 

There was/is nothing fundamentally wrong with 459MHz. I've used it without issue for decades. The "Rolls-Royce" of UHF sets was probably the Cotswold system, which had an enviable reputation! My own design sold in numbers that exceeded my expectations, but I was never going to get rich from it! 😉 I still get asked to service systems from time to time, and usually, all that is needed is new batteries and maybe the pots cleaning!

 

However, it was always going to be more expensive that 27 or 35 MHz gear, and once we got the 35 MHz allocation, the need for it died. Also, because 459MHz was/is unique to the UK, none of the major international manufacturers was interested.

 

The Reftec was problematic by design. The whole point of UHF was to get away from the interference issue on 27MHz. The problem with the Reftec was that the receiver was a double superhet that used 27 MHz as the first IF frequency! This was compounded by putting the receiver in a plastic case! Whilst it wasn't susceptible to distant CBs, it most certainly WAS susceptible to the surrounding 27MHz model control transmitters when you were carrying the model out to the flight-line! Add to that poor quality soldering, and Reftec did a lot of damage to the reputation of UHF systems.

 

After Reftec went bust, I managed to buy a set cheap from someone who bought up the remaining stock. I managed to get it working up to a point, but gave up after a component fell of the receiver board in flight! The model crashed into a bush, with minimal damage, but a clue as to the problem came when I shook the receiver, and it rattled!

 

Re-soldering the errant component (and a few others!) restored operation, but I eventually sold it to someone who wanted it for a boat. There was less chance of it doing any damage there....!

 

--

Pete

 

[Andy Stephenson]

I used my 2 channel Vendene/Reftec set for 1/12 carpet car racing in the 80s where there were a raft of other 27MHz TXs on in close proximity with no problems at all. I changed to UHF for this branch of the hobby because of all the interference between 27MHz sets not because of CB.

[Peter Christy]

Then you were very lucky!

 

Someone I knew bought a Reftec for car racing at the world champs in Monte Carlo, many decades ago. He arrived there to discover that the local TV station transmitted on 459 MHZ.... (Not the fault of Reftec, but there is a sequel...)

 

On arriving back home (having borrowed some 27 MHz gear out there) he went to re-install the Reftec receiver, only to find it was dead. On opening up the receiver case, a transistor had fallen off the board! All three solder joints holding it in place were "cold"!

 

My own experience with the one that I briefly owned showed erratic control jitter when carrying it from the pits to the flight-line, past other 27 MHz transmitters. I also had to be careful to land and take-off a short distance away from everyone else for the same reason.

 

I still fly my own prototype 459 MHz system in my oldest Lark helicopter. Must be 40 years old, now! The only time its let me down was when the receiver aerial lead fractured after some 15+ years use. Even then, I retained enough control to get it down with minimal damage. That lead is now secured with silicone sealant... (Production receivers used a different case and didn't suffer the problem, for those still using one!)

 

--

Pete

 

[Andy Stephenson]

I knew there was a good reason why I never had any trouble with all the 27MHz floating around. I just hauled this receiver out of a junk drawer and guess what I found. It is indeed a dual conversion but the oscillator crystal says 10.245MHZ which almost certainly makes the first IF 10.7MHz and the ceramic filter says 455kHz. So it was conventional set up.

See all that crazy 80s component jungle.

[gangster]

12 minutes ago, Andy Stephenson said:

I knew there was a good reason why I never had any trouble with all the 27MHz floating around. I just hauled this receiver out of a junk drawer and guess what I found. It is indeed a dual conversion but the oscillator crystal says 10.245MHZ which almost certainly makes the first IF 10.7MHz and the ceramic filter says 455kHz. So it was conventional set up.

See all that crazy 80s component jungle.

I have just been doing the maths on the re image,oscillator harmonics etc and believe there could be other reasons for you not having issues on 27.  Ie good installation and good flying. I am not sure that 27 MHz CB was as big an issue as some like to think. 40 odd years later with the rock solid links modellers are still blaming interference.  I am willing to believe tha 99% of incidents blamed on interference are modeller instigated. Poor installation, battery issues switch harness corrosion etc etc etc.  in 40 odd years of RC flying, involved a huge number of “black bags” probably hundreds of crashes ranging from no damage to total write offs I have only had one issue that I could put down to interference. That was due to switch on by someone without the peg.  As for dual conversion that was only advantageous on 72MHz with certain combination of channels. 

[Peter Christy]

Andy: That doesn't look much like a UHF receiver! (Un)fortunately, I no longer have a Reftec receiver for comparison, but I seem to recall it had a few helical filters in it.

 

The way the Reftec receiver worked was weird. 459 divided by 27 gives 17. So if you started with a 27 MHz crystal, and multiplied it by 16, you got 27 MHz below 459MHz, which gave you a first IF of - Ta-Da - 27 MHz. By careful choice of receiver crystal frequency, you could then use that same 27 MHz crystal against the 27 MHz IF to derive a 455 KHz second IF.

 

In many ways it was quite clever, as you only needed one crystal to generate both IFs. The downsides were that 1) the first IF was 27 MHz and 2) neither IF was particularly accurate - they both varied slightly depending what channel you were transmitting on. This meant that the receiver was "sloppy" - ie, it was not very selective, as it had to cater for a varying 2nd IF.

 

As far as I recall, they only ever offered the even numbered channels (50 KHz channel spacing) to get around this problem. This wasn't much of an issue, as there weren't that many sets out there. Very few clubs had more than one on their flight-line! 20 channels was more than enough, and a big improvement over the six or seven available on 27 Mhz. (Ignoring the "split" frequencies on 27 MHz, which were only introduce shortly before 35 MHz became available.)

 

The early Reftec transmitters (the ones with the helical aerials) had NO FILTERING of the transmitter output - other than the tuned aerial! The first time I got one on a spectrum analyzer, I was horrified to discover that it was splattering right across the 459 MHz band and beyond! The later ones with the rod aerial were much better, though its just as well that most clubs only had one Reftec set at most! It would have been interesting to see two operating in close proximity!

 

My own set was designed to be 25 KHz channel spacing from the outset, and was quite happy at that channel spacing, using 10.7 MHz and 455 KHz as the IFs. 10.245 MHz crystals (used to derive 455KHz from 10.7 MHz) were readily and cheaply available, as were 10.7 MHz crystal filters (MUCH tighter than ceramic ones at that frequency) for the first IF, and 455 KHz ceramics for the second.

 

If I were doing it again today, I would do things slightly differently. Crystals accurate enough to allow crystal swapping were very expensive. This was rarely a problem, with 40 channels available, but for a commercial item, you had to be prepared for it. Nowadays a synthesised oscillator would offer better performance cheaper, both in the Tx and in the Rx, but back then we worked with what was generally (and cheaply!) available.

 

To give you some idea of UHF Rxs, here's some pix of mine:

 

The one in the middle is my original prototype (still flying!) with the Rx board underneath, and the decoder board on top (note the hand drawn PCBs!) The one on the left is a micro version made by Peter Valentine (of Lark Helicopter fame), and the one on the right is the single board version - the last one we made.

 

--

Pete

 

[Andy Stephenson]

Pete,

I can assure you it is a 459MHz receiver. I would imagine it was designed specifically for surface use which is why it has a different conversion system that would work in a crowded 27MHz environment. It used a main crystal in the 74MHz region. I didn't like the helical Tx antenna so I changed it for rod antenna. I didn't have access to a spectrum analyser so it was a bit of educated guess work. Crystals were swappable in these sets and there were no problems when doing this.

 The system worked well enough with other similar sets in close proximity but it did require some extra suppression when used with electronic speed controllers of the day. You can see the ceramic capacitor I added to the board next to the servo connectors which fixed the problem of glitching from interference from the ESC.

[Peter Christy]

All I can say is that it doesn't look like any of the Reftec receivers I've seen before. Are you absolutely sure it was a Reftec?

 

74 Mhz (or thereabouts) is what I used in my receivers to get to 448 MHz (459-10.7).

 

The helical antennas actually provided a pretty good impedance match at 459 MHz. I've actually got one - think it came from a Cotswold system - and it was a better match than a rod antenna. The rod was cheaper and easier, though and worked well enough!

 

Just before they went bust, they came out with a modular system. Never managed to get my hands on one, but I guess its possible they did a complete re-design, late in the day. Certainly too late to save them!

 

Yes, Reftec did use swappable crystals, but got away with it because of the "sloppy" receiver (not very selective). I had to go to military spec crystals (at some expense!) to achieve the same with a "tight" receiver. Even then, we had about a 15% rejection rate on crystals!

 

--

Pete

 

[Andy Stephenson]

Pete,

The crystal says on it "REFTEC LANITZ" and I believe the transmitter used the same construction method as Reftec with a formed metal front and a vac-formed ABS back secured with a single screw. I'd have to have a major search around to show you the one I had.

It was manufactured under the name Vendene which we understood to be a trade name of Reftec for the 2 channel ground based system.

[Peter Christy]

Well, it looks as if they did a complete re-design of the receiver for that system, then! It looks nothing like the original Reftec, and that's a good thing!

 

Looking closely at the picture of your receiver, I can see ceramic filters for both 10.7 and 455 KHz IFs. I used a crystal filter for the 10.7 as it provided a much narrower filter, though the "stop-band" rejection wasn't so deep. I felt it was necessary to prevent the second stage mixer from being overloaded due to the possible close proximity of other 459 MHz transmitters and the gain of the 1st IF stages. For the second stage I used the same type of ceramic filter used in 27/35MHz FM systems, but for a slightly wider bandwidth (25KHz channel spacing instead of 10KHz).

 

Certainly the 10.7/455 design would not be susceptible to 27 MHz interference, but I can assure you that the original Reftec design most certainly was! Interestingly, the later transmitters (with the rod aerial) also had some proper filtering of the output stage, to avoid splattering all over the band, so they obviously did become aware of some of the short-comings of the original design.

 

Looks like they learned their lesson, but a bit too late...

 

--

Pete

 

[Brian Dorricott 1]

The above topic is music to my ears this is what the E in RCME is all about . I remember dabbling around in the workshop of my then employer who supplied radios that every copper in London had on him for something I could convert to 459Mhz for RC use but it was all to big . It was all a bit over engineered for RC use but beautifully made with helicoils in the front end , high spec crystals and every module shielded in tinplate and no worries about any spurious from those Danish designed lovelies . Nice to hear a proper retro radio discussion by people who understand the issues and I would hazard a guess that some of you were radio amateurs as well judging by your knowledge .

[Andy Stephenson]

Look what I found, it's the RF board from a discarded 2 channel Tx, it's obviously a modified 433MHz module. There's no crystal so I don't know what exact type it used.

 

Could it be that they used the marketing name Vendene for this design to avoid associations with the reputation they had under the name Reftec.

[Martin Harris - Moderator]

1 hour ago, Brian Dorricott 1 said:

I would hazard a guess that some of you were radio amateurs as well judging by your knowledge .

At least one of the contributors was more of a radio professional!

[Peter Christy]

That does actually resemble my recollection of the later Reftec Tx module. You can clearly see two helical filters in there - they look like two IF cans stuck together and have white nylon slugs for tuning. This significantly improved the "cleanliness" of the transmitter, compared to the original helical aerial model.

 

Its a long time since I looked at one, but that T433 does ring a bell. Since the legal frequency in Europe was 433/4 MHz - rather than our 459 MHz - they could have been aiming for a larger market, and simply retuned them for the UK. I retuned quite a few Multiplex UHF sets for Roy Lever back in the day. Or they could have bought them in from outside, as you suggested. I simply don't know!

 

The Multiplex sets were generally pretty good, but not easy to tweak for 459 MHz use! Some of the tuning coils had very fine (1/16") ferrite rods attached to a plastic slug for tuning. I had to carefully sand these down a bit to shorten them and raise the tuned frequency! A very delicate operation, as ferrite is very brittle, and we couldn't get spares!

 

The receiver was very large, and used a 3rd overtone crystal running at around 115 MHz for 459 MHz operation! VERY expensive to get made! Once going, it worked well.

 

I ended up throwing my Reftec Tx in the bin and gave the receiver to a boat modeller who wanted a spare!

 

--

Pete

 

[Peter Christy]

Update: Saying I threw my Reftec in the bin jogged a vague memory! I was sure I kept the RF board out of it, dumping the encoder and case.

 

I've just had a look in one of my junk boxes, and look what I found:

 

It looks just like your board! You can even just about make out the T433 up by the yellow sticker!

 

As I said, this was from one of the later Reftecs with the rod aerial and was much, much "cleaner" than the original one.

 

Brian: I was never a radio amateur, but my qualifications and jobs were in electronics.  I did spend some time working on VHF and UHF broadcast TV transmitters, doing a spell at Holme Moss, the 405 line transmitter for the north of England and Wales. At Holme Moss we were also responsible for the BBC transmitters at Emley Moor (on top of the next hill over). Emley Moor was an IBA site, and the BBC transmitters were operated by remote from Holme Moss.

 

Most of my career was in video tape, which also involved some interesting RF work. The quadruplex VTRs that were the backbone of the broadcast TV industry for 3 decades were miracles of precision mechanical and electronic engineering. Google "Ampex VR2000" or "RCA TR70" to see the kind of things I used to work on. 😄

 

--

Pete

 

[Brian Dorricott 1]

As I suspected pro's and hams as I am . My career started when a car telephone was a roughly 45x30x15cm box that went into your car boot and you worked it from a little control box on the dash and you called the operator to dial the number , today it sits in your shirt pocket . Just as in modelling electronics it got smaller every generation and more complex until by the time cellular came along we didn't open them anymore just sent them to a specialist workshop . We use 2.4Ghz for our models the highest I ever worked on was 1.5/1.6 Ghz analog microwave systems for the water industry in the North East , a few watts of that went a long way but they were very directional and gainy aerials .

[Andy Stephenson]

Back on the subject of R/C technology, I found this fascinating thread on RCU some while ago...  Who really invented Digital Proportional?

And why was it never patented?

 

[Outrunner]

3 hours ago, Andy Stephenson said:

Back on the subject of R/C technology, I found this fascinating thread on RCU some while ago...  Who really invented Digital Proportional?

And why was it never patented?

 

Err, I thought the topic was LHF's old radio set he would like to sell.

 

[Andy Stephenson]

Outrunner,

 

Oh do keep up, the thread has drifted quite a lot since the beginning, it happens!