Opinions on another driver?

[shuffy]

I always used doubler (even tripler) based exciters for the longest time. It was easy to prevent RF feedback problems from the PA to the VCO, and it was also easy to get cheap 74HC CMOS to work at 54 MHz.

Interesting stuff as ever, Albert. I've used single and double tuned LC doublers, but as I said earlier in response to Mixin, both need tuning and setting up with an analyser (and careful screening, as you can end up susceptible to taking off when close to resonance). I can see how you get around it with the dual common base (or gate) arrangement but it's more components, transformers, looking for balanced devices etc so I just made the call that for my application, there was nothing lost in setting up rigs manually. Diode doublers have never been an option, I had too many bad experiences with those horrible SBL1/SRA1 things.

My earliest exciter efforts, before I did any commercial electronics, were on-frequency and in the absence of the internet as a teenager I learned from PMR service manuals. When the penny dropped about how a PLL worked, my first effort was (I think) a 4069 crystal oscillator at 2MHz divided by 2 with a 4013, into a 4046 and followed by a passive loop filter with quite a long time constant. The on-frequency exciter was derived from, IIRC, a TAIT Band III VCO modded for 100MHz into an SP8629 prescaler, into the 4046. The phase comparison therefore took place at 1MHz. Crude but it worked.

I used the 2MHz/4013 arrangement rather than 1MHz because it was quite a lot more expensive to get crystals cut for 1MHz. I had the rocks cut by Quartslab, 2MHz ones were far cheaper and I always presumed, aroused less suspicion (not that I ever had a problem with them during my time on the AM bands )

The VCO was followed by a couple of buffers also from the TAIT and onwards to a variety of PAs, usually modified PMR. This stayed the same for a few years, but the synthesizer got more sophisticated (MC145151, I possibly still have a very battered photocopy of a cheat sheet from R+EW). I think I got into frequency multiplier chains in the mid 90s after suffering feedback with the PMR VCO which as you say possibly wasn't built to the same exacting standards as TAIT had done...

[Albert H]

My earliest PLL used a Plessey SP8629 to divide by 100 from the output frequency. then that fed a 4024 to divide by a further 16. The Phase comparator worked at around 60kHz, and used a quad NAND gate (4011) and a 4013. The three "spare" NAND gates were used for locked / unlocked detection. The crystals I used were (usually) 4MHz, divided down to the reference frequency, using a 4040 and diode programming (or a 4068 eight-input NAND gate).

My VCO used an SL560 IC - if you have a look at the internal circuit, you'll see that the base and emitter of the first transistor come out on a couple of pins, so it was easy to make a nicely buffered Colpitts oscillator. It gave about 150mW out, which was ideal for driving a BGY33.

The whole 20 Watt rig was built on to a big heatsink, with the VCO and the crystal oscillator parts of the PLL on a separate PCB which was stood off the rest of the rig with a couple of pieces of ceiling tile. I made (I think) about a dozen of these early PLL rigs, then I discovered the joys of half frequency generation and the four-chip CMOS PLL. I also stopped using the BGY33 because the cheap source of them dried up.

When I got the balanced doubler really cracked, I had the first 200 PCBs etched. They were nice quality, double-sided and slightly smaller than the RDVV boards. Lots of them were "lost" over the years to the authorities. They were distinctive on the air because of their utter stability (most stations were still drifting around with VFOs) and their fabulous mod. Many stations that used them commented on how good they sounded.

Quite a lot of them are still in use - albeit with a different PLL, but the same RF strip - in the Far East and Eastern Europe. I received an enquiry just last week about how to change the frequency on one of the earlier, diode-programmed ones!

I reverted to "at frequency" when I went to work in the 'States, designing and manufacturing 19" rack-mounted exciters. Those guys call anything up to about 100 Watts "an exciter", since they're always used to drive big PAs - often valved ones.

The standard box we did in the 80s used a parallel-programmed Motorola PLL IC and an ASIC (a specially programmed, dedicated processor) to control the PLL and carry out the performance monitoring. The ASIC also drove the front panel LEDs and would indicate the output frequency, forward and reflected power, heatsink temperatures and modulation depth. The ASIC came from Panasonic and was specially made at their chip fab in Kobe, Japan. This was the precursor of using a PIC for the same purpose - and was a hell of a lot more expensive than a PIC!

There was also a dedicated stereo coder and audio processor unit that was made to directly compete with the Inovonics and Orban products. I think we did a pretty good job, and stations using this system used to consistently be the "loudest" in their vicinity.

There were also some rack-mounted PAs - at 500W and multiples. They used four TRW transistors per module and were pretty unburstable. The biggest practical solid-state rig was 5kW - above that, you had to go with bottles.

[MiXiN]

Do you sell your drivers to the general public, or are they just for your own use mate?

Mixin, you must have more drivers than Finglands.

Neither, really. I make them individually and the way they're set up is specific to the need. The PLL controller chip, for example, is programmed and then soldered in place, so it's hellish difficult to change frequency. This is to keep the expense down. There's no LCDs, no DIP switches, no diodes or solder bridges, just an 8 pin SMD device. I know it might not sound flexible but for a station using one frequency, it doesn't need to be! Also you need an analyser to set the doubler up properly. There are none of these in the wild that didn't start life in the TX they were designed to go in.

If I was going to design something anyone could use to make a rig by mixing and matching components, I'd probably end up with a broadband on frequency design and I'd need to redesign the PLL controller. Actually I do have some part written code intended to use the same 8 pin PIC and PLL but allowing the frequency to be set using a button and an LED. Other stuff's getting in the way of finishing it though...

Hahahahaha, yeah, I've got a few drivers.

I tend to buy some & have others given, then have a tendency to test them out into a dummy load for 10 min's & fling them in a box with all my other impulse purchases.

I'm turning into a bit of an hoarder. Lol.

[shuffy]

Mixin, you should focus your energy into other areas, like getting that thing on air.

Albert, You can tell we were both building stuff in the 80s with whatever we could get our hands on, eh. As you know, I didn't stay in commercial electronics. For everyone else's benefit - I had a fair crack, and earned the distinction of having been whizzed by (not naming any names but) a large British Telecommunications concern, a large British Corporation and a geriatric Antipodean megalomaniac who took over the company I was working for and promptly binned it. I did however make off with some state-of-the-art DACs, so up yours. I messed around in IT for a couple of years and then briefly tried to get back into commercial electronics, but the scene had changed quickly and was moving further away from the reason I got into it in the first place.

So I packed it in and became a rock god, and I intend to do that until the rest of my hair falls out.

[Albert H]

I had to leave the UK to stay in commercial electronics - first to Japan, then the USA and even New Zealand (for a 3 month design project). Real Engineering has largely died out in this country. The only manufacturer of broadcast gear is Roger at Broadcast Warehouse, and his stuff isn't really ever taken seriously in most of the world.

We still have a couple of very small scale manufacturers of weird laboratory instruments, specialised computers, and guitar electronics. The rest of British manufacturing was finally killed off by a combination of Blair and the EU - it became much cheaper to manufacture stuff in Eastern Europe or the Far East (and import through Spain or Italy to avoid the Duty!).

The Soviets got what they wanted - a crippled UK, ruined by appalling educational standards, insane "political correctness", radical feminism, religious tolerance and an underclass of welfare claimants.

It should be obvious why I do most of my business abroad - people in this country can't afford to pay for the kind of service I (and my company) can provide, and are happy to hire the big conglomerate "engineering" companies to occasionally wipe gear down and call it "maintenance". This is why the infrastructure of this country is in a perpetual state of disrepair.

[shuffy]

I know we're getting off topic here but I largely agree (except about feminism, political correctness and religion, all of which I ignore) and I suspect there are probably a number of frustrated engineers out there who can't find a suitable manifestation of their vocation. These are probably slightly older now, from what I can see the kids aren't taught about engineering, either hardware or software (The youngest member of my family looked scornfully at me when I asked her what LOL meant and said "didn't you do the IT course". I wonder what you get in your GCSE's for knowing SMH.)

I used to work in a research lab. When the managers had gone home, you had: me designing my FM transmitters (The offices had huge high ceilings, and I used to string a dipole up into the free space to test the things with - we had a minicomputer in there doing something vaguely important which used to go down every time I fired one of my creations up), another guy knocking out Filmnet decoders (analogue subscription satellite film channel employing typical pedestrian scrambling of the era) to flog to his mates, and a third guy making CB linear amplifiers out of three 813's in parallel ("You're coming through like the BBC" - German CB'er).

I didn't last very long - actually I failed an interview for my own job - but I doubt the other two did either because when I approached the same group for a job a couple of years later, I was disappointed to find there wasn't a soldering iron in sight - everything was designed on CAD workstations and manufactured offshore. Actually there were also a lot of offshore contractors doing the design work too. Like I said earlier, that wasn't the reason I sought a career in commercial electronics so I decided I was probably better off out of it.

Anyway, I like a good rant, but that's it from me! I feel a bout of metal bashing coming on!

[Albert H]

I know we're getting off topic here but I largely agree (except about feminism, political correctness and religion, all of which I ignore)

Sadly, I can't ignore the three - I do quite a lot of work for a Government department, and we're meant to adhere to the same standards as their directly employed staff. We have to tolerate irredeemably stupid women who've been promoted well beyond their abilities simply because of their gender; we have to behave in the same docile, politically correct, moribund manner that their own staff do; and we have to "respect" the religious sensibilities of their useless staff who take endless "religious holidays" (in addition to their mandated 38 days per year!), so that they're seldom in the office if you need to talk to them!

I worked for that very Big Telecommunications outfit at their research labs out in Suffolk. I had a nice office with views over farmland, and a big adjacent workshop / laboratory. I was given a design project and a "due by" date and left to get on with it. It was a great job, and allowed plenty of time for design and experimentation with various bits of broadcasting equipment. I also had very comprehensive instrumentation, so could actually measure the characteristics of a Lecher Line (for example)! They also paid me a hell of a lot of money - which was nice - and they never quibbled about the components I was buying in.

Eventually, I left when they demanded that I worked on "security" equipment for the Military..... Having enjoyed an expensive lifestyle (and having an expensive wife and daughter) I had no option other than to set up my own business! Their insistence on me working on "defence" projects gave me the push I needed to get off my lazy backside and do some serious work!