Look what I dug out of the internet

[Albert H]

Busted! "Bob" was a broadcasting pseudonym I used for a long time in the 70s and 80s. (And no - NOT Bob Tomalski!)

[3metrejim]

Busted! "Bob" was a broadcasting pseudonym I used for a long time in the 70s and 80s. (And no - NOT Bob Tomalski!)

I think it's about time I apologised for being quite a d**k. I probably remembered reading it all the first time and managed to forget that now there is a new generation asking the same questions.

Quite something to read those old messages again, I never posted to those forums, just read the messages using the ancient outlook express - yes I know, you can't stand windoze...

[radium98]

3metrejim IS an ADD+ to the forum members . like few of my freinds .

[MiXiN]

I have a "Veronica" PLL3 board here, but was under the impression it was a Hollings built board.

Even though it locks, the PLL unlock LED also always stays illuminated, so I need to look for the fault.

At what stage of PLL board revision did he take over?

[Albert H]

Hollings' version of the PLL has a missing "balance" transistor. There should be four transistors in the oscillator stage - the two that generate the ½f signals and two buffers - one of which feeds the PLL and the other just provides a balancing load to ensure that the two signals are exactly equal, thereby giving the cleanest possible signal at the output frequency when combined. The PLL Pro III uses a pair of FETs for the buffers, earlier versions use BF199s (or even BF494s on the really early ones).

Hollings didn't understand the operation of the oscillator, and how essential accurate balance actually is. If the balance is degraded, lots of ½f breaks through, and there can also be an amount of 1½f as well.....

[Albert H]

I think it's about time I apologised for being quite a d**k.

No problem. "Bob" was instrumental in the original creation of BIAS Comms. BIAS was an acronym (of course) and stood variously for "Bodge It And Scram" or "Bung In And Scarper"! We actually had a limited company registered in Urbana, Italy, and made a range of PA units for the amateur bands (and for Band II), and had a range of broadcasting gear that was sold in quite huge amounts in much of Europe (and beyond). Most of us met at University in the 60s and 70s, and most of us had "run ins" with the telecommunications or broadcasting authorities in various parts of the world. All of us were professional engineers (of one sort or another) and many of us remain in close touch all these years later....

[sinus trouble]

Haha! This Historic knowledge is exactly what i used to (annoyingly) hassle engineers for when i was a kid!

This is not a battle for who is right or wrong! It is a discussion!

I have argued with ALOT of others on this Forum! Not once have i taken it as personal!

Its all good fun!

[Albert H]

Sinus - your attitude is laudible! Knowledge should be shared. I've been a teacher (mostly part-time) ever since my Uni days. I taught remedial mathematics to first year University engineering students while I was at college to pay my way through.....

A lot of real radio engineering is close to being a "black art". The interdependence of components - even their physical alignment - is often just down to experience and experimentation. It was always an amusing exercise to give an apprentice an RF circuit to lay out on a PCB. They'd almost always go for the most compact, neatly laid out, audio-type PCB design. It was also fun too to etch their board, have them populate it and then measure the results against a properly laid out example. They invariably got it completely wrong, but they learned a lot from the exercise.....

[MiXiN]

Hollings' version of the PLL has a missing "balance" transistor. There should be four transistors in the oscillator stage - the two that generate the ½f signals and two buffers - one of which feeds the PLL and the other just provides a balancing load to ensure that the two signals are exactly equal, thereby giving the cleanest possible signal at the output frequency when combined. The PLL Pro III uses a pair of FETs for the buffers, earlier versions use BF199s (or even BF494s on the really early ones).

Hollings didn't understand the operation of the oscillator, and how essential accurate balance actually is. If the balance is degraded, lots of ½f breaks through, and there can also be an amount of 1½f as well.....

Thanks for the reply, Albert.

Upon inspection, the Oscillator stage in my PLL3 only has 3 Transistors like the version above, so it's an Hollings variant.

With regards the PLL unlock LED not fully extinguishing even when the board is in lock, where do you think I should start looking for the fault? I'm thinking a leaky collector/emitter junction on the Transistor that drives it, but apart from that I'm not sure where to look?

When in lock, the PLL lock LED is fully lit, and the PLL unlock LED is around 50-60% brightness simultaneously.

Operation appears fine, but it's just an annoyance.

[Shedbuilt]

I got a similar 1 watt exciter with the improvements you describe around 90/91 from S I, it came on a double sided tinned pcb, BSX20's in the oscillator, buffer, doubler, a 2n4427 output, a yellow toko coil in the doubler stage, the buffer i seem to recall had a hand wound 8 turn coil.
I don't think S I designed or built the one i recieved as when i got a second exciter from him it was a rats nest of components on a scrap of copper clad board that didn't work, i think he'd tried to copy the one he sent me, it could have been designed/made by roger as they later went onto work together, not 100% sure who designed/built it as i've never seen another, i copied the circuit and pcb layout and made a couple.

The tinned version you described, sounds like the exciter boards which D.B used to knock out.

[Shedbuilt]

From my pirate memories of the mid 80s, Pyers, Albert, and at least one person I remember around Albert, were all held in high esteem. All were well known to the serious players, Pyers was probably better known to the newer comers to the scene, because, in his early days at least, he often made it his business to introduce himself to them. It wasn't unknown for Pyers to track the location of a direct transmitting station, and knock on the door. Albert and co tended to keep their profiles somewhat lower.

[Shedbuilt]

Hollings' version of the PLL has a missing "balance" transistor. There should be four transistors in the oscillator stage - the two that generate the ½f signals and two buffers - one of which feeds the PLL and the other just provides a balancing load to ensure that the two signals are exactly equal, thereby giving the cleanest possible signal at the output frequency when combined. The PLL Pro III uses a pair of FETs for the buffers, earlier versions use BF199s (or even BF494s on the really early ones).

Hollings didn't understand the operation of the oscillator, and how essential accurate balance actually is. If the balance is degraded, lots of ½f breaks through, and there can also be an amount of 1½f as well.....

Thanks for the reply, Albert.

Upon inspection, the Oscillator stage in my PLL3 only has 3 Transistors like the version above, so it's an Hollings variant.

With regards the PLL unlock LED not fully extinguishing even when the board is in lock, where do you think I should start looking for the fault? I'm thinking a leaky collector/emitter junction on the Transistor that drives it, but apart from that I'm not sure where to look?

When in lock, the PLL lock LED is fully lit, and the PLL unlock LED is around 50-60% brightness simultaneously.

Operation appears fine, but it's just an annoyance.

I'm not sure on this, but I think it may be normal for the unlock LED to stay partially on. Are you (frequency tuning wise), in the middle of the oscillator's lock range ? I tend to doubt a leaky LED driver transistor, especially as the LED brightness is varying. I'm more inclined to think that the transistor is being held partially on.

[Shedbuilt]

I got a similar 1 watt exciter with the improvements you describe around 90/91 from S I, it came on a double sided tinned pcb, BSX20's in the oscillator, buffer, doubler, a 2n4427 output, a yellow toko coil in the doubler stage, the buffer i seem to recall had a hand wound 8 turn coil.
I don't think S I designed or built the one i recieved as when i got a second exciter from him it was a rats nest of components on a scrap of copper clad board that didn't work, i think he'd tried to copy the one he sent me, it could have been designed/made by roger as they later went onto work together, not 100% sure who designed/built it as i've never seen another, i copied the circuit and pcb layout and made a couple.

One of these ? (although this has much the same oscillator as the one in the schematic). If it had a more conventional colpitts oscillator, it may have been one of a run of boards which S(I)+N had made....

DBBoard.jpg

[Shedbuilt]

I got a similar 1 watt exciter with the improvements you describe around 90/91 from S I, it came on a double sided tinned pcb, BSX20's in the oscillator, buffer, doubler, a 2n4427 output, a yellow toko coil in the doubler stage, the buffer i seem to recall had a hand wound 8 turn coil.
I don't think S I designed or built the one i recieved as when i got a second exciter from him it was a rats nest of components on a scrap of copper clad board that didn't work, i think he'd tried to copy the one he sent me, it could have been designed/made by roger as they later went onto work together, not 100% sure who designed/built it as i've never seen another, i copied the circuit and pcb layout and made a couple.

Or maybe one of these ?

[shorty]

Looks similar to this one but without the active preemph circuit, it had a colpitts oscillitor, the buffer circuit had a 8 turn hand wound coil, but apart from that the rest of layout looks identical from memory, the one i got maybe an early version.
I haven't been able to find the copy of the pcb layout i made using transfers, tape and ink for the ground plane, it must be long gone in one of my clearouts.

[Shedbuilt]

Looks similar to this one but without the active preemph circuit, it had a colpitts oscillitor, the buffer circuit had a 8 turn hand wound coil, but apart from that the rest of layout looks identical from memory, the one i got maybe an early version.
I haven't been able to find the copy of the pcb layout i made using transfers, tape and ink for the ground plane, it must be long gone in one of my clearouts.

To me, like the “Horizon” schematic, that oscillator configuration is Clapp; rather than Colpitts (LC in series to ground, rather than inductor to ground, with a capacitor in parallel); albeit given that Clapp is generally considered a variant of Colpitts. The ratios of the capacitors, is more like generally used in Colpitts though. With those LC ratios, it’s never clean. I’ve not played too much with LC ratios in that oscillator configuration, but changing to a more conventional Colpitts configuration (lower value inductor, to ground, with some reduction in some of the capacitances too), yields a much cleaner carrier.

[Albert H]

One of these ? (although this has much the same oscillator as the one in the schematic). If it had a more conventional colpitts oscillator, it may have been one of a run of boards which S(I)+N had made....DBBoard.jpg

That looks like the board that Bonex used to sell in the late 80s / early 90s. The Acton branch of Bonex was where several of us would meet up on a Saturday afternoon to swap war stories and occasionally buy and sell gear. At one point, there was a competition to see who could come up with a kit exciter that "anyone" could build and get going. That board was the only real entry (from DW as I recall), as most of the others didn't get beyond the "lands on copperclad" stage!

I remember doing a stereo coder board at the time, that included some (slightly) unusual resistor values and a couple of odd electrolytic capacitor values - they were not critical at all - the next E12 value up or down would have been equally OK - but it was really funny to find that Maplin and Marshalls both ran out of those weird values..... The amount of brainless copying that went on at that time was astonishing!

[shorty]

To me, like the “Horizon” schematic, that oscillator configuration is Clapp; rather than Colpitts (LC in series to ground, rather than inductor to ground, with a capacitor in parallel); albeit given that Clapp is generally considered a variant of Colpitts. The ratios of the capacitors, is more like generally used in Colpitts though. With those LC ratios, it’s never clean. I’ve not played too much with LC ratios in that oscillator configuration, but changing to a more conventional Colpitts configuration (lower value inductor, to ground, with some reduction in some of the capacitances too), yields a much cleaner carrier.
[/quote]

Has you say your schematic is a clapp oscillator, the first one i got from SI was inductor to ground, it may have been a slight redesign of a db board.
The reason i thought it wasn't a SI design/build the first one i got from him was on a professionally made tinned pcb that worked, it was stable for a vco exciter for that time, the second exciter a week later was a rats nest of components on a small scrap of copper clad board that didn't work, i assumed he'd had a go at copying it.

[Shedbuilt]

That looks like the board that Bonex used to sell in the late 80s / early 90s. The Acton branch of Bonex was where several of us would meet up on a Saturday afternoon to swap war stories and occasionally buy and sell gear. At one point, there was a competition to see who could come up with a kit exciter that "anyone" could build and get going. That board was the only real entry (from DW as I recall), as most of the others didn't get beyond the "lands on copperclad" stage!

Bonex did sell that as a kit at one time; as well as a stereo coder. I think both ceased at or before the time they moved, from their old location by the park / green, to the industrial estate. I think both kits were from someone I’m sure we both knew, who lived out that side.

I remember doing a stereo coder board at the time, that included some (slightly) unusual resistor values and a couple of odd electrolytic capacitor values - they were not critical at all - the next E12 value up or down would have been equally OK - but it was really funny to find that Maplin and Marshalls both ran out of those weird values..... The amount of brainless copying that went on at that time was astonishing!

Yes. Then there was the stereo coder design which Elektor published. It used analogue mixing, PLL to phase lock the 19kHz and 38kHz. The main glaring error was in the pre-emphasis. They published the schematic and board layout, with active pre-emphasis, but without resistive bypass; so that the response just kept falling off below 3.183khz. I heard a few “it’s sh*t” “it’s got no bass” comments. That didn’t take too much thinking to put right.

[Albert H]

It's really funny - the amount of copying that went on. Way back in the late 70s we came up with a fairly simple doubler, doubler exciter, that kept the VCO at 21.8 to 27 MHz to avoid the use of an expensive (at that time) prescaler IC. We'd discovered that ordinary TTL would work at 5.6V without frying, and would go quicker than if it was run at 5V. The dividers were (usually) programmed 7490s set up to divide down to where the reference was. The reference usually used the cheapest crystal we could find that would easily give the reference frequency we wanted (often 4MHz). The phase comparator used a 7474 and a 7400, and a passive loop filter feeding into a transistor buffer.

The rig itself used BSX20 oscillator, buffer, doubler (to 40+MHz), then a pair of BSX20s for the second doubler, followed by a buffer / filter amplifier using a further pair of BSX20s, then a 2N4427 (we could get real ones in those days) or a little TRW 1 Watt CATV transistor, then a TP1028 or R5174 for around 8 Watts, followed by either a 2N6084, MRF238 or (rarely) a BLY90. Occasionally we'd build a PA with a pair of output transistors (if it was for a bank holiday broadcast when Gotts & Co usually wouldn't bother) and get as much as 110 Watts!

The very earliest versions of the rig used a free-running oscillator, and by careful selection of the capacitors in the oscillator, we could get stability to around 20 kHz over a fairly wide range of temperatures (not bad at 96 MHz output!). We sprinkled trimmers throughout the circuit - they were really cheap in those days and allowed you to squeeze the last bit of gain out of a stage!

I recently was asked to fix one of these really early transistorised rigs, and found that it was one of the earliest PLL jobs, with a pair of 2N6084s in the final, and using a couple of reverse-biased 1N914s for the mod varicaps. I was delighted to find that the rig itself still worked - the paint-pot sized supply smoothing capacitor had dried out, gone short and had blown the secondary fuse in the power supply. A new capacitor and fuse, and it still generated about 75 Watts on 96.4MHz! Some of the copperclad had started to go green! I didn't remember building that particular one, but it still had my little "trademark" under the exciter PCB. The rig was 44 years old!!! It even included a basic compressor (using a light bulb and an LDR) to prevent people turning the mod up too high and making it sound horrible.

We used to find that exciter circuit everywhere - often running without the PLL. It was copied hundreds of times!