Re: Look what I dug out of the internet
Posted: Sun May 21, 2023 1:14 am
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.
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....
Thanks for the reply, Albert.Albert H wrote: ↑Sun May 21, 2023 4:56 pm 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.....
shorty wrote: ↑Sat May 20, 2023 3:38 pm 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.
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.MiXiN wrote: ↑Mon May 22, 2023 4:23 amThanks for the reply, Albert.Albert H wrote: ↑Sun May 21, 2023 4:56 pm 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.....
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.
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....shorty wrote: ↑Sat May 20, 2023 3:38 pm
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.
Shedbuilt wrote: ↑Tue May 23, 2023 10:33 amOr maybe one of these ?shorty wrote: ↑Sat May 20, 2023 3:38 pm
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.
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.shorty wrote: ↑Tue May 23, 2023 2:36 pm 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.
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!
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.
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.Albert H wrote: ↑Tue May 23, 2023 4:32 pm
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!
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 wrote: ↑Tue May 23, 2023 4:32 pm
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!