Old Rig

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Albert H
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Re: Old Rig

Post by Albert H » Mon Apr 22, 2019 1:22 am

Doubler stages are just Class C amplifier stages with the output filter (connected to the collector) tuned to twice the input frequency. A Class C stage will always produce harmonic energy, and you just select the harmonic you want! A tripler is the same thing, but with the tuned circuit tuned to three times the input frequency.

A doubler will usually only give out about 80% of the drive power, and a tripler is worse, giving out around 45% of the drive power. You'll usually have to add amplification stages after the frequency multiplier stage, but this is good since it allows you to use tuned filters to clean up the multiplier output.
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Re: Old Rig

Post by radium98 » Mon Apr 22, 2019 6:49 am

thank you.

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THE GOVERNOR
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Re: Old Rig

Post by THE GOVERNOR » Thu Apr 25, 2019 11:20 pm

[/quote]
Is that the best you can do! Its a legal requirement to label AC mains in all Electronic equipment.
Thanks for the Add, do you know what? I never have liked Strongbow! lol
Fucking Muppet! Go and do some more Photoshopping!
[/quote]


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Re: Old Rig

Post by Shedbuilt » Mon May 06, 2019 5:39 pm

teckniqs wrote:
Fri Apr 19, 2019 8:32 am
Looks to me like an old Bowman VCO (who's stopped building now) :whistle
I can see what you’re thinking. It bears a resemblance, but not the same design. This one’s more complex than the ones DB used to knock out.

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Re: Old Rig

Post by Shedbuilt » Mon May 06, 2019 5:51 pm

Albert H wrote:
Sun Apr 21, 2019 6:15 pm
Bonex sold a kit for a "1 Watt" VFO exciter that used a neat row of Toko S18 coils, but wasn't particularly frequency stable, and could be tuned up to deliver lots of different frequencies at the same time!
This was the VCO which Teckniqs mentioned. Bonex also sold an encoder kit - from the same source. I think they may have sold his ubiquitous Band 1 receiver as a kit too. The oscillator in that exciter design was problematic. The “close in” spectrum, could be improved a lot, with small changes to the oscillator. The rest of the exciter was bare bones, with just a single tuned doubler, and basic impedance matching at the output; no other filtration.

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Re: Old Rig

Post by thewoodstarr » Mon May 20, 2019 11:52 pm

teckniqs wrote:
Fri Jan 18, 2019 10:32 am
^^ With equipment like that, it's no surprise to see articles like this....

https://www.gazette-news.co.uk/news/551 ... air-alert/
That is one of my old Amp`s <1999 B4 we had proper PCB`s made, they have taken the lowpass filter out? Amazing that gear is still about. As for rest no idear who built that?

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Re: Old Rig

Post by thewoodstarr » Mon May 20, 2019 11:59 pm

THE GOVERNOR wrote:
Sat Jan 19, 2019 8:54 am
I believe it's from the 90s, when I get a chance I plug it in and see what it does, it looks like the PLL is wrapped up in tin foil. The builder is still about
Is he well he nicked my design, looking at it, its a copy.
That`s is not built by me.

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Re: Old Rig

Post by SamTheDog » Mon Jun 17, 2019 5:12 pm

THE GOVERNOR wrote:
Thu Jan 17, 2019 9:47 pm
20190117_213433.jpg
I wonder who made this ;)
Superb!... There used to be so many rigs like this back in the mid-late eighties... I have even buils ugly-bug-style rigs... Dave-Martins early rigs wer tiny pieces of PCB material super-glued on a piece of copper-clad.. But even back then a half-decent LPF was between the PA and output....
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Re: Old Rig

Post by SamTheDog » Mon Jun 17, 2019 5:17 pm

Shedbuilt wrote:
Mon May 06, 2019 5:51 pm
This was the VCO which Teckniqs mentioned. Bonex also sold an encoder kit - from the same source. I think they may have sold his ubiquitous Band 1 receiver as a kit too. The oscillator in that exciter design was problematic. The “close in” spectrum, could be improved a lot, with small changes to the oscillator. The rest of the exciter was bare bones, with just a single tuned doubler, and basic impedance matching at the output; no other filtration.
I still have one of those old BONEX stereo encoders... Bought a couple of them back in the eighties.
They were supplied in kit-form.... They were ok but the output is very low... Just a bit of a curiosity now...!
Use more modern stuff....
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Re: Old Rig

Post by SamTheDog » Tue Jun 18, 2019 5:43 am

here is one of my 1987 exciters... all of those tranststors and all for a watt... It's a free-runningosc
so drifts like a bitch too....
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Re: Old Rig

Post by Albert H » Wed Jun 19, 2019 2:42 am

If you replaced the 65pF yellow trimmer in the oscillator with a NPO fixed ceramic cap, the stability would be about a thousand times better!

My old VFOs used a single-gate FET and a bipolar buffer. They ran at one-third frequency, and the buffer went into a tripler stage, followed by a couple of stages of amplification and filtering for about a Watt out. Frequency stability was about 8 kHz over the first five minutes, and then as long as the temperature didn't change much, they would stay on frequency for hours on end.

As soon as cheap 74HC ICs became available, PLLs became easy. I started to use half-frequency oscillators, and came up with a really cheap four-chip, diode-programmed PLL (74HC4060 reference / divider, 74HC4020 to divide the 50 MHz by four, then a 74HC4040 programmable divider, and a 4046 for the phase comparator and loop filter). I also came up with a better phase comparator using a 74HC74 and some NAND gates, which would also give reliable lock detect output. The crystal was (usually) 4 MHz, since I got a job-lot of 20,000 of them in an auction!

Just to wind up a well-known London rig builder of the late 70s / early 80s, I built a fairly neat point-to-point exciter on a piece of copper-clad in a small diecast box. It delivered a Watt and had a very usual concealed circuit below the PCB - it was a "huff & puff" frequency-locked-loop that went in 100 kHz steps. As you turned the VFO coil core, it would "jump" up the band in 100 kHz steps, and if you set it on a frequency, it would stay there! The first part of the wind-up consisted of spraying the oscillator with freezer spray - it stayed on frequency. The next step was to warm it up with a hair-dryer.... it stayed on frequency.... The thing that gave it away was when it was grossly over-modulated, and it would "jump" to adjacent frequencies!
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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Re: Old Rig

Post by SamTheDog » Wed Jun 19, 2019 11:40 am

Albert H wrote:
Wed Jun 19, 2019 2:42 am

Just to wind up a well-known London rig builder of the late 70s / early 80s, I built a fairly neat point-to-point exciter on a piece of copper-clad in a small diecast box. It delivered a Watt and had a very usual concealed circuit below the PCB - it was a "huff & puff" frequency-locked-loop that went in 100 kHz steps. As you turned the VFO coil core, it would "jump" up the band in 100 kHz steps, and if you set it on a frequency, it would stay there! The first part of the wind-up consisted of spraying the oscillator with freezer spray - it stayed on frequency. The next step was to warm it up with a hair-dryer.... it stayed on frequency.... The thing that gave it away was when it was grossly over-modulated, and it would "jump" to adjacent frequencies!
Superb !
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Re: Old Rig

Post by Electronically » Wed Jun 19, 2019 1:33 pm

These rigs put me in mind of the good old sbs FMTX35 it was called .but sadly they went bust and they don't have a website .from memory of what I remember of it it was two flat copper clad boards side by side between them was a black small heatshrink with two voltage capacitors attached to it which one wire attaches to the drive and other attaches amp board.i remember seeing something called a 19khz like the shape of a resistor but with aluminium wrapped round it .on the out side of the chassis had a volume control and audio to plug in .same chassis box as veronica and nrg used .good old transmitter it was also had fuse on it too with toko coils for tuning the circuit .I can't mind the output chip all I remember is something with blx or something like that .anyway it was a 30watt .

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Re: Old Rig

Post by Albert H » Thu Jun 20, 2019 9:47 am

I found an old rig in a box of miscellaneous junk yesterday. I'll take some photos of it later and post them here. As I recall, it was thrown together for a Bank Holiday broadcast, and delivered about 75 Watts, using a pair of BLW60 transistors in the final. It uses the transformer out of a Halfords car battery charger (the cheapest transformer anywhere at the time), and an aluminium flange from a room divider for the heatsink!
"Why is my rig humming?"
"Because it doesn't know the words!"
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