was this smart kit any good

[radionortheast]

it used one of those big pll’s maybe an mc145152p2, I know years ago there were smart kits and they weren't very good, the 1w and 4w didn't work at all, the interview with the engineer made me think of the type of kits you could get in magazines, db bulluck? don't exactly remember the name, was another they had, a power oscillator, 3w transmitter you could get, you would get 2 big thick mains leads wires in the kit cut to 50cms each you were meant to use as an antenna, the two transistors worked as the oscillator and rf amplifier at the sametime it almost certainly never worked at all or would be outside the fm band, mostly they would sell dj equipment, I guess noone out there got these things to work or they never got used in a real pirate station, the engineers could of used the parts, maybe Pyers.

https://www.smartkit.gr/pll-fm-synthesizer-m.html

[Albert H]

Your link doesn't work! I think that I know the kit you mean...It used one of the big Motorola PLL chips and a prescaler to get the oscillator frequency divided down to a frequency that the Motorola CMOS IC would be able to handle.

The IC was a very good device (for its time) and had a reliable lock detector output. However, it used up a huge amount of board space, and when it was current, it cost a fortune!

The "Smart" stuff was - frankly - rubbish. It was poorly designed, and they bought the cheapest components they could find (in most cases). They tried to copy some of the "Josty" and "Amtron" kits, which suggests that they were not actually engineers, and the "Smart" versions were always inferior!

The only kits that were any real use were the NRG ones - discontinued now because of the demise of Stephen Moss, and the FRB ones from California. Stephen Dunifer's boards are of good quality, the designs are first rate, and the components supplied are of good quality. The kits presuppose that you're able to solder competently, can read and understand circuit layout diagrams, have the basic tools and test equipment you'll need, and an understanding of the principles involved.

Building a transmitter isn't trivial, and if you don't understand fully what you're doing, your chances of success are small. You need basic test equipment, tools, somewhere to work with plenty of light (and ventilation - solder fumes can be detrimental to health), and some understanding of the underlying theory and principles.

Unfortunately, the Pirate Radio game has an inordinate number of solder-jockeys who claim to be engineers, but have no proper understanding of electronics and usually lack the real skills to do a good job. It's like getting your mate who polishes his car every weekend to try to diagnose a fuel injection fault on a V8 engine. It's seldom going to go right!

If you want to learn how to design and construct competent equipment, you need to start small, with a couple of really basic electronic projects, and do copious amounts of reading too. You'll also need a rudimentary grasp of mathematics, and an ability to do at least basic algebra. You'll have to get hold of the right tools and instruments, You're going to need (amongst other things) a reasonable quality multimeter, an RF bridge, a dummy load, a bench power supply, a frequency counter and - at least - a calibrated absorbtion wavemeter. These will get you started. You'll have the means to see if your creation is on the right frequency and if it's producing outputs that it shouldn't.

When we were kids, we made little two-transistor, voltage-tuned rigs that were built into the centre box of a VHF receiving aerial. They were powered up their coax, and the modulation was added to the supply voltage, deviating the frequency of the rig. If constructed carefully, using the right components, they were ridiculously stable despite their simplicity. We'd install them on the rooftop TV mast on our houses, and it was possible to be heard over several kilometers! They were great fun, and the way that a lot of us got into illicit broadcasting!
I'll see if I can find the details to make one.....

[shorty]

I've used the MC145152, plessey sp8793 prescaler and a tl071 in the past, they worked well not only on the fm 88 -108mhz but for link transmitters on band 1 & 3.

As albert says they were expensive at the time from memory both ic's were around 15 quid each, i have a stack of new old stock motorola MC145152 & plessey sp8793 that are unlikey to ever get used as there's alot of cheaper options these days.

[EFR]

I think this is the old rooftop classic what Albert is talking about.

I build couple as kid, and it works.

[Albert H]

That's pretty similar to the ones we used to make! Mine didn't have any trimmer capacitors in them - I used fixed silvered-mica capacitors instead (for stability), and they were tuned by screwing brass screws in and out of the coils. You could get them to tune over about 1½ MHz by varying the supply voltage, so they were "remote tuned". My power supply for them used a 723 regulator IC and a small plastic power transistor (BD131, I think). The power supply / modulator was built into a small diecast box, and operating the thing was quite amusing:

About 15 minutes before the start of programmes I'd tune my receiver to a gap around 106 MHz, then fire the rig up, and turn up the voltage until I heard it! The frequency would drift a little as the transistors heated, so a small tweak to the supply voltage was always necessary after a few minutes (before programmes started). The "modulator" was a little 8 Watt transistor audio amplifier that I built from a magazine article, which was also housed in a diecast box. It had a preamplifier stage that added pre-emphasis, too. Later, I added a simple limiter to prevent over-deviation.

Considering the simplicity of the system, it worked really well. Over a 4-hour broadcast, the frequency might move around 5 kHz, which was remarkable! My little station got reception reports from as far away as 45km. From the supply voltage and the current drawn, I would estimate that the output power was around 1500 mW at most.

[EFR]

We did drive them straight from cheap bench power supply, just adjusting voltage to stay on frequency, audio was just stolen from old casette player speaker.

Rain, birds etc landing on antenna made it to dive under whole FM band, on winter it might start on air band, and when it did heat up, slowly drift back to FM band.

Someone did sell these as kit, I dont remember who. It was so expensive that we just build our own.

[radium98]

i have 1 , i can take picture to them later , for nostalgic purposes Only. My first transmitter was a smart kit and was expensive for 15W bly88c , at first start i blow the driver stage 2n3924 and the bly , cause i reversed the ps , have a good sound , and i make it drift about 0.25 (25khz) vfo , with a good ventilation and just sized metal box and good meanwell 12V/5 A power supply , but was awfull , to tune stage , and you have to take care of the 7 trimmer vishay philips , after time i discovered that they copy their kits . i also copied from the greek itself the stereo coder and the 3W vco and i have assembled the pll , having U893 replaced by U664 prescaler division factor 64 , my aerial was a ground plane , that i paid a fortune for it , in that decade 25 years ago .Love that nostalgie.

[Albert H]

I remember that a bloke that I used to know had one of those BLY88 "15 Watt" rigs, and asked If I could make it work properly for him.

After examining it for about 2 minutes, I decided that there was no way to make it work properly, so I stripped the board for the parts, and built him a nice little rig out of the parts, and added quite a few too. I gave it a PLL (just my usual 5 IC diode programmed job running at ½f), and a four stage exciter (using 2N2369 transistors - BSX20 equivalents). The PA ended up being an under-run 2N4427 into a 2N6080 then into the BLY88, since the 2N3924 didn't have enough "go" to drive the BLY88 properly.

When completed and tuned, it did a little over 18 Watts with a fully charge car battery. I gave it a reasonably generous heatsink, and the exciter was in a little tinplate box to screen it from the rest. The whole thing was fitted into a folded aluminium box (an H. L. Smiths special!).

He ran that rig on Sundays for a couple of years from field sites in Surrey, and it got into South-West London really well, using a 3-element Yagi. He had four stacked auto-reverse car cassette decks to play out the programmes, and he used to use C90 cassettes for a six-hour broadcast. There was a big relay (a car headlamp relay) that was used to turn everything off when the last tape finished.

[radium98]

Love this .@Albert , a quick question , as you may know well the nrg kits era , afterthe experience of you , do you remember well and can gave a bit of technical storie , of about if the stereo two channel compressor limiter was a good to so loud audio that really amplifiy quiet and decrese high level , with no or near no overshoot modulation deviation of 80Khz .

[radionortheast]

lol I was just trying to work out why the antenna in 1 watt fm zender picture isn’t connected to ground, someone likes buzzing an awful lot

[EFR]

lol I was just trying to work out why the antenna in 1 watt fm zender picture isn’t connected to ground, someone likes buzzing an awful lot

Direct feed to the dipole, no need for coax.

It was meant to build inside antennas connection box.

[Albert H]

lol I was just trying to work out why the antenna in 1 watt fm zender picture isn’t connected to ground, someone likes buzzing an awful lot

Those little rigs could sound really good. The modulation was at low impedance and big amplitude from the loudspeaker terminals of a small amplifier, so didn't pick up any noise on the way to the rig. There was a passive resistive attenuator at the rig end to reduce the audio to the right level for the required deviation.

The actual transmitter was built inside the waterproof dipole centre box. The second one I built was in the centre box of an "Antiference" Band II "H", with a folded dipole and a reflector. It was used near the coast, and pointed inland, so many people believed that it came from a radio ship! That one used a pair of 2N2866 transistors, and a (roughly) 24V DC supply, so had plenty of output.

[Albert H]

I think this is the old rooftop classic what Albert is talking about.

I build couple as kid, and it works.

Translation:

This simple FM transmitter was used by many pirates from 1970 to 1980. Built into the connection box of an FM antenna it was practically impossible to find and yet often had a range of up to 10 km. Sometimes the antenna cable was used as a power supply and the modulation was set there. By adjusting the voltage slightly the frequency could be adjusted.

[Albert H]

There were a couple of anarchist stations in Berlin that used little rigs like these to interfere with the national radio news over a small area during a rent strike! They built loads of them, and as the authorities tried to locate one, another would fire up! They used doctored cheap CB power supplies (the ones with 723 regulators) as their supplies and modulators. Back then, they reckoned that each site would cost about DM40 (about £16) to set up!

[radium98]

Love this .@Albert , a quick question , as you may know well the nrg kits era , afterthe experience of you , do you remember well and can gave a bit of technical storie , of about if the stereo two channel compressor limiter was a good to so loud audio that really amplifiy quiet and decrese high level , with no or near no overshoot modulation deviation of 80Khz .

Albert H what about to reply here . As u overlapped me .

[Albert H]

Hi Radium

I've got the paperwork for the stereo limiter. It's quite a good design, with an option of "stereo expand" for an enhanced stereo effect, but it proved to be problematic. It was OK for its day, but suffered from second harmonic distortion (because of the crude FET attenuator) and it needed very accurately matched pairs of FETs to maintain the stereo image, I remember Stephen and Christine going through bags and bags of 2N3819 FETs with their test jig to identify pairs. They matched for pinch-off voltage and Gm, Stephen decided that this design wasn't cost-effective (because of the amount of work involved in selecting the components) and only a few dozen of them were ever supplied as kits.

Stephen had plans for an OTA-based limiter (I was working on the design), but it was never completed. I have the original circuit sketches for that improved Limiter. It used the OTAs (a pair of them in an LM13700) and good quality op-amps (NE5532s), with the OTA giving variable negative feedback around the op-amp. This meant that the noise and distortion introduced by the OTAs was largely cancelled because of the negative feedback effect. The sidechain was simple, with two rectifiers (one per channel) combined together to give equal attenuation to both channels, keeping the stereo image intact. It includes gain reduction metering (using LEDs). We were going to include guard clippers to handle excessively loud transients, so that the device could be used for RSLs. I was experimenting with a split-band version, which experimentation showed could be as much as 6 dB "louder" without over-deviation. We were debating the cost-effectiveness of this more complex desgn.... but again, it never got finished.

[Albert H]

I'll put the paperwork for the stereo limiter up here shortly.

[radionortheast]

yeah it wasn’t db bulluck or whoever, it was b.k electronics, the 3w transmitter not very good quailty, my dad had to solder it together I wasn’t allowed near a soldering iron, didn’t have the heart to tell him i’d broken the legs off the transitors i’d spent all day sliding them in and our of the circuit board, I used some black ones instead. When it was switched on there were lots of other signals on my steepletone radio went up into to the airband, it was switched off. Its funny it says varcap tuning, don’t think there was anything like that, what I remember about the circuit it was meant to be 2 power transistors facing each other, they were both acting as the oscilator and rf amplfier, the other was a preamplifier.
https://www.worldradiohistory.com/UK/Ev ... 995-01.pdf

there were lots of adverts for fm bugs in the everyday one, i’m pretty sure it was suma, may of been a different advert I remember a secret agent, maybe it was for something else, up until then i’d used the local oscilators from little radios to make transmitters, i’d strip out the capacitors, put the voltage up to something like 9v to get a boost, they could be heard 150 meters away. I made my own 19khz generator, would spend hours trying to get the stereo to come through, there was nothing but a page in an audio hifi book how it worked, I suppose they weren't going to put anything in these magazines how it worked, going to a library was not something I did.

The vt500 bug does ring a bell, I got the one that had the most range, don’t know if it said 3000feet or meters, some kind of surveillance bug advert thing. It was about 0.2w, it had an audio buffer, oscilator, a little rf amplifier, it was very stable tuned with a ferrite slug. I replaced the mic, with a 3.5mm lead, used a cd player or something into it. When I went on hoilday it was the first time I heard a signal coming through 1km, weakly, it was quite something to know it was my own, i’d taped the wire aerial to ceiling were we where staying. It was hard to test back at home, as there was no countryside within 1kms away, I suspect it got out better then the local oscillator things, it was the start of listening to these things.

was a better a magazine, theres lots of useful circuits in just the one magazine
https://www.worldradiohistory.com/UK/Wi ... -S-OCR.pdf

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[radionortheast]

Bugging you, this was the other suma one, i’m not sure if it is the advert or not as it was such a long time ago, they were tiny things. I don’t know were the smart kits were got from, quasar electronics rings a bell, they are still around have all the velleman kits, there are a few other adverts there for a 4w transmitter which suspect would of been a smart kit. Maybe a smart kit could of been for a secret agent too, I suppose the bugs were probably used for spying on people, not the more interesting thing of transmitting music across. There was also a hifi broadcaster but it was quite low power, obviously you'd want something you could hear so you were better getting the bugs

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