Carshalton Pirate station 1980???

Discuss & sharing nostalgia relating from the pirate stations of the 60s up to modern day inactive stations.
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toshiba1
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Carshalton Pirate station 1980???

Post by toshiba1 » Sun Jul 31, 2022 8:21 pm

Possibly located at the back of St Heliers or The Grove, Just remember a couple or so lads pulling wires up into the trees, vividly remember the tape cassette deck and radio and car battery. I was a about 11 so memory is a little sketchy but we used to occasionally go there. I Guess it must have been Shortwave?? do any of the older heads have an idea what station it might have been within that time frame?

Albert H
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Re: Carshalton Pirate station 1980???

Post by Albert H » Mon Aug 01, 2022 3:51 pm

Could have been any of several medium wave or short wave stations. Jackie came from that area (as just one example).
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

toshiba1
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Re: Carshalton Pirate station 1980???

Post by toshiba1 » Wed Aug 03, 2022 6:52 pm

Yes I do remember Radio Jackie as the old dear used to listen to that quite often. Did they do a phone in talk show as she often phoned up, the radio shows which in them days would have been a pretty slick operation for a pirate. But more likely I think that could have been Radio London. What were the short wave stations Albert in that vicinity?

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Re: Carshalton Pirate station 1980???

Post by Albert H » Sun Aug 07, 2022 2:52 am

"Radio Alpha" came from that vicinity, and ran stereo FM on a couple of weekday evenings, and SW on Sundays. This was back in the late 70s / early 80s when most pirates on FM were Sunday-only efforts.

There were several SW pirates at weekends back then, mostly running valve rigs. I was one of the first - from a field site in North Kent - to run a transistorised Short Wave rig. I managed about 15 Watts carrier / 60 Watts peak on the first couple of rigs, which was similar power to the usual single 807 valve rig.

My first ever PLL rig was on 6.3MHz short wave in the Netherlands in 1977, using TTL to keep the thing on frequency, without having to buy expensive custom-cut rocks! That one had a transistor exciter driving a couple of 807s for the PA. The modulator was a pair of EL34 bottles and a "Wodan" modulation transformer. It even had a crude built-in compressor to keep the mod level high!
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

toshiba1
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Re: Carshalton Pirate station 1980???

Post by toshiba1 » Sun Aug 07, 2022 5:57 pm

Albert H" post_id=37356 time=1659837138 user_id=1343]
"Radio Alpha" came from that vicinity, and ran stereo FM on a couple of weekday evenings, and SW on Sundays. This was back in the late 70s / early 80s when most pirates on FM were Sunday-only efforts.

My first ever PLL rig was on 6.3MHz short wave in the Netherlands in 1977, using TTL to keep the thing on frequency.

For some reason, the name Radio Alpha sounds familiar? I quite like the sound of Sunday Radio just popping up for a few hours and then disappear keeping you wanting more. For me as a listener that was a special time, often waiting in vain same time the following weekend chasing up and down the dial in the hope you get another broadcast. Guess in some ways it was just as much fun as broadcasting. PLL I understand sort of, is TTL a basic PLL without using a crystal, which will drift either side but does get pulled back to frequency? I think my first converted Pye & Westminster would of had something similar.

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Re: Carshalton Pirate station 1980???

Post by Albert H » Mon Aug 08, 2022 2:57 am

No. TTL (Transistor - Transistor Logic) was the second generation of logic ICs (after "DTL" Diode - Transistor Logic).

I used to use several 7490 decade dividers to divide the carrier frequency down in a "preset" divider. The reference was a crystal oscillator (usually 1 MHz) divided down to something ultrasonic. The phase comparator used a 7474 dual bistable and a 7400 quad NAND gate. There was an active loop filter (using a couple of 741 op-amps) giving a really smooth DC control voltage to tune the carrier oscillator.

Th biggest problem with early TTL-based PLL circuits was that the upper frequency that they could count at was in the order of about 12 MHz, so I had to use frequency multiplication to get up to the output frequency. Shortly after my first PLL adventures, Plessey brought out their SP8629 which would divide anything up to 150MHz by 100. This meant that I could sample the output frequency of the exciter (at 90ish MHz) and get an output that was well within the range of all the cheaper logic families. The '8629 was cheaply available from RS and Farnell, and became a staple of my early designs.

I came up with a VCO that used the Plessey SL560 (an RF amplifier IC) to deliver 10mW on the output frequency. That was amplified by a BSX20 and a 2N4427 to 1 Watt. The '560 had (effectively) two output pins, and I used the "gain set" pin as the "sniff" point to feed the PLL prescaler. It made for a neat little board, with two 8-pin ICs at one end (the '560 and the '8629) and five or six 14-pin TTL chips for the logic.

The next series of PLLs did away with the prescaler, and used a half-frequency VCO and frequency doubling to the output frequency. When the 74HC series of logic chips arrived, my PLL became much simpler, just using four cheap ICs:

A 74HC4024 as a "prescaler" - because it would go to 70 MHz with ease

A 74HC4040 as the diode-programmed preset divider

A 74HC4060 for the crystal reference oscillator and a couple of diodes to programme the divider in that chip to allow the use of really cheap 4MHz crystals

A 4046 - I disabled the internal VCO in that IC, and just used one of the phase comparators. I also found a way to get reliable "lock detect" from that IC, which was used to switch the driver stage on when the loop was stable.

I had a heap of PCBs commercially etched, and literally thousands of that exciter were built.

I still see them occasionally today. Recently, a friend brought over a defective (and rather old) rig. The driver and final transistors had died when it was run for several hours into an aerial that had fallen down, and was shorting on its mounting tower! I was delighted to see the old exciter in the box, still in working order! I replaced the PA board in the rig with something more modern using a FET, and used the 1 Watt from the exciter board to drive the single device to 110 Watts (the original PA used two critically tuned stages to get to 45 Watts!).
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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