198 kHz qrt

[SparkyTris]

thought I ought to mark the occasion
not that anyone cares

 

[JohnW2]

thought I ought to mark the occasion ... not that anyone cares

Thanks.

It was always going to happen sometime, even though that's never been inevitable (it would have been easy {and cheap} enough to continue the service using 'modern technology' if anyone had actually wanted to)!

 

[jj4091]

I thought they had finished it a while ago as I haven't bee able to tune my car radio to it and FM signals are poor up here and you have to keep manually retuning as auto tune doesn't seem very effective either

 

[endecotp]

Thanks for posting!

A couple of months ago I decided that I really ought to make a crystal set before this was turned off. Or at least, something that would pick up the 198 kHz signal so I could see it on my 'scope. I bought some enamelled wire and followed plans from some random website for winding a coil on a bit of cardboard. I did get a ~ 200 kHz signal on my scope's most sensitive range (about 30 mV RMS I think), but I couldn't see much modulation. And tellingly, if I changed the capacitor I could see a 250 kHz or 150 kHz waveform with about the same amplitude - so basically, I'd built a tuned circuit with about the right resonant frequency but it wasn't actually picking up the Droitwich signal.

I then looked more carefully at the website that I'd got the plans from, and it turned out that the author lives about 20 miles from Droitwich. In contrast, I'm about 300 miles away. So my chances of it working were slim! I guess I could have made it work with a ferrite rod and a long wire aerial, but it's too late now.

Who else remembers the R4 emergency personal messages? I recall being in northern Spain, probably in the late 80s or early 90s, listening to R4 LW, and hearing these. "And now an urgent message for Mr John Smith, believed to be caravanning in western France. Would Mr John Smith, believed to be driving a green Ford Cortina with a caravan in western France, please urgently contact Bognor General Hospital, regarding his father, Mr James Smith, who is dangerously ill. That's Mr John Smith, holidaying in France, to please urgently contact Bognor General Hospital, regarding his father, Mr James Smith, who is dangerously ill. And now the Archers, where Jethro is having trouble in the cowshed." If you're unfamiliar: https://www.bbc.co.uk/news/magazine-35815747 and

 

[ericmark]

I made a crystal set as a lad, the unit needed a high impedance earpiece and in latter years their supply seems to have dried up. I had not realised it was long wave, it could have been medium wave, but we lost the ability to listen to radio hams due to use of sideband, and VHF due to use of FM, I do have one radio with a BFO which will receive sideband, not used it in years.

Furthermore, I have two radios which can turn into the VHF band and use sideband, both 290s one Icom the other Yaseu always thought it odd both called 290s. But not lessened into VHF sideband in years.

In fact only lesson to VHF FM in the car, where I live not even that works, except for the local heritage railway, who use an FM repeater as mobile phones simply don't work for most of the route. Originally there would have been telephones at the cross-over points.

So one radio still in use, well it also covers PMR466 and we have two other radios which we did use on the push bikes, we found something which recived the message without needing to stop to answer it was good. So my chain has come off, will you wait for me, or my chain has broken will you return to rescue me, was handy.

The same with local heritige railway, a broadcast Mr & Mrs X and children are not on the train can you cheak car park, so as car park attendents we looked, but were found in the museum they had got the times wrong. And they heard the museum guys hand held ask the question, and yes we held back the train so they could catch it.

 

[JohnW2]

I made a crystal set as a lad, the unit needed a high impedance earpiece and in latter years their supply seems to have dried up.

Both eBay and Amazon, to name but two, seem to be currently still offering a good few.

.... but we lost the ability to listen to radio hams due to use of sideband, and VHF due to use of FM, I do have one radio with a BFO which will receive sideband, not used it in years.

A BFO was not exactly rocket science, and one didn't even need one to receive SSB if one was using a ('frowned upon') receiver with a 'regenerative' RF stage Most of my activity was on VHF/UHF bands (mainly 2m and 70cm) and a lot of that was still AM (not FM) (or CW) into the late 70s, if not beyond, and there was, if I recall correctly, still a fair bit of AM still on HF bands at that time. In fact, moving to transmitting, I'm pretty sure that I have never had anything that could transmit either SSB or FM!

 

[ebee]

A Crystal Earpiece was the must have for any Nerdy Schoolkid when we were young, 4 of us got hold of some high Impedance Headphones of WW2 vintage and had a great time talking from house to house at nightime using long spans of random wires we picked up here and there and an earthed pipework at the extreme ends.
Used as phones - speak into one headphone earpiece and listen in the other - our parents banned them because we were all supposed to be in bed asleep and our voices were a bit too loud when conversing.

We never need batteries (in fact batteries never helped) , it was all powered by radio 4 and if were all quiet we could listen for hours.

An accidental "Crystal Set"

 

[davelx]

My dad and I used to listen in to SSB transmissions placing a second, superhet receiver close to the main receiver, tuned so that it's IF oscillator acted as the BFO.

 

[JohnW2]

..... A couple of months ago I decided that I really ought to make a crystal set before this was turned off. .... I did get a ~ 200 kHz signal on my scope's most sensitive range (about 30 mV RMS I think), but I couldn't see much modulation. And tellingly, if I changed the capacitor I could see a 250 kHz or 150 kHz waveform with about the same amplitude - so basically, I'd built a tuned circuit with about the right resonant frequency but it wasn't actually picking up the Droitwich signal.

A tuned circuit, per se (and 'alone'), obviously could not create a waveform of any frequency - whenever you saw something on your scope it must have been 'picking up' something from somewhere!

I then looked more carefully at the website that I'd got the plans from, and it turned out that the author lives about 20 miles from Droitwich. In contrast, I'm about 300 miles away. So my chances of it working were slim! I guess I could have made it work with a ferrite rod and a long wire aerial, but it's too late now.

Sure. I've never lived particularly close to any broadcast transmitter, so my crystal sets invariably needed a 'a ferrite rod and long wire aerial' (and I think the same was true of the earliest 'transistor radios' I built, although some of them may have managed with just the ferrite rod!

I never really worked out whether or not it was 'legal' but very many moons ago I had a friend who lived very close to Droitwhich who lit most (maybe all!) of his house with 'aerials' rather than his grid supply

Who else remembers the R4 emergency personal messages?

I certainly do,but I'm pretty ancient

 

[JohnW2]

My dad and I used to listen in to SSB transmissions placing a second, superhet receiver close to the main receiver, tuned so that it's IF oscillator acted as the BFO.

I'm not sure I get that. A superhet won't have any oscillator running at IF frequency (unless the oscillator IS "its BFO").

I seem to recall that some people used to make one of the IF amplifiers unstable (and slightly tuneable) so that it oscillated and could be used as a BFO. Don't forget that we needed BFOs (or, at least, 'BFO functionality') for CW as well as SSB, so it was not a 'new requirement' which came when SSB appeared..

 

[davelx]

The second set has a mixer oscillator that runs 465kHz (the IF) offset from the frequency being received, to create the IF signal which is then filtered, amplified and demodulated. That Oscillator radiates and some of that is received by the set receiving the SSB signal. Tune the second set correctly and non-linearities in the first set circuitry ( there are several places where they often occur) results in sum and difference frequencies which replace the missing carrier (SSB being short for SSBSC (suppressed carrier)

And yes, we used it to listen to CW too, so I learnt Morse.

 

[JohnW2]

The second set has a mixer oscillator that runs 465kHz (the IF) offset from the frequency being received, to create the IF signal which is then filtered, amplified and demodulated. That Oscillator radiates and some of that is received by the set receiving the SSB signal.

Indeed. All very true.

Tune the second set correctly and non-linearities in the first set circuitry ( there are several places where they often occur) results in sum and difference frequencies which replace the missing carrier ....

Yes, there will be plenty of places (not the least being the mixer itself of the first set) where sums/differences (and harmonics) could be generated, but this is where I'm struggling a bit (probably because I'm being dim - or not yet recovered from the effects of the recent heat ) to understand what you're saying ... what sum or difference (between the second set's VFO and what are you suggesting) would result in a frequency which 'replaced the missing carrier'?

On the face of it, it could only result in a sum/difference frequency which replaced the desired signal's ('fixed frequency') 'missing carrier' (after it had been converted to IF) if the 'missing carrier' existed for it to mix with, which it obviously doesn't - so a sort of Catch 22! What am missing?

(SSB being short for SSBSC (suppressed carrier)

Indeed - because one sideband is all one needs. The second sideband is merely a mirror image of the other one, so conveys no additional information (although, I suppose, it does provide 'redundancy'), whilst the carrier itself conveys no information at all - hence SSBSC carrier is much more 'efficient' and, since it is 'SSB' takes only half the bandwidth. Do you recall that some people played with DSBSC - still more efficient than standard AM, but no less 'wide'?

And yes, we used it to listen to CW too, so I learnt Morse.

Yep. One obviously doesn't hear much (if anything!) of CW without a BFO unless there is a reasonable amount of 'noise' about (for the 'marks' of the CW to 'silence')!

 

[mattylad]

Anyone want to buy a 500+kw transmitter and a set of large HF antenna masts, used but in VGC?

 

[JohnW2]

Anyone want to buy a 500+kw transmitter and a set of large HF antenna masts, used but in VGC?

Do we know anything about what (if anything) is to become of the site?

 

[SUNRAY]

One of our simple mods on things like 19 sets was to poke the centre of pieces of coax into 2 IF coils and add a high resistance pot between them, the objective being to mix the 2 antiphase signals together. The pot setting was very critical to provide enough positive feedback to allow it to work but not enough to make it unstable.