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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#81
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Do crystal radios still pick anything up?
On 26/02/16 14:27, Chris Hogg wrote:
On Fri, 26 Feb 2016 14:15:26 +0000, The Natural Philosopher wrote: On 26/02/16 11:40, Cursitor Doom wrote: On Fri, 26 Feb 2016 00:12:41 +0000, The Natural Philosopher wrote: You can still buy oc71s all right But why not use something better? Can you name a better photo-transistor than the OC71? ;-) OCP71? IIRC if you carefully stripped the paint off an OC71 you had an OCP71. Nope. inside was blue opaque gunk after the first few years -- "What do you think about Gay Marriage?" "I don't." "Don't what?" "Think about Gay Marriage." |
#83
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Do crystal radios still pick anything up?
"Dave Plowman (News)" wrote in message ... In article , The Natural Philosopher wrote: Rubbish! we're going to cut the mooring ropes and row the islands across the Atlantic. And park it somewhere in the Caribbean, as a tax haven. Surrounded by blacks? Have you run this by your kipper pals? His kipper pals' ancestors are the reason the Caribbean is full of blacks. |
#84
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Do crystal radios still pick anything up?
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#85
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Do crystal radios still pick anything up?
On 26/02/2016 19:16, Terry Casey wrote:
In article , says... [quoted text muted] OCP71? IIRC if you carefully stripped the paint off an OC71 you had an OCP71. Nope. inside was blue opaque gunk after the first few years In other words after Mullard found that they weren't selling many OCP71's and realised what everyone was doing. That was what most people believed at the time but there was another reason: If the paint on a transistor got accidentally scratched and artificial light fell on it - though a ventilation grille, for example - the transistor would respond to the 50Hz light. I would imagine that the first engineer to have a battery operated transistor radio turn up on his work bench with a mains hum fault was very, very, surprised! Especially when he took the back off and the fault got worse ...! So, Mullard started adding the opaque gunk ... When I was young, I worked for the Beeb as a technician. One day, I had an outside broadcast mixer to check out. While I was 'lining it up' - checking signal levels at various points - I noticed a really bad mains hum. So I unleashed the oscilloscope. The hum was definitely there audibly, but seemed to disappear whenever I connected the scope probe. To cut a very long story short, whenever I leaned over to connect a scope probe, I put the PCB in the shadow of a fluorescent lamp and the mains noise went away. The mixer was all Germanium transistors. Of course, in normal use, with the cover on, there was no problem, but when the cover was off, small scratches in the black paint on the transistors was enough to make it pick up the fluorescent lights, and hum. It took a long time to find that. Nowadays, I'd just assume I'd gone totally fishkettle aardvark alumni. Cheers -- Syd |
#86
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Do crystal radios still pick anything up?
On Fri, 26 Feb 2016 17:05:21 +0000, Chris Hogg wrote:
On Fri, 26 Feb 2016 16:46:56 -0000, Terry Casey wrote: More years ago than I care to remember I heard a report on the radio about a woman living close to the Droitwich transmitter who could receive the Light Programme (in the days when it was on Long Wave) on her electric cooker ... Drainpipes were also said to receive broadcasts. A nice long conductor acting as an aerial probably naturally tuned by virtue of its length, a rusty bolt acting as a semiconducting rectifier, and the pipe resonating to create the sound. Some people living in Kingstanding E. Sussex were able to pick up the World Service whenever their fillings became loose. |
#87
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Do crystal radios still pick anything up?
On Fri, 26 Feb 2016 16:46:56 -0000, Terry Casey
wrote: In article , says... I did wonder if nearby you could receive the long wave transmissions - 198kHz @ 500kW - with just wire, a diode and a loudspeaker. More years ago than I care to remember I heard a report on the radio about a woman living close to the Droitwich transmitter who could receive the Light Programme (in the days when it was on Long Wave) on her electric cooker ... In the version I heard, I think it was a gas cooker. -- Graham. %Profound_observation% |
#88
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Do crystal radios still pick anything up?
On Fri, 26 Feb 2016 20:37:08 +0000, Syd Rumpo
wrote: On 26/02/2016 19:16, Terry Casey wrote: In article , says... [quoted text muted] OCP71? IIRC if you carefully stripped the paint off an OC71 you had an OCP71. Nope. inside was blue opaque gunk after the first few years In other words after Mullard found that they weren't selling many OCP71's and realised what everyone was doing. That was what most people believed at the time but there was another reason: If the paint on a transistor got accidentally scratched and artificial light fell on it - though a ventilation grille, for example - the transistor would respond to the 50Hz light. I would imagine that the first engineer to have a battery operated transistor radio turn up on his work bench with a mains hum fault was very, very, surprised! Especially when he took the back off and the fault got worse ...! So, Mullard started adding the opaque gunk ... When I was young, I worked for the Beeb as a technician. One day, I had an outside broadcast mixer to check out. While I was 'lining it up' - checking signal levels at various points - I noticed a really bad mains hum. So I unleashed the oscilloscope. The hum was definitely there audibly, but seemed to disappear whenever I connected the scope probe. To cut a very long story short, whenever I leaned over to connect a scope probe, I put the PCB in the shadow of a fluorescent lamp and the mains noise went away. The mixer was all Germanium transistors. Of course, in normal use, with the cover on, there was no problem, but when the cover was off, small scratches in the black paint on the transistors was enough to make it pick up the fluorescent lights, and hum. It took a long time to find that. Nowadays, I'd just assume I'd gone totally fishkettle aardvark alumni. Cheers There are some Raspberry Pi boards that crash if you photograph them with a xenon flash. When my daughter was little we bought her a VHS tape of cartoons. The top-loading Hitachi machine we had would not play this tape. Later we discovered it would play if the curtains were drawn. The cassette body was made of a translucent coloured plastic instead of the usual opaque black, allowing light to reach the optical tape end sensor that detected the transparent leaders. -- Graham. %Profound_observation% |
#89
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Do crystal radios still pick anything up?
Andrew Gabriel wrote:
In article , "Dan S. MacAbre" writes: Apologies to those who know about this stuff, if this is a stupid question. Seeing the electronics thread reminded me of some of my mis-spent youth. I never knew enough about electronics to design anything, but I could usually get something like an amp or a tape recorder from the tip, and fix it. That was about my limit. I used to enjoy making crystal radios from some of the bits I'd have lying around, but no matter what I used, I only ever seemed to be able to pick up what seemed to be radio 4. If you were to build one nowadays, would there be any suitable non-digital station left to pick up? Funny you should mention this... A couple of weeks ago, I stayed over at my parents, and in the bookshelf was my old Ladybird book on making a radio, which takes you through the stages of making the receiver and then adding an amplifier to it. If you can still buy OC71's, it would still work today. ;-) http://www.mds975.co.uk/Content/geor...trf_radio.html Just been having another read of it this morning. Why do they not make books like this any more? I've a six-year old boy, and we try to find interesting educational books for him, but there's nothing now that pulls you in like those beautiful Ladybird illustrations. I wonder how many people tried the spring of wire and piece of coke thing? I never did. |
#90
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Do crystal radios still pick anything up?
In article ,
pamela wrote: I've never had a crystal set where a station is spread over an excessively wide part of the dial. My crystal sets picked up MW stations quite well (or as well as a crystal set can be expected). Radio 3 used to be on 464m and it came storming in nicely even on the crummiest tuning coil but didn't spread itself across the band. Admittedly, those stations at the shorter wavelength end of the band didn't come through so well. When I was at school in Aberdeen in the '50s, schools broadcasts were recorded on a Ferrograph using a Truvox radio jack - basically a crystal set. It had two preset frequencies selected by a switch. Now in Aberdeen in those days all you'd get during daylight was the local BBC transmissions. Home Light and Third. And you could just hear another burbling away under the wanted one on this Truvox device. -- *Xerox and Wurlitzer will merge to market reproductive organs. Dave Plowman London SW To e-mail, change noise into sound. |
#91
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Do crystal radios still pick anything up?
In article ,
Dan S. MacAbre wrote: Just been having another read of it this morning. Why do they not make books like this any more? I've a six-year old boy, and we try to find interesting educational books for him, but there's nothing now that pulls you in like those beautiful Ladybird illustrations. I wonder how many people tried the spring of wire and piece of coke thing? I never did. Snag is kids see others playing with phones and computers. So that's what interests them. In the Ladybird days, radio might well have been the state of the art technology. -- *Reality is a crutch for people who can't handle drugs. Dave Plowman London SW To e-mail, change noise into sound. |
#92
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Do crystal radios still pick anything up?
In message , pamela
writes On 16:56 26 Feb 2016, Johnny B Good wrote: On Fri, 26 Feb 2016 11:52:33 +0000, pamela wrote: On 02:08 26 Feb 2016, Johnny B Good wrote: On Thu, 25 Feb 2016 16:14:31 +0000, pamela wrote: On 15:03 25 Feb 2016, Graham. wrote: ====snip==== It would if you didn't LPF it first, which would be essential. No, you are going to have to LPF? Low Pass Filter. In this case, the placement of a smoothing capacitor of a few tens of microfarads (as opposed to a few nanoFarads usually used to block only the rf ripple after the detector diode) - (modern stand-in for the original lead galena crystal and cat's whisker used to build the very first crystal sets) so that it smooths not only the rf ripple but the audio frequency modulation as well - you're only interested in harvesting a few milliwatts at best (unless you live right next door to the Tx in question) of DC voltage produced by the detector diode that's rectifying a conveniently strong signal to power a simple transistor amplified radio receiver tuned to a wanted but weaker radio station. If you're lucky enough to pick up a very strong 198Khz signal to power a MW transistor receiver, it's job done. However, if you're relying on a very strong MW signal to power your MW receiver, you'll have to get a bit more inventive and use a second detector diode wired to give opposite polarity with the usual rf ripple capacitor to allow the modulation to get through, via a HPF, unmolested via a variable attenuator to the detector of the transistor assisted reciever so as to null out the unwanted audio that would otherwise swamp the weaker signals you're trying to listen to. I have to admit though, this isn't something I've ever tried. It's purely theoretical on my part (and it's just possible there might be a flaw in this excellent theory of mine :-). Why would a MW "power" station have to be treated differently to 198lHz in the way you describe in your second paragraph (which I can't say I fully understand)? Lack of selectivity in the MW tuning filter. A suitably strong enough MW broadcast is likely to be heard "Right across the dial". I've never had a crystal set where a station is spread over an excessively wide part of the dial. My crystal sets picked up MW stations quite well (or as well as a crystal set can be expected). Radio 3 used to be on 464m and it came storming in nicely even on the crummiest tuning coil but didn't spread itself across the band. Admittedly, those stations at the shorter wavelength end of the band didn't come through so well. I'm not sure how your, albeit tentative, design (which you point out may be somewhat flawed) would help with poor selectivity. Wouldn't the most effective thing be an improvement to the "power host" tuning circuit rather than the second diode arrangement you mention? To be honest, I can't really visualise your suggested circuit but that may be because I don't really understand all the necessary considerations when designing a circuit. Maybe you're trying to overcome the problem of such a parasitic design providing power only momentarily (when the radio signal is carrying loud audio). The selectivity of a crystal set is greatly affected by how much the aerial impedance damps the basic selectivity of the tuned circuit. The selectivity might be sufficiently narrow if you have a short-ish aerial (essentially a high capacitive impedance) connected right at the top end of the coil - but being short, the signal it picks up might be rather weak. A longer aerial will pick up more signal, but will have a lower impedance. It will have more capacitance (which will change the tuning point of the tuned circuit) - and in particular, the resistive part of the impedance will be lower, and this will damp (broaden) the selectivity of the tuned circuit. To help overcome the broadening of the selectivity, the coupling of the aerial to the tuned circuit can be reduced either by connecting it to the top end of the coil through a suitably low-value capacitor, or (maybe better) by connecting it to a tapping point lower down the coil. Either may reduce the signal somewhat, and it is a question of experimentation to get the best results. The other thing which broadens the selectivity is the damping effect of the headphone(s). For best sensitivity and selectivity, these must be high impedance, and again it may be desirable to move where the detector diode connects to the coil to a tapping point lower down. Those who are aficionados of crystal sets (I'm not one, BTW) may go much further with circuit variations and complexity in order to optimise their performance. For those interested, I'm sure that Google will reveal all. -- Ian |
#93
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Do crystal radios still pick anything up?
In article ,
pamela wrote: I never heard of a Truvox Radio Jack until you mentioned it but it looks lovely. http://www.g1jbg.co.uk/dom1.htm That's the one. I was hoping it was an Ebay ad showing they were now worth thousands. As I've got one somewhere. ;-) It reminds me of a crystal set a friend showed me when I was young. From memory, they had essentially wound a coil around what I think was a capacitor and attached a crystal earpiece. There was a long wire aerial feeding it. I still can't understand how that could work as a crystal set but maybe the crystal earpiece was somehow acting as a diode detector. By some total fluke, this contraption actually received Radio 3. (Which I should really be calling the Third Programme). The whole device was smaller than that little Truvox Radio Jack. There's not much inside them. Just a large enough case to make handling easy - and made from metal. These days you could probably make a plastic one much smaller but strong enough. -- *I don't suffer from insanity -- I'm a carrier Dave Plowman London SW To e-mail, change noise into sound. |
#94
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Do crystal radios still pick anything up?
On Thu, 25 Feb 2016 12:02:29 +0000, "Dan S. MacAbre"
wrote: Dan S. MacAbre wrote: Apologies to those who know about this stuff, if this is a stupid question. Seeing the electronics thread reminded me of some of my mis-spent youth. I never knew enough about electronics to design anything, but I could usually get something like an amp or a tape recorder from the tip, and fix it. That was about my limit. I used to enjoy making crystal radios from some of the bits I'd have lying around, but no matter what I used, I only ever seemed to be able to pick up what seemed to be radio 4. If you were to build one nowadays, would there be any suitable non-digital station left to pick up? Okay, thanks for the great replies. I had a Ladybird book that showed how to make them. Beautiful illustrations that I still look at fondly. The first version was without batteries, and then it evolved into something amplified with an OC71. It said to drive a long copper tube into the ground for the earth side, but I just used a mains plug. And the aerial was supposed to be something like a washing line, but I used a bit of wire dangled across the room; and once, an old mattress in the loft (which was no better). That may have reduced what I was able to pick up :-) The BBC transmitted at least one experimental broadcast of stereo, using the Home Service and Third Programme for the left and right channels. According to the BBC Genome website it might have been in 1958. I built two crystal sets in series, using germanium diodes, feeding my left and right high-impedance ex-WD headphones. The aerial was strung across the room in south London. One item was of a theatre musical chorus, which sounded truly wonderful. -- Dave W |
#95
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Do crystal radios still pick anything up?
In article ,
Dave W wrote: The BBC transmitted at least one experimental broadcast of stereo, using the Home Service and Third Programme for the left and right channels. According to the BBC Genome website it might have been in 1958. I built two crystal sets in series, using germanium diodes, feeding my left and right high-impedance ex-WD headphones. The aerial was strung across the room in south London. Don't remember that. Those I do remember used TV sound for one channel. IIRC on a Saturday morning when there were no broadcasts on TV - only the test card. To use two radio services meant disrupting them both. One item was of a theatre musical chorus, which sounded truly wonderful. I did try the 'TV' ones. But with a TV and radio - with obviously very different speakers etc. They played quite a large selection of material. -- *Preserve wildlife - Go pickle a squirrel* Dave Plowman London SW To e-mail, change noise into sound. |
#96
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Do crystal radios still pick anything up?
In article ,
Cursitor Doom wrote: On Fri, 26 Feb 2016 09:10:38 +0000, charles wrote: They've left the area They're now in Edgeware itself. Tottenham Court Road used to be the mecca for electronic hobbyists back in the day. They stocked *real* stuff back then; today it's just a load of brand new consumer tech gadgets. and Lisle Street before that. -- from KT24 in Surrey, England |
#97
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Do crystal radios still pick anything up?
In article , Dave Plowman (News)
writes In article , Dave W wrote: The BBC transmitted at least one experimental broadcast of stereo, using the Home Service and Third Programme for the left and right channels. According to the BBC Genome website it might have been in 1958. I built two crystal sets in series, using germanium diodes, feeding my left and right high-impedance ex-WD headphones. The aerial was strung across the room in south London. Don't remember that. Those I do remember used TV sound for one channel. IIRC on a Saturday morning when there were no broadcasts on TV - only the test card. To use two radio services meant disrupting them both. One item was of a theatre musical chorus, which sounded truly wonderful. I did try the 'TV' ones. But with a TV and radio - with obviously very different speakers etc. They played quite a large selection of material. I remember that! There was a broadcast of Shakespeare's 'The Tempest' - very effective sound effects. -- Chris Holford |
#98
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Do crystal radios still pick anything up?
In article , Chris Hogg
wrote: On Sun, 28 Feb 2016 08:13:18 +0000, Chris Hogg wrote: On Sat, 27 Feb 2016 20:03:38 +0000 (GMT), charles wrote: In article , Cursitor Doom wrote: On Fri, 26 Feb 2016 09:10:38 +0000, charles wrote: They've left the area They're now in Edgeware itself. Tottenham Court Road used to be the mecca for electronic hobbyists back in the day. They stocked *real* stuff back then; today it's just a load of brand new consumer tech gadgets. and Lisle Street before that. http://tinyurl.com/gn69z3a 3-34 Lisle Street! They occupied almost the entire length of it, IIRC. Actually, memory deceives, it was two separate shops! There were some at each end of the street as well as one in the middle on the north side. And then the chinese took over. -- from KT24 in Surrey, England |
#99
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Do crystal radios still pick anything up?
On Sat, 27 Feb 2016 17:54:07 +0000 (GMT), "Dave Plowman (News)"
wrote: In article , Dave W wrote: The BBC transmitted at least one experimental broadcast of stereo, using the Home Service and Third Programme for the left and right channels. According to the BBC Genome website it might have been in 1958. I built two crystal sets in series, using germanium diodes, feeding my left and right high-impedance ex-WD headphones. The aerial was strung across the room in south London. Don't remember that. Those I do remember used TV sound for one channel. IIRC on a Saturday morning when there were no broadcasts on TV - only the test card. To use two radio services meant disrupting them both. One item was of a theatre musical chorus, which sounded truly wonderful. I did try the 'TV' ones. But with a TV and radio - with obviously very different speakers etc. They played quite a large selection of material. The radio+TV broadcasts were in 1962, and I didn't have a TV. -- Dave W |
#100
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Do crystal radios still pick anything up?
In article ,
Dave W wrote: On Sat, 27 Feb 2016 17:54:07 +0000 (GMT), "Dave Plowman (News)" wrote: In article , Dave W wrote: The BBC transmitted at least one experimental broadcast of stereo, using the Home Service and Third Programme for the left and right channels. According to the BBC Genome website it might have been in 1958. I built two crystal sets in series, using germanium diodes, feeding my left and right high-impedance ex-WD headphones. The aerial was strung across the room in south London. Don't remember that. Those I do remember used TV sound for one channel. IIRC on a Saturday morning when there were no broadcasts on TV - only the test card. To use two radio services meant disrupting them both. One item was of a theatre musical chorus, which sounded truly wonderful. I did try the 'TV' ones. But with a TV and radio - with obviously very different speakers etc. They played quite a large selection of material. The radio+TV broadcasts were in 1962, and I didn't have a TV. nor did I, but the FM tuner that I'd built to a PW design could tune down to Band 1 if I inserted an iron dust slug in one of the coils. It can't have been a very good tuner since it managed the AM on Band 1. -- from KT24 in Surrey, England |
#101
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Do crystal radios still pick anything up?
On Sun, 28 Feb 2016 11:21:42 +0000 (GMT), charles
wrote: In article , Dave W wrote: On Sat, 27 Feb 2016 17:54:07 +0000 (GMT), "Dave Plowman (News)" wrote: In article , Dave W wrote: The BBC transmitted at least one experimental broadcast of stereo, using the Home Service and Third Programme for the left and right channels. According to the BBC Genome website it might have been in 1958. I built two crystal sets in series, using germanium diodes, feeding my left and right high-impedance ex-WD headphones. The aerial was strung across the room in south London. Don't remember that. Those I do remember used TV sound for one channel. IIRC on a Saturday morning when there were no broadcasts on TV - only the test card. To use two radio services meant disrupting them both. One item was of a theatre musical chorus, which sounded truly wonderful. I did try the 'TV' ones. But with a TV and radio - with obviously very different speakers etc. They played quite a large selection of material. The radio+TV broadcasts were in 1962, and I didn't have a TV. nor did I, but the FM tuner that I'd built to a PW design could tune down to Band 1 if I inserted an iron dust slug in one of the coils. It can't have been a very good tuner since it managed the AM on Band 1. I too built an FM tuner that could get TV sound - it might have been the same one as yours as PW was my regular buy. However the sound from the speaker was so different from the radio headphones, I didn't think it would be worth trying the stereo experiments. I was so impressed with the radio experiment that it was just a question of waiting for proper stereo broadcasts. -- Dave W |
#102
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Do crystal radios still pick anything up?
In article , Chris Hogg
scribeth thus On Sat, 27 Feb 2016 20:03:38 +0000 (GMT), charles wrote: In article , Cursitor Doom wrote: On Fri, 26 Feb 2016 09:10:38 +0000, charles wrote: They've left the area They're now in Edgeware itself. Tottenham Court Road used to be the mecca for electronic hobbyists back in the day. They stocked *real* stuff back then; today it's just a load of brand new consumer tech gadgets. and Lisle Street before that. http://tinyurl.com/gn69z3a 3-34 Lisle Street! They occupied almost the entire length of it, IIRC. Did you have to publish that!. Spent all afternoon reading it all through!. Remember most all of those suppliers, a teenage childhood of sending off postal orders and stamped addressed envelopes, and the excitement when the package for the latest project turned up:!. -- Tony Sayer |
#103
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Do crystal radios still pick anything up?
To use two radio services meant disrupting them both.
terial. The radio+TV broadcasts were in 1962, and I didn't have a TV. nor did I, but the FM tuner that I'd built to a PW design could tune down to Band 1 if I inserted an iron dust slug in one of the coils. It can't have been a very good tuner since it managed the AM on Band 1. Charles, do you remember which one that was at all, valve or transistor?. I remember one i think it had a pulse count detector used IIRC AF117's and or 118's in the front end and was supposed to be a very good performer, never did get the damm thing to work checked it and re checked tested all the transistors. I wish i had it around still, years on better test equipment and know how etc?. Often wondered if it could have worked!, anyone know where the circuit is at all? must have been around 1966 to 68 or even a bit later. -- Tony Sayer |
#104
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Do crystal radios still pick anything up?
In article ,
tony sayer wrote: To use two radio services meant disrupting them both. terial. The radio+TV broadcasts were in 1962, and I didn't have a TV. nor did I, but the FM tuner that I'd built to a PW design could tune down to Band 1 if I inserted an iron dust slug in one of the coils. It can't have been a very good tuner since it managed the AM on Band 1. Charles, do you remember which one that was at all, valve or transistor?. Valve. Using an ex-government IF strip. [Snip] Often wondered if it could have worked!, anyone know where the circuit is at all? must have been around 1966 to 68 or even a bit later. Mine must have been about 1958/9. -- from KT24 in Surrey, England |
#105
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Do crystal radios still pick anything up?
In article , charles
scribeth thus In article , tony sayer wrote: To use two radio services meant disrupting them both. terial. The radio+TV broadcasts were in 1962, and I didn't have a TV. nor did I, but the FM tuner that I'd built to a PW design could tune down to Band 1 if I inserted an iron dust slug in one of the coils. It can't have been a very good tuner since it managed the AM on Band 1. Charles, do you remember which one that was at all, valve or transistor?. Valve. Using an ex-government IF strip. [Snip] Often wondered if it could have worked!, anyone know where the circuit is at all? must have been around 1966 to 68 or even a bit later. Mine must have been about 1958/9. Ah!, a very early FM tuner then. That government surplus IF strip what was it originally for surely not FM broadcast radio?. -- Tony Sayer |
#106
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Do crystal radios still pick anything up?
In article , tony sayer
wrote: In article , charles scribeth thus In article , tony sayer wrote: To use two radio services meant disrupting them both. terial. The radio+TV broadcasts were in 1962, and I didn't have a TV. nor did I, but the FM tuner that I'd built to a PW design could tune down to Band 1 if I inserted an iron dust slug in one of the coils. It can't have been a very good tuner since it managed the AM on Band 1. Charles, do you remember which one that was at all, valve or transistor?. Valve. Using an ex-government IF strip. [Snip] Often wondered if it could have worked!, anyone know where the circuit is at all? must have been around 1966 to 68 or even a bit later. Mine must have been about 1958/9. Ah!, a very early FM tuner then. That government surplus IF strip what was it originally for surely not FM broadcast radio?. Of course not. I think it came from a Radar unit. -- from KT24 in Surrey, England |
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