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The "Two Transistor challenge" - taking things a bit too far?
On 2/18/2014 6:02 PM, Jim Mueller wrote:
On Tue, 18 Feb 2014 15:31:18 -0500, Jerry Stuckle wrote: I remember back in the 70's we had radar sets with ZERO volts on the magnetron's anode (DC ground). Of course, there was -3KV or so on the cathode :) I haven't done anything with radar in well over 30 years, so I don't know if they still do it or not. But I wouldn't be surprised. At first glance it sounds crazy - but it made for a very simple and efficient way to couple the output of the magnetron to the waveguide. Microwave ovens still do that. At least, my Toshiba does. Probably. Although I could kick myself. In the last 4 years I threw away two microwaves - an 1100W one and a 1300W one (both had control boards fail). It wasn't until later I thought about taking them apart and using the power supply for a homebrew amplifier. Not going to do that again! -- ================== Remove the "x" from my email address Jerry Stuckle ================== |
The "Two Transistor challenge" - taking things a bit too far?
I still have the HP-35 and an HP-25 that can be programmed up to 49 steps.
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The "Two Transistor challenge" - taking things a bit too far?
On Wed, 19 Feb 2014, Phi wrote:
I still have the HP-35 and an HP-25 that can be programmed up to 49 steps. What happens when you turn off the HP-25? Is it one that keeps the memory alive, or do you lose everything after you typed it all in? Michael |
The "Two Transistor challenge" - taking things a bit too far?
On 18/02/2014 10:58, gareth wrote:
There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? Not carping, just curious. There is something challenging about restricting your resources. My most memorable receiver I ever built was made from a toilet roll tube, wire, a crystal earpiece, tinfoil and paper hand-rolled capacitor and some galena crystal as a detector. I think I got more satisfaction out of that that I ever did from a digitally programmable oscillator based beast. (but then I enjoy retro-tech like making Baird televisors) If you only have 2 transistors then you have to make everything do multiple duty; it pushes your technical ability. IME if you have unrestricted resources then there is a tendency to think in functional blocks and not an integrated system. Good engineering is not achieved when you can add nothing more, it is achieved when you can take away nothing else. You of all people should appreciate that. Andy |
The "Two Transistor challenge" - taking things a bit too far?
On 18/02/2014 15:21, Phi wrote:
I paid about £180 for an HP35 in 1973, this calculator used reverse polish notation (no equals key). HP15C was my best calculator (still use it) its quality is such that it still sells for £150+ on ebay. Complex maths, matrix manipulation, polar to rectangular conversion all in a 1981 calculator. Lovely bit of engineering. Andy |
The "Two Transistor challenge" - taking things a bit too far?
"AndyW" wrote in message
... (but then I enjoy retro-tech like making Baird televisors) Mirror-drum, or Nipkow disk? LED or nitro-benzine as the polariser? |
The "Two Transistor challenge" - taking things a bit too far?
On Wed, 19 Feb 2014, AndyW wrote:
On 18/02/2014 10:58, gareth wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? Not carping, just curious. There is something challenging about restricting your resources. My most memorable receiver I ever built was made from a toilet roll tube, wire, a crystal earpiece, tinfoil and paper hand-rolled capacitor and some galena crystal as a detector. I think I got more satisfaction out of that that I ever did from a digitally programmable oscillator based beast. I think that's something that may be lost. People lament that in this day and age, it's difficult to attract the young to the hobby, because how can it compete with the Internet? And you don't compete with it, you show off things that are unique. A simple project for a beginner is identical to what it was forty or fifty years ago, a first project and when it actually gets working, what an accomplishment. It's not because the simple project is comparable with the electronic wonders of the 21st century, it's that you built it and it worked. Michael |
The "Two Transistor challenge" - taking things a bit too far?
On 19/02/2014 16:30, Michael Black wrote:
A simple project for a beginner is identical to what it was forty or fifty years ago, a first project and when it actually gets working, what an accomplishment. It's not because the simple project is comparable with the electronic wonders of the 21st century, it's that you built it and it worked. Absolutely true. One of my foundation types constructed a simple bit of circuitry to comply with the course. He rang me afterwards in a state of excitement - "It works - it bloody works!" he exclaimed. Les. |
The "Two Transistor challenge" - taking things a bit too far?
On 19/02/14 03:09, Jerry Stuckle wrote:
On 2/18/2014 7:06 PM, FranK Turner-Smith G3VKI wrote: "Jerry Stuckle" wrote in message ... On 2/18/2014 4:29 PM, Percy Picacity wrote: In article , Brian Reay wrote: On 18/02/14 20:31, Jerry Stuckle wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? Not carping, just curious. There have always been "contests" like that, though sometimes they were about "build a whole receiver using the same transistor type", or "build a receiver without any ICs" after ICs had come around. What I find intriguing is the realisation that valves ("tubes" to you?) can be operated with only 12V on the anode. No unusual at all. Not only were a number of valves for the car radio (and possibly other) markets available, I recall designs which use 'ordinary' valves with 6.3V AC heaters and a voltage doubler and rectifier to provide the "HT". I recall a one valve design in Radio Constructor, which I build. It was the 'cover article'. The design called for an Eddystone Box, far too expensive, so I used a tin box from some short bread. I remember back in the 70's we had radar sets with ZERO volts on the magnetron's anode (DC ground). Of course, there was -3KV or so on the cathode :) I haven't done anything with radar in well over 30 years, so I don't know if they still do it or not. But I wouldn't be surprised. At first glance it sounds crazy - but it made for a very simple and efficient way to couple the output of the magnetron to the waveguide. No reason why it shouldn't be done. I can imagine some of the more "technically challenged" struggling with it but there are always those who insist that all who have been designing kit for years have got it wrong. Indeed it is rather similar to what was done with TV and monitor CRTs, to interface the screen with people's living rooms at an appropriate potential! Hmmm, they must have done it differently over there. I've been bitten a number of times by not being careful around the anode lead on a CRT. The cathode is nearer ground potential because it's exposed on the back of the tube. You'd think being bitten by 25KV the first time would teach me a lesson. But some people never learn :) I was a 1960s TV engineer in the UK. 15kV or so on the CRT anode was normal. The viewer was protected by a thick layer of glass that also formed an implosion guard. Colour CRTs had around 25kV on the anode, and in early models with anode currents of 1mA or so the line output stage was lead shielded to reduce X-radiation. Happy days. Yup, same here. Except when you jig the chassis up for testing, the anode lead is basically hanging in the air. Also, the CRT makes a great capacitor - if you don't discharge it enough times before disconnecting the anode lead, it can still set you back on your backside :) If you discharged it by simply shorting the anode to chassis you could damage the CRT. -- ;-) .. 73 de Frank Turner-Smith G3VKI - mine's a pint. .. http://turner-smith.co.uk .. Ubuntu 12.04 Thunderbirds are go. |
The "Two Transistor challenge" - taking things a bit too far?
On 2/19/2014 1:35 PM, Frank Turner-Smith G3VKI wrote:
On 19/02/14 03:09, Jerry Stuckle wrote: On 2/18/2014 7:06 PM, FranK Turner-Smith G3VKI wrote: "Jerry Stuckle" wrote in message ... On 2/18/2014 4:29 PM, Percy Picacity wrote: In article , Brian Reay wrote: On 18/02/14 20:31, Jerry Stuckle wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? Not carping, just curious. There have always been "contests" like that, though sometimes they were about "build a whole receiver using the same transistor type", or "build a receiver without any ICs" after ICs had come around. What I find intriguing is the realisation that valves ("tubes" to you?) can be operated with only 12V on the anode. No unusual at all. Not only were a number of valves for the car radio (and possibly other) markets available, I recall designs which use 'ordinary' valves with 6.3V AC heaters and a voltage doubler and rectifier to provide the "HT". I recall a one valve design in Radio Constructor, which I build. It was the 'cover article'. The design called for an Eddystone Box, far too expensive, so I used a tin box from some short bread. I remember back in the 70's we had radar sets with ZERO volts on the magnetron's anode (DC ground). Of course, there was -3KV or so on the cathode :) I haven't done anything with radar in well over 30 years, so I don't know if they still do it or not. But I wouldn't be surprised. At first glance it sounds crazy - but it made for a very simple and efficient way to couple the output of the magnetron to the waveguide. No reason why it shouldn't be done. I can imagine some of the more "technically challenged" struggling with it but there are always those who insist that all who have been designing kit for years have got it wrong. Indeed it is rather similar to what was done with TV and monitor CRTs, to interface the screen with people's living rooms at an appropriate potential! Hmmm, they must have done it differently over there. I've been bitten a number of times by not being careful around the anode lead on a CRT. The cathode is nearer ground potential because it's exposed on the back of the tube. You'd think being bitten by 25KV the first time would teach me a lesson. But some people never learn :) I was a 1960s TV engineer in the UK. 15kV or so on the CRT anode was normal. The viewer was protected by a thick layer of glass that also formed an implosion guard. Colour CRTs had around 25kV on the anode, and in early models with anode currents of 1mA or so the line output stage was lead shielded to reduce X-radiation. Happy days. Yup, same here. Except when you jig the chassis up for testing, the anode lead is basically hanging in the air. Also, the CRT makes a great capacitor - if you don't discharge it enough times before disconnecting the anode lead, it can still set you back on your backside :) If you discharged it by simply shorting the anode to chassis you could damage the CRT. I've heard that, but it never happened to me or anyone I know. But I also agree that doesn't mean it can't happen. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
The "Two Transistor challenge" - taking things a bit too far?
"Michael Black" wrote in message news:alpine.LNX.2.02.1402190105000.16359@darkstar. example.org... On Wed, 19 Feb 2014, Phi wrote: I still have the HP-35 and an HP-25 that can be programmed up to 49 steps. What happens when you turn off the HP-25? Is it one that keeps the memory alive, or do you lose everything after you typed it all in? Michael With mine, memory is lost when turned off. |
The "Two Transistor challenge" - taking things a bit too far?
On 19/02/2014 09:32, gareth wrote:
"AndyW" wrote in message ... (but then I enjoy retro-tech like making Baird televisors) Mirror-drum, or Nipkow disk? Nipow disk. I built my first one while at school using plans in Hobby Electronics using my sister's 'The Partridge Family Album' LP, I thought that it was the best use that it could be put to; she disagreed. One of my later ones used a 'conveyer belt' instead of a disk which produces a square screen. LED or nitro-benzine as the polariser? Polariser? I used a neon as my light source, I didn't have any polarisation. My later ones use LEDs at light sources and produce a much better quality of image. Andy |
The "Two Transistor challenge" - taking things a bit too far?
On 19/02/2014 16:30, Michael Black wrote:
On Wed, 19 Feb 2014, AndyW wrote: On 18/02/2014 10:58, gareth wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? Not carping, just curious. There is something challenging about restricting your resources. My most memorable receiver I ever built was made from a toilet roll tube, wire, a crystal earpiece, tinfoil and paper hand-rolled capacitor and some galena crystal as a detector. I think I got more satisfaction out of that that I ever did from a digitally programmable oscillator based beast. I think that's something that may be lost. People lament that in this day and age, it's difficult to attract the young to the hobby, because how can it compete with the Internet? Because I am a bit of a geek I get asked to run Jamboree on the Internet for my local scout group in October (been doing it for about 10 years now). When we have computers set up for text chat, chat rooms, voip, skype video chat and multi participant video conferencing the kids are simply not interested in talking on the radio. They can get crystal clear communication and don't really care about some faint HF chat. It is sad but to compete radio has to offer something new or different. I would like to get them to build simple qrp sets and use WSPR to see how far they can reach and also see how far they can communicate on qrp with morse (albeit with some help). They simply cannot make an internet capable computer and OS but they can make a QRP set like a pixie on a breadboard in an hour and be picked up around the world on WSPR. Catch that buzz and then it is a short step to (very slow) morse communication and hopefully getting them hooked. And you don't compete with it, you show off things that are unique. A simple project for a beginner is identical to what it was forty or fifty years ago, a first project and when it actually gets working, what an accomplishment. It's not because the simple project is comparable with the electronic wonders of the 21st century, it's that you built it and it worked. I was asked to run a technology based badge for some scouts and had them making crystal radios, some of them swore blind that it could not work because there were no batteries despite building it themselves and hand winding the coils. The reaction by many is pure amazement that a bundle of wire and junk can receive a radio station, it remind me of the buzz I first got as a kid making a crystal set from plans in the eagle annual (I'm not old enough to get one from new, I bought it in a jumble sale in the 70s) The buzz is still there if you get them young enough and pre internet chat. Andy |
The "Two Transistor challenge" - taking things a bit too far?
"AndyW" wrote in message
... On 19/02/2014 09:32, gareth wrote: LED or nitro-benzine as the polariser? Polariser? To my eternal regret, because I disposed of them 38 years ago, I had a pile of "Amateur Wireless" from the 1930s within which were designs for mirror-drum scanners, and the modulation was not by a neon light but with a constant light source which was then modulated by a series of polarising filters, with one being variable to rotate the polarisation. ISTR (38 years ago!!!) that the liquid used was nitro-benzene |
The "Two Transistor challenge" - taking things a bit too far?
On 20/02/2014 11:51, gareth wrote:
"AndyW" wrote in message ... On 19/02/2014 09:32, gareth wrote: LED or nitro-benzine as the polariser? Polariser? To my eternal regret, because I disposed of them 38 years ago, I had a pile of "Amateur Wireless" from the 1930s within which were designs for mirror-drum scanners, and the modulation was not by a neon light but with a constant light source which was then modulated by a series of polarising filters, with one being variable to rotate the polarisation. ISTR (38 years ago!!!) that the liquid used was nitro-benzene OK I follow you now. I had a quick google and found out about nitrobenzene and modulating polarisation. Never heard of it before. Live and learn. My original set up was as simple and agricultural as they come, vinyl LP, scrap motor from a cassette player, Neon attached to am amplifier behind the 'screen' and a camera made from a lens and an LDR recording onto a cassette player - the bandwidth was low enough to record on audio. My latest televisor was made from a circle of black plastic spinning on a hand fan with a very small torch behind it modulated by the sound from a small mp3 player. It all folds up and fits in a pocket. Andy |
The "Two Transistor challenge" - taking things a bit too far?
"AndyW" wrote in message
... On 20/02/2014 11:51, gareth wrote: "AndyW" wrote in message ... On 19/02/2014 09:32, gareth wrote: LED or nitro-benzine as the polariser? Polariser? To my eternal regret, because I disposed of them 38 years ago, I had a pile of "Amateur Wireless" from the 1930s within which were designs for mirror-drum scanners, and the modulation was not by a neon light but with a constant light source which was then modulated by a series of polarising filters, with one being variable to rotate the polarisation. ISTR (38 years ago!!!) that the liquid used was nitro-benzene OK I follow you now. I had a quick google and found out about nitrobenzene and modulating polarisation. Never heard of it before. Live and learn. My original set up was as simple and agricultural as they come, vinyl LP, scrap motor from a cassette player, Neon attached to am amplifier behind the 'screen' and a camera made from a lens and an LDR recording onto a cassette player - the bandwidth was low enough to record on audio. My latest televisor was made from a circle of black plastic spinning on a hand fan with a very small torch behind it modulated by the sound from a small mp3 player. It all folds up and fits in a pocket. Wow! How many lines and frames / sec? |
The "Two Transistor challenge" - taking things a bit too far?
"gareth" wrote in message
... Wow! How many lines and frames / sec? A quick google yielded ... http://www.tvhistory.tv/1935%20TV%20...20Part%202.htm .... and look for "Kerr Cell" |
The "Two Transistor challenge" - taking things a bit too far?
On 19/02/2014 18:51, Jerry Stuckle wrote:
On 2/19/2014 1:35 PM, Frank Turner-Smith G3VKI wrote: On 19/02/14 03:09, Jerry Stuckle wrote: On 2/18/2014 7:06 PM, FranK Turner-Smith G3VKI wrote: "Jerry Stuckle" wrote in message ... On 2/18/2014 4:29 PM, Percy Picacity wrote: In article , Brian Reay wrote: On 18/02/14 20:31, Jerry Stuckle wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? Not carping, just curious. There have always been "contests" like that, though sometimes they were about "build a whole receiver using the same transistor type", or "build a receiver without any ICs" after ICs had come around. What I find intriguing is the realisation that valves ("tubes" to you?) can be operated with only 12V on the anode. No unusual at all. Not only were a number of valves for the car radio (and possibly other) markets available, I recall designs which use 'ordinary' valves with 6.3V AC heaters and a voltage doubler and rectifier to provide the "HT". I recall a one valve design in Radio Constructor, which I build. It was the 'cover article'. The design called for an Eddystone Box, far too expensive, so I used a tin box from some short bread. I remember back in the 70's we had radar sets with ZERO volts on the magnetron's anode (DC ground). Of course, there was -3KV or so on the cathode :) I haven't done anything with radar in well over 30 years, so I don't know if they still do it or not. But I wouldn't be surprised. At first glance it sounds crazy - but it made for a very simple and efficient way to couple the output of the magnetron to the waveguide. No reason why it shouldn't be done. I can imagine some of the more "technically challenged" struggling with it but there are always those who insist that all who have been designing kit for years have got it wrong. Indeed it is rather similar to what was done with TV and monitor CRTs, to interface the screen with people's living rooms at an appropriate potential! Hmmm, they must have done it differently over there. I've been bitten a number of times by not being careful around the anode lead on a CRT. The cathode is nearer ground potential because it's exposed on the back of the tube. You'd think being bitten by 25KV the first time would teach me a lesson. But some people never learn :) I was a 1960s TV engineer in the UK. 15kV or so on the CRT anode was normal. The viewer was protected by a thick layer of glass that also formed an implosion guard. Colour CRTs had around 25kV on the anode, and in early models with anode currents of 1mA or so the line output stage was lead shielded to reduce X-radiation. Happy days. Yup, same here. Except when you jig the chassis up for testing, the anode lead is basically hanging in the air. Also, the CRT makes a great capacitor - if you don't discharge it enough times before disconnecting the anode lead, it can still set you back on your backside :) If you discharged it by simply shorting the anode to chassis you could damage the CRT. I've heard that, but it never happened to me or anyone I know. But I also agree that doesn't mean it can't happen. Dead shorts to ground tend to smoke things. -- J |
The "Two Transistor challenge" - taking things a bit too far?
On 2/20/2014 4:15 PM, Brown Sugar wrote:
On 19/02/2014 18:51, Jerry Stuckle wrote: On 2/19/2014 1:35 PM, Frank Turner-Smith G3VKI wrote: On 19/02/14 03:09, Jerry Stuckle wrote: On 2/18/2014 7:06 PM, FranK Turner-Smith G3VKI wrote: "Jerry Stuckle" wrote in message ... On 2/18/2014 4:29 PM, Percy Picacity wrote: In article , Brian Reay wrote: On 18/02/14 20:31, Jerry Stuckle wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? Not carping, just curious. There have always been "contests" like that, though sometimes they were about "build a whole receiver using the same transistor type", or "build a receiver without any ICs" after ICs had come around. What I find intriguing is the realisation that valves ("tubes" to you?) can be operated with only 12V on the anode. No unusual at all. Not only were a number of valves for the car radio (and possibly other) markets available, I recall designs which use 'ordinary' valves with 6.3V AC heaters and a voltage doubler and rectifier to provide the "HT". I recall a one valve design in Radio Constructor, which I build. It was the 'cover article'. The design called for an Eddystone Box, far too expensive, so I used a tin box from some short bread. I remember back in the 70's we had radar sets with ZERO volts on the magnetron's anode (DC ground). Of course, there was -3KV or so on the cathode :) I haven't done anything with radar in well over 30 years, so I don't know if they still do it or not. But I wouldn't be surprised. At first glance it sounds crazy - but it made for a very simple and efficient way to couple the output of the magnetron to the waveguide. No reason why it shouldn't be done. I can imagine some of the more "technically challenged" struggling with it but there are always those who insist that all who have been designing kit for years have got it wrong. Indeed it is rather similar to what was done with TV and monitor CRTs, to interface the screen with people's living rooms at an appropriate potential! Hmmm, they must have done it differently over there. I've been bitten a number of times by not being careful around the anode lead on a CRT. The cathode is nearer ground potential because it's exposed on the back of the tube. You'd think being bitten by 25KV the first time would teach me a lesson. But some people never learn :) I was a 1960s TV engineer in the UK. 15kV or so on the CRT anode was normal. The viewer was protected by a thick layer of glass that also formed an implosion guard. Colour CRTs had around 25kV on the anode, and in early models with anode currents of 1mA or so the line output stage was lead shielded to reduce X-radiation. Happy days. Yup, same here. Except when you jig the chassis up for testing, the anode lead is basically hanging in the air. Also, the CRT makes a great capacitor - if you don't discharge it enough times before disconnecting the anode lead, it can still set you back on your backside :) If you discharged it by simply shorting the anode to chassis you could damage the CRT. I've heard that, but it never happened to me or anyone I know. But I also agree that doesn't mean it can't happen. Dead shorts to ground tend to smoke things. Not necessarily with static charges - which is what's on the CRT with the HV removed. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
The "Two Transistor challenge" - taking things a bit too far?
"Jerry Stuckle" wrote in message
... On 2/20/2014 4:15 PM, Brown Sugar wrote: On 19/02/2014 18:51, Jerry Stuckle wrote: On 2/19/2014 1:35 PM, Frank Turner-Smith G3VKI wrote: On 19/02/14 03:09, Jerry Stuckle wrote: On 2/18/2014 7:06 PM, FranK Turner-Smith G3VKI wrote: "Jerry Stuckle" wrote in message ... On 2/18/2014 4:29 PM, Percy Picacity wrote: In article , Brian Reay wrote: On 18/02/14 20:31, Jerry Stuckle wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? Not carping, just curious. There have always been "contests" like that, though sometimes they were about "build a whole receiver using the same transistor type", or "build a receiver without any ICs" after ICs had come around. What I find intriguing is the realisation that valves ("tubes" to you?) can be operated with only 12V on the anode. No unusual at all. Not only were a number of valves for the car radio (and possibly other) markets available, I recall designs which use 'ordinary' valves with 6.3V AC heaters and a voltage doubler and rectifier to provide the "HT". I recall a one valve design in Radio Constructor, which I build. It was the 'cover article'. The design called for an Eddystone Box, far too expensive, so I used a tin box from some short bread. I remember back in the 70's we had radar sets with ZERO volts on the magnetron's anode (DC ground). Of course, there was -3KV or so on the cathode :) I haven't done anything with radar in well over 30 years, so I don't know if they still do it or not. But I wouldn't be surprised. At first glance it sounds crazy - but it made for a very simple and efficient way to couple the output of the magnetron to the waveguide. No reason why it shouldn't be done. I can imagine some of the more "technically challenged" struggling with it but there are always those who insist that all who have been designing kit for years have got it wrong. Indeed it is rather similar to what was done with TV and monitor CRTs, to interface the screen with people's living rooms at an appropriate potential! Hmmm, they must have done it differently over there. I've been bitten a number of times by not being careful around the anode lead on a CRT. The cathode is nearer ground potential because it's exposed on the back of the tube. You'd think being bitten by 25KV the first time would teach me a lesson. But some people never learn :) I was a 1960s TV engineer in the UK. 15kV or so on the CRT anode was normal. The viewer was protected by a thick layer of glass that also formed an implosion guard. Colour CRTs had around 25kV on the anode, and in early models with anode currents of 1mA or so the line output stage was lead shielded to reduce X-radiation. Happy days. Yup, same here. Except when you jig the chassis up for testing, the anode lead is basically hanging in the air. Also, the CRT makes a great capacitor - if you don't discharge it enough times before disconnecting the anode lead, it can still set you back on your backside :) If you discharged it by simply shorting the anode to chassis you could damage the CRT. I've heard that, but it never happened to me or anyone I know. But I also agree that doesn't mean it can't happen. Dead shorts to ground tend to smoke things. Not necessarily with static charges - which is what's on the CRT with the HV removed. Lightning is a static discharge, are you saying that doesn't smoke things? -- ;-) .. 73 de Frank Turner-Smith G3VKI - mine's a pint. .. http://turner-smith.co.uk |
The "Two Transistor challenge" - taking things a bit too far?
In article ,
"FranK Turner-Smith G3VKI" wrote: "Jerry Stuckle" wrote in message ... On 2/20/2014 4:15 PM, Brown Sugar wrote: On 19/02/2014 18:51, Jerry Stuckle wrote: On 2/19/2014 1:35 PM, Frank Turner-Smith G3VKI wrote: On 19/02/14 03:09, Jerry Stuckle wrote: On 2/18/2014 7:06 PM, FranK Turner-Smith G3VKI wrote: "Jerry Stuckle" wrote in message ... On 2/18/2014 4:29 PM, Percy Picacity wrote: In article , Brian Reay wrote: On 18/02/14 20:31, Jerry Stuckle wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? Not carping, just curious. There have always been "contests" like that, though sometimes they were about "build a whole receiver using the same transistor type", or "build a receiver without any ICs" after ICs had come around. What I find intriguing is the realisation that valves ("tubes" to you?) can be operated with only 12V on the anode. No unusual at all. Not only were a number of valves for the car radio (and possibly other) markets available, I recall designs which use 'ordinary' valves with 6.3V AC heaters and a voltage doubler and rectifier to provide the "HT". I recall a one valve design in Radio Constructor, which I build. It was the 'cover article'. The design called for an Eddystone Box, far too expensive, so I used a tin box from some short bread. I remember back in the 70's we had radar sets with ZERO volts on the magnetron's anode (DC ground). Of course, there was -3KV or so on the cathode :) I haven't done anything with radar in well over 30 years, so I don't know if they still do it or not. But I wouldn't be surprised. At first glance it sounds crazy - but it made for a very simple and efficient way to couple the output of the magnetron to the waveguide. No reason why it shouldn't be done. I can imagine some of the more "technically challenged" struggling with it but there are always those who insist that all who have been designing kit for years have got it wrong. Indeed it is rather similar to what was done with TV and monitor CRTs, to interface the screen with people's living rooms at an appropriate potential! Hmmm, they must have done it differently over there. I've been bitten a number of times by not being careful around the anode lead on a CRT. The cathode is nearer ground potential because it's exposed on the back of the tube. You'd think being bitten by 25KV the first time would teach me a lesson. But some people never learn :) I was a 1960s TV engineer in the UK. 15kV or so on the CRT anode was normal. The viewer was protected by a thick layer of glass that also formed an implosion guard. Colour CRTs had around 25kV on the anode, and in early models with anode currents of 1mA or so the line output stage was lead shielded to reduce X-radiation. Happy days. Yup, same here. Except when you jig the chassis up for testing, the anode lead is basically hanging in the air. Also, the CRT makes a great capacitor - if you don't discharge it enough times before disconnecting the anode lead, it can still set you back on your backside :) If you discharged it by simply shorting the anode to chassis you could damage the CRT. I've heard that, but it never happened to me or anyone I know. But I also agree that doesn't mean it can't happen. Dead shorts to ground tend to smoke things. Not necessarily with static charges - which is what's on the CRT with the HV removed. Lightning is a static discharge, are you saying that doesn't smoke things? The practical point is that the capacitance of a CRT is quite low, limiting the amount of energy stored at a given potential. It's not a negligible amount though. I suppose you could describe the charge on a large power supply capacitor as a static charge too, but that is definitely not negligible. -- Percy Picacity |
The "Two Transistor challenge" - taking things a bit too far?
In article
, Brian Reay wrote: Percy Picacity wrote: Not necessarily with static charges - which is what's on the CRT with the HV removed. Lightning is a static discharge, are you saying that doesn't smoke things? The practical point is that the capacitance of a CRT is quite low, limiting the amount of energy stored at a given potential. It's not a negligible amount though. I suppose you could describe the charge on a large power supply capacitor as a static charge too, but that is definitely not negligible. Energy stored in the cap is 0.5 CV^2 If V is large, as in a CRT, V^2 is going to be something to worry about. On reflection, I agree. The capacitance of a CRT is about 10^7 lower than of a PSU capacitor, but V^2 is about 10^7 higher - so about the same energy. That simple formula is the reason, in applications requiring a brief 'hold up', PSUs in aircraft etc often have a voltage doubler on their input so the can extend the hold up time by storing more energy for a given C. (Adding a battery is not permitted by the aircraft design rules.) -- Percy Picacity |
The "Two Transistor challenge" - taking things a bit too far?
On 2/21/2014 3:12 AM, FranK Turner-Smith G3VKI wrote:
"Jerry Stuckle" wrote in message ... On 2/20/2014 4:15 PM, Brown Sugar wrote: On 19/02/2014 18:51, Jerry Stuckle wrote: On 2/19/2014 1:35 PM, Frank Turner-Smith G3VKI wrote: On 19/02/14 03:09, Jerry Stuckle wrote: On 2/18/2014 7:06 PM, FranK Turner-Smith G3VKI wrote: "Jerry Stuckle" wrote in message ... On 2/18/2014 4:29 PM, Percy Picacity wrote: In article , Brian Reay wrote: On 18/02/14 20:31, Jerry Stuckle wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? Not carping, just curious. There have always been "contests" like that, though sometimes they were about "build a whole receiver using the same transistor type", or "build a receiver without any ICs" after ICs had come around. What I find intriguing is the realisation that valves ("tubes" to you?) can be operated with only 12V on the anode. No unusual at all. Not only were a number of valves for the car radio (and possibly other) markets available, I recall designs which use 'ordinary' valves with 6.3V AC heaters and a voltage doubler and rectifier to provide the "HT". I recall a one valve design in Radio Constructor, which I build. It was the 'cover article'. The design called for an Eddystone Box, far too expensive, so I used a tin box from some short bread. I remember back in the 70's we had radar sets with ZERO volts on the magnetron's anode (DC ground). Of course, there was -3KV or so on the cathode :) I haven't done anything with radar in well over 30 years, so I don't know if they still do it or not. But I wouldn't be surprised. At first glance it sounds crazy - but it made for a very simple and efficient way to couple the output of the magnetron to the waveguide. No reason why it shouldn't be done. I can imagine some of the more "technically challenged" struggling with it but there are always those who insist that all who have been designing kit for years have got it wrong. Indeed it is rather similar to what was done with TV and monitor CRTs, to interface the screen with people's living rooms at an appropriate potential! Hmmm, they must have done it differently over there. I've been bitten a number of times by not being careful around the anode lead on a CRT. The cathode is nearer ground potential because it's exposed on the back of the tube. You'd think being bitten by 25KV the first time would teach me a lesson. But some people never learn :) I was a 1960s TV engineer in the UK. 15kV or so on the CRT anode was normal. The viewer was protected by a thick layer of glass that also formed an implosion guard. Colour CRTs had around 25kV on the anode, and in early models with anode currents of 1mA or so the line output stage was lead shielded to reduce X-radiation. Happy days. Yup, same here. Except when you jig the chassis up for testing, the anode lead is basically hanging in the air. Also, the CRT makes a great capacitor - if you don't discharge it enough times before disconnecting the anode lead, it can still set you back on your backside :) If you discharged it by simply shorting the anode to chassis you could damage the CRT. I've heard that, but it never happened to me or anyone I know. But I also agree that doesn't mean it can't happen. Dead shorts to ground tend to smoke things. Not necessarily with static charges - which is what's on the CRT with the HV removed. Lightning is a static discharge, are you saying that doesn't smoke things? Now you're just trolling. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
The "Two Transistor challenge" - taking things a bit too far?
On 21/02/2014 01:35, Jerry Stuckle wrote:
On 2/20/2014 4:15 PM, Brown Sugar wrote: On 19/02/2014 18:51, Jerry Stuckle wrote: On 2/19/2014 1:35 PM, Frank Turner-Smith G3VKI wrote: On 19/02/14 03:09, Jerry Stuckle wrote: On 2/18/2014 7:06 PM, FranK Turner-Smith G3VKI wrote: "Jerry Stuckle" wrote in message ... On 2/18/2014 4:29 PM, Percy Picacity wrote: In article , Brian Reay wrote: On 18/02/14 20:31, Jerry Stuckle wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? Not carping, just curious. There have always been "contests" like that, though sometimes they were about "build a whole receiver using the same transistor type", or "build a receiver without any ICs" after ICs had come around. What I find intriguing is the realisation that valves ("tubes" to you?) can be operated with only 12V on the anode. No unusual at all. Not only were a number of valves for the car radio (and possibly other) markets available, I recall designs which use 'ordinary' valves with 6.3V AC heaters and a voltage doubler and rectifier to provide the "HT". I recall a one valve design in Radio Constructor, which I build. It was the 'cover article'. The design called for an Eddystone Box, far too expensive, so I used a tin box from some short bread. I remember back in the 70's we had radar sets with ZERO volts on the magnetron's anode (DC ground). Of course, there was -3KV or so on the cathode :) I haven't done anything with radar in well over 30 years, so I don't know if they still do it or not. But I wouldn't be surprised. At first glance it sounds crazy - but it made for a very simple and efficient way to couple the output of the magnetron to the waveguide. No reason why it shouldn't be done. I can imagine some of the more "technically challenged" struggling with it but there are always those who insist that all who have been designing kit for years have got it wrong. Indeed it is rather similar to what was done with TV and monitor CRTs, to interface the screen with people's living rooms at an appropriate potential! Hmmm, they must have done it differently over there. I've been bitten a number of times by not being careful around the anode lead on a CRT. The cathode is nearer ground potential because it's exposed on the back of the tube. You'd think being bitten by 25KV the first time would teach me a lesson. But some people never learn :) I was a 1960s TV engineer in the UK. 15kV or so on the CRT anode was normal. The viewer was protected by a thick layer of glass that also formed an implosion guard. Colour CRTs had around 25kV on the anode, and in early models with anode currents of 1mA or so the line output stage was lead shielded to reduce X-radiation. Happy days. Yup, same here. Except when you jig the chassis up for testing, the anode lead is basically hanging in the air. Also, the CRT makes a great capacitor - if you don't discharge it enough times before disconnecting the anode lead, it can still set you back on your backside :) If you discharged it by simply shorting the anode to chassis you could damage the CRT. I've heard that, but it never happened to me or anyone I know. But I also agree that doesn't mean it can't happen. Dead shorts to ground tend to smoke things. Not necessarily with static charges - which is what's on the CRT with the HV removed. good point -- J |
The "Two Transistor challenge" - taking things a bit too far?
On 2/21/2014 4:54 PM, Brian Reay wrote:
Brown Sugar wrote: On 21/02/2014 01:35, Jerry Stuckle wrote: Not necessarily with static charges - which is what's on the CRT with the HV removed. good point Really? What matters is the energy stored. There is enough stored on the CRT to kill or at least do serious harm. Calling it static charge doesn't make it any safer. Static charge can kill, it depends how quickly the charge is transferred (the current). Which is the whole reason for discharging the CRT (multiple times) before working on it. Did you read the entire thread? Or just the one post? rest of irrelevant information snipped). -- ================== Remove the "x" from my email address Jerry Stuckle ================== |
The "Two Transistor challenge" - taking things a bit too far?
On 2/21/2014 5:35 PM, Brian Reay wrote:
Jerry Stuckle wrote: On 2/21/2014 4:54 PM, Brian Reay wrote: Brown Sugar wrote: On 21/02/2014 01:35, Jerry Stuckle wrote: Not necessarily with static charges - which is what's on the CRT with the HV removed. good point Really? What matters is the energy stored. There is enough stored on the CRT to kill or at least do serious harm. Calling it static charge doesn't make it any safer. Static charge can kill, it depends how quickly the charge is transferred (the current). Which is the whole reason for discharging the CRT (multiple times) before working on it. Did you read the entire thread? Or just the one post? rest of irrelevant information snipped). Why then had you mentioned 'static'? If you would have read the entire thread, you would have understood. I'm not in the habit of repeating myself for those too lazy to read. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
The "Two Transistor challenge" - taking things a bit too far?
On 21/02/2014 21:54, Brian Reay wrote:
Brown Sugar wrote: On 21/02/2014 01:35, Jerry Stuckle wrote: Not necessarily with static charges - which is what's on the CRT with the HV removed. good point Really? What matters is the energy stored. There is enough stored on the CRT to kill or at least do serious harm. Calling it static charge doesn't make it any safer. Static charge can kill, it depends how quickly the charge is transferred (the current). That is determined, as basic circuit theory dictates, by the source impedance. A Van deGraff generator can generator perhaps 10's of thousands of volts. Enough to generate huge sparks. When I was at school, it was common practice for the teacher to have a ring of pupils touching it and have sparks jumping between metal rods they held. They all lived to write it up. It was safe because the source impedance was high (rate of energy transfer low). Had he tried it with 240V, he would be up on a murder charge. Low source impedance, the mains can supply a lot of energy quickly. good point -- J |
The "Two Transistor challenge" - taking things a bit too far?
I remember a value of ~500pf for a 28" colour tube. It will of course, vary
according to the thickness of glass and surface area of coatings etc. |
The "Two Transistor challenge" - taking things a bit too far?
On 20/02/2014 15:08, gareth wrote:
"AndyW" wrote in message ... On 20/02/2014 11:51, gareth wrote: "AndyW" wrote in message ... On 19/02/2014 09:32, gareth wrote: LED or nitro-benzine as the polariser? Polariser? To my eternal regret, because I disposed of them 38 years ago, I had a pile of "Amateur Wireless" from the 1930s within which were designs for mirror-drum scanners, and the modulation was not by a neon light but with a constant light source which was then modulated by a series of polarising filters, with one being variable to rotate the polarisation. ISTR (38 years ago!!!) that the liquid used was nitro-benzene OK I follow you now. I had a quick google and found out about nitrobenzene and modulating polarisation. Never heard of it before. Live and learn. My original set up was as simple and agricultural as they come, vinyl LP, scrap motor from a cassette player, Neon attached to am amplifier behind the 'screen' and a camera made from a lens and an LDR recording onto a cassette player - the bandwidth was low enough to record on audio. My latest televisor was made from a circle of black plastic spinning on a hand fan with a very small torch behind it modulated by the sound from a small mp3 player. It all folds up and fits in a pocket. Wow! How many lines and frames / sec? 64 lines of low definition glory, I could not tell you of the frames per second as I use the same TV as a camera by using the same disk, once the frame starts are synced it works fine. The syncing is carried out by the highly technical method of slowing the fan with an index finger. Andy |
The "Two Transistor challenge" - taking things a bit too far?
"AndyW" wrote in message
... On 20/02/2014 15:08, gareth wrote: "AndyW" wrote in message ... On 20/02/2014 11:51, gareth wrote: "AndyW" wrote in message ... On 19/02/2014 09:32, gareth wrote: LED or nitro-benzine as the polariser? Polariser? To my eternal regret, because I disposed of them 38 years ago, I had a pile of "Amateur Wireless" from the 1930s within which were designs for mirror-drum scanners, and the modulation was not by a neon light but with a constant light source which was then modulated by a series of polarising filters, with one being variable to rotate the polarisation. ISTR (38 years ago!!!) that the liquid used was nitro-benzene OK I follow you now. I had a quick google and found out about nitrobenzene and modulating polarisation. Never heard of it before. Live and learn. My original set up was as simple and agricultural as they come, vinyl LP, scrap motor from a cassette player, Neon attached to am amplifier behind the 'screen' and a camera made from a lens and an LDR recording onto a cassette player - the bandwidth was low enough to record on audio. My latest televisor was made from a circle of black plastic spinning on a hand fan with a very small torch behind it modulated by the sound from a small mp3 player. It all folds up and fits in a pocket. Wow! How many lines and frames / sec? 64 lines of low definition glory, I could not tell you of the frames per second as I use the same TV as a camera by using the same disk, once the frame starts are synced it works fine. The syncing is carried out by the highly technical method of slowing the fan with an index finger. Picking up on your BW comment, AIUI, the Baird transmssions of 30 line pictures were also of the audio BW, and were transmitted as part of the normal broadcast, but not at the same time as the audio; it was either speech or video, but not simultaneously! |
The "Two Transistor challenge" - taking things a bit too far?
On 24/02/2014 08:12, gareth wrote:
Picking up on your BW comment, AIUI, the Baird transmssions of 30 line pictures were also of the audio BW, and were transmitted as part of the normal broadcast, but not at the same time as the audio; it was either speech or video, but not simultaneously! I read that. You would think that it would be trivial to transmit on 2 channels; one for the video and one for the sound. The bloke who invented thermal socks should have thought of that. Andy |
The "Two Transistor challenge" - taking things a bit too far?
"AndyW" wrote in message
... On 24/02/2014 08:12, gareth wrote: Picking up on your BW comment, AIUI, the Baird transmssions of 30 line pictures were also of the audio BW, and were transmitted as part of the normal broadcast, but not at the same time as the audio; it was either speech or video, but not simultaneously! I read that. You would think that it would be trivial to transmit on 2 channels; one for the video and one for the sound. Not at that time, when what most people could afford was a blooper, although admittedly it was probably the rich who could afford Baird Televisors and therefore could have stretched to another set for a second channel. |
The "Two Transistor challenge" - taking things a bit too far?
On Tue, 25 Feb 2014, AndyW wrote:
On 24/02/2014 08:12, gareth wrote: Picking up on your BW comment, AIUI, the Baird transmssions of 30 line pictures were also of the audio BW, and were transmitted as part of the normal broadcast, but not at the same time as the audio; it was either speech or video, but not simultaneously! I read that. You would think that it would be trivial to transmit on 2 channels; one for the video and one for the sound. But at the time, it would have been expensive, another receiver for the second channel, two transmitters at the transmitting end. And wasn't it the era of silent films, or at least silent films weren't that long in the past? "Who needs the hear sound while watching a picture?" Much later, some used ISB (independent sideband) to send SSTV and have audio at the same time. Audio on one sideband, the SSTV signal on the other. But that's even worse, two whole receivers and two whole transmitters at both ends, all that selectivity and stability that wouldn't have been available earlier. Michael The bloke who invented thermal socks should have thought of that. Andy |
The "Two Transistor challenge" - taking things a bit too far?
"Michael Black" wrote in message
xample.org... On Tue, 25 Feb 2014, AndyW wrote: On 24/02/2014 08:12, gareth wrote: Picking up on your BW comment, AIUI, the Baird transmssions of 30 line pictures were also of the audio BW, and were transmitted as part of the normal broadcast, but not at the same time as the audio; it was either speech or video, but not simultaneously! I read that. You would think that it would be trivial to transmit on 2 channels; one for the video and one for the sound. But at the time, it would have been expensive, another receiver for the second channel, two transmitters at the transmitting end. And wasn't it the era of silent films, or at least silent films weren't that long in the past? "Who needs the hear sound while watching a picture?" Much later, some used ISB (independent sideband) to send SSTV and have audio at the same time. Audio on one sideband, the SSTV signal on the other. But that's even worse, two whole receivers and two whole transmitters at both ends, all that selectivity and stability that wouldn't have been available earlier. TX could have been simpler had they combined audio and video using quadrature modulation and a pilot tone, much as is / was used for the colour subcarrier in PAL (also NTSC?) TV, but I doubt that anyone, even the filthy rich (or even those who like to boast about how rich they are :-) ), could have afforded the concomitant RX complexity on their household budgets! And talking of colour TV encoding, ISTR ... NTSC - Never Twice the Same Colour SECAM - System Essentially Contrary to the American Method PAL - Peace At last! BUT, didn't Logie Baird (not to be confused with Yogi Bear :-) ) do some experimentation with colour TV on the mechanical approach anyway? |
The "Two Transistor challenge" - taking things a bit too far?
On 25/02/2014 16:00, gareth wrote:
BUT, didn't Logie Baird (not to be confused with Yogi Bear :-) ) do some experimentation with colour TV on the mechanical approach anyway? He did indeed produce colour TV, and the video recorder and, of course, thermal socks. Andy |
The "Two Transistor challenge" - taking things a bit too far?
"AndyW" wrote in message
... On 25/02/2014 16:00, gareth wrote: BUT, didn't Logie Baird (not to be confused with Yogi Bear :-) ) do some experimentation with colour TV on the mechanical approach anyway? He did indeed produce colour TV, and the video recorder and, of course, thermal socks. That Baird was living and working in a largely pre-techincal age, puts to shame all those grown-ups of today who exist with beginners' licences; especially where those licences are targetted at the 5-year-old. |
The "Two Transistor challenge" - taking things a bit too far?
On 2014-02-18, gareth wrote:
There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? I remember my first home build radio: a earphone with just a 1N34 diode in parallel, an outdoor antenna and a good ground. Lots of listening hours of a nearby AM 1230 KHz transmiter. With a single FET regenerative receiver I could listen shorwave radios from all over the world. I like to work with very simple electronic equipment: I am reading and replying to this news group with a 20 MHz 80286, 1 MBy memmory and all programs in a 1.44 diskette (no Hard Drive). Alejandro Lieber LU1FCR Rosario Argentina -- SDF Public Access UNIX System - http://sdf.org |
The "Two Transistor challenge" - taking things a bit too far?
On 2/26/2014 11:09 AM, Alejandro Lieber wrote:
On 2014-02-18, gareth wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? I remember my first home build radio: a earphone with just a 1N34 diode in parallel, an outdoor antenna and a good ground. Lots of listening hours of a nearby AM 1230 KHz transmiter. With a single FET regenerative receiver I could listen shorwave radios from all over the world. I like to work with very simple electronic equipment: I am reading and replying to this news group with a 20 MHz 80286, 1 MBy memmory and all programs in a 1.44 diskette (no Hard Drive). Alejandro Lieber LU1FCR Rosario Argentina I can understand this. Back in Junior High (middle school nowadays), my parents got me an electronics projects kit. It used a 1T4 for the active element; a D cell provided filament voltage and a 45V battery (looked like a long 9V battery) provided the plate voltage. I built all kinds of things from the examples, including regen receivers. I spent hundreds of hours with it - probably one of the best money my parents spent to keep me out of trouble :). It was advanced enough to keep me occupied, yet simple enough that it taught me a lot about how more advanced (at least to me, at the time) circuits work. I still like the simple electronics. However, simple receivers like that just won't work for me now. Something about the 5KW AM transmitter in my back yard... There is a lot to be said for simplicity! -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
The "Two Transistor challenge" - taking things a bit too far?
"Alejandro Lieber" wrote in message
... On 2014-02-18, gareth wrote: There was a time, back inthe 1920s and 1930s, that any active device (valves in them thar days, tubes for the leftpondians) would cost nearly a week's wages for the average working man, and so it was good economical sense to try and use it as many ways as possible simultaneously. Times have changes, and active devices with performance into the tens of MegaHertz are now ten-a-penny, so what is achieved by competitions such as the "Two Transistor Challenge" where it is the costs of switching (manual, relays) which would be the major outlay? I remember my first home build radio: a earphone with just a 1N34 diode in parallel, an outdoor antenna and a good ground. Lots of listening hours of a nearby AM 1230 KHz transmiter. With a single FET regenerative receiver I could listen shorwave radios from all over the world. I like to work with very simple electronic equipment: I am reading and replying to this news group with a 20 MHz 80286, 1 MBy memmory and all programs in a 1.44 diskette (no Hard Drive). Well done, that man! |
The "Two Transistor challenge" - taking things a bit too far?
"Jerry Stuckle" wrote in message
... I still like the simple electronics. However, simple receivers like that just won't work for me now. Something about the 5KW AM transmitter in my back yard... The same for me 50 years ago. Home town was Portishead, and the TXs of the international shipping Portiishead Radio were half a mile away across the valley! |
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