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Old 8th Jun 2022, 7:42 pm   #81
commie1
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Default Re: Magazine projects

Hi,

If you don't understand electronics, in detail but can construct a project from the circuit diagram and pcb layout, etc, such was the case when I first got started, the constructor doesn't know if their constructional effects are simply going to end up building a pile of pooh.

I am highly suspicious of magazine projects, in general, if you want to get serious about it, I always try and understand circuits published in service manuals of actual products that have sold for good money in the past.
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Old 8th Jun 2022, 9:26 pm   #82
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Default Re: Magazine projects

Quote:
Hi SH, Thanks but that is not the unit, never had that mag
I would be interested to know more about your units if you can ever find them or the related information. Sometimes the PCBs (if you have them) have the initials of the magazine on them and even a part / order number for the PCB which might be traceable back to the article.

I'm sure that in the main most magazine projects did work as conceived, the main problem was errors creeping into the text or artwork at the being-transferred-to-magazine stage.
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Old 8th Jun 2022, 9:34 pm   #83
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Hi SH, I only got the components, never ordered the PCBs. So nothing built. I wish I had seen the mag in your other post I may have bought the ready made units, a fair outlay for 3 three units in 1982.

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Old 8th Jun 2022, 9:59 pm   #84
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I looked at the R&EW article in some detail, seems to use a remote control transmitter receiver chip which uses 'Manchester' encoding to switch an audio tone on and off, and an NE567 tone detector IC to demodulate the signal back to Manchester data on receive. One crash or blurp or click on a noisy channel would be enough to knock one of the digits out and render the received data packet invalid so it probably wasn't very robust. The article even alludes to the fact that it is more likely to work on a nice clear frequency, but back in the day there wasn't really any such thing on CB, that would be why you were trying to use selcall in the first place.

The incorporation of a 40-way twin wafer switch (ie, CB radio channel switch) in the R&EW project makes it difficult to just go out and buy the parts for now, but you could perhaps use a couple of BCD thumbwheel switches instead. The remote control IC which forms the basis of the project is obsolete but still available at reasonable cost from the usual places.

If I was attempting the same thing now I would use a small Arduino and a DTMF transceiver chip because the makers of those specific-purpose chips really honed their signal processing side to the point where they were good at extracting DTMF tones over a wide range of input levels from a background of other sounds.

Nowadays there are off the shelf CB radios which include CTCSS, which is a less complicated way of hearing only the transmissions you want to hear.

Have a read through the rest of the R&EW magazines if you ever have time, there are a few CB related projects and articles in there.

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Old 9th Jun 2022, 12:03 pm   #85
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Thank You SH, I gave up with CB during the late 1980s. There were 3 of working us in a 1 mile radius with a hill and buildings in the middle trying to keep in contact. We would keep to the same channel all summer. There were blind spots for reception. Also we would occasionally get blasted out with people passing in their cars, resulting in CB being turned down, hence useless. The whole system was scrapped around 1987.

I will have a read through the mag and see what I missed.

John.
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Old 9th Jun 2022, 9:25 pm   #86
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I built the "Valve/Transistor Short Waver" from a 1961 Practical Wireless, using a valve found on a rubbish-dump, along with some "Red Spot" transistors and driver/output-transformers ordered C.O.D. from an ad in Practical Wireless... [delivered to my school; the school-secretary was not amused and I got a telling-off from 'the beak'].

With this I discovered hams operating on 3.5MHz...
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Old 10th Jun 2022, 9:14 am   #87
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Default Re: Magazine projects

Expanding on the main topic of this thread - has anyone got any suggestions for 'classics' in terms of magazine projects? i.e. one that became either an essential piece of test or entertainment equipment etc and possibly worthy of commercial production?

How about a magazine project that 'set the standard' (if there ever was one!)?

In the hayday of magazines there were many (imho) innovative ideas which persist to this day.
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Old 10th Jun 2022, 12:41 pm   #88
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Around the same time I passed my morse test in 1987 I built this 13.8V 20A linear power supply from the September 1987 issue of Amateur Radio Magazine.

https://warc.org.uk/?page_id=404

I still have the power supply today and it still works fine although I rarely use it nowadays. I've used it to help start a car a few times and it has survived plenty of abuse over the years. Everything worked as per the magazine article during the build and test phase and it just seems to keep on going...
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Old 10th Jun 2022, 5:19 pm   #89
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The PW "Marchwood" regulated 12V PSU was one that I find myself coming back to regularly; with a bit of additional RF-hardening it's still a good design for powering low/medium-power gear.

PW's "Take-20" series also has some good starting-points for circuit designs.

And their "Out of Thin Air" book on antennas is a good idea-source too... with various 'real-world' designs by the late Fred Judd G2BCX
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Old 14th Aug 2022, 4:45 pm   #90
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I built loads of things when I was a lad back in the 80’s These were mostly from “Hobby electronics” magazine. I think there was a bench power supply, an audio mixer, a timer of some sort, a couple of model railway projects among others. I also tried some things from library books, such as crystal sets, but despite building half a dozen or so, never got one to work. I guess I just don’t have the knack.
ISTR some disco lights from a Maplin kit too, which did work.
Very few of them worked, often due to errors in the information given in the magazine, and sometimes( very likely) a mistake I had made myself.
The PSU and the audio mixer worked( still have the mixer, gave the PSU to female friend starting out in electronics in the vain hope that perhaps we might be more than friends. PSU worked, my “ cunning” plan didn’t!). Most of the others, including the almost obligatory “ Ladybird” transistor radio didn’t work.
Built a few things off the interweb recently( only on breadboard)and most of them worked so maybe I’m improving. I prefer to repair things designed by other people, as presumably they worked once.
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Old 14th Aug 2022, 5:36 pm   #91
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Default Re: Magazine projects

The PW Marchwood power supply was one of the most thorough designs I've seen in a magazine.

There is one design oversight and one weakness that's come to light.

Firstly, although it uses multiple series pass transistors in parallel with proper current sharing resistors in their emitters, current sensing is taken from only one of them, so if that transistor pops, your current limit goes AWOL.

The transistors specified are the inevitable 2N3055, and many of the things which you get when you buy some are far faster than originals, and they can start singing all to themselves due to coupling in the wiring to them from the PCB.

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Old 22nd Aug 2022, 12:32 am   #92
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My first project in about 1956 was a wind up gramophone with a plastic p/u arm and cartridge driving a PM22 in a circuit from PW to play my Dad's 78 collection and the few records I bought in second hand shops and Woolworths.

Dad was a radio engineer trained in the 1920's and brother a keen amateur, so it was inevitable I would follow them. I mainly built audio kit for friends drawn from RC and PW, a few of which were absolute duffers and migrated to semiconductors in the 70's. The most complex item I built was the September '75 PW Easybuild clock using 7 segment LEDs. Couldn't afford the PCBs so built it on perf board, nearly went blind ! It died about 3 years ago when one of the LEDs failed.

Work and family halted my hobby in late 70's until I turned 72, since when I have built a number of valve regens, superhets and a preselector taken from 50's and 60's mags, several did not work as expected / at all. The best of these from a magazine source being FG Rayer's Bandspread Superhet from the October 68 issue of RC, it worked first time and is a joy to use, it's sensitive and selective whilst being really simple to build.

IMHO the likelihood of a successful build increased significantly across the UK electronics magazine industry during the 70's, I have always suspected this was driven in part by the introduction of Elektor in English, which was a game changer in both innovation and quality.
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Old 2nd Sep 2022, 4:14 pm   #93
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I built a fair few projects from Practical Electronics such as the dynamic transistor tester that fed the output of a flip flop into a test biased transistor and measured the hfe by nulling out the audio produced - that worked well. Also an audio function generator which the sun in my shed window has fried the labels off and now I don't know what control does what. Then there was the digital frequency meter that was OK at low frequencies but you could not get two coinsistent readings at higher frequencies - never have figured out why. I too loved the mags and still have a decent collection of Practical Electronics, Practical Wireless, Radio and Hobbies, Electronics Australia and a number of others. I aslo built a fair number of Dick Smith kits that had come from Electronics Australia originally - the ESR meter and the LOPD transformer tester spring to mind. I still intend one day building the analogue computer series in Practical Electronics 1970's issues (Back then 2N2926's used in the design cost an arm and a leg I recall) as well as a Valve tester from Practical Wireless that used plug in cards to programme it. Oh and yep there's a valve signal tracer design I never built - had the additonal advantage that you could use it as a radio when otherwise engaged. Great fun folks.
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Old 2nd Sep 2022, 4:22 pm   #94
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Default Re: Magazine projects

Quote:
Originally Posted by kellys_eye View Post
has anyone got any suggestions for 'classics' in terms of magazine projects? i.e. one that became either an essential piece of test or entertainment equipment etc and possibly worthy of commercial production?

How about a magazine project that 'set the standard' (if there ever was one!)?
The Texan amplifier, along with the Nelson-Jones tuner and the Integrex Dolby box were all classics of a kind, and still sought after. True, the N-J would benefit from a birdie filter and the Texan had its foibles, but good stuff nonetheless.
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Old 2nd Sep 2022, 5:34 pm   #95
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Default Re: Magazine projects

Working in component retail we supplied many project builders, indeed most of us
bought the magazines and built many projects, and could offer guidance.
Circuits given in the RS data sheets were also popular.

One example we could not recommend was a 9 volt DC power supply with a capacitor
dropper from live mains, especially if the customer was a beginner.
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Old 2nd Sep 2022, 6:23 pm   #96
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I built a few things from the ETI 100-projects compilation book back in the late 1970s, their 100Watt audio amplifier and capacitor discharge electronic ignition come to mind.

Elektor was good for sure fire projects, I built a 70Cm receive converter from one of their designs, the double sided PCB available from them was really well designed and the converter worked first time.

I also built the Elektor Junior Computer, another good design which I adapted as a bi directional RTTY converter, sampling the audio in software to detect the FSK transitions, and converting 5-bit Baudot to ASCII. Doing the same on transmit. Generating 170Hz shift audio in software.
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Old 2nd Sep 2022, 11:48 pm   #97
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Speaking of projects. I have been collecting stuff for my valve tester design. I bought a few different SMPS modules that are adjustable from some of the auction houses. They all adjust very well, ESPECIALLY the noise. I wont need an ascillator to test valves as its built in.

I am going to build another of these. I origionally built one about 35 or 40 years ago, and it worked perfectly, as did every project I made from this magazine. I post the circuit for critisisms and suggestions.
I wont build it identically though, the old power transformer (used in MANY aussie TV sets ) Is no longer available. BUT, I do have a nice big fat 600 watt toroid that I intend to use.
A question for the boffins : I want to increase the range of the output to go from zero
( or near to it, say 30 volts or so ) to 400 volts. I know I need another 807 ( I will be using 5B/254 as I have loads of them ) to get 150 mA across most of the range. ( I wont need 150 mA at 30 volts ). Apart from changing the resistors associated with the voltage control pot ( 500k and 150k ) what else would I need modify ?. QS150 regs are no impossible to find so I will be using 0A2's as I have plenty of them. Rectification will be sand, as BIG rectifiers collect eyewatering prices, and are not all that reliable.
I have taken care of metering, as I have upteen dozen el-cheapo digital panel meters that I have modified to suit my purposes. That is, I have switching to change shunts to suit currents and voltages suitable for any particular range I wish to use.

I will essentially make two of the circuit, so that I have a fully adjustable screen supply as well as plate supply. Bias is already taken care of with a separate winding on the toroid, and will use a single 0B2 as the reference. Heaters will only be available in 6.3 volts , or 12.6 volts, mostly because all those weirdo valves that you guys use are totally unavailable here. In fact 99% of them I have never seen !!!.

All critisism accepted, and all suggestions will be examined carefully.

Thanks in advance,

Joe
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Old 3rd Sep 2022, 9:12 am   #98
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Originally Posted by E93AFAN View Post
The most complex item I built was the September '75 PW Easybuild clock using 7 segment LEDs. Couldn't afford the PCBs so built it on perf board, nearly went blind ! It died about 3 years ago when one of the LEDs failed.

.
I also built the clock, I can only imagine the job you had with Perf Board. It was easy with the proper PCB. I have mentioned the clock a number of times on this forum. Going back 4 or 5 years a chap from I think Holland had an unused chip if I had needed it.
I have some of 7 segment LEDs not sure if common Cathode or Common Anode, I would have to find them. Just say if you would like a couple assuming they are correct ones.

Picture of my 47 year old clock taken this morning, may have had a week or two off in that time while we've been away.

John.
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Old 3rd Sep 2022, 10:57 pm   #99
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I thought this was a good one from back in the mid 60s.
https://www.vintage-radio.net/forum/...d.php?t=116579
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Old 4th Sep 2022, 8:14 am   #100
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I built the PW Easybuild Organ in my cabin in HMS Collingwood in March 1975. I made the case out of bits of broken lockers and wardrobes in the Collingwood 'woodwork' club.

It did work but the keyboard was almost impossible to adjust. There were two gold plated spring contacts on each of the 49 keys and they had to be adjusted so that they both made contact at the same time and the distance travelled for the key to make the contact had to be the same for every key.

I never did get it right so I eventually dismantled it. I enjoyed building it though!

John
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