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Old 20th Jul 2017, 1:44 pm   #1
Skywave
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Question Build your own? A discussion.

For general discussion.

In one of M.G. Scroggie's books - dating from the 1950's - he makes the observation that sometimes it is necessary for the hobbyist / experimenter to design and build his own item of test equipment when his need cannot be met from what is commercially available. (N.B.: he makes no reference to 'cost' in that remark )

Since then, electronics technology has come a very long way. So is the above comment still applicable today? I think it is, possibly more so, especially when it comes to making relatively simple 'gadgets' for occasional use.

What do other's think?

Al.
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Old 20th Jul 2017, 2:19 pm   #2
kalee20
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Default Re: Build your own? A discussion.

It depends what you want to test!

A multimeter, no. Buy one. A signal generator, probably not worth making - but maybe, if you just wanted to inject a fixed 470kHz from a matchbox-sized gubbins for lining up IFT's.
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Old 20th Jul 2017, 2:36 pm   #3
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Default Re: Build your own? A discussion.

It's probably not worth bothering on grounds of cost or availability of the required equipment but on grounds of satisfaction and experience gained, maybe...

Regards,
Paul
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Old 20th Jul 2017, 4:23 pm   #4
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Default Re: Build your own? A discussion.

Ref post 2. I don't have a sig gen so when I wanted to test the IF stages in a few VHF FM sets I just built a 10.7MHz crystal osc, rough and ready but it did the job.

Frank
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Old 20th Jul 2017, 4:23 pm   #5
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Default Re: Build your own? A discussion.

I build my own stuff because it's fun. There is no other reason. I have far superior professional equipment but that doesn't stop me.

Voltmeter: https://www.vintage-radio.net/forum/...d.php?t=135797

RF probe: https://www.vintage-radio.net/forum/...d.php?t=132296

Frequency counter: https://www.vintage-radio.net/forum/...d.php?t=132559 (this is finished - need to write it up in a new thread)

Another frequency counter: https://www.vintage-radio.net/forum/...d.php?t=131165

Unfinished stuff I have lying around: VVM (this actually mostly works), RF signal generator (this mostly doesn't), various attenuators, dummy load (this is a massive failure so far), half an oscilloscope (3JP1 based), spectrum analyser (sweep gen and VCO work but nothing else yet)

Last edited by MrBungle; 20th Jul 2017 at 4:29 pm.
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Old 20th Jul 2017, 4:26 pm   #6
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Default Re: Build your own? A discussion.

I don't have them now but yes 20 years ago I built a variety of test equipment, freq counter, two tone audio osc, Fet Voltmeter, wideband noise source etc.

I enjoyed making them.

Frank
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Old 20th Jul 2017, 6:04 pm   #7
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Default Re: Build your own? A discussion.

I built my first oscilloscope as a schoo lkid in the sixties. I learned a lot from it. (Never a belt from its mains derived EHT!)

I built component bridges and all sorts of stuff.

The test gear I designed at HP doesn't count as home built by any stretch of the imagination, but several hifi amplifiers and speakers and a tuner do. Oh and a number of amateur radio transmitters/transceivers/receivers.

Mostly built because I thought I could do better, sometimes because what I wanted wasn't available, sometimes to try out new ideas or to demonstrate something. Oh and the dual directional wattmeter for the G-QRP club was homebrew and seems to have become a classic.

Today, professionally, I sometimes build special test rigs specifically for some product to be tested.

It keeps my hand in.

David
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Old 20th Jul 2017, 6:31 pm   #8
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Default Re: Build your own? A discussion.

I have built several gadgets to simplify testing in various jobs over the years. I always have the proper test gear, but who wants to hump that about when you can just plug in a little test box which fits in your pocket. For example I needed a quick test for our external phones and built a DTMF decoder, audio checker etc in a little box to quickly check them out. In a previous job, there was a need to quickly check control room operator's headsets to see whether the problem lay in the actual set, the socket, or distribution equipment. When I got calls for transmission/reception problems, quick plug in plantronics headset, wiggle the wires while listening for crackles etc and away you go, diagnosis in seconds. The trouble was, when you were spotted checking one, all the operators used to shout check mine! But it saved loads of time. So yes, it is necessary sometimes to build your own test gear.
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Old 20th Jul 2017, 6:38 pm   #9
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Default Re: Build your own? A discussion.

I find that building test equipment is enjoyable and educational. Over the last 30 or so years II have built simple oscilloscopes, transistor curve tracer, function generator, eht voltmeter, simple rf and af signal generators, valve tester and recently a spectrum analyser. The amount of knowledge gained is great, I am currently building the PE Investigator oscilloscope with modifications based on a Cossor oscilloscope to enable a triggered timebase, this led to a lot of reading about timebase design.

Dave

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Old 20th Jul 2017, 6:45 pm   #10
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Default Re: Build your own? A discussion.

As others have said, it depends on what the test gear is....

I am a great believer in building my own stuff, I know how it (should) works, I know what it does, etc. But I would buy a multimeter, 'scope, etc.

But a test load unit for the power supply of an HP9836 computer? You can't buy it. Building it took me a morning (mostly mechanical, drilling the box and making spacers to get the edge connectors in the right place). Saved a lot of time since then. Or the test board for some obscure minicomputer? Yes, they probably do exist but it's a lot quicker and easier to make one. A test rig for the IF strip of a complex radio? Make it (but use a commercial sig-gen and 'scope with it).

And what is 'test gear'? Does the adapter to use your PC soundcard as a telephone dial tester (a few resistors and a 9V battery I think) count as 'test gear'. Or is using the commercial soundcard 'cheating'? To me it is test gear, and it is making it yourself.

There is also the joy making accurate measurements with something you made yourself. I guess that's not a part of the hobby that interests everyone but it does interest me.
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Old 20th Jul 2017, 6:52 pm   #11
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Default Re: Build your own? A discussion.

Well Mr Scroggie knew a thing or two!

I still build all sorts of bits to suit myself but I think we need to consider the original idea for the times that they were in.

In the 50's and indeed for at least another 2 decades there was a lot of surplus kit hitting the market but it was in the main too specialised to be of immediate use to the "experimenter"

It wasn't until the late 60's when suddenly cheap and plentiful tools like multimeters signal generators became available.

An AVO 7 was a massive investment for joe public in the 1950's so not surprising many made their own meter using surplus parts.

By the 70's quite good 100K per volt japanese multimeters were available at pocket money prices.

Before I bought my first Japanese Multimeter I relied on a PIFCO all in one and a home made meter using a surplus 100uA movement.

I wish I had more time I would build even more I have so many projects i need these special 100 hour days

Cheers

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Old 20th Jul 2017, 7:54 pm   #12
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Thumbs up Re: Build your own? A discussion.

Quote:
Originally Posted by Cobaltblue View Post
Before I bought my first Japanese multimeter I relied on a PIFCO 'all-in-one' and a home-made meter using a surplus 100uA movement.
I wish I had more time: I would build even more. I have so many projects I need these special 100 hour days
Ditto: my first attempt at a 'multimeter' was same as yours (built in an Oxo tin) and prior to that, I used a 'clock' type PIFCO meter. And when I did splash out and buy a Japanese multimeter, it was a 100 kΩ job - and I still have it.
As for 'available time', ditto again. Seems that creativity brings its own special curse.

----------------------

Thank you, fellow members, for your input so far. I'm quite impressed with the collective ambition and achievement reported.

Al.
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Old 20th Jul 2017, 9:48 pm   #13
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Default Re: Build your own? A discussion.

Hi.

I love building test gear circuits, some of which aren't readily available so were built for a specific need.
Over the years I have built loads of gear including three transistor testers one of which tests RF transistors giving an indication of fT.
I also built the Radcom spectrum analyser which is yet to be tested. I made two different electrolytic capacitor ESR meter projects which have certainly earnt their keep. A 'Television' magazine LOPT ringing tester another very useful piece of gear. A 500V insulation tester built from an Everyday Electronics design has also proved invaluable as has my Radio Constructor electrolytic capacitor reformer.

Other gear built includes various resistor/capacitor substitution boxes, an LCR bridge, a Q meter, a gate dip meter, a low range inductance meter adapter, various high voltage power supplies for TV work, one for 90 degree sets and the other for 110 degree sets. Various TV pattern generators, signal injectors, scope calibrators, electromagnetic field meters and the Maplin frequency counter were also constructed. I designed and built a harmonic distortion meter in my 2nd year at polytechnic many years ago.

Something I must try and use more is the Raymond Haigh wobbulator that I built from the Radio Bygones magazine, Mr Haigh always produced some highly professionally finished radio related projects over the years. I haven't seen anything recent from him as he used to contribute quite a lot to the EPE magazine.
There are a number of projects I'm considering including an EPROM programmer for the old 2516/2716 EPROMs, a Droitwich 198kHz frequency standard and a FM stereo generator.
These days it's hard to find the time for these projects as there are so many other things which seem to take priority. The important thing is if you enjoy building electronic gear and learn something from the experience then it's all been worthwhile and gives you the incentive to make more projects.

Regards
Symon.
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Old 20th Jul 2017, 10:09 pm   #14
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Default Re: Build your own? A discussion.

I really enjoy making my own equipment , but it is a bit 'doubled edged' as I seem to spend a lot of time designing and building power units and test equipment rather than radio's or audio equipment.

Examples being my own valve tester (a distributed system, comprised of modules, as I find it more versatile than a dedicated unit as it can be used for circuit development as well as testing), and recently a 10 channel dedicated voltmeter (principally for valve test) which provides 20MOhm resistance input on all ranges with processing via an Arduino board to laptop PC display. My thoughts were that most cheap meters have limitations with valve equipment (although far better than AVO's) and I got fed up of switching between terminals with the limited number of meters I have.

Currently I have just constructed a low voltage crystal controlled valve / semiconductor hybrid audio oscillator for equipment tests and am in the process of testing.

I suppose though, that I spend most of my time working on new ideas and sketching circuits / doing research. I have an extensive library (mainly downloaded) which I presume many others have too. Only a small number of my designs ever make the workshop.
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Old 20th Jul 2017, 10:27 pm   #15
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Default Re: Build your own? A discussion.

The book The Boy Electrician (the past really is another country .....) describes the construction from scratch and calibration of a multimeter which, although it has a sensitivity of 5 mA (= 200 Ω/V), is still much better than no meter at all.

When I worked in the R&D lab at an electronics factory, we designed and built all our own end-of-line test equipment. The state of the art then was an 80486 PC fitted with a 4 * 8-bit I/O port card, running a BASIC program under MS-DOS; though some of the less demanding products were tested on 80286s and even XTs. The I/O card could be used to drive relays, opto-isolators, level shifters and D-to-A converters; and read logic inputs and A-to-D converters. We also built various devices for experimental purposes, some of which were retained if they could be modified for more general use.
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Old 20th Jul 2017, 10:43 pm   #16
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Default Re: Build your own? A discussion.

Some of the simplest homebrew items can be the most educational, even for professionals...

I've always tried to make my own couplers, bridges, filters and probes where possible. If you want to learn a few things about electromagnetic waves, a near field (E and H field) probe kit is a great thing to make and experiment with. It should work about as well as a commercial kit so there's no need to splash out lots of dosh to get the same level of performance.

However, the test equipment market is undergoing a revolution at the moment (because of the versatility and performance of modern chipsets) and the other option is to buy 'homebrew' kits from china for all sorts of RF based test gear. Often it is going to be cheaper and easier to just buy a simple detector or meter on ebay compared to designing and building it at home. Also, fairly decent test gear from Chinese manufacturers Siglent and Rigol can now be bought new at affordable prices.

But there is always that rewarding feeling when a homebrew meter or widget delivers the anticipated performance! It's hard to put a price on this
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Old 20th Jul 2017, 11:03 pm   #17
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Default Re: Build your own? A discussion.

Quote:
Originally Posted by G0HZU_JMR View Post
Some of the simplest homebrew items can be the most educational, even for professionals...
Totally agree making your own meter makes you totally aware of the device's limitations and the effects it has on the item your measuring.

Otherwise there seems to be a belief what you are seeing is real

Maybe more like an illusion

How many threads have I seen where volts are quoted using a digital multimeter where as the volts were quoted on service data with an AVO 7?

I find it more or less too frustrating to get involved anymore.

I think that's how most of us of a certain age ( OK 50+) learned.

We are probably the last to learn this way.

I still work with design Engineers daily (all better than me) although that's no longer my role, they are all ageing the best already in their 50's to early 60's I don't see any new ones coming, and they all learned same way as me.

If something doesn't change there will soon be a massive skills gap

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Old 20th Jul 2017, 11:27 pm   #18
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Default Re: Build your own? A discussion.

Quote:
Originally Posted by Cobaltblue View Post
I still work with design Engineers daily (all better than me) although thats no longer my role, they are all ageing the best already in their 50's to early 60's I dont see any new ones coming, and they all learned same way as me.
If something doesn't change there will soon be a massive skills gap
Yes, apologies for briefly going off topic but where I work I've seen a big change in the way (RF) engineers develop during their career.

Sometimes it can be quite scary when I realise how much they don't know about classic component level design. For example, I'd expect a lot of them to fail badly if given a few classic circuits to identify or describe.

But I think they are developing different skills. The component level design is done for them in modern chipsets and the skill comes in exploiting these modern chips to make powerful products that our customers want. So maybe it's irrelevant that they can't design/describe a classic RF circuit from 30 years ago. Maybe it doesn't matter if they can't design a small lumped RF filter because they can browse the internet and buy the most suitable one from MiniCircuits or someone else. The (modern) skill is knowing what to do with it rather than how to make the filter. The younger engineers of today are definitely better (much better) when it comes to things like product lifecycle management. They have much better discipline generally and are very good at keeping up with modern trends. Oldies like me are still 'special' but in a different way
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Old 20th Jul 2017, 11:38 pm   #19
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Arrow Re: Build your own? A discussion.

Quote:
Originally Posted by ionburn View Post
I suppose though, that I spend most of my time working on new ideas and sketching circuits / doing research. Only a small number of my designs ever make the workshop.
Re the last sentence: yes, that I do understand.

Related to that sub-topic, there arises the subject of 'prototyping'. I'm reading a book called "Think Like an Engineer" by Guru Madhaven.* The book has a chapter entitled 'Prototyping' in which he makes reference to the 'prototyping trap'. What he is referring to is that after the initial design work is done and a prototype is built, but then when things don't 'work out' as expected, there can be a strong tendency to modify the original design at the prototype stage to get it to 'behave' and to 'keep going'. The danger the author refers to is that by so persisting with the design at the prototype stage, one can easily miss the possible essential point that the basic concept of the design was flawed in the first place and that going right back to square one and starting again is the sensible option, but once the prototype stage is reached, psychologically, that can be a difficult thing to do.

* ISBN 978-1-78074-637-1; eISBN 978-1-78074-633-8.
Paperback; A5 size; 253 pages; retail price £12.99
The author is an American and much of the text uses 'American English', so for me, the 'going' gets a bit difficult sometimes. It's also substantially geared to American culture and ideologies, which are O.K. as they stand, but do seem a bit alien to a U.K born-and-bred oldie like me! However, overall, it is a fascinating read - and, in places, quite insightful.

Al.

Last edited by Skywave; 20th Jul 2017 at 11:44 pm. Reason: Correct eISBN number; reduce the waffle!
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Old 20th Jul 2017, 11:47 pm   #20
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Default Re: Build your own? A discussion.

Quote:
Originally Posted by G0HZU_JMR View Post
Yes, apologies for briefly going off topic but where I work I've seen a big change in the way (RF) engineers develop during their career.

Sometimes it can be quite scary when I realise how much they don't know about classic component level design. For example, I'd expect a lot of them to fail badly if given a few classic circuits to identify or describe.

But I think they are developing different skills. The component level design is done for them in modern chipsets and the skill comes in exploiting these modern chips to make powerful products that our customers want. So maybe it's irrelevant that they can't design/describe a classic RF circuit from 30 years ago. Maybe it doesn't matter if they can't design a small lumped RF filter because they can browse the internet and buy the most suitable one from MiniCircuits or someone else. The (modern) skill is knowing what to do with it rather than how to make the filter. The younger engineers of today are definitely better (much better) when it comes to things like product lifecycle management. They have much better discipline generally and are very good at keeping up with modern trends. Oldies like me are still 'special' but in a different way
It's the old problems they are poor at solving spurious, interactions, interference masking the GPS badly spec'd ethernet isolaters excessive noise from power suplies all the things us old hands have developed 40+ years in resolving and as for product lifecycle I think 25 years they think 5 we are still supporting 40 year old products I am the last one in the office who can support these items.

In the main I can do what they can do but they struggle with the old products.

I always slay them with what second war device is in your kitchen.

Bless they think a Microwave is modern technology

I don't think myself special just have a sell by date thats approaching

Oh and by the way the facilities the customers want are so bug ridden they wished they hadn't bothered.

Cheers

Mike T
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