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You have a couple of interesting VHF transistor receivers on your site.

Extremely unlikely methinks... :-)

Interesting tale. When the EE8 set worked for me, it was always a bit internittent because of the horrible springs used for the connections. One always had to bang it a few times to see if that made it burst into life... I think it's fair to say that I didn't manage to make several of the projects work either. Yes, the transistors could well have been vapourised. I have to admit that although I built the radio set, many times over, I hadn't a clue about the circuit diagram and I had no idea how each bit worked either.. A year or two after the demise of the set (in 1966 to be exact), I was given a copy of "The Beginners Guide to Radio" by Newnes books. I still have it in front of me as I type this! The first set I built from this was a one valve radio and it worked! Hence it became the first radio that I'd built outside of a kit. At last I really began to understand a few things!

Most interesting. I hadn't heard of that being done before. These receivers were very popular here in the UK after the war and there still seem to be a lot of them around today. I've always been impressed with the high quality of construction from the US with their equipment, plus the superb maintenance manuals - IF you can find one!

@@lishaton Sadly, I've never owned an American receiver of that era: I was always jealous of my friend's National HRO (so much better than my clapped out British R107 and PCR). Most US sets were masterpieces of precision engineering, especially the tuning mechanisms. ♥

Most interesting observations. All points notes and quite valid. I tend to start using it with the smallest noticeable movement on the meter, then slowly increase this to give a better accuracy until one reaches the setting at which the issue with the frequency suddenly 'snapping' as you say, manifests itself. Back off slightly from this setting and take the reading. Thanks for the feedback!

@@lishaton I think that maybe one way to prevent the undesirable frequency pulling is to add a buffer amplifier after the oscillator, and to connect the output of the buffer amplifier to an untuned coupling loop, which then goes through a diode and through a microammeter to ground. The buffer amplifier will drive the oscillator's output through the coupling loop, through the diode, through the meter, to ground, creating a current readout on the meter. Then, if an LC tank is brought near the coupling coil, it will suck out energy from the buffer amplifier (not directly from the oscillator's LC tank itself), causing less current to flow through the diode and the meter, thus showing a dip. This approach should prevent frequency pulling of the oscillator because the oscillator's LC tank is never coupled to directly; we only couple to the coupling loop on the buffer amplifier. I've seen a similar approach recommended in some articles, and I think the MFJ dip meter also uses this approach. I haven't had a chance to try it myself yet.

If you ever try an example, do let me know how well it worked.

Thank you! :-)

Good luck with your endeavour. I think that this may take you some time if the sets are totally original and untouched as there could well be many pieces of rubber covered wire all in need of replacement! Let us know how it goes.

@@lishaton Thank you. I have inspected the wire and it looks in good condition, but I will find a good military replacement as I don't want it to catch fire. Lots of other items to test. Yes it is going to take a long time, but best to get it right. Ill keep in touch.

Thank YOU Clare!

Ah! The ARC-5 R28.. Quite an amazing bit of kit to see actually working properly with all its electro mechanical bits :-) I have a second one of these I must try and fix one day, plus the matching VHF transmitter....

It sounds as if your kit was really worth the money paid for it then. I'm afraid that my own EE8 / A20 died many years ago and I'm not sure if anything survived from it. The 'photosI used in the video were from all over the Internet to show what it used to look like. The actual circuits I used for the video, were exact copies from the original 'cards' that were supplied with the EE8. I was given the A20 add-on kit a bit later on which gave two loudspeakers, a third transistor, a few more bits and many more circuit cards. I made the radio and the intercom many times from this!

Thanks Clare! Though I'm sure it could be improved upon with a little work :-)

I think that I was about the same age as yourself when I received mine :-) You are quite right about the AM radio today. Here in the UK, there are very few 'National' type transmissions left. When I built my radio from the kit, it worked really well as we were reasonably close to a main BBC transmitter. You'll no doubt have noticed that for my demo. in the video, I had to use an external aerial AND an earth to make it loud enough to hear it working. At time of writing (April 2024) the BBC, our National broadcaster, is in the throws of permanently closing down our large Long Wave transmitter, which is such a shame, as there are many who live miles from any other transmitter yet can still receive Radio 4 on Long Wave - 198KHz.

Yes, it's surprising just how many useful measuring tasks one can do with a simple bit of circuitry like this!

.

Еще раз спасибо :-)

Thanks Clare! Hopefully someone will find it worth making..

Somente em código de máquina Z80. Você quer dizer para o 8051?

Hola! Me alegra que te haya gustado. Estoy muy interesado en echar un vistazo a su sitio web GDO para saber cómo lo ha hecho funcionar.

Gracias por anticipado por su amabilidad. Saludos cordiales, Miguel.

I agree. The whole philosophy behind the 'Radar Room' being to make things actually work, even if that means using artificially created data sources for items such as GEE, Loran and Chain Home, as they are no longer transmitted over the ether.

A good question! In keeping with all my own micro' work, I wrote this in machine code. (I always do things the hard way!) The idea behind using this technique for my videos is to keep things as simple as possible. I remember when I started writing my first few lines of code, I didn't own a computer at that point and knew nothing of assemblers either. For this reason you can see why machine code was the only way forward for me. Obviously for a beginners perspective today, using an assembler must be the logical way forward, as everyone must at least have access to a computer. As far as compiling from C++ is concerned, according to a quickie Google search, there are plenty of them out there that will. Do check this out yourself and see if any suit your purposes. It goes without saying, that there are many assemblers for the 6502 if that's your choice in the end.

Спасибо за ваш интерес!

Positive comment appreciated :-) Thanks!

Yes, even though it is far from 100% perfect, it works surprisingly well.

Thank you :-)

Absolutely! Even from a smallish speaker.

Я рад, что вам понравилось!

Thank YOU Clare :-)

Glad to have been some help. Have fun!

Thanks Clare :-)

Go for it I say! And let's face it, it's quite a simple circuit to build as well.

@@lishaton You know, its the simplicity that makes it so special - one active device. Today we throw millions or billions of transistors to do simple tasks like this.

Thanks for the positive comment!

Thanks again Clare!

As this only has one waveband, I tried to make it work for some well listened-to bands. In the end, by taking into account the fact that I was going to use a 50pF tuning capacitor, I adjusted the coil windings to give me about 5.9 - 8 MHz. This therefore encompasses the 41 and 49 Metre broadcast bands, plus the 40 Metre amateur band. A larger tuning cap. would have increased this coverage if it had been built with one.

@@lishaton Thank you for your reply. 5.9-8MHz is good. I will try to build one and maybe add 2 bands.

Do let me know how well it works. If you tweak the number of turns on the aerial coil, then you can probably tailor it to your exact needs. Do take note that if you increase the size of the tuning cap too much, it will be much more difficult to tune if you want to keep the small case footprint. Tuning in SSB signals even now is a bit of a challenge!

@@lishaton I have a 36mm small VERNIER DIAL. It rotate 4 times when the capacitor rotates 180 degrees. I think it's helpful for turning. May I ask what ferrite you use for the coil? Is it medium wave antenna ferrite? Thank you.

Yes, it's a short length of an ordinary medium wave or long wave ferrite rod aerial. i.e. nothing special. That vernier should make tuning much easier if you want to increase the size (capacity) of your tuning capacitor.

Aw - thanx Clare!

Hi. I'll be honest that I haven't really considered doing this as there are many other people giving this kind of detail in their videos already. I'm assembling many of these videos because there are far too many 'tried and tested' circuits and ideas out there on the Internet that have had neither done. Mine are therefore realistically as short as possible, but show that here's a circuit that actually works. (Useful as well, as you can see what performance to expect if you make your own) The same applies to my microprocessor videos. Lots of these out there already, often with hugely complex circuits and programming, or simply 'ideas' that are probably above most peoples heads. I therefore do mine from the ground upwards, describing any detail necessary for the beginner to actually have the enjoyment of making a micro. work for them.

It is indeed, hence the regeneration (reaction /tickler) control. Without this there would probably be no reception, unless one used a seriously good, high aerial.

Thanks for the suggestions. Interesting. Of course a lot depends on where one is in the world! Ironically, the easiest items to obtain are usually the valves. Why? Well historically, someone might throw away an old set, but make sure they keep the valves, but not the valve holders, transformers, variable capacitors etc. I will certainly give this idea of your some serious thought.

Thanks for that.

What a really nice bit of feedback. Thank you! :-)

It was fun doing it, although it's taken a while - seeing as I started it before Christmas... I like to think that a video like this might encourage someone out there to try their hand at making one!

@@lishaton I'll bet it was fun. It would really be nice to see someone built it and put in in a nice box to make a practical. One other nice thing about this is it show how much you do with just a few active devices ie tubes/valves as we often saw in old radios and TVs. A far cry from the million or billion transistors we throw at every simple task today.

I remember when the first ICs came out, I wondered even then why they needed so many more transistors than the equivalent discrete component circuit. If course in reality, when it costs no more to include a transistor rather than a resistor on a die, then if there is only going to be a very small improvement in the performance, they'l add the extra transistor. I'm sorely tempted to rebuild this circuit into a box, but seeing as the place is already littered with oscilloscopes of all shapes and sizes, there seems little point in doing so :-(

@@lishaton I must be just slightly younger than you because ICs were already in all the electronics magazines when I was a kid. It always some like cheating to use an IC instead of building a circuit with discrete parts. When I took a VLSI course in university, one of the eye opening things was how the technology of a particular process (NMOS, CMOSm whatever) can often dictate which circuit elements take up a smaller surface area and therefore are cheaper. In many cases replacing a resistor with a FET in constant current configuration tool way less space so I think that's also partially why many more transistors are used. Funny - I also way to many old scopes lying around!

In my early teens the first IC amplifiers were advertised by Radiospares - now RS components here in the UK. I remeber buying a 3 watt one for £3.00 It didn't take me long to short out one of the pins it says not to short out and ... it blew up. Mind you, before it did, I was amazed just how good it was! As far as 'cheating' is concerned, I concur. I don't MIND using an IC in many situations, but that might include 'not enough room for discretes', so I make up my own rules as I go along :-) As for 'scopes... I currently have several 1940s offerings, such as the Test Set 43, Test Set 73, Test Set 34, Monitor 28, GEC Miniscope, my own 'big' commercial scope from a couple of years ago, plus my 1979 one seen in the video.. Too many I say! In the last few yearsI must have sold a few too including a Tektronix and others... Can one use them all?!!

Now there's an original idea! Only recently I was trying out some ideas for a practical TOG circuit... (top octave generator)

Nice😎@@lishaton

Thanks for the positive feedback! I think it is always interesting to find out just how much one can do with a microprocessor as you say, without the added complication of a sohisticated circuit.

Indeed it is. GEE is the more accurate of the two, but Loran works over a much larger distance.

Apologies. Comments noted.

Aw.. Thanx Clare! :-)

Thank YOU Clare :-)

Good question! If one does an overview of the most popular 8 bit micros of the time, (all using 40 pin packages), then one can easily see the differences between what features and facilities are considered to be the priority for that particular cpu. I believe that the main issue was probably the limitation of just having 40 pins to play with. Drop back a year or two into the middle of the '70s and we saw the Fairchild F8 with its system of several 40 pin packages for each 'cpu system', then there was the 8080 in a 40 pin package which also needed an 8224 clock chip and an 8288 system controller in order to make a working cpu. The Z80 being the logical step forwards for this particular one because of the instruction set compatibility. (8080 to Z80 but not Z80 to 8080 unless one only used the compatible 8080 instructions...) An interesting history lesson I guess.

Sorry - my error it's a 8228 system controller for the 8080

The 6809 had a companion paged MMU, the 6829, which expanded the address range to a whopping (at the time) 2 MB. Pages were 4 kB, so 16 pages were mapped to 512 physical pages. (Never seen the 6829 in the wild though; only datasheet I've ever seen was "Advance information")

This one is in fact a well-worn hand-me-down from an old friend, but it's still soldiering on - or should I say 'soldering on'? :-) I can't think of a better way to build a microprocessor based circuit board as a one-off.

Hi Clare it's Chris :-) Interesting. I see that the 'valve museum' show the 6D4 as being able to do this. Have you tried any other thyratrons? I'll investigate this myself when I have a spare min'.... Do drop me a mail from the address on our website if you want a decent exchange off TH-cam. ( www.radar-room.co.uk )