Will this simplest AM receiver work in theory or even in practical?

One important specification for a radio is its selectivity. You want to select only one radio station and reject all the other stations.
Many years ago when a crystal radio was used it heard only one radio station even though its selectivity was poor because there were few radio stations. Now there are MANY radio stations.

I didn't count the AM and FM radio stations near me. Maybe 100? Then selectivity is very important which is not available in a simple crystal radio.

unclejed613 said:

another good detector would be a silicon carbide (SiC, also known as carborundum). with a SiC detector, you will need a local battery to bias the junction to just below it's conduction threshold (actually this method works with silicon and germanium diodes as well, but the threshold voltages are lower). this is the technique used by the Marconi company back in the early 20th century. the bias is supplied through very large (1Meg) resistors, so that the battery doesn't act as a low impedance path for RF across the diode.

SiC has the added advantage of ZERO reverse recovery time, which makes it work better at high frequencies.

EDIT: SiC Vf=2V, Ge Vf=0.3V, Si Vf=0.7V

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Wow! You said another exciting thing! But I cannot visualize from your explanation, are there any article or link? Silicon diode...

BobW said:

It is also possible to build a true FM detector using two diodes and a 90￾0„3￾0Š0 phase shift arrangement to make a quadrature detector. I built one a few years ago with a helical resonator (unloaded Q of about 2000, and loaded Q of about 500).
View attachment 74400
It works quite well picking up all the local stations with an indoor dipole antenna. I did a detailed writeup on it:
**broken link removed**

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Another nice work! But I am little unfamiliar with matching BalUns! Also there are lots of coils you arranged them in a box, looks complicated

audioguru said:

One important specification for a radio is its selectivity. You want to select only one radio station and reject all the other stations.
Many years ago when a crystal radio was used it heard only one radio station even though its selectivity was poor because there were few radio stations. Now there are MANY radio stations.

I didn't count the AM and FM radio stations near me. Maybe 100? Then selectivity is very important which is not available in a simple crystal radio.

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Till now, I am lucky to test any radio even with the Baddest quality! Here is only a AM station and almost 8 strong FM stations with 5 weak stations! I don't know about power of AM station but almost all stations of here has 500Watt and 100 watt but one has 10KW. Newly stablished stations are limited to 100W by government.

Willen said:

almost all stations of here has 500Watt and 100 watt but one has 10KW. Newly stablished stations are limited to 100W by government.

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I listen to a local FM station that has 4,700W and another that has 31,000W.

I found a unique radio called- Foxhole Radio (lots of foxhole). Designer used a blade and safty pin instead of point contact germanium diode.

At first, I laughed and now I am thinking that it is not hard to make Point contact germenium diode. But I don't know what is actually it! Looks amazing! Thinking that how these type of radio can work!

hi Willen,
Look up 'Cats whisker radio'.

https://www.google.co.uk/search?q=c...s=org.mozilla:en-US:official&client=firefox-a

We used to make transistors using two pieces of razor blade and a half of a diode, all mounted on a bottle cork,,, gain of about 3!

ericgibbs said:

hi Willen,
Look up 'Cats whisker radio'.

https://www.google.co.uk/search?q=c...s=org.mozilla:en-US:official&client=firefox-a

We used to make transistors using two pieces of razor blade and a half of a diode, all mounted on a bottle cork,,, gain of about 3!

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hahaha within few days, I am being mad on ancient electronics because of its simplicity! How shocking they were! But I am not familier with Galena crystal and with its equivalent minerals to build Cat's whisker radio

Now I knew that how Germenium diode were invented. The Germenium diode has not been changed till now anymore. It looks like detector stage of cat's whisker detector; has spring wire (whisker) pointed on Germenium Wow!

I am too much excited listening about your blade's transistor which had gain of 3! Wow! I cannot think that I can make a transistor myself! Do you have any schematics, guides or links of your work or others?

hi,
Look through these links.
https://www.google.co.uk/search?q=h...s=org.mozilla:en-US:official&client=firefox-a

Many, many years ago (54 years ago) I became interested in electronics. In schooool I was not taught anything about it but I found magazines with lots of info.
There were some huge electronics parts distributor stores near me so I bought the latest and best American and European parts and made many projects from those magazines. Every circuit worked perfectly. Then I designed my own circuits that also worked perfectly.

I never made a crystal radio but I made a Superheterodyne AM radio and a Superheterodyne FM radio with a stereo adapter. Then I made a few stereo amplifiers, a low distortion audio generator, an oscilloscope and an FM transmitter.
I learned electronics in university then my first job was with Philips in their car radio and TV factory. I saw their first LED and their first compact tape cassette recorder-player.

I think almost all Americans has knowledge of electronics due to their education policy. So there are lots of factories, distributors and shops. Wish to be in America! I would buy lots of components for interesting and exciting projects, wow! America is most expensive part of the world but they has quality. Here almost few persons can know basic electronics!

A friend of mine cannot understand what is FM transmitter. And I had to say- It is my own FM station, and he cannot believe me

what type of radio is called superheterodyne radio? Has vacuum tubes?

Oscilloscope is a expensive device, and you made it, wow! Hope it is very useful work bench tool for you. A basic version can we make?

ericgibbs said:

hi Willen,
Look up 'Cats whisker radio'.

https://www.google.co.uk/search?q=c...s=org.mozilla:en-US:official&client=firefox-a

We used to make transistors using two pieces of razor blade and a half of a diode, all mounted on a bottle cork,,, gain of about 3!

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My Ladybird book of How To Make a Transitor Radio circa 1975 showed how to do this with a piece of wire and a piece of coke. I found coal worked just as well but invested in the OA81 germanium diode in the end as it created less mess. Basically any joint with a disimilar metal would work on AM.

At Droitwich in the UK (A high power AM transmitter site) you used to be able to hear radio stations from the fence due to the rust forming such junctions. Likewise at Rugby when MSF used to transmit from there, you could hear the 1 second clicks on the fence if you got close enough.

My Ladybird book of How To Make a Transitor Radio circa 1975 showed how to do this with a piece of wire and a piece of coke. I found coal worked just as well but invested in the OA81 germanium diode in the end as it created less mess. Basically any joint with a disimilar metal would work on AM.

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hi,

That brought back memories.

I had some circa 1936 'Practical Wireless' magazines, I built a 'coke' detector radio in about 1943, I could get BBC Long Wave 'Light' program on 1500mtrs, really clear.

E

Likewise at Rugby when MSF used to transmit from there, you could hear the 1 second clicks on the fence if you got close enough.

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Not just MSF (60kHz), but also GBR on 16kHz.
You could hear morse or the time ticks on most things electrical in Rugby!

I should add that I was "educated at Rugby"....


No not the public school, but Rugby College of Engineering Technology, which like most other organisations in my past has long since closed down.

JimB

WTP Pepper said:

My Ladybird book of How To Make a Transitor Radio circa 1975 showed how to do this with a piece of wire and a piece of coke. I found coal worked just as well but invested in the OA81 germanium diode in the end as it created less mess. Basically any joint with a disimilar metal would work on AM.

At Droitwich in the UK (A high power AM transmitter site) you used to be able to hear radio stations from the fence due to the rust forming such junctions. Likewise at Rugby when MSF used to transmit from there, you could hear the 1 second clicks on the fence if you got close enough.

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Very amazing experience and exciting moment you all have.

If any dissimilar metal act as as AM detector then fox hole radio (with razor blade and safety pin) might act as nice AM radio! Wow!

-What is coke please? (Google couldn't help me)
-You found with mine coal or wood coal? I guessed mine coal but before burning or after burning? Can I use mine coal directly from mine without processing it on factory?

Willen said:

-What is coke please? (Google couldn't help me)
-You found with mine coal or wood coal? I guessed mine coal but before burning or after burning? Can I use mine coal directly from mine without processing it on factory?

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https://en.wikipedia.org/wiki/Coke_(fuel)

It's basically coal burnt with limited oygen. As a result, it doesn't have the filthy black tar like coating and burns very hot when reused. Used for barbequeing food.
Coke furnaces in the countryside are quite common place in Derbyshire. A pile of coal the size of a car, set alight and then covered in earth and left for about a week.

Being high in carbon, when metal is touched on its surface you get the disimilar conducting interface similar to a diode hence their use in old crystal sets. Not an ideal diode by today's standards but good enough for this use.

WTP Pepper said:

Coke furnaces in the countryside are quite common place in Derbyshire.

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Are they?

Nigel Goodwin said:

Are they?

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Yes. Lathkill Dale between Monyash and Over Haddon. Last year I passed about nine of them smoking away on the paths in the valley over about 3 miles.

What are you trying to say? I am lying? Take a walk down there. it's bliss away from town life.

WTP Pepper said:

Yes. Lathkill Dale between Monyash and Over Haddon. Last year I passed about nine of them smoking away on the paths in the valley over about 3 miles.

What are you trying to say? I am lying? Take a walk down there. it's bliss away from town life.

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No not at all, I was purely asking - I wasn't aware of it.

I've also walked down Lathkill Dale on a number of occasions, and both went to school and worked in Bakewell

However, back to the question, how did you know they were coke fires? (and can coke be made that way?) - it would seem strange to transport coal many miles to burn it in a beautiful country setting. Unless you have reason to believe otherwise it would seem much more likely to be charcoal burning and not coke?. Certainly, historically, charcoal burning has been carried on in many such places.

i used to find pieces of coke along old unused railroad tracks. they're black like coal, but they're mostly carbon with a lot of small air bubbles (kind of looks like pieces of acoustic foam, but hard and brittle). i never thought about using them as part of a detector, even though carbon IS in the semiconductor portion of the periodic table. i have seen some rather odd effects from dissimilar metals. i had a tape deck come in for repair once, and when the very slightly oxidized tinned RCA connectors on the tape deck output had gold plated audio cables plugged into them, there was a slight diode potential set up that caused a small (but clearly audible) amount of distortion in the signal. i actually had to show the customer on an oscilloscope the difference between the dissimilar metals (gold/tin) and similar metals (tin/tin), and that because of this the customer's original cables with tinned ends did not distort the signal, but his new, expensive gold plated ones did distort the signal... that was back in the very early days of gold plated ends on cables, and i sort of suspect that there was some other unknown metal in the alloy of the gold plating that had a much higher barrier potential than just gold/tin would have. considering the humidity and climate, i suspect, as i said earlier that there might have been a slight oxidation layer on the tin plating as well. i've actually only seen that effect that one time, so the possibility of some unknown metal alloyed in the gold plating seems more plausible to me.

unclejed613 said:

i used to find pieces of coke along old unused railroad tracks. they're black like coal, but they're mostly carbon with a lot of small air bubbles (kind of looks like pieces of acoustic foam, but hard and brittle). i never thought about using them as part of a detector, even though carbon IS in the semiconductor portion of the periodic table.

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OH Yes! I can also find these black and hard materials on unused old railroad tracks, I do not know it is burnt out coal or coke.

Will it work as a detector if I contacted a small spring wire on it?

Nigel Goodwin said:

However, back to the question, how did you know they were coke fires? (and can coke be made that way?) - it would seem strange to transport coal many miles to burn it in a beautiful country setting. Unless you have reason to believe otherwise it would seem much more likely to be charcoal burning and not coke?. Certainly, historically, charcoal burning has been carried on in many such places.

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I was told they were coke fires by a very old bearded gentleman tending to one when I passed once and asked. As for the logistics of transporting it there, I have no idea.

Like you say, why bother transporting it there (not exactly an easy place to drive a truck to) when B&Q sell charcoal in bags - mass produced somewhere but I doubt in the Derbyshire Dales.

Maybe there are natural coal seams in Derbyshire. I have no idea of that either. In Lathkill Dale, there are certainly many deep man made tunnels into the rock faces. Just past the crossing in the Dale from the steep road upto Over Haddon.

You were lucky to grow up in such a nice part on the country. I grew up on the edge of the West Pennine Moors in Lancashire.

Maybe we should get back on topic Coke works as do diodes