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Post by Admin on Thu Apr 11, 2019 11:00 pm

Hi Ivan,
Sorry, I could have written more.
WBFM is practical, but the audio level will still be low. 150kHz total at 10.7MHz is still only 1.5% of the frequency, so the M/S variations at the output of the gate will still be low.

The gate circuit will make a nice simple detector, but a ratio-detector or other FM demodulator will give a much larger audio signal, and perform well for audio frequencies up to 60kHz.

As usual, it all depends on what you want to achieve, and the requirements. It could be an interesting experiment to compare a variety of FM detectors, from quadrature, radio-detector, PLL, etc.

PS - One of the most famous NBFM was the PYE telecom PF1. The TX and RX were each standalone, and i use to work on them in the factory in Cambridge.


The receiver used a pulse-counter FM detector, but to get a decent audio level they used a dual-conversion IF (10.7MHz then 100kHz). This brought the Frequency/modulation ratio down to only 10:1. The FM deviation was +/-5kHz in those days. They were the first handportable TX/RX used by the UK police.


The biggest problem was that when you pushed the TX PTT button, the antenna shot out, and it had a little plastic cap (after fears of poking out eyes). Unfortunately the antenna often found its way up policemen's noses, and if the little plastic clip came off while it was up there, then it was a trip to the hospital.

VBR Harry

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Post by Ivan on Thu Apr 11, 2019 7:43 pm

Well, I expect the simple demodulator is meant for WBFM, where IF = 10700 +/- 75 KHz.

VBR from Ivan

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Post by Admin on Wed Apr 10, 2019 8:06 pm

Glenndk wrote:
zsolt wrote:hi
browsing through the links provided by Glenn i found this fm demodulator
old radio circuits  R3911
How does this work?

If you are interested in that, you should also look at:

10.7MHz FM DETECTOR.
by Harry Lythall - SM0VPO:
http://213.114.131.21/use/fmif-det.htm

Admin can tell us, which are best :-)

Really interesting topic.

The method using the inherent delay of a gate to form a fixed delay is interesting. It can give a very good response for frequency to voltage, but take a look at the frequencies involved.

NBFM - +/- 2.5kHz with narrow-band FM at 455 kHz the "normal" deviation of +/-2.5kHz is about 1000:1 ratio. So this will give you in the region of 5mV peak-to-peak (3mv RMS) audio. It assumes perfect R/C values. Can be a little difficult at the higher modulating frequencies.

With my PLL method you can get 500mV for the same FM deviation. Higher signal level, but also true signal up to 100kHz, which allows Stereo FM demodulation.

Think not only the output voltage, but also the noise level.

One is simple/cheap the other is higher quality recovered AF.

BR Harry - EA/SM0VPO

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Post by zsolt on Wed Apr 10, 2019 2:25 pm

HI
does anyone have info about this radio ?
old radio circuits  Gamma_10

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Post by Ivan on Sat Apr 06, 2019 9:11 am

Hi all,
these two FM detectors employ different principles.
The circuit provided by Harry uses PLL. It needs setting the oscillator frequency into the IF band.
The circuit provided by Zsolt converts the FM signal into a stream of very narrow pulses of equal width and gets AF by integrating that stream. It should work without any setup. IMHO the quality of AF may be a bit worse than with PLL.

VBR from Ivan

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Post by Glenndk on Sat Apr 06, 2019 12:44 am

zsolt wrote:hi
browsing through the links provided by Glenn i found this fm demodulator
old radio circuits  R3911
How does this work?

If you are interested in that, you should also look at:

10.7MHz FM DETECTOR.
by Harry Lythall - SM0VPO:
http://213.114.131.21/use/fmif-det.htm

Admin can tell us, which are best :-)

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Post by zsolt on Fri Apr 05, 2019 9:25 pm

hi
browsing through the links provided by Glenn i found this fm demodulator
old radio circuits  R3911
How does this work?

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Post by Admin on Sun Mar 31, 2019 8:55 pm

Maybe it is possible that they didn't publish the full and correct circuit diagram  Cool

I remember a circuit produced by PYE telecom in the UK. It was a 600Ω line amplifier. There was a 5.6v zener, and operational amplifier and capacitive coupling to the TX audio chain, via a 100K pot. The circuit was in really noise generator. The customer's specification was:
Signal:noise ratio = -55dB
Crosstalk = -65dB

With -57dB injected noise it was not possible to make the crosstalk figure that the designers could not meet  Wink

If you have a clever money-making circuit then some things you keep secret, even if it means confusing those who try to reverse-engineer their work, or adding seemingly useless bits that hide reality.

Just MHO. Harry - SM0VPO

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Post by zsolt on Sun Mar 31, 2019 8:27 pm

hi,
the paper claims that T1 is BF214/215 and T2 is BC170/171/109. It should receive the MW band.
Iam not interested to build it, i just noticed that he uses the emiter and not the colector of t1.
The links are great source of radio circuits

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Post by Glenndk on Sun Mar 31, 2019 12:13 pm

Hi all

Have a look on these circuits:

-

A Shortwave receiver with automatic regeneration control:
https://web.archive.org/web/20170718183222/http://zpostbox.ru/a_shortwave_receiver_with_automatic_regeneration_control.html

-

The only "bad" thing is that he uses a 6AS6 pentode - in a 2012 design (paper page 26):

Frequency compensated LC networks for oscillators with the wide tuning range:
http://www.kearman.com/vladn/hybrid_feedback.pdf
https://web.archive.org/web/20161022044737/http://www.kearman.com/vladn/hybrid_feedback.pdf
Quote: "...
The end result was a surprisingly well behaved regenerative receiver. It has a very good frequency
stability and does not require adjusting regeneration level as you tune from 3.3MHz to 9.1MHz which
is highly unusual for a conventional regen. The oscillation threshold level is so flat that it is completely
feasible to have just two fixed regeneration presets - one for AM and a higher one for the SSB/CW
modulation types. To illustrate these somewhat unconventional results I put several videos on youtube.
..."

-

Best simple regenerative receiver?:

A 1.2-volt Vackar-style minimalist regenerative receiver: Design, analysis, and implementation (updated 2017/05):
http://qrp-gaijin.blogspot.dk/2015/08/a-12-volt-vackar-style-minimalist.html
The circuit:
http://1.bp.blogspot.com/---Zk3BzGY6U/Vdlqr-suY_I/AAAAAAAAAT8/PXHfTZe_ipM/s1600/regen-circuit.png

https://www.qsl.net/df7tv/datasheets/1SV149.pdf

KV1236 or BB212 can be used instead of 1SV149.

-

qrp-gaijin:
Re: Varactor-tuned, hybrid-feedback, low-voltage BJT regen:
http://theradioboard.com/rb/viewtopic.php?t=5140#p46288

-

Look at the schematic in this article:
https://da.wikipedia.org/wiki/Superregenerativ_modtager

Both reflex and regeneration.

I you remove the 30pF trimmer you "only" have a reflex tuner.

Reflex: The transistor is both used as a RF-amplifer and a LF-amplifer.

.

Another example:

http://www.arrl.org/files/file/Technology/tis/info/pdf/0009061.pdf

How can he put a 1N34A (D1) and a capacitor (C4) in series? That is wrong.

-

Why is the C3 directly coupled across collector to common?

One Transistor Regenerative AM Receiver:
http://web.archive.org/web/20080517002144/http://home.pacbell.net/lengal/ip/amregen.pdf

-

If somebody wants superregenerative theory; it is here:
Designing Super-Regenerative Receivers. By Dr Eddie Insam:
http://www.eix.co.uk/Articles/Radio/Welcome.htm
backup:
https://web.archive.org/web/20190227205400/http://www.eix.co.uk/Articles/Radio/Welcome.htm

-

Some theory with a very simple and versatile example:

Super Regenerator:
http://zpostbox.ru/super_regenerator.html

-


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Post by Glenndk on Sun Mar 31, 2019 10:57 am

zsolt wrote:this analog circuits require a lot of know how

This is actually a rather simple circuit.

No regeneration.

No reflex.

No neutralisation.

Regarding img_2010.jpg:

Can you tell us, which transistor was recommended in the book?

What frequency range was it made for? Medium wave?


Circuit: I am missing a RF-capacitor across plus and common.

-

Used decimal mark ",".

Assumption: Vbe ca.= 0,2V (germanium)

I am not considering the collector-base leak current, which might be max. 10uA@Vce 5-10V@25°C for low power germanium transistors. (doubles every time the temperature increases 10°C)

.

I have tried to "reverse engineer" the design at img_2010.jpg:

T2 Vce ought to have V/2=2,25V.

Ic ca.= Ie ca.=2,25V/10kohm = 225uA

Base current:

(4,5-0,2)V/470kohm ca.= 10uA

This means that the transistor design beta is around 225/10 ca.= 22,5 ?

Even AC121 has a higher beta?

OC70 has beta = 20..40

-

T1 Vce ought to have V/2=2,25V.

Ic ca.= Ie ca.=2,25V/4,7kohm = 480uA

Ibe ca.=(2,25-0,2)V/33kohm ca.= 62uA

This means that the transistor design beta is around 480/74 ca.= 7,7 ?

This is wrong.

-

We guess the beta is 22.

We have:

Ic = Ie = (4,5-Vce)V/4,7kohm

Ic = Ie = Ibe x beta = Ibe x 22

Ibe = (Vce-0,2)V/33kohm

Putting it all together:

Ibe = (4,5-Vce)V/4,7kohm/22

Ibe = (Vce-0,2)V/33kohm

(4,5-Vce)V/4,7kohm/22 ca.= (Vce-0,2)V/33kohm
<=>
(4,5-Vce) x 33kohm ca.= (Vce-0,2)V x 4,7kohm x 22
<=>
(4,5-Vce) ca.= (Vce-0,2)V x 3,13
<=>
4,5-Vce ca.= 3,13 x Vce - 0,626
<=>
5,1 ca.= 4,13 x Vce
<=>
Vce ca.= 1,23 V

Ic ca.= 700uA

Ib ca.= 31uA

-


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Post by zsolt on Sat Mar 30, 2019 9:30 pm

this analog circuits require a lot of know how

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Post by Ivan on Fri Mar 29, 2019 1:25 pm

Hi,
why do you mean the transistors affect each other? IMHO T1 is an emitter follower (common collector), which has big input impedance, so that it minimizes the load of the tuned  circuit. Its B-E junction may also serve as a detector. T2 is simply an AF amplifier with common emitter.

VBR regards from Ivan

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Post by zsolt on Thu Mar 28, 2019 8:26 pm

ok, but why does the high impedance from collector of t2 bacwards affect t1?
if this works like this it means that the lc circuit is backwards affected by t1's load which is t2... , and the whole receiving capability of the radio is affected by the circuit itself

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Post by Admin on Wed Mar 27, 2019 10:26 pm

Glenndk wrote:What is D8 doing?

I have seen something similar before. I believe it is an attempt to make the meter voltage less-linear. The forward voltage drop across a diode does vary logrythmically with increasing current.

But ok on the Grundig(s). I do envy you. They were really something. I should really keep my eye on E-Bay as I have been looking for something similar for a long time.

When I was a lot younger I always fancied a Yacht-Boy 210:
old radio circuits  S-l300
But the Yacht-Boy 212, world receiver, would be a better choice for me.
But it is just to keep my eyes open. I flatly refuse to buy any "modern" radio like this;
old radio circuits  S-l1600
Unfortunately it feels like plastic, uses trimmer potentiometers with knobs on, and that sort of penny-pinching thinking. Not even propper push-buttons, they press rubber/carbon onto PCB pads. One clean with switch-cleaner and the carbon is gone (can be repaired with a soft pencil).

Yes, it is a shame that so many MW stations are shutting down. I used to listen to "Radio Atlantic 252" in 252kHz on the Long Waveband. But they shut down a couple of years ago. I suppose now all I can do is make playlists of MP3's from the 50's, 60's and 70's then play them on an AM modulator. A good station to listen to is Radio London "The Big-L" (www.bigl.co.uk), who play mainly oldies, just like Luxenburg 208 did.

Anyway, my 60 minutes for e-mail, homepages, forum and workbench have now expired. I am being summoned!

Catch you later, and good look with the other Grundig.
Very best regards from Harry - SM0VPO / EA/SM0VPO

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Post by Glenndk on Wed Mar 27, 2019 7:16 pm

Admin wrote:
...
One of the receivers has a line-up of OC44, OC45, OC45, OC81D and a pair of OC81s. Also an OA79 diode. Remember when you counted the active components? 6 transistors and one diode was the "bees knees".

In 1966 I bought a Vesta Vixen 2-Band + bandspread, from Woolworths (£4/2s/6d) with leather case.

My brother bought one better than mine, his has 7 transistors (although one transistor was used as a diode).

Thank you for sharing the links. BR Harry - SM0VPO

I have bought two Grundig Transistor 6002/Satellit 1000. One of them I have repaired with a new belt for band switching - and almost all movable parts and the "revolver" contacts have been greased with a synthetic grease. I have also bought the Grundig SSB-adaptors (plugged in via the SSB-socket). (I have not calibrated/aligned all the resonators yet).

I have not looked at the second Satellit 1000 at all - I have too many other things I would like to do :-)

Look at the schematic:
http://www.owdjim.gen.nz/chris/radio/Grundig/large/CircuitDiagram.jpg
backup:
https://web.archive.org/web/20180210175649/http://www.owdjim.gen.nz/chris/radio/Grundig/large/CircuitDiagram.jpg

What is D8 doing?

Look at D3 and D4 - they are doing AGC.

The receiver even has got silicium transistors - and it even has two FETs (BF245) in the FM-tuner!

At MW and LW it uses variable inductors for tuning. It is incredible that it works that good.


I made a broadbanded two port screened loop-antenna, that is great at receiving many ham bands. I am measuring it with a VNWA ( https://www.sdr-kits.net/introducing-DG8SAQ-VNWA3 ). But what really was stunning, was that it is really great at receiving the british and russian stations in medium waves. Much better than the Grundig Satellit 1000 ferrite antennas. When receiving with an indoor TC2M-antenna (also two-port: https://ham.brugtgrej.dk/forum.php?mode=thread&obj=66497 ), the signal seems to be 6-12dB (1 to 2 at the S-meter) lower with the loop-antenna than the TC2M, but the noise plummet more than 36dB (from S7-S8 to less than S1 (s0) at the S-meter). This happens to MW, 160 meter, 80 meter, 40 meter... (and between).

But where was the german and french stations? They left LW, MW and SW in 2015. :-(

12/30/2015, Medium-Wave Transmitters in Germany and France Shutting Down at Year’s End:
http://www.arrl.org/news/medium-wave-transmitters-in-germany-and-france-shutting-down-at-year-s-end

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Post by Glenndk on Wed Mar 27, 2019 6:38 pm

Admin wrote:
...
Wonder if I can have a library in "the smallest room"?
...
Thank you for sharing the links. BR Harry - SM0VPO

Hi Harry

Have you heard about sneakerNet?:

https://what-if.xkcd.com/31/
Quote: "...
That means FedEx is capable of transferring 150 exabytes of data per day, or 14 petabits per second—almost a hundred times the current throughput of the internet.
...
Those thumbnail-sized flakes have a storage density of up to 160 terabytes per kilogram, which means a FedEx fleet loaded with MicroSD cards could transfer about 177 petabits per second, or two zettabytes per day—a thousand times the internet’s current traffic level.
...
So the bottom line is that for raw bandwidth, the internet will probably never beat SneakerNet.
..."

https://en.wikipedia.org/wiki/Sneakernet

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Post by Glenndk on Wed Mar 27, 2019 6:25 pm

zsolt wrote:
hello

why does he take the signal from theemiter of T1 and not from colector like usual?

My guess is that it is a crystal earpiece, so it is a high-impedance load (around 20kohm). (100nf in series can not work for electrodynamic ear-phones 8 ohm...1kohm.) 100nF and 20kohm gives -3dB at 80Hz.

https://en.wikipedia.org/wiki/Crystal_earpiece
Quote: "...
One remaining use for crystal earpieces is in crystal radios. Their very high sensitivity enables them to use the very weak signals produced by crystal radios, and their high impedance (on the order of 20 kilohms) is a good match for the typical crystal radio
..."

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Post by zsolt on Tue Mar 26, 2019 8:20 pm

hello
old radio circuits  Img_2010
why does he take the signal from theemiter of T1 and not from colector like usual?

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Post by Admin on Sat Mar 23, 2019 7:46 pm

Ok, those were interesting books, thanks for the links Glenn.
I got Teleport to download them at work. 5GB of PDFs.

File-names are a bit cryptic but there is some interesting reading there. All I need is the time to do the reading.
Wonder if I can have a library in "the smallest room"?

Really liked the ARRL handbooks.

Hi Joy, you points were noted. I have a book with a collection of articled fro the 60's to 80s. There were loads f interesting articles in those days.
One of the receivers has a line-up of OC44, OC45, OC45, OC81D and a pair of OC81s. Also an OA79 diode. Remember when you counted the active components? 6 transistors and one diode was the "bees knees".

In 1966 I bought a Vesta Vixen 2-Band + bandspread, from Woolworths (£4/2s/6d) with leather case.
old radio circuits  Vintage-transistor-radio-band-vesta_360_ec43ac98103d96206bb3fe8d532dc12b
My brother bought one better than mine, his has 7 transistors (although one transistor was used as a diode).

Thank you for sharing the links. BR Harry - SM0VPO

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Post by zsolt on Tue Mar 19, 2019 6:58 am

hi,
no it's not from the internet. Actually i never tought about searching for books on the internet. Usually i visit local flea markets and used book dealers. I found a lot of goodies for almost nothing.This one is from a romanian editor from 1981, called (in direct translation) the radioamateurs book. Its a collection of radios, transmitters and some measuring devices spread on 800 pages.
By browsing it i found a chapter called SSTV (slow scan tv), i did not know that this existed. And it actually describes a circuit doing that.... Probably i will not build anything from it but some chapters are interesting
Buy the way i saw an article about a "tranzistored sstv monitor" built by a swedish radioamateur called SMOBVO

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Post by Glenndk on Mon Mar 18, 2019 5:16 pm

One of these books?:

http://www.tubebooks.org/technical_books_online.htm

Main page:
http://www.tubebooks.org/

http://n4trb.com/AmateurRadio/SemiconductorHistory/SemiconductorDocuments.htm

http://n4trb.com/AmateurRadio/GE_HamNews/ge_ham_news.htm

Main page:
http://n4trb.com/

-

How Can I Tell Whether a Copyright Was Renewed?:
http://onlinebooks.library.upenn.edu/renewals.html
Quote: "...
First of all, you need to know when renewal matters. In the US, books published before 1964 had to get their copyrights renewed at the Library of Congress Copyright Office in their 28th year, or they'd fall into the public domain. Some books originally published outside the US by non-Americans are exempt from this requirement, and in fact some such books had their copyrights restored recently. If you need to know more about the rules for books published outside the US, see this page from the Copyright Office, explaining recent changes in copyright law imposed by GATT. Basically a work is exempt from renewal requirements if all of the following conditions apply:
At least one author was a citizen or resident of a foreign country (outside the US) that's a party to the applicable copyright agreements. (Almost all countries are parties to these agreements.)
The work was still under copyright in at least one author's "home country" at the time the GATT copyright agreement went into effect for that country (1 January 1996 for most countries).
The work was first published abroad, and not published in the United States until at least 30 days after its first publication abroad.
If you can prove any of these conditions don't apply, and the work was originally published or copyrighted before 1964, then the work had to be renewed in order to stay copyrighted in the US.
..."

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Post by Ivan on Mon Mar 18, 2019 5:21 am

Hi,
the germanium transistors often have less amplification factor than modern silicon ones. I expect some resistors will have to be changed. More, Ge transistors required some temperature compensation circuitry, redundant with modern ones.
Not only the base, but all electrodes must be polarized correctly. PNP types were more common with Ge.

VBR from Ivan

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Post by zsolt on Sun Mar 17, 2019 7:03 pm

hi there,
i recently found an old book with (much older) radio circuits in it. Most of the circuits are with tubes so they are just interesting but some circuits are with transistors. Wery old and obsolete germanium transistors. I wonder if some circuits could be made with now days transistors? like c547 transistor for example. I know that the base should be polarised correctly but would that be enough to replace a germanium transistor?
i know that it sound like a really general question but i really like some reflex circuits that claim to deliver local stations at high audio level

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