Simple radio circuit (AM)

Admin wrote:I saw that one of the tubes you quoted was a power pentode. I wonder if that could make a nice HP PA stage?

Hi Harry,
at least four types of power pentodes exist. I found an example of 12 W VHF PA (also here) and a simple QRP PA. The TXs on Sputnik 1 were based on these tubes, too.

BTW, the whole article on pages from http://www.antentop.org/016html/016_p89.htm to http://www.antentop.org/016html/016_p92.htm is worth reading.

VBR from Ivan

Hi Ivan,
No problems. I guessed the tube you quoted was something similar.
Thanks for the data. I see that these tubes are still available, and 60 Volts is easy with 20x CR2032 or similar.

I saw that one of the tubes you quoted was a power pentode. I wonder if that could make a nice HP PA stage?
I have loads of ideas, but no time. Tonight my evening after work is yet more cleaning for another house viewing: SSDD  

Very best regards from Harry - SM0VPO

Hi Harry,
I apologize myself. I wrote a wrong number, I had 1ZH24 in mind. And there may be an issue with transcription of the Russian characters "soft zet" and "B" to the latin alphabet.
The range of these tubes should be:

Hi Ivan,
In Spain there are many more such hoops you have to jump through to sell or buy a house. You can usually reckon that the seller has to pay 15% of the selling price, and the buyer also has to pay 15%. To have the land registry updated in Malaga can take a long time. Ours took 6 years. That was completed late last year, but now the new owners will have that to go through. also, the Spanish authorities value the house you bought, and if they think you paid too little for it then they send you a hefty tax bill.

Sorry to hear that your back is taking so long to heal. I sincerely hope that it gets better soon.

I tried to google the 1ZH29 but could not find any reference to it. I have some of these, are they the same beasty?



I was thinking about a nice little pocket regen-receiver and also a GDO using a real grid. But I dare not think about that just yet. Just making a PCB can take several days, working between the haftas.

Anyway, get better soon.

Very best regards from Harry

Hi Harry,
your troubles with bureaucrats and lawyers are horrible. We often complaint about authorities here in Czechia. Now I see they are nearly the same elsewhere.
We have a proverb:"It is better if the home burns down than to move twice." It is rather exaggerated of course...

My projects stay in my head currently. My ill backbone caused me severe problems with the sensitivity and mobility of my hands.   I firmly believe I can get it better again. After I cure, I want to make some tests with ultraminiature vacuum tubes from Russia, like 1ZH29. I have bought some from military surplus recently.

VBR from Ivan

Hi Ivan,
Like all my projects, I have loads of ideas, but as I get older I seem to have my time stolen from me for other "more important" issues.

We have just been told that out offer on a Swedish house (good QTH )has been accepted, so I have a lot of contact with the bank.
We are selling our apartment so I am doing a lot of cleaning to make the apartment into a show-home that is attractive. Last week we has a showing, and I have another on Thursday.

As if that is not enough, we also have had an offer for our villa on Spain. In Spain they want all manner of documentation. The latest is called a DAFO. It is issued by the local council to say that the house is legal and will not be subject to a demolition order. This means that the house must be legal (which it is), or more than 6 years old (ours is 220 years old), and that the septic tank is legal. The cost of the certificate is 11000 Euros! They sent a helicopter over the house last week to compare aerial photos and we got an approval just this morning. But they will not issue the certificate for six months. Talk about beurocracy  

Anyway, back tot he projects.

I have a 3D printed 90-volt battery. As soon as I have a gap between panics I will add the project to my homepages. the 1.5v battery is no problem. A modern 5A/H (parallel cells) will power DF91 etc for many hours.

by the way, the CN-381 is now working ok, but it is a bit deaf. I re-wired for a DF96, but the filament wiring requires the other filament terminal to be grounded, otherwise it affect the biasing. I just bought a DF91 and I will put it back to the original, then I think that re-alignment should do the trick.

Ivan wrote:I considered making a 90 V anode battery of 10 pcs 6LR61 (6F22) batteries, like this one. But your design is really interesting!

Interesting. So what project are you building? Anything you want to share?

BR Harry

Admin wrote:At the moment I am doing a bit of work on the AM band. I have an old Vidor CN-381 that I am refurbishing. I have made a genuine (looking) B-126 90v battery with a 3D printer, a battery skin scan, and 30x CR2032 button cells.

Hi Harry,
I considered making a 90 V anode battery of 10 pcs 6LR61 (6F22) batteries, like this one. But your design is really interesting!

VBR from Ivan

Hi,
666 is the devil's number. And the devil hides in details.
And seriously now: 5 or 6 turns of coupling coil should not IMHO make much difference.
The HF litz wire gives better quality of coils mainly on LW and MW frequencies, so it may improve the sensitivity and selectivity of the receiver. If you do not have one (it is quite rare nowadays), an enameled wire cca 0,5 mm dia is not much worse. Placing the coils to the center or end end of the ferrite rod has its influence, too.

BR from Ivan

Hi,
The turns ratio i usually tried was 60 with 5 . But thinking back i suspect that the difference between success and failure was in the details .... I never had available that wire that is used in factory . What i had was thin wire from 24Vdc relays .
I see this special wire is made of 4 or 5 thinner wires isolated with email and textile material .
Maybe this was the fault . 
They did work but only 1 or 2 stations was all i get . Sometimes 2 stations together .
The first radio i built was a 6 tranzistor radio with 3V supply and a 0.5W speaker. For some reason i still remember the circuit. I think i can still draw it from memory ( probably with error ) . I clearly remember that first 2 tranzistors where BF214 making rf amplification , than 2 diodes for detector followed by one BC171 preamp . The final audio stage had a BC171 attacking a AC180 & AC181 pair. Those tranzistors are obsolete anyway .. it was the first one that worked right away . Probably radio is the best thing humans ever invented till now.

Hi again,
It looks really good.

The ferrite "loopstick" antennas are really easy. Just 66 turns of wire for the tuned winding, and 6 turns for the output coupling. Easy to remember - 66 + 6.

At the moment I am doing a bit of work on the AM band. I have an old Vidor CN-381 that I am refurbishing. I have made a genuine (looking) B-126 90v battery with a 3D printer, a battery skin scan, and 30x CR2032 button cells.

The RF oscillator/mixer was a damaged DK91, so I changed it for a DK96 and connected the grid that was not internally connected. It sort of works now, but I believe that there is a problem with biasing the valve - the filament polarity appears to be reversed, so the filament battery is biasing the tube incorrectly. I have ordered a new DK91.

When I have finished my oscilloscope (or want another break from it) I will be making a multi-carrier MW oscillator/modulator fed with a few MP3 players. Already downloaded MP3 files with many hours of Radio Luxemburg, BBC Light Program, Radio Caroline, VOA and many more.

But now Maj-Lis is in Spain I hope to have more time for my wireless hobby :-)

BR Harry

Admin wrote:Wow, that is fantastic. A REALLY simple TRF receiver.
Did you get the stations with just the loopstic ferrite rod antenna? Or did you use an external antenna?

I did some experiments with audio, up to 37kHz (the limit of my sound cad). I connected a huge 21-turn loop of wire (probably about 20 metres diameter) into the sound card without an amplifier. Left it recording overnight for many days.

I managed to get a few (weak) "whistlers".

Just shows what you can do with very little equipment.





Thank you for sharing with us.

BR Harry - SM0VPO

this is it.
I measure 2.3V on ce when it works. One station is on 880kHz and the other is on 1135 kHz . It is selective enough the 2 stations are far apart compared to my experimental loop antenna radio, and don't mix  at all . Because it was to loud for the sound card input i added a 10 K resistor in the collector . Now the voltage across ce is 0.99V .
So the final schematicus is like this

Without the 10K resistor one station was to loud. From the cv i could set it a little off from the station so volume did go down but the treble and high tones where accentuated . Now with the 10k it has a nice warm sound for both stations . I believe that changing the 1M to 2.2M or bigger would have made the same effect so no extra resistor needed. Just that i had no such resistor at hand. Also using a shielded cable could make useless the 10nF cap so it could be omitted but i am not shore about that.
Also i think that the success of this circuit comes from the fact that i found the L antenna ready made by factory. I never get that part right when i try to wound it myself. 
There is no better way to begin a new year than making a little radio

Wow, that is fantastic. A REALLY simple TRF receiver.
Did you get the stations with just the loopstic ferrite rod antenna? Or did you use an external antenna?

I did some experiments with audio, up to 37kHz (the limit of my sound cad). I connected a huge 21-turn loop of wire (probably about 20 metres diameter) into the sound card without an amplifier. Left it recording overnight for many days.

I managed to get a few (weak) "whistlers".

Just shows what you can do with very little equipment.

Thank you for sharing with us.

BR Harry - SM0VPO

Hi,
I wanted to here some MW station so i trowed together this little circuit

I did absolutely no calculations . The L1 & L2 are on a 10 cm log flat ferite  rod. L2 looks like to be 7..10 turns and L1 like 6 or 7 times that. Just found it like that together with Cv . It takes it's power from the PC soundcard. 
This must be on the internet because it works 100 % . I found 2 stations . 
PS happy new year