anyone got diagram for SW radio?

[Spencervs]

hi guys I'm looking to create a SW radio then move on to an FM one. I got a spare ECL83 valve and was hoping to encorperate it into the circuit... are there any circuits that I could do that isn't too complicated? I heard a range of 6-7.3 MHz would be good could this valve do that?

[Alf]

From what I can remember, the ECL83 was designed for low frequency work, audio output or TV frame output with its P version.

[paulsherwin]

The triode is probably ok for at least the LF end of SW, and the pentode will only be used for audio. There are lots of valve SW projects here.

[Ed_Dinning]

The "classic" home constrctor circuits often used EF80's or EF91's, both easily and cheaply available. Coils would have been Wearite P or Denco etc and the circuit would be a simple TRF.
There should be some good circuits associated with Radio Constructor if you Google that.
Famous battery version of an SW set was the HAC (heard all continents), often advertised as a kit set in the mags of the 50's.

Ed

[ms660]

I have often wondered how a PFL200 would perform in a simple receiver with it's Gm of 21.

Lawrence.

[G8HQP Dave]

Possibly badly? High gm can lead to poor handling of strong signals, and a tendency to oscillate at the slightest provocation. High gm valves were intended for either baseband video or broadband RF, in either case with lowish impedance circuits. Not suitable for normal receivers, which are narrowband.

[ms660]

Hello Dave, I was thinking of the high 21 Gm "L" section for audio/headphone amplification and the lower 8.5 Gm "F" section for RF etc, say for a simple one or two valve 160/80/40m receiver or a LW NDB receiver, I remember building a simple direct conversion receiver years ago with just a couple of valves or so, one of them was an double diode (EB91?) fed via a triflar wound coil. I remember it performed quite well considering, but I can not remember wether I designed it myself or if I pinched the circuit from a mag!

Lawrence.

[Brian R Pateman]

Originally Posted by Spencervs

I got a spare ECL83 valve and was hoping to encorperate it into the circuit...

Strangely, most valves rarely read the data books and tend to work to some extent in applications their designer didn't intend.

In the true sprit of homebrew, try it and see.

[kalee20]

Originally Posted by Alf

From what I can remember, the ECL83 was designed for low frequency work, audio output...(

It was. And so was the 6V6.

But that didn't stop the 6V6 operating to tens of MHz in amateur transmitters as power output valve. And I'd expect the ECL83 to be usable up to a few MHz at least. The things that will probably limit you are, cathode lead inductance, and inter-electrode capacitance (particularly triode-anode to pentode-anode).

While not being my valve of choice (for SW I'd avoid compound valves like triode-pentodes), I'd be 90% confident you could build a respectable SW receiver with it.

[G8HQP Dave]

Originally Posted by pwdrive

and the lower 8.5 Gm "F" section for RF etc

I read somewhere that for simple regen sets you want lowish gm. 8.5 is high. Many of the classic designs would have used octal valves with gm around 2mA/V.

[ms660]

It might do as RF amp before detection the Gm is similar to the EF91 but thats not to say it would perform the same, I suppose it depends on the design of the receiver etc, if I should ever come across one I will do a rats nest on the bench and see what it can do, time permitting that is. May be "F" (PFL200) = RF amp, EB91 = Balanced Det. EC?? = BFO, "L" (PFL200) = AF Amp. or something like that...I love mucking about.

Lawrence.

[dave_n_t]

Originally Posted by pwdrive

I have often wondered how a PFL200 would perform in a simple receiver with it's Gm of 21.

Lawrence.

Lawrence,

I think it does quite well!

See my post in this thread (post #24):
https://www.vintage-radio.net/forum/...=PFL200&page=2

dave

[ms660]

Hello Dave (NT) I thought it might under the right circuit conditions as it has to be good to 6Mhz for it's TV application, I suspect it will go a lot higher with carefull circuit design. For some unknown reason I have always been fascinated by the PFL200, we used to get through boxes of them in my TV days as they seem to have been driven hard in the tellys especially in the Thorn chassis, I always had one in my "top 10" box whenever I was pulled off the bench to do field service. I like your low HT idea. The PFL200 I think was an amazing piece of design ie; cramming all that into a standard envelope, another one that intrigued me was the ECLL800 I remember buying half a dozen when they first came out, I used to build guitar practice amps with them and flogg them to me mates, happy days.

Lawrence