LF: Re: PORTADYNE

["captbrian" <captbrian@ukonline.co.uk>]

You should be able to make out the circuit just by looking at the underside of chassis. 

 

 I thought all G3's could draw the circuit of a simple 4 valve TRF rx from memory and first principles having built several as teenagers ?

 

 

 

 One of the v. condensers is almost certainly the "reaction"  control.   [positive feedback in modern terms ] although the same result could be obtained by the variometer you describe.

 

Start with loudspeaker leads (high impedance in series with the anode of output stage) one will got to output valve anode. the grid of that will take you (via condenser) to anode of audio stage and the grid of audio stage to the detector valve.

 

Bryan G3GVB

----- Original Message -----

From: hamilton mal

To: rsgb_lf_group@blacksheep.org

Sent: Tuesday, September 21, 2004 4:48 PM

Subject: LF: PORTADYNE

    Hi All.

Thanks to the response about the Portadyne radio. Here are the answers to the questions asked.

Tech details:

 

4 valves

 

Battery leads consist of 2 leads poss LT,  2 more for HT and a couple of others poss bias. The set is so old that the leads have virtually disentegrated along with the internal wiring on the chassis.

 

2 independent tuning condensers, each with own knob each side of cylinderal dial on top middle of RX facia, to left is on/off

 switch and to the right is what looks like a small variometer that would appear to interact with the loop antenna winding.

(looks like a lollipop) The dial has lost its markings so cannot identify any anything, would not be freq or wavelength because its so narrow. Possibly just graduations.

 

There is a very crude loudspeaker to the front of cabinet and on the outside there is a screw adjustment about the centre of the speaker for some sort of sensitivity adjustment I suppose.

 

The cabinet is wooden 15 inches high and 14 inches wide. The front appearance is fretted and flaired. The controls are under a lift up pannel on top of the cabinet.

 

There are no coils except what appears to be a choke type inductor and the frame aerial winding around the inside of the cabinet.

 

This would be a TRF type radio with a RF stage, top of the range in its time !!!!

I expect is must be one of the first valve type radios and some of you old timers will know its exact age and maybe have a cct for it.

 

Thanks for the 11 replies showing a lot of interest, it probably covers MF and LF, the tuning is odd ball with both condensers moving the dial independently.

 

The valve bases seem small compared to the UX5 and UX7 type but similar pin displacement.

 

There could be a pint or a wee whiskey for the first one to come up with a cct diagram

 

The cabinet is in good condx but the chassis is corroded but not too bad, the wiring has just about gone.

 

More info welcome.

 

de Mal/G3KEV