1j42b Valves

[Mike Watterson]

Missing from last post
   

[Murphyv310]

Clever! Is that a strip of copper laminate Trevor?

Sure is, along with some double sided laminate as a ground plane.

[Geordie McBoyne]

Here's another valve tbat employs a space charge grid, the 12K5.

From the Radiomuseum:    http://www.radiomuseum.org/tubes/tube_12k5.html

The 12K5 was employed as a driver for the transistor output stages in car radios.
One of a series of American 12volt HT valves. These were also made and marketed in the UK by Brimar.

Geordie McBoyne.

[Mike Watterson]

The Rod tubes though are not space charge grids like 12K5, they don't actually have ANY grids in the conventional sense. It's only the 1j37b and 1j42 "misused" in Gammatron mode (g1a used as grid and g1b used as anode and the other electrodes earthed to f-) where "space charge" mode comes into it at all.

Or are you referring to ECH81/ECH83, etc and other valves used with 12V HT and usually 0V or slightly positive grids? It's not how the 1j42a achieves 6V HT

[Pat Pending]

Sure is, along with some double sided laminate as a ground plane.

Ah, so! Its valves, Manhattan style. Ive normally punched out chads of copper laminate as pads then superglue them down to the ground plane but your method looks stronger.

One of my recent Manhattan style hybrid radio lash up's shown in attached photos

Mike, that diecast box assembly is a neat example, never got on with vero myself, always got lost and cut the wrong tracks or something, always admired anyone who didn't make a dogs dinner of it. I've always had more success building over a groundplain for RF or pinboard for LF discreet component circuits. In my professional life PCB design was part of the job but I never saw the point for a one off.

Cheers, 
Andy.

[Geordie McBoyne]

The other valves in the American series for operation on 12volt HT were the 12AC6, 12AD6 and 12AE6.
http://www.radiomuseum.org/tubes/tube_12ac6.html
http://www.radiomuseum.org/tubes/tube_12ad6.html
http://www.radiomuseum.org/tubes/tube_12ae6.html

It could be possible that the 12AD6 is a development of the 6BE6/12BE6 just like it is suggested that the ECH83 is a specially selected ECH81.

Geordie McBoyne.

[Pat Pending]

May be of interest to others interested in low ht valve circuits. http://members.iinet.net.au/~cool386/12v...vsrrx.html 

[Murphyv310]

   
Hi.
Made up a very simple pantry transmitter using a 1566Khz Crystal, one valve and 6 passive components. The valve works best with G2 & Anode strapped, the crystal is connected between Anode and G1(1) a 5.6meg is between this grid and F-. on the opposite G1(2) audio is applied via a 1000pf cap and 47k series resistor at line level, the grid is returned to F- via a 4.7meg, the G3 is returned to F-.
The Anode & G2 is fed via an HF choke to HT (9v)
Too long an aerial and the circuit stops oscillating but with a couple of meters of wire off the anode you get about the same in range, feed it to my frame aerial and tune it up then the range goes to 15 meters outside, audio quality is reasonable so long as you dont go over 80% modulation.
It really needs a buffer to work correctly and a proper Tank arrangement.

[Mike Watterson]

What is HT current? Less than 1mA?
End point of a PP3 is 5.5V, probably still work if the load was large tuned loop.
It's practically transistor power consumption territory as it also probably works down to 10mA or less filament current, maybe 1V?

[Terry]

Made up a very simple pantry transmitter using a 1566Khz Crystal ...

Interesting choice of frequency, Trevor.
I note that you've managed to find a crystal that is an exact multiple of 9kHz - a rare find unless you had it cut specially - but it is also the modern equivalent of the frequency of the first European pirate radio station: the Dutch pirate Radio Veronica (1562kHz/192m) - before WARC '79 there were some 8kHz channels crammed in at the HF end of the MW band.

   

Transmitters in the upper, white, section were stations authorised under the Copenhagen plan; those in the shaded area, including Caroline & Veronica, of course, were unauthorised stations.

It is alleged that a girl friend of Ronan O'Reilly told him about Radio Veronica and that was the inspiration behind Radio Caroline (Veronica started 5 years before Caroline in 1959)