Do you remember your first receiver?
Did you build it from a kit or were you more adventurous and
make one that was described in a magazine?
A few errors have crept (as they do) into this month's column. They're all on page 49. At the bottom of the first column on that page, it's capacitor C4 which is required if the power supply leads are more than a few centimetres long, not capacitor C1. Next, at the top of the second column, it's Fig. 2 which shows two input configurations, not Fig. 1. Finally, regarding components R2, D1 and D2: D2 is NOT optional (if protection against high transient voltages is needed). BTW - these goofs aren't mine. I can admit to a lot of mistakes, but not this lot!
One other point: transformer T2 in Fig. 2, is representative of a centre-tapped heater winding of the mains transformer already present in a receiver (or whatever). It is not meant to be a seperate transformer added simply to power the featured TDA7052 amplifier.
If you take a look at a miniature valve you'll usually find both
a three-character code and a four-character code printed near the pins.
These are manufacturing codes.
They identify the valve type and where and when it was made.
I finally found out what all the characters mean.
Rather than split the full description I've put the details on the
June 2001 page.
Do you remember your first receiver?
Did you build it from a kit or were you more adventurous and
make one that was described in a magazine?
I've recently received several letters which mentioned old one-valve regenerative receivers. My asking for information about my 'thirsty' PM2DX 2V battery valve stirred quite a few memories. You see.... I'd found a PM2DX amongst my valves. I'd then knocked it over. Fortunately, the valve didn't break. Indeed, it works rather well considering it must be over sixty years old. Strange thing is, however, the filament takes almost 200mA (at 2V) rather than the data book figure of 100mA. In June's column I asked if any readers had got a PM2DX and, if so, could they possibly measure the filament current.
Several readers with PM2DXs did take the trouble (thank you) to measure the filament current. In total, three valves measured close to 200mA while the remainder measured between 90mA and 113mA. I had come across a reference to a filament current of 250mA (Keith Thrower's History of the British Radio Valve To 1940) for the PM2DX but all other references give the filament current as 100mA. While 200mA isn't 250mA, it does seem that there are (at least) two versions of the PM2DX in existence.
My first regenerative receiver was a H.A.C. -
which stands for Hear All Continents - model 'DX' one-valver.
(See the photograph on the right.)
Although I'd been interested in radio for a couple of years,
I'd still not built a valve receiver.
About time I did, I thought.
The set worked - in retrospect as good as it should have done -
but having been used to a short-wave superhet receiver, the H.A.C.
was nothing more than an interesting diversion.
Over the last few weeks I've been playing with the H.A.C. again, this time trying different valves. The set is actually designed to take 2-volt battery triode valves but I tried it with mains valves as well. (I didn't change the valve holder, just wired another in parallel.) With the coils - made by Denco, incidentally - supplied, best results were obtained with a 6C4 valve with 45V on the anode. (The 6C4 is electrically the same as half an ECC82.) Despite their simplicity, regenerative receivers can work extremely well. And there is definitely an 'art' in their design and construction. Almost any regenerative receiver will work, but it's quite a challenge to get a design to work at maximum efficiency. But when you do get everything right, there's nothing in engineering - electronic or otherwise - to compare with its simplicity and efficiency. Except maybe the wheel! Okay, so I'm biased. But regens are darn good when they're done right. (Apologies for the Americanisms there.)
I'd like to know what one and two valve receiver kits
have been available over the years.
I know of a few but I'm sure there were many kit
manufacturers and lots of kits.
So which receiver - kit or otherwise - did you build? And what valve(s) did you use?
I wonder if anyone has an unbuilt kit? I still have the box (label pictured right) my kit came in but an original kit would be a wonderful find. By the way, there's data on my H.A.C. set on my documents page.
My thanks to G3ZPF for the work he did on the H.A.C. label.
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