Electron Coupled 1 Valve Receiver

18th June 2009, 07:24
Urge to build a radio came over me a few days ago. Toiled all day at it and finally got it working very well. Used a 1T4 battery pentode. Two 47uH RF chokes inside empty 1 1/4 inch glass fuses as coils. Reaction controlled by varying voltage on screen grid. Aerial actually connected to grid via one filament leg on valve, RF choke and grid leak network. Great fun.

18th June 2009, 10:51
Neat job! Especially like the idea of the chokes inside glass fuse case, easily swappable. That style of construction takes me back many more years than I care to remember. My first (after crystal sets) was a TRF in a biscuit tin :)

K urgess
18th June 2009, 12:33
I like the classy wooden chassis.
Very neat work almost modern sculpture. (Thumb)

18th June 2009, 19:03
It is a bit laborious building them like this though. I first build them on a normal piece of wood with graph paper stuck on it in case I get any components in the wrong place, or have to drill extra holes. Once it is working, I can transfer the positioning of the holes to the varnished base using another piece of graph paper. Then the whole thing has to be taken to bits and re-assembled on the varnished base. It gets really heavy going when working up to four valves. I don't do this sort of thing very often, it is usually weeks or months between each one.

19th June 2009, 07:21
I'm overawed by the neatness of it, reminds me of something from a science exhibit in a museum.
Clever B7G valveholder arrangement too.

19th June 2009, 17:29
Impressive - that's really nice! You can (almost) smell the hot valve and the varnished wood...

19th June 2009, 19:11
Thanks for comments. Unfortunately, this sort of thing will soon be ended, terminated, kaput, if things go to plan (and I hope they don't!). I refer to the intended UK switch to digital radio in the near future. I sincerely hope that some pirate stations will continue to broadcast on AM in the UK so that folk like me can continue their "occasional" hobby of radio construction. Of course short waves will no doubt remain the last stronghold of AM for the foreseable future, but it is a bit more difficult to deal with than medium wave when it comes to home construction and most of the interesting CW stations have ceased to exist now!

charles henry
20th June 2009, 16:51
I refer to the intended UK switch to digital radio in the near future.

Am a bit puzzled, could understand them switching to SSB, but digital?? However there is no doubt that it saves bandwidth.

The US TV stations have switched to digital, the only down side for the user is tht with to old tv if you were trying to improve the signal by moving the antenna direction you could tell whether it was getting better or worse.

Rotating your antenna on a digital tv signal you have abosolutely no indication of whether you are moving in the right direction or not, tuned off the signal you get garbage, On the signal you suddenly get your full and good picture.

Tremendous savings in used bandwidth which will allow the licencing of many many more tv station in the same bands.

Like it or not it makes sense for tv but dont know about radio.

de chas

K urgess
20th June 2009, 17:49
I can't understand why we would want more TV stations.
There isn't enough decent content to keep the ones going that we've already got. (Cloud)
The only benefit appears to be less interference. Although I'm not too sure that it will disappear. It now manifests itself in blocks missing from the picture or and absence of signal.

charles henry
21st June 2009, 14:34
I can't understand why we would want more TV stations.

The answer is MONEY, big brother has more spectrum to licence out, big brother's minions will have greater numbers to control, therefore larger departments, more bodies - greater resposibilities and higher salaries.

Remember in '47 paying FIVE POUNDS which was a helluvalot of money in those days (Weeks salary) for the privilage of sitting the 1st pmg exam,
why? ------ because they could, and that in my opinion is the answer to all and any governmental process.

de chas