Unusual EM34 style tuning indicator display! - UK Vintage Radio Repair and Restoration Discussion Forum

Chris55000 · 7th Feb 2015, 10:26 pm

Hi!

Unfortunately I've no means of scanning the article for the moment, but there was an article in the late 1940s/early 1950s "Wireless World" of a possible type of EM34-type tuning indicator for FM use operated from the discriminator that showed the correct point of tune as a vertical bar of light on top of a single shadow, but off-tune the bar of light would be at an angle to the shadow, either left or right depending on the direction of mis-tuning, and the angle between the light/shadow dependent on the amount of mis-tuning.

The article made reference to "two deflection-rods" but gives no circuit or type details!

Would a display like this have needed a specially-constructed eye, and does anybody know more about it?

Chris Williams

paulsherwin · 7th Feb 2015, 10:45 pm

Yes, this would need a new internal design, but I can't see it would have been technically difficult. Presumably the potential market was too small for economic production. The same functionality was achieved with FM tuners with a meter, and later in the analogue tuning era with a couple of LEDs. Digitally tuned receivers don't need this sort of tuning indicator of course.

I own a fairly cheap Trio KT-30 tuner from around 1980 which achieves a similar effect using an LED positioned on the end of the dial pointer. When the station is mistuned the LED blinks. Tuning correctly causes it to stay on.

Mike. Watterson · 8th Feb 2015, 5:37 pm

The 6ALGT is for FM
http://www.radiomuseum.org/tubes/tube_6al7gt.html

as is EMM803 (stereo indicator!)
http://www.radiomuseum.org/tubes/tube_emm803.html

Pattern
http://www.radiomuseum.org/forum/mag..._patterns.html

Any eye tunes fed from discriminator. Some two bar Eye can be wired to give +/- tuning. Some valve sets had AFC too.
See EM83
http://www.radiomuseum.org/tubes/tube_em83.html
Possible to wire it so bars move opposite and are same length when tuned.

7th Feb 2015, 10:26 pm	#1
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,874	Unusual EM34 style tuning indicator display! Hi! Unfortunately I've no means of scanning the article for the moment, but there was an article in the late 1940s/early 1950s "Wireless World" of a possible type of EM34-type tuning indicator for FM use operated from the discriminator that showed the correct point of tune as a vertical bar of light on top of a single shadow, but off-tune the bar of light would be at an angle to the shadow, either left or right depending on the direction of mis-tuning, and the angle between the light/shadow dependent on the amount of mis-tuning. The article made reference to "two deflection-rods" but gives no circuit or type details! Would a display like this have needed a specially-constructed eye, and does anybody know more about it? Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

7th Feb 2015, 10:45 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: Unusual EM34 style tuning indicator display! Yes, this would need a new internal design, but I can't see it would have been technically difficult. Presumably the potential market was too small for economic production. The same functionality was achieved with FM tuners with a meter, and later in the analogue tuning era with a couple of LEDs. Digitally tuned receivers don't need this sort of tuning indicator of course. I own a fairly cheap Trio KT-30 tuner from around 1980 which achieves a similar effect using an LED positioned on the end of the dial pointer. When the station is mistuned the LED blinks. Tuning correctly causes it to stay on.

8th Feb 2015, 5:37 pm	#3
Mike. Watterson Heptode Join Date: Dec 2014 Location: Limerick, Ireland. Posts: 901	Re: Unusual EM34 style tuning indicator display! The 6ALGT is for FM http://www.radiomuseum.org/tubes/tube_6al7gt.html as is EMM803 (stereo indicator!) http://www.radiomuseum.org/tubes/tube_emm803.html Pattern http://www.radiomuseum.org/forum/mag..._patterns.html Any eye tunes fed from discriminator. Some two bar Eye can be wired to give +/- tuning. Some valve sets had AFC too. See EM83 http://www.radiomuseum.org/tubes/tube_em83.html Possible to wire it so bars move opposite and are same length when tuned.