maybe a single conductor wire ran in the attic and the other was ran to a ground, I could be mistaken but i used to take apart many old radios that would have these, back when the electromechanical speaker would weigh like 25 lbs :), with a big autotransformer driving the speaker.
Obsolete? Absolutely - especially since all TV has since gone digital.
The 300 ohm aerial system in my house is alive and well with clean digital signals issuing forth on both VHF and UHF. It's only the modulation that's changed, not the bands in which it is transmitted.
The 300 ohm aerial system in my house is alive and well with clean digital signals issuing forth on both VHF and UHF. It's only the modulation that's changed, not the bands in which it is transmitted.
Absolutely Aussie, I know of quite a few people over here that still have 300 ohm ribbon feeding their TV sets, with (in some cases) a better picture than some RG-6 installations.
They are happy with it that way and I would never get them to change either. All you need is a balun at the TV end to match the ribbon to the set impedance. Magic.
I could be mistaken but I used to take apart many old radios that would have these, back when the electromechanical speaker would weigh like 25 lbs, with a big auto-transformer driving the speaker.
Doug, In some of the radios of that era, the matching transformer on the speaker had more than one function, hence the wieght.
I have seen a bizzare set-up in an old Bell radio-gram here that had a single (E-I) laminated steel core and the audio windings were on one side of it and on the other side was a single winding that acted as a choke for the power supply section, for smoothing purposes.
This is not an un-usual thing, considering the layout of radios of the day, there wouldn't have been room for a decent sized choke, it is strange that it was put on the same core of the audio output transformer, without any interference.
It worked like a charm though, them radios sold like hot cakes here in their day.
I could be mistaken but I used to take apart many old radios that would have these, back when the electromechanical speaker would weigh like 25 lbs, with a big auto-transformer driving the speaker.
Doug, In some of the radios of that era, the matching transformer on the speaker had more than one function, hence the wieght.
I have seen a bizzare set-up in an old Bell radio-gram here that had a single (E-I) laminated steel core and the audio windings were on one side of it and on the other side was a single winding that acted as a choke for the power supply section, for smoothing purposes.
This is not an un-usual thing, considering the layout of radios of the day, there wouldn't have been room for a decent sized choke, it is strange that it was put on the same core of the audio output transformer, without any interference.
It worked like a charm though, them radios sold like hot cakes here in their day.
Never saw a combination choke and audio OPT here in the states, but a combination choke and speaker was quite common in early sets. They saved on the cost of a strong permanent magnet by using an electromagnet as a combination speaker field and filter choke.
I have seen a bizzare set-up in an old Bell radio-gram here that had a single (E-I) laminated steel core and the audio windings were on one side of it and on the other side was a single winding that acted as a choke for the power supply section, for smoothing purposes.
It's a cost saving scheme I've seen in some low cost foreign radios, where half wave rectification is used with low value electrolytic filter capacitors.(i.e. lots of 50c/s hum on the B+). The filter choke winding on the output transformer is connected out of phase with the normal high impedance winding fed from the output valve. Effectively the ripple present on the B+ supply is cancelled out. It's still there but you no longer hear it.
