What make/model is this radio please

[Radio Fixer]

Pics 19 to 22 in the upcoming BVWS auction at WB

Auction Photos - Royal Wootton Bassett - 3rd December 2023 - British Vintage Wireless Society (bvws.org.uk)

thanks Gary

[Geordie McBoyne]

Looks like a Marconi TRF receiver made by EMI. C 1932.

Geordie McBoyne.

[Cobaltblue]

It looks like a Marconi 256 but the PX4 has been replaced by a PM24M

PX4 are hard to find for such sets these days.

Cheers

Mike T

[Mike Watterson]

It looks like a Marconi 256 but the PX4 has been replaced by a PM24M

PX4 are hard to find for such sets these days.

Yes
https://www.radiomuseum.org/r/marconi_256_1.html

[Radio Fixer]

Thanks to all. I thought it must be a Supie with 7 valves: most of the ones I have come across used 7. Early at 1932.

Gary

[Mike Watterson]

There are some superhets from perhaps 1926. RCA had a patent, though should not have (USPTO broken since 19th C., as 1. it's maths, 2. French did it first. No-one should have had an FM patent either.). So most in USA were sold as kits. The mixer was and issue till pentodes and originally a separate triode oscillator was needed. The IF needed to be low at about 120 KHz, so image rejection was an issue. However they would often have used 6 to 8 valves and a rectifier. They had to have an RF stage to stop LO leakage to the big aerial. The US continued to add an RF stage into the 1950s for that reason on otherwise quite ordinary superhets.

VHF tuners used the 1st valve more to block radiation from the triode mixer osc (or triodised) than gain.

Later with ferrite rod aerials the AM mixer /osc was deemed to not be the issue it was on valve sets with long wire aerials.

[Radio Fixer]

Good tech summary there Mike. RF stage, tuned or not, continued on maybe for increased RF gain, up to 10dB is quoted.

Gary