Quote:
Originally Posted by allan
Very interesting om and I've never looked into those receivers you mention. Now that I have looked them up I can see the similarities and the AW125 does look very similar to the Moreton Cheyney. The T69A front layout and bandwidth markings 5/10/15/20Kc looks very similar too. It would be interesting to see the exact dates for the Armstrong and Dynatron sets. Usually established companies products evolved from early days with new bits being added as time progressed.
|
As far as I know, the Armstrong AW125PP was released during 1939, so would have had a short production life. The EXP125 was added to the post-WWII range in time for Radiolympia 1947, advertised in WW 1947 October. It was replaced by the EXP125/2 as part of the substantially reworked Armstrong Radiolympia 1949 range, advertised in WW 1949 October, and still priced at £33.6.
The Dynatron T69A/LF59 Ether Conqueror appears also to have dated from Radiolympia 1947, and was advertised in WW 1947 October. As best I can work out, its replacement, the T99/LF612 Ether Conqueror V, was first advertised in WW 1951 October, but I haven’t seen that advertisement.
Quote:
Originally Posted by turretslug
Looking at your block diagram on Radiomuseum, this tuner was certainly an ambitious undertaking that tried hard not to leave any stones unturned. It would certainly have made an excellent broadcast monitor with aspirations of fidelity beyond most comms receivers. As Synchrodyne says, there is a definite stranding between these two classes of receiver- a few, such as GEC's approximately contemporaneous BRT400, managed or endeavoured to straddle the divide, I wonder how this large, heavy and quite complex set compared in price.
|
The BRT400 was £120.00 in 1949 – professional class pricing I think. It was known to have been used in HF broadcast relay service, before the change to point-to-point SSB/ISB receivers for this purpose. It was also an optional fitting in the GEC Export Club Radiogram, for which one of GEC’s domestic receivers was the normal fitting. The BRT400 went through an iteration or two, but stayed in place until superseded by the solid-state RC410/R in 1967.
To round-out the contemporary price comparison, the Peerless 1546 receiver was £50.40. This was broadly similar to the MC, but had a single chassis, a four-gang front end (bandpass input) and a tetrode push-pull output. It also had a full communications specification in that it had a crystal IF filter and a BFO. IF bandwidth choices may have been more limited, though. Peerless advertised in WW from 1946 November, and subsequently introduced some lesser models. It was at Radiolympia 1949; the WW report of which in 1949 November was its last mention that I can find, so presumably it was wound up very soon thereafter.
No price given, but the Mullard GFR520 was also displayed at Radiolympia 1949. This was another broadcast/communications combination that covered 0.54 to 110 MHz AM and CW, 27 to 110 MHz FM, with AM IF bandwidths that ranged from 10 Hz (crystal filter) to 25 kHz. It looks to have been similar to the Hallicrafters SX-42 of 1946, but with a wider maximum AM bandwidth. (I wonder if it used the EF42 or EF91 in the front end?) That was its only apparent mention, so it may not have fared too well in the marketplace.
Returning to the MC, it will be interesting to see how the AGC system was configured. From the viewpoint of high quality reception, separating the delay function from rectification, to avoid differential distortion, was considered to be a desideratum, as was having fractional or zero AGC bias applied to the final IF stage to minimize modulation rise distortion. Delaying the RF AGC more than the IF AGC was an approach to getting the best quieting curve, but not so common, I think. (The GEC BRT400 had this, as did the Ekco A182 domestic receiver.) Fractional or zero AGC bias on the mixer was used to minimize pulling at HF. All features on one receiver would be very rare, I think, but one would expect some of the above on a receiver at the MC level.
Cheers,