An interesting old Coil

[Alan Douglas]

I found that same Formo ad in Modern Wireless in June and August 1929 (my only issues for that year). John L. Reinartz published his short-wave design in QST around 1924 and there is one reference in the BVWS index to a British Reinartz set but that's 1924 also and would have been thoroughly obsolete by 1929. I don't know of any good indexes. The "Abstracts and References" section of Wireless Engineer is too highbrow to have taken any notice of the popular magazines. Reinartz dropped from view after 1925 and I vaguely recall that he joined RCA but don't quote me.

I don't see anything in the BVWS index on Peto-Scott but I thought I had read something there, or that they reproduced a catalog (but if so I don't have it).

[AlanBeckett]

That's fooled me because I swear I put a Post on last night. It must be a case where I 'Previewed' it but forgot to hit the 'Post Reply' Button

If you put the 'Big' Winding sin Series Aiding then a Capacitor with a swing of 55 - 220pF would over the presumed Range.  That still doesn't explain the advantage of a 'Split Secondary' or why there are separate Windings.
Perhaps it was just 'Marketing'.

Alan

[AlanBeckett]

Morning Alan,

I admit that the only place I know Peto Scott from was as a Manufacturer of '60s TVs. I'll see if I can trace anything further back.

Alan

[Refugee]

It could be an early superhet coil.
Mixer coils often have three separate windings.

[pwdrive]

Alan,, are both of the main coils wound in the same direction? If not it still could be a tunable notch filter set up as mentioned earlier. that type of arrangement was not uncommon in early TRF receivers, the notch filter (parallel tuned) was often in series with the antenna to reduce hetrodyne whistles from adjacent or nearby stations.

Lawrence.

[AlanBeckett]

Lawrence,

As far as I can tell all the Windings are indeed in the same direction

While the 'Notch Filter' and 'Early Superhet' theories are interesting and plausible it seems to be a bit complex to me. However, possibly time will tell.

The early history of Peto Scott seems to be a bit obscure. I came across the attached Booklet which has a full page Peto Scott Advert on Page 13, but no mention of Coils.
COPEX written on the top is completely obscure.

Alan

[pwdrive]

Peto Scott did a lot of kit components etc in the early days, have trawled the web for Copex, not a lot that I can find, according to your measurements the two high value inductors are more or less the same value, maybe another take on it could be dual tuning (switchable stations) singly a 500 pf variable would appear to tune to what is I presume metres engraved on the top (1,000-2,000...150Khz to300 Khz) it would do the low end of that band more or less spot on at maximum capacitance, the high end would need some extra capacitance than you would normally expect a 500 pf variable to have when fully unmeshed, maybe that extra capacitance is accounted for in the other windings plus antenna capacitance/valve input capacitance etc.

All guess work at the moment from me.

I searched the online Wireless World archives, Copex came up zilch for early stuff, quite a few for Peto Scott but not what we are looking for so far as I can see, radiomuseum have a Copex coil listed, I think it was prefixed SG (usually means Screen Grid as in "TheScreen Grid Three" etc) there's a reference to a Copex SG coil in Google books, it could have been a Wireless World extract (can't remember) I think it was a sales listing from some component supplier, all it gave was the coil and it's price, can't find anything yet as to who Copex were or where they operated from.

Lawrence.

[AlanBeckett]

That's another interesting theory Lawrence.

How about Double Tuning in the way that Murphy were fond of. You often see them with a three Gang but it's not for an rf Stage it's for a double tuned Front end.

   

The only snag is why 'SPLIT SEC?  or more to the point why 'SPLIT'? That implies to me 'In two Parts' but the Inductances don't make sense if they're meant to be added..

Alan

[AlanBeckett]

Post #36 would have made more sense if I'd attached the Booklet


  pw_xtal_experimenters_hdbk.pdf (Size: 2.3 MB / Downloads: 31)

Alan

[Alan Douglas]

"Copex" seems to have been used for a lot of Peto-Scott parts.  At any rate I found this in Modern Wireless in September 1927: