[Boatanchors] Cheap & Easy Selectivity

[Edward Swynar]

Hi Again Everyone,

If anyone is interested, I just finished scanning  the regenerative IF article from the November 1940 issue of "RADIO" magazine, and would be more than pleased to send it along to whomever it is that might be interested...

It's two pages in length---I reduced the size & converted the files to jpeg format, so that they might be a bit easier to download for those of us (myself included!) who are still still on dial-up internet service.

As mentioned previously, this particular design---according to the author---goes one step beyond the simple "...two wires side by side to achieve regeneration in an IF stage" approach. Indeed, he says that not only is the signal of interest boosted in strength by virtue of this circuit, but interfering signals are actually reduced by a corresponding amount.

As anyone knows who has ever tried a regenerative IF stage, this does not happen by design, i.e. the reduction in signal strength of adjacent frequency QRM.

Anyway, it all sounds like a very neat design, albeit requiring the trouble of having to wind a scramble-wound coil & installing it at the base of the secondary winding of the IF transformer.

~73!~ Eddy VE3CUI - VE3XZ


****************************************************
  ----- Original Message ----- 
  From: Edward Swynar 
  To: hbr at mailman.qth.net ; homebuilttuberadios ; Old Tube Radios ; AmRadGear at yahoogroups.com ; boatanchors at mailman.qth.net ; Welcome to the Novice Rigs List! ; antiquewirelessassociation at egroups.com 
  Sent: Thursday, August 20, 2009 11:13 AM
  Subject: Cheap & Easy Selectivity


  Good Morning All,

  I just ran across a sweet little article in a 1940 issue of the old "RADIO" magazine on a fool-proof way of adding selectivity & gain in an IF stage that (supposedly) approaches that obtainable with a resonant crystal filter...but without the filter insertion loss, of course.

  The design is rather obscure in that I've never seen anything quite like it in any ARRL publication. Suffice it to say that it goes a bit extra beyond the mere "...place-the-plate-lead-into-the-IF-can" approach of achieving feedback, yet it still looks very "do-able", and I plan to incorporate it into my 1929-style 12-tube superhet here.

  If anyone has access to any of the West Coast Handbooks of the late 30's, you'll see the design used in the "Super/Ultra Gainer" receiver designs described therein...

  Wish me luck!

  ~73~ Eddy VE3CUI - VE3XZ