[Boatanchors] National Rx.

[howard holden]

It's an early HRO senior, probably second generation. Round IF cans and the metal outer part of the PW dial are the giveaway. There should be a serial nr by the antenna terminals which should date it and indicate which iteration. 

The insulator/spacers on the tuning cap look like the older ones stamped from phenolic sheet. 

I have a third generation which has rectangular IFs and an all-black PW dial. Dated 1938 by the serial nr, 129A.

Check out this website for good info on dating HROs and the different series of them.

http://www.prismnet.com/~nielw/datghro/datghro.htm<http://www.prismnet.com/~nielw/datghro/datghro.htm>

Howie WB2AWQ


  ----- Original Message ----- 
  From: Carl<mailto:km1h at jeremy.mv.com> 
  To: Richard Knoppow<mailto:1oldlens1 at ix.netcom.com> ; Al Klase<mailto:al at ar88.net> ; boatanchors at mailman.qth.net<mailto:boatanchors at mailman.qth.net> 
  Sent: Wednesday, June 29, 2011 6:31 PM
  Subject: Re: [Boatanchors] National Rx.


  ----- Original Message ----- 
  From: "Richard Knoppow" <1oldlens1 at ix.netcom.com<mailto:1oldlens1 at ix.netcom.com>>
  To: "Al Klase" <al at ar88.net<mailto:al at ar88.net>>; <boatanchors at mailman.qth.net<mailto:boatanchors at mailman.qth.net>>
  Sent: Wednesday, June 29, 2011 7:19 PM
  Subject: Re: [Boatanchors] National Rx.


  >
  > ----- Original Message ----- 
  > From: "Al Klase" <al at ar88.net<mailto:al at ar88.net>>
  > To: <boatanchors at mailman.qth.net<mailto:boatanchors at mailman.qth.net>>
  > Sent: Wednesday, June 29, 2011 3:22 PM
  > Subject: Re: [Boatanchors] National Rx.
  >
  >
  >> Larry,
  >>
  >> That's clearly an National HRO (Senior).  Note the sockets
  >> for "big-pin"
  >> tubes and the presence of the crystal filter on the right
  >> side.  The
  >> real cognoscenti could tell you more from the style of the
  >> IF cans, etc.
  >>
  >> Al
  >
  >    I replied to the original sender and meant to copy the
  > list. National changed from glass to metal tubes around 1936
  > or 37. The advertising in the 1936 ARRL handbook shows glass
  > tubes but remember that the handbook is set up the year
  > before. I would have to look through a bunch of old QSTs to
  > find the date of the change to metal tubes. I also don't
  > know the date of the change of the IF transformers from air
  > to ferrite core. National made a lot of changes, some of
  > them small, over the production life of the "original" HRO
  > from the first to the 5Ta1. All shared essentially the same
  > circuit although there were some changes and National
  > offered to modify existing receivers at the factory.
  >    Its hard to tell just how much of this receiver is
  > missing, its possible it could be restored but it would
  > require replacing the meter, finding plug in coils, etc. I
  > agree with Gary Pewitt that it looks like a restoral job
  > that got inerrupted. Perhaps the seller has the missing
  > parts sitting around somewhere (wishful thinking but you
  > never know).
  >
  >
  > --
  > Richard Knoppow
  > Los Angeles
  > WB6KBL
  > dickburk at ix.netcom.com<mailto:dickburk at ix.netcom.com>


  National did not change to metal tubes until the middle of WW2.
  They did change from 2.5V to 6.3V large pin tubes for AC operated sets 
  around 36-37 when Millen was satisfied the hum problem from RCA was fixed.

  Carl
  KM1H 

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