[Boatanchors] USS Midway notes

[WA5CAB at cs.com]

My mistake.  The filter circuit wasn't where I expected to find it on the 
schematic and I didn't look further.  Both the CHC-46140 and the CHC-46163 do 
have the crystal filter.  

The down side of the 25 cps power supply is that the set weighs 5 pounds 
more.

In a message dated 3/1/2011 4:47:09 PM Central Standard Time, 
1oldlens1 at ix.netcom.com writes: 
>      The CHC-45140 is shown at:
> http://www.radiomuseum.org/r/hammarl_mf_rbg_2_chc_46140.html
>      It pretty definitely has the crystal filter in it.
> However, if the tube line-up given is correct it is not an
> HQ-120-X but a modified version with single-ended octal
> tubes and somewhat different tubes than were used in the
> later HQ-129-X (6SK7 where the HQ-129-X had 6SS7).
>      There are a couple of clear photos of the front panel
> at:
> http://www.ohio.edu/people/postr/bapix/RBG2.htm
>      Again showing the crystal filter.
>      While Hammarlund evidently made a version of the HQ-120
> without the filter I have never see one. The Hammarlund
> crystal filter was patented by them and was first introduced
> in the HQ-120-X, being made available for the Super-Pro
> after that. The Hammarlund xtal filter was excellent
> overcoming the defects of the original Lamb circuit as used
> by National and Hallicrafters (and others). This is the same
> circuit later used by Collins, TMC, etc in their receivers.
>      RE 25hz power. The military version of the Super-Pro
> was avaiable with a 25hz supply. The difference is in the
> power transformer and chokes, they will run fine on 60hz
> where a 60hz transformer will overheat badly on 25hz power.
> 25hz was mostly used for large industrial motors of the sort
> used on some electric railways and manuacturing plants. In a
> few places home current was also 25hz. I remember this from
> visiting the Canadian side of Niagra Falls with my parents,
> perhaps in the late 1940's. The local current was 25hz
> making lights flicker quite noticably.
> 

Robert & Susan Downs - Houston
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