[Boatanchors] [DRAKE-RADIO] Heathkit Manual Repository

[Bill Cromwell]

Hi Richard,

There is no attachement in the message on QTH.net (BoatAnchors). There
is what looks like a reference to a "Drake-Radio" mail list so maybe
crossposted there. I am not on any Drake list.

If you could email copies of those patents I would like to have them
both in the same place at the same time. The filter in my HQ-145X did a
great job.

Happy Holidays and..

73,

Bill  KU8H

On Sun, 27 Dec 2020 15:10:24 -0800
Richard Knoppow <1oldlens1 at ix.netcom.com> wrote:

>     This is a great resource, thank you.
>     I noticed that you rebuilt a Hammarlund HQ-129-X and comment 
> on its ability as a CW receiver. You may be interested that its 
> predecessor, the HQ-120-X, which is very similar, introduced the 
> patented Hammarlund crystal filter, which is one reason it works 
> so well. Since this list is not very busy lately I am attaching 
> the patent, by Donald K. Orem. Orem was the chief engineer of 
> Hammarlund at the time. A very similar filter is used in the 
> later Super-Pro receivers, the SP-600 and also by Collins in the 
> 51J and A series, also by TMC in the GPR-90.
>     I am also attaching the original Lamb crystal filter patent. 
> This was used by National and, in various forms, by nearly every 
> other receiver manufacturer.
>     I find the filter in the R4B with the notch filter at least 
> as effective as any of the crystal filters.
>