[Boatanchors] [DRAKE-RADIO] Heathkit Manual Repository

[Richard Knoppow]

    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.

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL