[HomeBrew] A homebrewed "Dedicated" Longwave Beacon (NDB) receiver

[Philip B Atchley]

Hi All,
I don't know if anyone here chases "NDB's" (Longwave Non directional
Beacons) or not.  These beacons are my primary listening "passion".  But
if you do you know that the receiver requirements for the really weak,
tough to hear beacons are extremely rigid, requiring extreme selectivity
(20 Hz or less!) and stability as well as small tuning steps (1 Hz is
ideal).  Another requirement is a "bullet proof" front end to eliminate
IMD from BCB stations that tend to clutter up the 200KC to 530KC range. 
Most "Beaconeers" use  high quality receivers with sharp IF selectivity 
of 125-250Hz, outboard tunable pre-amps with LPF filters and audio
filtering to get the required selectivity etc.

NOW, Mitch Lee has designed a receiver especially for NDB's and other
narrow LF signals that can be easily built at home.  It tunes 0-500KC (or
whatever range you wish), has 20Hz "IF" selectivity along with a slight
amount of audio selectivity to eliminate audio hiss.  Of course
selectivity of this order can ONLY be used for various CW modes (standard
CW, QRSS for Lowfers etc) .

This receiver uses a novel IF strip using 5 common base amplifiers with a
2 MC Xtal in each stage.  Each Xtal is individually tuned and requires NO
matching of larger quantities, just 5 of similar types.  Overall cost of
parts for the receiver is reported to be on the order of 50 dollars from
Mouser, NOT counting the required DDS and it's associated rotary encoder
and display panel.  A number of different DDS's should work so long as it
tunes 2-2.5 MC and can drive the balanced mixer in the front end of the
receiver.  Other IF frequencies can be used depending on what Xtals one
may have on hand, though higher frequency Xtals will produce a wider
bandwidth.

IF YOU WANT THE "BASIC" PLANS (Theory of operation, alignment and
schematic) EMAIL ME AND I'LL SEND A PDF FILE WITH THE INFORMATION.  The
PDF file is 222K in size.
   
73 from the "Beaconeers Lair".
Phil, KO6BB

Where DX begins at the noise floor!
Merced, Central California, 37.3N  120.48W  CM97sh

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