[Boatanchors] Pictures of my Homebrewed LF Regen receiver

[Phil]

I'm not sure if I posted this link to this mail list or not.  It's a zip 
file of pictures I took after I completed building my homebrewed LF (low 
frequency, 150-530KCs in two ranges) Regenerative receiver.

I wanted to get a "tube radio" again and decided to build my own. I'm 
too old to handle the REALLY HEAVY iron like SP-600's and R-390A's.

It has 5 tubes + silicon bridge rectifier, but is actually a 7 tube + 
rect circuit as two tubes are double triodes.  The tube line-up is. . .
6AK5 Grounded Grid RF Amp, 1/2 12AU7 Armstrong detector, 1/2 12AU7 
cathode follower coupled to the plate of the detector to provide an 
output for an external frequency counter (the counter is the blue 
display on the shelf above the set), 1/2 12AT7 First audio amp/AF filter 
driver, 1/2 12AT7 post filter AF amp, 6AQ5 audio output, 0B2 105 Volt 
regulator for detector & RF amp.

The audio filter section has 6 bandwidths, "Wide", 400Hz CF, 600Hz CF, 
1020Hz CF, Low-Pass 1 & Low-Pass 2.  The three BP filters each uses a 
separate 10H adjustable AF choke that is tapped part-way up from 
ground.  Each is resonated by it's own capacitor, and each is fed 
through a 27K resistor to the tap.  Output from the filters is via a 
270K resistor to the high side of the volume control, then the 
"Post-filter" AF amp.  The isolating resistors are there to keep the "Q" 
and selectivity of the tuned circuits high.

It is entirely a "retro" receiver with technology that was available in 
the 1930's, except I used a silicon bridge rectifier simply because I 
didn't feel the power Xformer could handle the filaments of a 6X4 tube, 
and besides I wanted full wave rectification as it's easier to 
effectively filter 120CPs.  Most of the circuitry is entirely my own 
design, though I can't lay claim to anything that hasn't been done 
before, circuit wise.

The output for the frequency counter is entirely a convenience function 
to simplify calibration of the National reduction drive, it doesn't add 
anything to the DX performance of the set.

So far the set is performing far better than I expected a regen to do, 
especially in the tough NDB band where signals are weak, the band is 
noisy, and summertime is NOT the best time to chase beacons!  Over 60 
NDBs have been heard on it in the past couple weeks, from Hawaii to 
Puerto Rico, Canada to Mexico. . .

Here's the pictures (you DON'T need a Box account to download the zip file).
  https://app.box.com/s/60cemuh38aaz0f5gra0egclf4ph0lnpg

-- 
73 de Phil,  KO6BB
http://www.qsl.net/ko6bb/  (Web Page)

PRESENT RADIOS:
Grundigs:    S-350 (~2006), G6 (2011) & S450DLX (2014).
HOMEBREW:    7 Tube+Rect Regenerative RX for LF (built 2015)
Icom:        R-75 With Cascaded 250 & 125Hz CW Filters. (~2005)
Icom:        IC-7200 Transceiver (~2015).
Radio Shack: DX-380 digital portable (~1990).
Zenith:      Royal-7000 Transoceanic Portable (~1968).

ACCESSORIES: HOMEBREW LF-MF Pre-Amp, MFJ-993B HF Auto-Tuner.
              HOMEBREW 8 Hz Audio Filter.

ANTENNAS:  88 foot Long Ladder-line fed dipole at 35 feet AGL for MW/SW.
            HOMEBREW Active Mini-Whip at 36 Feet AGL for LF/MW/SW.
            HOMEBREW 37 foot "Low Noise Vertical" at 11 feet AGL for LF/MW/SW.

Merced, Central California, 37, 18, 37N   120, 30, 6W CM97rh