[Boatanchors] Improving the Novice "Two Tube Beginner's Receiver"

[David Stinson]

How many of us remember or even built this simple 2-tube regen from this 
book?  I'll bet some of you still have one on the shelf or in the attic. 
   It's a simple and fun circuit and taught one how to make the most of 
a simple regen.

https://photos.app.goo.gl/6mkuXKN18UjjWhkw5
https://photos.app.goo.gl/cDJybxoUSj1oyQDH8

  However, it has one design flaw which, once corrected, makes it much 
easier to use.
In the piece, the "Band Spread" capacitor, C1, sets the frequency the 
set tunes from one end of the tuning cap to another.  In order  to 
"spread it out" to a usable range- say, from 7000 KC to 7100 KC, one 
moved the coil tap which connected C1 to the tuning coil, moving the tap 
up toward the "hot end" of the coil.

https://photos.app.goo.gl/aepZMY8JcitTsCNo9

The value of C1 works well on 160 or 80 meters, but there is a problem 
with this if one is using it on 40 meters or higher:  The higher one 
moves the C1 tap on the tuning coil, the harder it is to get stable 
regeneration.  This is because as the 140 pFd C1 moves higher on the 
coil, it begins to act not only as a tuning capacitor, but also as an RF 
Bypass, draining energy from the tank circuit to ground and lowering the 
tank Q.

We can fix this.  First, put the C1 tap back where the author first said 
to put it.  Use an RF-quality, NP0 100 pFd cap in series with C1, 
mounted on the 40 Meter coil between pin 3 and the "bandspread" tap, 
effectively reducing the "Bandspread" cap to a lower value and reducing 
its bypassing and Q-killing problems.  You'll find you have good 
bandspread without the difficulty getting enough regeneration.  If 
you're using your set on 20 or 15 meters, reduce the series cap value 
until you get the bandspread range you need.
Note:
Don't use those "blue dipped"  Chinese caps from Amazon.
They are useless junk at RF

GL IN 23 OM ES 73 DE Dave AB5S

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