[HBR] HBR2K Chapter 9 -- Cleanup, Round One

[hbr@mailman.qth.net]

In the last chapter it was working 'all the way through' -- but with 
some problems and unfinished business.

In the last couple of days I wired a simple two tube electronic 
regulator using an NE-2 as a reference; the VFO now runs on 
regulated voltage.  The NE-2 is unquestionably not the world's best 
reference tube and mine is showing a classic misbehavior -- the glow 
is sometimes unstable, leading to variations of around a volt in 
supply output.  I can probably select one that will work okay.   But I'll 
wait a while first -- they usually stabilize somewhat in the first few 
hours of service. 

The result was not unexpected; 35 years ago I got a 'B' on a master's 
thesis with just about that bottom line.  

Medium and long term stability aren't an issue since the total change 
of frequency with voltage changes is well under 100 cps.  I just want 
to stabilize the voltage against the effects of fading sigs.

Since then I have wired the calibrator and gotten that working.   The 
circuit I stole (from Yaesu's FR-100B, ca. 1965) is the only one I've 
seen that delivers an S-9 reading on 20, S-7 or so on 10 meters 
*and* requires no tuned circuit.   Pentode ECO with the crystal as 'L' 
in a Colpitts circuit.  

The triode section of this stage -- a 6U8 -- serves as the cathode 
follower driver for the IF filters.   In preparation for wiring the calibrator, 
I replaced one new tube with another one and got one of those rare 
happy surprises -- the slight audio distortion noted last time, 
disappeared.   As my wife said "Clear as a bell!"  I suspect a partial 
heater-cathode short; but for the successful application of the good 
luck technique, I don't know how long it would have taken to find it.   

The most important remaining problem is an excessive noise level.  
This may be no more than too much gain in the mixers or the 1st IF, 
or something more interesting may be going on.   Haven't measured 
the weak signal performance yet so 'excessive noise' is just an 
impression.   

Strong signal handling is fine, subjectively.   Signals are nice and 
clean on 40 broadcast stations at night.

There are still a bunch of missing features.  In addition to those listed 
last time, it needs a STANDBY switch, provision for muting by a 
transmitter, probably some kind of RIT.   

I have started on construction notes and will start the diagram 
shortly.  Thinking about the front panel.

Moving along ...

Walt Hutchens
KJ4KV