🚀 go-pugleaf

In article <1993Jul8.135410.1@ducvax.auburn.edu> ,
anderjh@ducvax.auburn.edu writes:
>One of the knobs (labeled Freqency) has 5 bands from .55Mhz to 54Mhz.
It tunes
>normally but the other knob doesn't make sense.  The other (Selectivity)
tunes
>a second dial which is calibrated around the amateur bands.  The two
knobs
>work at the same time and one affects the other in some unknown fashion.
>A functions switch allows you to change from FM, AM, SSB-CW (with a
separate
>BFO knob) and two other modes I don't understand- CAL, and ANL.  The
radio
>also has two other switches I don't understand-a MVC AVC switch and a
REC SEND
>switch.  I think the REC SEND switch is for using the radio with a
transmitter.
>Is the radio very good.  It seems to receive OK with a long wire antenna.

I'm not sure I know this specific radio, but I've fooled with most of
them at
one point or another. In a lot of the older general coverage receivers
with a ham orientation (or marketing slant) there was a second tuning
knob that did fine tuning calibrated for the ham bands. The variable caps
attached to each knob are wired in parallel - so they interact. The way
it
is supposed to work is you set the fine tuning knob (apparently labelled
"Selectivity" on your radio) to one of it's endpoints, usually the high
frequency end of it's marking. When it is there, then the other knob is
calibrated correctly.

Now, when you tune the the main tuning (Frequency) knob to a spot near
the ham bands, you'll find some kind of marker on the scale at the
upper end of the band (i.e. 4.0 Mhz for 80 meters, 7.3 mhz for 40, etc).
If you put the Frequency knob there, then tune the Selectivity knob, it
will move you lower in frequency across the various ham bands, with
slower tuning rates than you would get with the main knob. Of course it
will do that from any tuning point, but from those specific marks the
Selectivity knob will be somewhat calibrated for the ham band.

I hope that is clear - what you basically have is the usual 365pf
variable on the main (Frequency) knob in parallel with something like
a 25 pf variable on the fine tuning (Selectivity) knob. My R100 and
many other receivers of the period (50's-early 70's) did the same
thing.

CAL - runs the receiver in normal mode but applies power to a
crystal calibrator - which may be an option not installed. The
crystal calibrator is a harmonic rich 100 khz oscillator that will
produce a steady carrier every 100 khz up to 20-30 mhz and beyond.
The cal switch might disconnect the antenna so you hear only the
calibrator, but I don't think I've seen any that do that. Usually they
just turn the extra signal on and off.  To calibrate the Selectivity
knob you would find the band edge by listening to the traffic (i.e. find
the
cw starting and assume it's at 7.000) put the 7.0 did under the marker
and
move the main tuning (Frequency) knob until you hear the calibrator signal
zero beat. (be careful, it's easy to end up off by 100 khz)

ANL - Automatic Noise Limiter - usually a pair of diodes someplace in
the audio chain to clip the high peak value impulse noise - acts as
a crude noise limiter. May also junk up the signal by clipping a loud but
desired signal. I never found them very effective, but everyone had them.


MVC/AVC - Manual Volume Control/Automatic Volume Control - allows
you to use the automatic gain control detector (AGC circuit) or not
as you see fit. AGC/AVC in these older receivers was used primarily to
even out the various AM signals you would tune across. For SSB/CW
you normally had to turn it off.

REC/SEND switch - usually removed B+ from all or some (maybe just
the audio section) when sending. Sometimes a second set of contacts
on the switch comes out to a terminal strip on the back for use in
controlling a T/R antenna relay.  Sometimes it ran the B+ for
the tubes through the terminal strip and allowed it to be
controlled *by* a spare set of contacts on the T/R antenna
relay (most Dow Relays had spare contacts for this) - in which
case RCV meant the switch was shunting that connection.

Is it very good - probably not in terms of todays performance, but
doesn't mean you can't enjoy it and even use it for some hamming. It
most likely has poor selectivity (although at least one Lafayette radio
did have a mechanical filter, but I think that was a ham band only
version).
It's probably fine for listening to AM shortwave stations and if you can
hear hams on it, great. If you want to use it for day to day SSB use on
20 meters, you might be disappointed. But at least it tunes continuously,
not in 1 or 10khz steps! :-)

73 de Kevin, WB2EMS.