[Boatanchors] Questions on 51J4 as Ham receiver

[Glen Zook]

"S" meter readings are pretty meaningless!  However,
the "40" reading on the meter corresponds to S-9 (this
is the same on the "S" Line, "A" Line, etc.).  You can
estimate the readings below S-9 based on a 5 or 6 dB
per "S" unit (Collins used 5 dB on the "A" Line). 
Thus, "35" would be "S-8", "30" would be "S-7", etc. 
A "60" reading would be "20 over", etc.

On virtually all of the older units the "S" meter will
increase in reading when the r.f. gain is turned down.
 The only time you can use the meter is when the r.f.
gain is all the way up.

Zero-beating is just that, zeroing the transmit
frequency to the receive frequency.  It doesn't matter
how the BFO is tuned so long as it is adjusted to show
NO beat note on the received signal.  This is "zero
beat".  You then adjust your transmitted signal so
that there is no tone and you are then "zero beat". 
Of course when you go to either side of the frequency
a beat note is produced.

For SSB the BFO frequency is placed on one side of the
i.f. filter or the other.  Which side depends on which
sideband you are receiving.  Set the BFO to around 1.5
KHz to either side and then tune the main tuning dial
to hear the signal.  If you cannot tune that
particular sideband very well then tune the BFO to the
other side and you will then be able to receive the
SSB without any problems.  Make a note as to which
side you have to tune for USB and which side for LSB
for each band.

This is the same for all of the older receivers that
have variable BFOs.

Since the PTO tunes in a different direction for the
lower frequencies you will find that the sidebands are
actually reversed between the lower end and the higher
frequencies.  Thus, 160 meters will be different from
the higher frequency bands.  Once you have actually
"calibrated" for the sidebands then you will not have
any problems.  For CW either sideband will work fine.

I don't have a 51J4 but do have a 51J2.  Also have a
75A2, 75A3, and 75A4.  All of them tune SSB in
basically the same manner.

Glen, K9STH


--- Eugene Hertz <ehertz at tcaf.org> wrote:

1. The meter on the J4 is calibrated in DB (why not
dbm?). So how would I give a signal report in terms of
"S" or db over S?
 
2. When I reduce the RF gain, the meter shows larger
DB. When the RF gain is all the way down (off), I see
the max reading on the meter.  Why increase the db
readings with lower rf gain?
 
3. Tuning: When I am listening to CW, I can change the
beat note either by adjusting the VFO or the BFO.  As
a listener I would not normally care.  But now I want
to zero beat my transmitter (central electronics 100V)
so that it is transmitting on the frequency I am
listening to.  Problem is, depending on the BFO dial
position in the J4, my transmitter could be +/-
hundreds of hertz (possibly 1k? I haven't measured). 
If I want to transmit on the same frequency the other
operator is on, what is the best method to adjust the
BFO so when I zero beat I am on his frequency?
 
4. Nearly the same question but for SSB. I have the
dallas lankford product detector mod in my J4 which
works marvelously (thanks W8UT!).  But here too I can
vary the intelligibility both by VFO and the BFO knob
(product detector control).  How do I know when I have
it "right?"









Glen, K9STH

Website:  http://k9sth.com



 
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