Bob and all,
There is a difference in which frequencies will produce the lowest/highest
VCO voltage if the K60XV is installed. Without the K60XV, the lowest
reading is usually 7 mHz, but after the K60XV installation, 1800 kHz and
4000 kHz become the more critical points. With the K60XV added, it is good
practice to check all the band ends to be certain they are within range.
Your observations about the AGC Threshold are correct - there is some
variation for the proper threshold voltage from K2 to K2 (but normally not
as wide as you report). However, be certain you are doing the AGC On/Off
check on a quiet band because even an S-1 noise level will alter your
adjustments from the norm. For my own - if I had a high noise level, I
would want the AGC Threshold set so no AGC action occurs because of the
noise - even if it results in 'strange' value settings. Bottom line, your
abnormal settings could be due to conditions present at your QTH.
73,
Don W3FPR
----- Original Message -----
I needed to open up my K2 serial no. 4168 to tinker with the AGC threshold
setting so took the time to measure what the VCO voltages at R30 were on
160m.
The results are:
1800kHz = 1.68V
2000kHz = 3.83V
On my particular K2 on initial testing the lowest reading VCO voltage
reading came out on 7000kHz rather than 3500kHz so made that the reference
setting
at 1.50V. This shifted up 3500KHz to 2.40V and 4000kHz to 6.85V. All
still
within the stated goal posts.
As a side issue the optimum AGC threshold seemed to be at 3.70V rather
than
the initial 3.80V on this K2. Another item noticed during testing was that
even with the S LO and S HI correctly adjusted for the new threshold the
signal
level required for S9 reduced with lower threshold settings. On this K2
with
the preamp off the settings for S9 came out as follows:
AGC threshold V. uV PD for S9.
3.80V 63uV (-71dBm)
3.70V 40uV (-75dBm)
3.60V 25uV (-79dBm)
With the new setting of 3.70V the audible low level band noise from AGC
on
to AGC off is just reached the point of no change. This compares with the
initial AGC threshold setting of 3.80v, where there was a small increase
in noise
when the AGC was switched off.
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