I think I am having some problem with sideband transmission – Other stations
give me the report that my audio is underpowered but my signal is otherwise
S9+. I thought that wasn’t possible with sideband. I have not kept up with
modulation/mixers etc. since I built a 6 meter AM transmitter in 1962 that used
two 6L6’s to modulate a 2E26 with 25 watts out. Anyway I went to college the
next year and got sidetracked from my plan to become an electrical engineer and
have ended up in medicine as a psychiatrist working with teenagers and parents.
Being a ham is a wonderful escape from my work and makes me feel like I haven’t
totally missed out by not becoming an EE.
I love following all the technical talk on the reflector since I got my SDR1K
a month ago. I’m Totally Blown Away with all that it can do. I am upgrading
from A Kenwood 440 that I bought when I got re-licensed 17 years ago so it
doesn’t take a lot for me, (who hasn’t operated with more sophisticated
radios), to be impressed. I don’t mind all the wires – XYL & kids say my wires
going all over the house are my first love anyway.
Anyway I need some help with my SDR1K setup. I am using a Firebox which I
bought a year ago for audio recording, I have not installed the Beta firmware
so far. I am using an Astron “Heavy Iron” power supply, (and do not have
“meandering signals”). When I first got the radio I thought I was clever when I
measured the output from the FB at 1.56 Volts on "tune" and entered this value
in the setup form despite a warning that it should not vary more that 40 mV
from the 6.4 Volt default value for the FB. This apparently resulted in a blown
FST 3253 multiplexer chip on the TRX board. Eric graciously mailed me a
replacement. I got my first experience soldering Surface Mount and felt that I
was successful because ohm-meter readings between each of the chip leads and
the pads where I soldered them were “Zero Ohms”. It turned out that I had
replaced the output chip (IC2?) rather than the input chip (IC1?) so the radio
continued to be an excellent receiver but no transmit. Eric again sent me
another chip which I soldered in the right place and got the “Zero Ohms” which
I interpreted as "go ahead" measurements again. I was concerned that the 1 or 2
volts from the VOM might damage the chip but assumed that this could not happen
since all the readings were “Zero” and think that no current had gone thru the
chip as a result.
I calibrated the rig on WWV for freq, on a Elecraft XG-2 50 uV at –73 dB for
signal strength and on a strong signal from my KNWD 440 into my dummy load for
image rejection. On this last procedure I got a little better image rejection
by manually moving the sliders, however the images were not 11 kHz above and
below but were more like twice or three times this. I believe I was running the
FB at 96 kHz which I do not think should make a difference. I then ran the PA
adjustment routine with the Dummy load attached to the SDR1K and got values
very similar to those that were shipped with the radio.
The situation now is that I routinely get the reports of low audio strength on
sideband both on 40 and 80 (LSB, have not tried getting a report on USB yet).
When I adjust the Mic input so that I am going way over the recommended 0 dB
adjustment with the multimeter set to “mic”, I am told that my audio improves
but is still weak and that I am definitely NOT over modulating or splattering.
I have this report from several separate QSO’s on different days. I note that
the readings on the Multimeter voice peaks using the readings from “comp” and
“ALC” still seem to hover around “0 dB” even though the readings on “mic” are
way over the top. I was able to get one report of overdriving distortion when I
turned the mic gain al the way up to 70, maxed the input pot on the front of
the FB for channel 1, (where I plug in the output from the UA-610 mic pre), and
turned the output from the UA-610 mic preamp all the way up. Perhaps the
distortion was from overdriving the mic pre or overdriving the FB channel 1?
Additionally, I see “Ghost Images” of received signals at 48 kHz above and
below the actual signals on the panadapter in all modes, (using 96 kHz on the
FB). I do not see this when running the FB at 48 kHz. I do not think this is
because I haven’t installed the Beta firmware in the FB. I could be wrong.
I do not seem to have any problems with CW which I mainly use because it is a
further escape from the oral back and forth I employ in my office all day. I am
concerned that I may have damaged the chip in replacing it or that I am not
adjusting something else correctly. I have been using the SVN updates as they
become available. As a psychiatrist I am aware that my concern over being
underpowered has other implications for my internal psychology than just my
rig. In any case, I really love the radio and all the time I get to spend
setting it up, operating and reading all the comments here on the reflector. I
would appreciate any help/suggestions/advice from the community. ->Steve, KK6WP
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