Mark,
I have to admit, before I started using WINMOR, I didn't know the
information I'm about to tell you. I was probably splattering all over
the place too. Also, I think this only has to do with AFSK not FSK
(someone correct me if I'm wrong). I know you asked about the AGC, but
*usually* this has to do with ALC of the transmitting station.
Splattering *usually* (I say usually because *always* is too definite)
has to do with TX audio gain. On both the KX3 and the K3, you want to
watch your ALC. Adjust your transmit audio (another reason to use an
external soundcard for AFSK modes and not rely on the rig to do it
IMNSHO) so that your ALC shows four bars with the fifth bar flickering
(most other radios require *no* ALC, but the Elecraft rigs are different
due to where their ALC actually kicks in). An example of when this is
not the case is another PSK station within a mile or so of your station.
Splattering is not dependent on output power of the rig. I can (and do
on WINMOR) transmit 100W and have a clean signal by adjusting my ALC so
that it is four bars with the fifth flickering. I have seen folks
running 20W and be all over the place. I worked a station on FD who was
all up and down the passband with artifacts. I kindly told him that he
was splattering and that he needed to adjust his transmit audio - within
a few minutes, he was clean. No one need be an "alpha-hotel" when it
comes to correction.
I will say that in AFSK modes, if you get much off center of the
passband (about 1500Hz), you will need to adjust ALC again. I have
started to just practice turning the VFO. This also helps with the
500Hz filter; especially if I want to tighten it up a bit. On the KX3,
this seems worse than on the K3 and I don't know why. I don't really
use the KX3 for digital modes because of having to constantly swap out
cables and no monitor of my transmit audio. I just turn down the power
on the K3 and "let 'er rip."
In all honesty, when I find a lot of folks moving to a mode, I start
moving away from it. I rarely work PSK31 anymore. I prefer Olivia
(8/250 for weak signal). I got on the JT65 bandwagon just long enough
to get my WAS and I haven't operated it since. Yeah, that's selfish I
know, but I got tired of folks all over the passband and outside the
passband interfering with other operations that were/are not JT65. It
seems a lot of folks get a license and forget about the part of the
rules that say only use the amount of power necessary to complete the
contact and don't interfere with others. I did work PSK31 on FD, but I
started out on RTTY and really enjoyed it. I may actually start using
it again since it seems folks are moving away from it on a regular
basis. That being said, I still like CW and operate (when I operate)
mostly in that mode.
Sorry for the long dissertation (I have a friend who calls me verbose).
I have tried to make sure that any of my signals never interfere with
anyone else. If I'm on the air and a nearby signal comes on, I usually
just go to another band. He's a friend of mine and he's doing nothing
wrong, we're just too close to each other to operate except into a dummy
load. There is plenty of space and lots of bands to work. I may even
add the 6M wire to my hexbeam and start going there for some VHF stuff.
Who knows. The hobby is vast and looking for explorers and adventurers.
73,
Joel - W4JBB
On 6/27/13 1:45 AM, Mark Petiford wrote:
Bill's message brought a question to mind:
I am relatively new to PSK (operate mainly CW), but after receiving my KX3, started to take an
interest in it. After listening for some time, I became curious as to why some hams were giving
out poor IMD reports and verbal reports of "You are splattering all over" when I wasn't
always seeing the same thing. Some folks were just downright rude with their reports. I realize
that different software packages may give different IMD measurements, but a few were grossly
different. There seems to be a lot of information about getting things set right on the transmit
side, but not so much on the receive side. Certainly, making sure the RF gain is down is important
to keep all the amplifier stages linear, but little is ever mentioned about AGC. It is similar to
ALC on the transmit side, and is certainly non-linear if you are operating near or
"through" the threshold (not sure I described that very well). For those reasons, I
would think that receiver
AGC could also generate the IMD that these stations are seeing causing them
to give out poor reports. Admittedly, reducing RF gain helps to keep you from
activating AGC, but seems like maybe turning AGC off before giving a signal
quality report would be advisable. Some of the comments I have heard have kept
me from jumping into PSK with both feet. They take the fun out of operating.
The website http://rsq-info.net/ has been most helpful, but I don't recall
seeing any mention of AGC, so maybe I am completely off base here. I am really
a PSK novice, so any comments would be appreciated. I haven't run any digital
modes (except cw) since I sold my Model 19 TTY. Back then, we didn't have an
easy way to measure IMD or even see the sidebands that you see on a waterfall,
and you almost couldn't hear the audio over the clatter of the Model 19 once
you had your signal sync'd up. We just operated.
Mark
KE6BB
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