On 30th January, Roy & friends wrote...
> > >You IC-7800 owners should set the menu item for CW rise time ... And
based on tests run by K1GQ and me, the same goes for the TS-950SDX.
> I wonder what the situation is with the TS-940. Maybe there is a pot
adjustment to adjust the rise time.
*****************************
I believe that a very critical & key piece that seems to be continually
missing in the puzzle of eliminating / reducing key clicks is the outboard
grounded-grid "linear" amplifier that may be in use at "offending"
stations --- specifically, I am referring to the FINAL ADJUSTMENT of the G-G
amplifier in this regard...
Bill Orr, in his various HANDBOOKS, states that "...for best linearity, the
output circuit of the grounded-grid stage should be over-coupled so that the
power output drops about 2 per cent from maximum value."
Far too many of us --- myself included --- take it to mean that any such
"...linearity preservation" is of consequence only to VOICE mode
transmissions...for CW transmissions, the old "...tune for maximum smoke"
adage seems to prevail, & the devil take the hindmost. It's CW anyway,
right? --- why worry about linearity? (we've been taught that the most
efficient amplifier for CW is class "C" anyway --- and look at how
"un-linear" THAT is!).
The lesson was driven home to me last year with my homebrewed 2x813 G-G
amplifier: gentle reminders & comments as to my excessive key clicks
practically drove me to drink. I can't recall now just how many times I tore
apart BOTH my Yaesu FT-980 and Icom 751A transceivers, in search of the
magical "fix" that might "soften" my keying.
Finally, almost by chance, I came to the realization that the fixed padder
transmitting capacitors in the final pi tank of the 813s were CHANGING under
load --- whatever linearity I may have initially had at the start of an
operating session, would cease to be so after the transmission of a few
exchanges, because the parameters of my amplifier's operation were changing
on me.
No wonder I would receive congratulations from nearby friends on a Monday
regarding my successful elimination of clicks, and on the following Tuesday
have these same friends ask me what had changed to bring about their
return...
The solution here was the replacement of ALL of the padder caps in the final
pi tank with fixed vacuum and air dielectric units. Additionally, I must
continually be vigilant to this very day with respect to the settings of my
G-G amplifier load & tune controls --- things CAN change with time, & it is
of benefit to once in awhile check the parameters of their settings, to
ensure everything is operating along those lines espoused by W6SAI
(especially if the amplifier essentially "sits" untouched on 160 100% of the
time, as mine does here during the DX season).
We may THINK that key clicks are merely the result of our having a potent
signal, strength-wise, at the receiving end --- and this is doubtlessly true
to a certain extent. However, if one considers the fact that the very
strength of our signal is attributable to our use of a G-G linear amplifier
in the first place, then one must give consideration to just what, exactly,
said amplifier really might be doing to our signal, besides just making it
loud.
I am seriously curious as to how many Hams owning G-G linear amplifiers
to-day actually take the time to tune them up --- ON CW --- in the way
recommended by Bill Orr...
I honestly do NOT recall reading much of ANYTHING along these lines in ARRL
publications from 36 years ago, when I was first licensed. What I DO recall
reading was the over-riding importance of incorporating a relative RF
output meter in the G-G circuitry, and to adjust the various controls for
maximum deflection therein. I also recall noting in different ARRL
references that the actual plate & grid current meter readings were of
little consequence --- and that, in fact, they could give rise to
confusion(!).
The watchwords as I recall were, in essence, tune for maximum output, while
not exceeding the tube's current-handling capabilities.
Therein may be the cause of some of the ills we hear on the band...
~73~ Eddy VE3CUI - VE3XZ
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