Oh yes, I've encountered those that are "backwards" in tuning as well. Even
in a commercial product as I recall.
But for a grounded grid linear amp, always adjust TUNE for maximum output
which should also be at the peak of the grid current.
73
Bob, K4TAX
----- Original Message -----
From: "Rick - DJ0IP / NJ0IP" <Rick@DJ0IP.de>
To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Sent: Sunday, March 02, 2014 1:58 AM
Subject: Re: [TenTec] In praise of older technology
Bob, I'm glad you added this "clarifier".
"The right side of resonance" is only true when minimum capacitance is
clockwise and max is CCW.
Normally that is the case but it might be a bit risky to assume it always
is. It is always better to know. The best way to know for sure is to
pull
the cover and look.
I don't recall ever seeing a commercial amp that didn't work like that,
but
I have seen some home-brew amps that were built backwards. Easy enough to
fix; just rotate the Plate Tune knob 180 degrees.
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Bob
McGraw
- K4TAX
Sent: Sunday, March 02, 2014 4:03 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] In praise of older technology
I comes from many years of tuning AM broadcast transmitters. The "right
side of resonance" refers to adjusting the tank circuit tuning capacitor
to
a slightly lesser value of C which is normally turning the knob to the
right. One will notice a slight increase in plate current, otherwise a bit
more than the current at the actual "dip" value. Typically about a 2% to
5%
increase is adequate. For my RCA BT the dip is about 425 ma and I run it
at
about 435 ma for 3300 volts DC.
With this method one will notice an increase in output power when tuned to
the "right side of resonance" by a few milliamps while tuning to the "left
side of resonance" the same amount will show a decrease in output. The
input power remains the same for both cases but the output is greater in
one
case and less in the other case.
73
Bob, K4TAX
----- Original Message -----
From: "Kim Elmore" <cw_de_n5op@sbcglobal.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, March 01, 2014 8:41 PM
Subject: Re: [TenTec] In praise of older technology
I've never been told of this trick for tuning for maximum efficiency of a
class C amplifier. Is there someplace I can go to learn a bit more about
it? I ask because I have a WRL Globe Champion AM transmitter (my Dad had
it before me and it's the first rig I ever operated) and this trick isn't
mentioned anywhere in the manual. My Dad never mentioned it to me,
either,
but that may not mean much as he may have thought the nuance wasn't worth
the risk of damage. But then, there's a lot that isn't in the manual and
a
lot of my Dad's knowledge that I never had a chance to have passed to me.
If this is one of the tricks that all the old hams used to know, I'd like
to know it, too.
Kim N5OP
On 3/1/2014 6:55 PM, Bob McGraw - K4TAX wrote:
Yes in a Class C amplifier one typically will adjust the plate circuit
tuning for a dip in plate current. Then one should adjust coupling for
rated plate current or rated output. Then adjust the plate tuning to the
"for right side of resonance", typically increasing PA current about 5%
which will produce maximum efficiency. All of this applies to only
Class
C amplifier stages.
In a linear amplifier, adjust plate circuit tuning for maximum output
which should also be at the same point as the peak in grid current.
Then
work your way up the power scale by increasing drive while adjusting
loading to keep grid current and plate current at or below maximum
ratings. Once the rated grid and plate current values are attained,
controlled by drive, the last step is a very minor adjustment of plate
tuning for maximum output.
Remember should one use light loading with a linear amplifier, splatter
abounds!
73
Bob, K4TAX
----- Original Message ----- From: "Rick - DJ0IP / NJ0IP"
<Rick@DJ0IP.de>
To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Sent: Saturday, March 01, 2014 4:14 PM
Subject: Re: [TenTec] In praise of older technology
"Dip" was pre-watt meter days.
No need to dip anymore.
Just tune for maximum smoke!
Precisely, running full drive power, you first tune the PLATE for max
smoke,
then repeat the sequence of slowly advancing the LOAD and peaking the
PLATE
for max smoke.
If you reach the point where increasing the LOAD and peaking the plate
brings no more increase in max smoke, but just an increase in Ig, then
you've gone too far. Back it off.
The idea is to find the exact point where max smoke is reached with min
LOAD
that can achieve it - and of course all of this is always subject to
the
Ig
not exceeding max specs.
Piece of cake.
The only thing I do different in practice is, I first tune for max
smoke
with about 30w of drive, just to get everything in resonance, then I
proceed
as described above.
Dip? 40 years ago, maybe!
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Bob
McGraw
- K4TAX
Sent: Saturday, March 01, 2014 10:00 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] In praise of older technology
The only thing I ever "dip" is a little chew.
73
Bob, K4TAX
----- Original Message ----- From: "Brian Carling"
<bcarling@cfl.rr.com>
To: "Ed Purvis" <wa4njy@yahoo.com>; "Discussion of Ten-Tec Equipment"
<tentec@contesting.com>
Sent: Saturday, March 01, 2014 2:18 PM
Subject: Re: [TenTec] In praise of older technology
Ed you must be talking about those XE stations tuning up on SSB on the
low
end of 40m. They groan "hoooooo-la" while they dip the plate control !
SOP
Best regards - Bry Carling
On Feb 22, 2014, at 8:29 PM, Ed Purvis <wa4njy@yahoo.com> wrote:
There are some on hi-fi sideband that I am not sure they are talking
or
their stomach is making noise.
________________________________
From: Steve Berg <wa9jml@frontier.com>
To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Sent: Saturday, February 22, 2014 8:12 PM
Subject: Re: [TenTec] In praise of older technology
As part of my collection, I have Drake 2B receiver and a Gonset
GSB100
phasing exciter. One night I wound up in a round table with a bunch
of
HiFi SSB aficionados 0n 40 meters. These guys were running advanced
equalizers and high-end microphones. Then had the latest Oriental
Transceivers. They even had audio spectrum analyzers to check out
each
others signals. So, I asked for an evaluation, and they were quite
complimentary. So, they asked what I was running, and I told them a
1957 vintage phasing exciter with a D104 mic. They were amazed!
Sure,
it drifts, and it is hard to get it right on frequency by zerobeating
the receiver BFO with the carrier on the exciter. But it is a lot of
fun to use.
Steve WA9JML
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