Good point Peter. That higher ZSAC is completely subsumed and absorbed into
the total plate current when the amp is producing RF output.
An EBS controlled amp provides its best efficacy in standard PTT SSB mode
operation. EBS yields lower heat dissipation improvement in VOX operation.
73
Leigh
VK5KLT
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Peter Voelpel
Sent: Wednesday, 4 April 2012 12:02 PM
To: amps@contesting.com
Subject: Re: [Amps] amp cooling / triodes vs tetrodes
Why should one care about an amplifier without EBS or high idle current at
all?
That current is only drawn if actually transmitting and not in standby mode
without output power.
73
Peter, DJ7WW
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Jim Thomson
Sent: Dienstag, 3. April 2012 17:46
To: amps@contesting.com
Subject: [Amps] amp cooling / triodes vs tetrodes
Date: Mon, 02 Apr 2012 12:59:10 -0700
From: Jim Barber <audioguy@q.com>
Subject: Re: [Amps] amp cooling / triodes vs tetrodes
Leigh,
Not to drive everyone up a tree with this topic, but do you know of any
non-proprietary designs that might serve at least as a basis for a
properly-done EBS implementation?
I'm not thinking so much of modifying my (newest) commercial amp, but I
do have a YC156 project that seems to be in eternal overhaul, as well as
a Henry 3KA that could benefit from such a beast.
Along that line I also (still) have one Alpha 77 left with their EBS,
but I'm not sure I'd qualify that one as more than a good start at
"properly done", at least by today's standards. (It's from before they
added the control pot, early design)
Thanks,
Jim N7CXI
### You can buy the entire TRI-state EBS from the Ameriton catalog.
They have 1-2 versions of it. Complete, ready to go.
It might need some tweaking to obtain higher V levels for a YC-156.
## I dunno why you would want to mess with EBS....if you use VOX on SSB.
You don't need to suck 350 ma of idle current on a YC-156. 150-200ma is
plenty. 150 ma idle on a 3CX-3000A7 triode is plenty for superb imd .
150-200 ma idle on a 3CX-6000A7 is ample for good imd.
## On CW mode, there is NO reason at all to suck 150-350 ma of idle current
!!!! On CW, just crank up the bias V...until the idle current is down to
10-20ma. Use a string of series 1N5408 or 6A10 diodes for this job.. and
or... a single wire wound resistor. On CW..with any GG triode you can not
run the idle current at zero ma...or you will get key clix.
With 10-20ma you wont get any at all. Tank eff will be improved a whole
bunch too. Your idle power will be so low, it's a non issue.
## EBS, even tri-state is a fubar way to go on CW..and also FM.
## EBS, if using PTT SSB is ok...and saves heat. If using VOX on ssb,
the ebs will not buy you much for heat savings at all. The only time it
kills heat is between when you stop talking..and when the VOX drops out.
The EBS is NOT gonna be fast enough to toggle between syllables !
## If you want to see something really stupid, check out the 3 x hole
tetrodes from QRO, etc. They idle at a whopping 750ma ! The 2 x holer idles
at 450 ma (225 ma per tube) Using the 3 holer with the same plate xfmr as
the 2 holer is even more silly. If any sb-220 etc, sucked 750ma, it would
burst into flames.
## sure the small tetrodes can be driven with 10-20 watts. Who cares.
The typ xcvr puts out 100-250w these days. You run a 200w xcvr at just 20
watts out..and the eff goes straight to hell, and ditto with the TX imd.
You really require a good 3-9db pad to run those low power tetrodes
properly...when driven from your typ xcvr.
Later........ Jim VE7RF
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