On Wednesday, October 29, 2003, at 01:00 PM, Mike Tubby wrote:
----- Original Message -----
From: "GGLL" <nagato@arnet.com.ar>
To: "Amplificadores Lineales" <amps@contesting.com>
Sent: Sunday, October 26, 2003 1:34 PM
Subject: [Amps] About single 4CX250b output power
Hello to the list, I want to know if is it possible to obtain 350
watts output from 160 to 10 with a single 4CX250b tube, for linear
amplifier service, and which working class? AB1, AB2?; 2000 Plate
volts
maximum is needed?.
Best reagrds
Guillermo - LU8EYW.
Page 65 of Eimac's "Care and feeding of power grid tubes" shows a
selection guide for SSB service for which the 4CX250B is listed as
being
capable of 348W "useful power output" in AB1 with a 3rd order
distortion
product of -25dB (doesn't say whether its relative to carrier power or
one
tone of two tones).
I suspect that this is in "ideal conditions", new tube, perfect
matching on
input and output, correct anode and screen voltage, etc. etc. YMMV.
Eimac measures IMD relative to two tones, so the IMD relative to PEP is
31db-down instead of 25db-down. However, I found that with 2400vdc on
the anodes of 4cx250s, and loading for a minimal amount of screen
current, the IMD products were no worse with the amp on than with the
transceiver alone. The reason for this is that most of the distortion
is produced at lower anode voltages, Thus, for SSB only, raising the
anode supply V, and minimizing screen I helps to minimize anode V
incursion into the distortion zone. // Another way to minimize IMD is
to select a tube with more peak emission. Eimac puts a "J" suffix on
such devices. Since there is no such thing as a free lunch, more peak
emission means more filament power is consumed. Typically, this is c.
35% more than for the normal version of the tube. Naturally, the
characteristic curves of J-version tubes are much flatter at the
low-end than the garden variety version. For example, the J version of
the 4cx10000D has an IMD of c. 47db-down below PEP, or far better than
any transceiver made today, but it has a 104A filament instead of a 75A
filament.
cheerz
Mike G8TIC
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
Rich Measures, AG6K, 805.386.3734. www.somis.org/
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|