[Amps] GS23B Plate load resistance for HF
g8on at fsmail.net
Fri Nov 1 04:16:42 EDT 2013
GS23B tetrode, not a GS35B triode.
What was the IMD on the 2 times GS35B amp?
Message Received: Nov 01 2013, 05:31 AM
From: "Jim Thomson" <jim.thom at telus.net>
To: amps at contesting.com
Subject: [Amps] GS23B Plate load resistance for HF
Date: Thu, 31 Oct 2013 18:54:18 +0100
From: peter chadwick <g8on at fsmail.net>
To: TexasRF at aol.com, keepwalking188 at yahoo.com, dezrat1242 at yahoo.com,
amps at contesting.com
Subject: Re: [Amps] GS23B Plate load resistance for HF
Assuming 3kV on the plate, 500 volts on the screen and AB1 operation in grounded cathode, I calculate a PEP output of 1540 watts, a dissipation of 1240 watts, efficiency 55% and a load resistance of 1570 ohms - calculation method as per RCA.
Peak plate voltage when loaded is 3700 volts.
The 4CX1000A has a much bigger allowable plate swing before the plate current curve starts to bend - which helps the efficiency.
## are u folks talking about a GS23B..... OR a GS35B ??? On a buddys 2 x GS35B 6M amp, we managed to get 5 kw out on 50.125 mhz with 225 watts of drive from a FT-2000.
He could easily bury the slug past 5 kw. At which point the 10 kw slug was inserted. The FT-2000 is capable of 250w out on 6m. Plate V was aprx 4300 NO load on RX...... and 4150 vdc under load.
The 150 vdc drop consisted of a 100 vdc drop from drawing 2A of plate current through the 50 ohm glitch Resistor.... + another 50 vdc drop from the B+ supply. I had him temp short out the glitch R..to see what the
real V drop was..... and it was only 50V. But this was an oddball case where a 253 lb dahl xfmr was used on one of its lower taps... + a 165 uf filter cap..and 2 ga wire back to the main 200A
panel. 4150 x 2A = 8.3 kw 5000 /8300 = 60.24 % eff.
## carl is correct though.... the GS35B is like a 4-1000. Gain goes WAY up when you crank the B+ up. On my old 4-1000 amps... I would get 600 w out with 2.5 kv under load + 120 w of drive.
With 4.4 kv under load, and same 120 w of drive.... power increased to 1980 watts out. Roller coil was optimized in each case to factor in the different plate load Z....and in both cases was tweaked
for a Q of 8-10 to maximize eff.
## 4100-4300 under load on a GS35B is about the max you can use on a good tube. Much above that..and you get into trouble.
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