[Amps] How to read the 3-500Z spec sheet?

[Joe Subich, W4TV]

> Sorry Joe, but that is wrong. WSJT is *ONE TONE AT A TIME*. It can
> and does not only tolerate Class C amplifiers, but thrives on it! I
> run my 2x4CX250B's class C at 1100 watts output on 2 meter EME JT65B
> with no issues at all.

WSJT may be one tone at a time but that still does not eliminate the
need for reasonable linearity unless one wants to generate "clicks"
every time the tone shifts.  With class C any attack/decay is made
much more sharp ... you can even hear it on CW with a class C amplifier.

 > I have run a SB-220 converted for 6 on EME at 800 watts output (CW
 > position). It worked OK as long as I operated it with the outside
 > cabinet removed.

Since that was two tubes, I suspect (hope) you were staying under
800 mA (400 mA per tube) - you should have been able to reach 800W
out with two tubes although running on the high tap would have
been easier.

 > BTW, WSJT JT65 modes as used for EME are true 40% duty cycle, IE 48
 > second out of every 2 minutes full carrier power followed by 72
 > seconds of standby and/or RX.

They may be 48% duty cycle on a long term average but they're
100% duty cycle while transmitting ... and as bad/hard on the
amplifier as RTTY contesting.  They're not 50% duty cycle while
transmitting (like CW) or even less like moderately clipped SSB.

I still would not push a single 3-500Z past 400 mA "DC" plate
current and would replace the SB-200 transformer with an AL-80
transformer (with additional filter caps) if it were my amp.

73,

    ... Joe, W4TV

On 5/23/2010 2:35 PM, Larry wrote:
>
> On 23-May-10 8:36 AM, Joe Subich, W4TV wrote:
>>
>> WSJT is a linear mode (multiple tone frequency shift keying) - it
>> does not tolerate clipping/compression well. Since the 3-500 is
>> specified for for 400 mA MAXIMUM you are running it well into
>> compression (current starvation).
>
> Sorry Joe, but that is wrong. WSJT is *ONE TONE AT A TIME*. It can
> and does not only tolerate Class C amplifiers, but thrives on it! I
> run my 2x4CX250B's class C at 1100 watts output on 2 meter EME JT65B
> with no issues at all.
>
> K1JT even mentions in the instructions for WSJT that none of the WSJT
>  modes require a "linear" amplifier. Now don't confuse WSJT FSK modes
>  with that crummy PSK31 crap that cannot tolerate even a little
> distortion in the amplifier without causing trouble.
>
> BTW, WSJT JT65 modes as used for EME are true 40% duty cycle, IE 48
> second out of every 2 minutes full carrier power followed by 72
> seconds of standby and/or RX.
>
> I have run a SB-220 converted for 6 on EME at 800 watts output (CW
> position). It worked OK as long as I operated it with the outside
> cabinet removed. Even so, I was really happy when I got the GS-35B
> going with it's 200 pound power supply!
>
> 73,
>
> Larry - W7IUV DN07dg - central WA http://w7iuv.com
>