-----Original Message-----
From: amps-admin@contesting.com [mailto:amps-admin@contesting.com]On
Behalf Of Richard
Sent: 01 July 2002 20:25
To: Harold E. Johnson; AMPS
Subject: Re: [Amps] 4CX250 IMD
Compared to poor regulation, yes. Compared to a well-engineered zener
shunt screen regulator, probably not a significant improvement. To
arrive at good linearity with a 4cx250B/R/BC/7203, load for less screen
current, use maximal anode supply V. and add c. 5-ohms of RF-NFB R in the
cathode (Rk). See Fig 10 on my Web site.
>G3SEK is vacationing in the states at the moment, but he gets significant
>improvement in IMD suppression with the tube by holding the screens within
>millivolts using active regulation.
>
>W4ZCB
There is exhaustive documentation about the improvement over zener
stabilisation in 250B's and similar tubes on G3SEK's website, most of the
research was done by GW4FRX and I'd say (having been subjected to both
flavours on the air with a high IMD sensitive VHF/UHF Rx) the improvements
for your neighbours are very worthwhile.
Regards
Conrad G0RUZ
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