Hello Mike!
A simple gg 3-400Z amplifier has been described in one of the RADIO
HANDBOOKs by W6SAI. The amp uses a pi-L output tank and a tuned input
circuit made of copper tube which is connected to one of the tubes
filament connectors - the other filament is fed via an insulated wire inside
the copper tube. Your driver is connected to a tap on the cathode coil.
Using 35 watts you get a 1kw input with the 3-400Z. More drive is perhaps
needed with the 3-500Z that you could use instead.
This is a far better solution than using 4CX250Bs with all the complicated
electronics around it and the glass tube is more linear too and delivers
500-600 watts with very little effort.
As I can not scan pictures into my MAC yet, send me a SAE and I send you a
photocopy.
Hej daa de Hans SM5KI
----------
>Från: "Mike Willis" <Mike@g0mjw.freeserve.co.uk>
>Till: <psmeaton@globalnet.co.uk>, <amps@contesting.com>
>Ämne: Re: [AMPS] 50MHz Amp Details
>Datum: mån 3 jan 2000 18.21
>
>
>> Gentlemen,
>>
>> I wonder if you may be able to help?
>>
>> I'm trying to find some details about a 50MHz amplifier, using possibly a
>> pair of 4CX250B's. Do you know of construction information of such a
>beast?
>
>It is entirely possible. I built one. However, if you age going for a PI-L
>type circuit, you really need to ensure the absolute minimum anode
>capacitance. I have done away with anode tuning altogether, employing a
>tuned L with the shorted turn approach commonly used with 3-500Zs.
>
>I abandoned 4CX250Bs on 6 in favour of the cheaper, simpler, quieter 3-500Z
>designs (no screen supply, axial blower). These are well suited to modern
>100W 6m multimodes.
>
>A pair of 250Bs is now developed for use on 4m where I have only a few watts
>drive. Again, parallel operation, PI with tuned inductance.
>
>Mike
>
>Mike
>
>
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