Tnx Tom:
I think my idea is much simpler than using 4CX400s or 4CX800s. There are
many SB230s, Henrys and MLA 2500s around using 8875s and 8873s collecting
dust and unusable. So my idea it is wortwhile trying. If it works, it is
rather simple to find a suitable nechanical workshop for the job for a
number of tubes. If you dont have them, there is a source in Scandinavia as
I said before. If the G2 current stays within the tubes limits, you maybe
even not need a new bifilar coil in a hi mu triode connection? Who knows?
73s de Hans SM5KI
----------
>Från: "Tom Rauch" <w8ji@contesting.com>
>Till: AMPS <amps@contesting.com>
>Ämne: Re: SV: [AMPS] MLA-2500 MOD FOR GG 4CX-800'S CONFIKGURATION
>Datum: lör 5 aug 2000 13.32
>
>
>> Why not use triode/or supercathode connected 8122s or 8072s instead of the
>> 8875s? Same socket. Cheap price and you can still get abt 50 of the 8072s
>> in Scandinavia. The G1 can take 100 mA and the G2 using the same cup
>> construction should be able to handle even more current as it has a
>> thermal connection with the outside world and larger diameter.
>
>You have to watch some of the "supercathode" configurations.
>Some destabilize the PA, especially near the operating frequency
>on the higher bands.
>
>The capacitor divider scheme only works properly when the tube is
>in a class 1 service, with no grid current. An inductive tap,
>assuming the the inductor is an autotransformer with high mutual
>coupling and low ESR, works OK if the tube has a bit of grid
>current.
>
>The screen or screen and suppressor or beam forming element
>should always be at RF ground, so don't use the system that
>elevates the screen or suppressor elements for RF.
>
>> Can anybody familiar with those tube curves look into the 8122/8072 curves
>> if they are linear enough run in my suggested application?
>
>Usually triode connection curves are not available for tetrodes. I
>have no idea how that tube would behave.
>
>
>73, Tom W8JI
>w8ji@contesting.com
>
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