[ETO_Alpha] 3CPX800A7

[Dave Haupt]

When Eimac developed the 3CPX version of the tube,
their intent was for identical performance, except in
the area of anode voltage capability.  The same
heater, cathode and grid were used.  The cathode/grid
structure is what predominantly determines IMD.

In my commercial working with both tubes, I was unable
to measure any difference in IMD between the tubes. 
In my application, I was operating a single tube at
2kW PEP output.  My tests were limited by driver
distortion to around -36dB IMD with respect to PEP. 
This is better than most ham transceivers.  At 1.5kW
PEP for a pair, the performance would most likely be
better, if the test equipment is capable of making the
measurement.

IMD performance from a tube is dependent not only on
the tube, but how the amplifier circuitry operates the
tube.  Alpha's conservative drive levels and proper
tuned input do a good job of extracting the best
performance from these tubes.

This was a good question - a lot of so-called
"upgrades" in the ham arena make serious trade-offs
between performance specs.  For instance, there is a
large number of SB-220s out there where the owners
reduced the idling current to make them run cooler. 
But the IMD was made worse by that mod.  

In this case, I can think of no drawbacks to using the
3CPX in place of the 3CX version of these tubes.

73,

Dave W8NF


--- Alex Gartshore <gd6ia@manx.net> wrote:
> I would be interested to hear of the difference in
> intermodulation distortion products between these
> two tubes
> before sticking them in the Alpha 89.
> 
> the 3CXP800 is not optimised for linearity.....is
> it?
> 
> I don't want to end up with an Alpha that performs
> like a shag
> brand amp.
> 
> Any knowledge out there???
> 
> Alex GD3UMW/GD6IA
> 
> 
> _______________________________________________
> ETO_Alpha mailing list
> ETO_Alpha@mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/eto_alpha


__________________________________________________
Do You Yahoo!?
Great stuff seeking new owners in Yahoo! Auctions! 
http://auctions.yahoo.com