[AMPS] Data Sheets YC156/3CX15000B7.

[Dave Kirkby]

W7CW Jay E Ostrem wrote:

> Hello fella's
>
> I have a point of confusion.
>
> I have been told that the 3cx15000b7 and the YC-156, share similar
> data
> constant current characteristics.   I have the constant current graphs
> for
> both tubes, and they are obviously different. Here is the confusion, I
> have
> been told that the curves do not change for pulse vs regular service,
> then
> I am told that pulse service results in an entirely different curve.(I
> do
> realize that the pulse data is carried out to much higher plate
> current
> curves due to the type of service)
>
> Any comments?
>                               73 Jay W7CW

I've looked at the data sheets for the YC156 and 3CPX15000B7, and the
constant current curve for anode currents are very similar indeed. The
pulsed tube (YC156) is plotted over a much larger cathode-grid voltage
range (-600 to +100) than the larger CW tube (3CX15000B7) which is
plotted over only -250 to + 100V, so they look quite different, but if
you inspect the numbers for anode current at any particular combination
of anode voltage and cathode voltage, they are the same:

eg at 4.7kV, -50 V cathode-grid voltage gives 10A anode current on both
tubes.

All other points I checked seem the same too. It would be useful to
perhaps stetech/compress one graph in a graphics package then overlay
one on the other, to make absolutely certain, but they seem similar
enough to me. (The files are on the ftp site, medphys.ucl.ac.uk  in
pub/users/davek, if anyone wants to try it).

The grid current curves do show some differences.  The magnitude of
these is difficult to tell because they is not a lot of data there -
i.e. no data between 0.1A and 1A grid current. However, the differences
seem within the the normal variation between tubes for grid current -
its never that tightly controlled.

As I have said before, Eimac told me to use the 3CX15000B7 data sheet to
get rough SSB data for a YC156 or 3CPX5000A7 - they sent me the
3CX15000B7 data sheet, following discussion on the YC156. They did not
say that they shared similar constant current curves, but on closer
inspection they do seem to do that too.

Certainly, I still intend using the 3CX15000B7 data sheet as a first
guess to using the YC156's I have. The main practical point is the
cathode needs to be biased to about +35 V. Later I'll use a spectrum
analyser, to see if the bias needs a bit of sweaking.

G8WRB.


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