Colin Lamb wrote:
> Care and Feeding of
>the POWER GRID TUBE published by Eimac states that the 3rd order distortion
>of the 4CX250B is -25 db.
It's nonsense to build a whole argument on the claim that the IMD of a
certain tube "is" any particular value. It all depends on the DC/RF
operating conditions.
Under other conditions, the IMD can be much better or worse. For
example, the Eimac recommended operating conditions for the 4CX250R are
too greedy for output power (400W per tube) and not surprisingly the IMD
is poor under those conditions (-21 to -23dB). However, it's equally
possible to get much better IMD from the same tubes by being less greedy
- see http://www.ifwtech.demon.co.uk/g3sek/cleansig/imd1.htm
for measurements made by GW4FRX.
>This one test seems to prove
...nothing beyond itself.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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