jeremy-ca wrote:
>
> ----- Original Message ----- From: "Steve Thompson" <g8gsq@eltac.co.uk>
> To: <amps@contesting.com>
> Sent: Thursday, September 27, 2007 9:36 AM
> Subject: Re: [Amps] New SB-200 owner
>
>
>>
>>> The 4CX250 family is another very poor choice. They were not
>>> developed for
>>> SSB use and the linearity is only in the mid 20's under the best of
>>> conditions. This includes the 250R. Ian, G3SEK/GM3SEK, has written
>>> extensively on that subject and even developed a set of bias
>>> regulators to
>>> at least improve the IMD a bit.
>>
>> I think they can do better linearity than that - the amps I built have
>> all done so at 250-300W/tube. The STC data sheet for 4CX250B gives IMD
>> figures under the typical operating conditions. At 2kV, 325W pep output
>> they give IMD3 -30dBc and IMD5 -50dBc. That's in line with what I've
>> seen.
>>
>> Steve
>
>
> Which method of testing do you use and did you read Toms recent post?
> There is a huge difference between true real world IMD and the
> advertising departments way of rating it.
My driver ran around -55dBc IMD3 and I never tried to measure IMD5, it
was off the screen. I use dBc to mean referenced to a single tone
(assuming that's what you mean by 'method of testing').
Steve
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|