On Tue, 26 Aug 97 15:27:48 -0800 Rich Measures <measures@vc.net> writes:
>>The Product Reviews of the Alpha 91b and the QRO 2500DX merit reading
>>since these are the first with the Svetlana 4CX800/GU-74B tetrodes.
>>To be honest, I am amazed at the IMD performance of both amps; the
>Alpha
>>is 45/49 dB and the QRO is 43/40 db for 3rd/5th orders. This sure
>beats
>>the old 25/28 dB typical of 4CX250's.
>>
>That's probably better IMD performance than any transceiver, Carl.
>However, a 4CX250B with 10 ohms of cathode RF negative feedback R,
>loaded
>to 5mA of screen current, has IMD performance that is comparable to
>the
>typical transceiver.
Unfortunately most 4CX250 sockets have the cathode pin internally
grounded to the mounting ring precluding any changes.
>...snip....
>>
>>Of particular interest is that all 3 amps experienced failures during
>>testing which IMO is a bit bizarre.
>
>Bizarre by far. What was the reported nature of the failures, Carl?
Alpha had a screen circuit ( not tube) problem, QRO blew a 4:1 output
matching toroid and Ameritron had an unexplained large increase in IMD.
The amps were replaced and testing resumed.
SNIP
73...Carl KM1H
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|