I am attempting to select between the Alpha 89 and the
Alpha 91B and would appreciate the advice of the experts
here assembled. I don't require automatic bandswitching.
I intend to keep this amplifier for a long while. My uses
are contesting and DXing (especially on 160, 80 and 40).
I value equipment that will chug along at legal limit for
the contest period without problems to distract me from the
operation at hand. It will be used with my C-Line and
FT-1000MP.
I've got the information provided by Alpha, (including QST
reviews of the 87A and the 91B) and the responses from a
request posted on the Topband list. A short summary of
the differences between the two amps is below. Comments /
Additions?
Alpha 91B Alpha 89
Tubes (2) Svetlana 4CX800A Eimac 3CX800A7
T/R Vacuum relay PIN diode
Dial Direct Geared (?), lighted
Grid Metering Min/Max LEDs Bar led meter
Transformer 3.5kVA Unisil-H ? kVA Hipersil
PS Diodes 5A discrete diodes Block diode
HV Single value Switched: "SSB / CW"
Input Tuned input not req'd Tuned Input
RF Ratings Same Same
Bandswitch 7 Position 9 Position
Size 7" High 7.5" High
Color, Finish Same Same
Parts Source Bulgaria, Russia, USA USA
Manufactured Bulgaria Colorado
Warrenty 4 Year 4 Year
Price (US$) $2700 $3700
Aux. Fan $ 40 $ 40
I have been told the following tidbits: confirmation or debunkments?
1) Early 91B production was plagued with heat-related problems,
and at some point they replaced the Bulgarian blower with the
same blower used in the 87A. (The reporter said that this is a
different blower than that in the 89: true?) The cause of the
heat problems was later traced to the bias circuit and solved,
but the blower was not switched back.
2) The 87A / 89 switch using PIN diodes, and had reliability problems
early-on. The ARRL review reported on these problems, and
reported that the problems had been solved: true?
3) The 91B is reportedly louder in operation (ignoring for the moment
the sound of the vacuum relay. I presume that this is the noise
of teh blower and (possibly) transformer hum. How significant is
the difference?
4) Opinions have been pretty evenly split on whether the construction
quality of the 91B and 89 is comparable.
5) Is the auxilliary fan a good idea for someone who will be making
contest use of one of these models? How much noise does it add?
I appreciate any inputs or guidance! I'm planning to make the
choice and purchase some time in June.
73,
Jeff Maass (jmaass@freenet.columbus.oh.us) Amateur Radio K8ND
USPSA/IPSC # L-1192 NROI/CRO NW of Columbus Ohio
25000 Members in 2000!
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