[1000mp] Linear Amplifier Recommendations for Use with FT1000 Mark V

Tue, 26 Feb 2002 07:57:53 -0800

This has nothing to do with the 120V/240V discussion.

I think that using the lower Vin tap on the Ameritron amplifiers'
transformer will cause the filament voltage to rise to life threatening (to
the expensive 3CX1200's life, that is...) values.

Otherwise, I second the nomination of the AL-1200. The fast warm-up is great
for generator-powered operations and other times when the 180-second delay
is close to 'forever'. It does take more than 100W to get to the rated
output on 10m/15m, so the higher B+ would be helpful. I've pondered a
separate filament transformer to deal with this (and another) issue.

Between the AL-1500 and Alpha 91b, if they can be found at similar used
prices, the nod definitely goes to the Alpha. Much quieter in operation and
something approaching QSK make a big difference. That's probably why the 91b
is so hard to find used...

BTW, I have and presently use all three of these amps.

73 de Bob, K6XX
[email protected]
www.k6xx.com

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Guy Olinger, K2AV
Sent: Monday, February 25, 2002 7:57 PM
To: [email protected]
Subject: Re: [1000mp] Linear Amplifier Recommendations for Use with
FT1000 Mark V

I think the reason that the lighter AL series amps look smaller is
because they are packed better.

I own an AL-1200, which is a workhorse, and there is just not much
room left over anywhere in there, except where the other 3-500Z goes
in the AL-82 which is an identical chassis.

Only beef I got with it is that the 3cx1200 could use another 400
volts on the plate. But a 9th cap in the filter string just really
wouldn't have any place to go. (Tom, they tell you not to put 240 to
the 220 HV tap. That just to stay below the WV on the caps keyup?)

I mentioned one of the older used alpha's just because it's a classic
and if you never really intend to get up to 1500 watts, you might just
keep it forever.

Then again, I'll probably never get rid of my AL-1200. It's my carry
around contest amp that no one has been able to break. Got "set tuning
here" little wedgie tape tuning marks and everyone gets it right, even
when they're 4 sheets to the wind at the end of the contest.

I think your real problem is that a MK V plus any near KW amp is going
to be a hard pull on a 110 circuit. Lights are gonna blink.

Think real hard about SOMEHOW pulling 220 to your shack.

73, Guy

----- Original Message -----
From: "Tom Rauch" <[email protected]>
To: <[email protected]>
Sent: Monday, February 25, 2002 8:32 PM
Subject: Re: [1000mp] Linear Amplifier Recommendations for Use with
FT1000 Mark V

> But if that's really where you are, I would suggest you look for a
> really clean Drake L4B, L7, SB-220/221 or TL-922A.  The 3-500Zs are
> almost bulletproof and will coast at 600-100w output.  The only
> precaution with these older amps is that you may need to use a
> soft-switch interface of some sort, because the voltage (at least on
> the SB-220/221) is too high to be within ratings, even for the Mark
> 5's TX GND relay. I looked over the "cross-needle meter" Ameritron
> amps at Dayton last year (I think the AL-811 is one of them) and was
> not impressed with the construction -- they just looked light
> throughout, compared with the older generation of Ameritrons such as
> the AL-1200 and 1500.

The older generation amps are 1500 watt+ output amps, with 34
pound hypersil transformers. They weigh about 70 pounds or so! Of
course they make an AL80 series look small! They also dwarf a
Drake L4 or SB-220.

The AL-80B, AL800, 572, and AL811H use the same bandswitch
as the L4B, L7 and SB-220. The voltage breakdown of the AL-
series switches is higher, because the contacts were changed and
insulation on the support bars improved.

The 922 uses an offshore switch, and I have never tested one to
compare.

The transformers in the AL-80B, 800, and 572 series all are heavier
and rated higher than the transformers in the L4B, L7, SB220, and
TL922. The AL-series  transformers, including the 811, all have
multiple voltage windings for power lines, allowing ~15 volt
adjustment steps.

The AL series (except the 811 series) have equal size tuning and
loading caps to the Drake, Heath, and Kenwood amps, but the
inductors in the AL-series tanks are larger.

The AL-series (except the 811 series) has step-start and inrush
limiting, and use 7-watt bleeders across each computer grade filter
cap and has higher total supply capacitance than any of the other
amps mentioned. (For example, the AL800 and AL-811 use a total
of about 55uFd of capacitance, as I recall that's almost twice the
filter capacitance in a SB220.)

The AL80B, with only a single 3-500Z, has more airflow than a 220
or a L7 Drake.

Of course the AL80 uses only one 3-500ZG tube, but other than
that

other than tube differences, I wonder what part of the amps are
actually smaller????
73, Tom W8JI
[email protected]
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