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[AB5YG at aol.com]

y Amplifiers, Comments?

In a message dated 96-02-21 16:49:53 EST, AB5YG writes:

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Forwarded message:
Subj:    Re: Ameritron/Henry Amplifiers, Comments?
Date:    96-02-21 16:49:53 EST
From:    AB5YG
To:      bmyers at primenet.com
CC:      AB5YG,R F Gerald

Hi Bob,

Here is my input / recommendations concerning the Ameritron AL-1200 and
AL-1500 amps:
I used a brand new AL-1200 with 3CX1200A7 tube during the CQWW SSB contest at
the end of last October and for about 2 months afterwards (a friend of mine
bought it for the contest).  I  ran the amp at 1500 watts out on all bands
for the entire contest and it was solid as a rock!  Tunes very nice on all
bands - the vernier loading contols are nice. The AL-1200 uses the Eimac
 3CX1200A7 ceramic / metal power triode out of the Varian power grid and
x-ray prducts division.
The tube is very rugged and has a Grid disdipation of 50 Watts! This tube is
just about an "instant on tube".  One would really have to try hard to kill
this tube.  A friend of mine has a Henry amp with a 5 volt filament verion of
this tube.  Henry runs around 4kv on the plate - Ameritron runs 3300 key
down--- I also used the AL-1200 during the ARRL 160M CW contest in December.
 The antenna tuner arced couple of times - never bothered the amp at all!!

I placed an order for the AL-1200 for me in November.  In January I changed
my mind and decided to buy the AL-1500 - this is why ---

1. The 3CX1200A7 takes a full 100 watts drive to get 1500 watts out.  That
means running my Omni-6 at full power out all of the time --- The AL-1500
3CX1500A7 takes about 50W max  to get 1500 Watts out on all bands! My Omni-6
loafs along at 30 - 50 watts output!!

2. The Filament on the 3CX1200A7 draws 21.3A at 7.5V = 160 Watts - 
    The Filament on the 3CX1500A7 draws 10.5A at 5.0V =  52.5 Watts --
    (The AL-1200 is a real heat generator)

3. The 3CX1500A7 is a ceramic and metal, power triode out of the Varian Eimac
Power Grid Tube Division. The maximum grid dissipation is 20 Watts -- So you
need to watch this a bit closer.  The AL-1500 does have a grid current
sensor/shutdown circuit that protects the tube. The tube is not instant on!
 It takes a full 3 minutes for the filaments to reach the proper temp and
then the power relays pull in via the 3 min timer.

If I was using a rig with over 100 Watts out I may have stuck with the
AL-1200.  It would not be good to hit the AL-1500 3CX1500A7 with 150 watts
drive!!, although the grid current protection circuit would take the amp back
to "stand-by". An inexperenced operator may be better off with the AL-1200
because it would be difficult to kill that amp.

Another thing of interest is the 3rd and 5th order Intermodulation Distortion
Products ratings of the tubes--

3CX1200A7  3rd is -30 db at 3500 EP, 5th is -43 at 3500 EP
3CX1500A7  3rd is -38 db at 3500 EP, 5th is -41 at 3500 EP

Other observations common to both amps:

1. The blower is very very noisey!!  A vaccum cleaner is louder though!!
2. The antenna relay is loud - but built like a rock
3. All coils are air wound - no torids in output -- Better?? I think so ---
    You can change the blower motor speed by moving a tap (soldering
required)
4. Modification to go above 15M is very easy!! (could do with eyes closed)

I thought about buying the amp with the internal QSK installed --- I decided
not to do so because if anything happended to the QSK pin diodes it would
mean returning the amp to the factory -- that would be a real pain!!  The
factory "rep" actually recommended that I buy the external QSK box -- as the
cost was the same and it could be used on any amp I have!  I have had my
AL-1500 for over a month and really like it -- Very rarely does the grid
current ever exceed  25Ma and I only triped the grid current once - Ran amp
into an open!! Not the best thing to do --- but the grid protection does work
fine!!.  The amp runs fairly cool at 1500 out -- The case next to the tube
warmed up a bit after a 1 hour SSB QSO where I did alot of talking.  I ran it
during the 160M CQWW CW contest this January  -  It remained cooooool ----  I
have not received the QSK box yet -- It has been on back order for over a
month -- 

Last May I had a deposit on an Alpha 89 - 3CX800A7 (2) Amplifier - for
considerable more money -- I cancelled the order when household expenses
became primary importance - hi hi --- I had the unit on order for 2 months
prior to cancelling the order --- thats one of the problems with having to
wait so long - one can change his or her mind!!! Oh well  --- The Alpha 87
and 89 are rock solid amps and they are QUIET!!  Not like being next to a jet
plane taking off!!  But the cost is $1000 more!! ETO had a Alpha 89 running
at 1500 Watts out for ever at Dayton last May!!  Getting back to the
Ameritron - I like meters!!! Don't know if I would have liked the Alpha
"Light Show" -

Well - Hope that this helps you with your selection -----

73's Bill  AB5YG     ab5yg at aol.com