I have built two amps using 4-1000's, both grounded cathode. The six meter
amp (still in use) started out with a tuned input network using a bifilar
toroid and small trimmer capacitor and presented a wonderful load to the
exciter, but made the amplifier so easy to drive I could hardly avoid
overdriving it. (Used 4200V Ep, 650V Eg2.) Replaced that with, and also
built the 160m amp using, passive input provided by a resistive swamping
network (-6 dB) and balun (on the tube side of the pad) which provides
precisely the right drive to achieve 1500W output when 100W is applied to
the chassis. Well, okay, it's a bit more than 1500W.
WB2WIK/6
"Each success only buys an admission ticket to a more difficult problem." --
Henry Kissinger
> -----Original Message-----
> From: Mike Baker [SMTP:k7dd@qwest.net]
> Sent: Monday, December 10, 2001 11:45 PM
> To: AMPS REFLECTOR
> Subject: [AMPS] Reflector thoughts about my future amp project
> wanted!
>
>
> Hello Gang,
> Went to the swap meet last weekend in Mesa AZ. and came home with a
> pair
> of medical pull 4PR-1000 tubes in what appear to be like new condition.
> (One
> is an EIMAC and the other a Triton and both have early 98 date codes.) I
> was told they were pulled due to the time in service, not performance so I
> am hopeful. The price was right even if only one is working. If both are
> NG then I have a nice pair of bookends or lamp basses. ;>} I'll remain
> optimistic for the moment.
> First order of business is to find someone who can put them on the air
> and check them out or a commercial tester who can test them to see what
> condition their condition is in. (OPPS, flashback to '60 rock.) ;>} If
> anyone has info either
> option, let me know.
> Second item is sockets and chimneys. Two would be nice but one of
> each
> will do for a start. Let me know what you have and what you want/need for
> them. A trade is ok by me as I do have a collection of stuff myself.
> Third item is knowledge. Once again the collective wisdom of the
> group
> is requested as I really don't like reinventing the wheel and for some of
> you this is old hat. Here is what I am curious about...
> 1. I remember from comments on this reflector that the 4-1000 takes a
> bit
> of drive to get full output and it likes lots of HV. Something like over
> 130 watts of drive is not unusual especially when you get to 10M. As I
> recall 4KV is preferred to say 3KV and I see from the one spec sheet I
> have
> that it can use up to 5.5KV under 30Mhz. I am thinking that 4KV is
> probably
> a good place to start as it is doable with what I have on hand. I
> question
> all this because I will most likely have only 100 watts or less drive
> available.
> 2. IF in GG service they are tough to drive to max legal smoke with
> 100W,
> then how about Grid Driving it and running AB2? Looks like it only needs
> something like 14 watts to get full tilt boogie out of the bottle that
> way.
> A switched attenuator on the input could help not cook things or overdrive
> the tube. What about matching the input to a solid state output rig?
> Switched Pi networks just like with cathode driven ok or does someone have
> a
> slicker idea in mind? Yep, I know I will need a screen supply of
> something
> like 750VDC but that looks a bit academic. I would likely use something
> like the English tetrode boards just for the safety factor they offer in
> case of an OOPS!
> 3. Stability. If I remember correctly there was some question to the
> stability of the 4-1000/4PR-1000. Can any one comment on problems they
> have
> encountered with this tube in that regard?
> 4. Matching. I do remember a few of you commenting that there were
> some
> problems with trying to get a good match in the final Pi net because of
> the
> high capacity in the tube. I thought that interesting at the time because
> this tube was used as an FM broadcast amp and has a max usable frequency
> of
> up to 110Mhz.
> Any tricks or methods that would make my work easier here would be nice..
> 5. The missing program...Somewhere I had been given/found on the net, a
> simple program. As I recall, you put in the type of tube,
> (triode/tetrode/pentode), the class of operation, the Q of the tank, the
> plate voltage and current and specified what frequency you wanted the
> values
> for and it and if it was a Pi or PiL net and hit enter. It would give you
> the values of all components in the tank circuit. You just went from
> freq.
> to next freq. and it would add them to the list. When done, you just
> titled
> the file for what ever you wanted to call it, (Example= 4-1k tank
> specs.txt) and away you would go. VERY NICE PROGRAM. Somewhere it has
> been
> lost to the software gremlins. DOES ANYONE RECALL THIS LOVELY BIT OF
> SOFTWARE AND KNOW WHERE I CAN GET IT AGAIN! My searching the net has
> gotten
> close a few times to something a bit like it but not what I recalled.
>
> Final comments.
> I am hoping to make this my first real long term amp. A solid beast
> that will do max legal amateur output with no sweat. It will laugh at
> contests, broken antennas, miss tuning and operator error all without
> TVI/RFI. QSK at 35 wpm? No problem. Fast warm up? Sure. Silky smooth
> tuning with repeatable settings from a chart? Of course. AND be driveable
> with less than 100w (maybe down to less than 20watts) on any band.
> OH, and did I mention that like most projects this one is also on a
> limited fairly long term budget? Yep, after two years of working E-Bay and
> the swap meets I have a fairly good start of parts but it is time to make
> the final plan to put them all together and make my version of "Godzilla!"
> So break out your thinking caps, get a cup of your favorite beverage
> to
> rethink your past 4-1000 projects and give me your best shot. What did
> you
> do and what would you have done differently and why?
>
> Again, in advance I will respectfully thank you for your thoughts and
> comments..
>
> Best 73
> Mike Baker K7DD
> Peoria AZ.
> k7dd@qwest.net
>
>
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