[AMRadio] Ongoing Quest: Legal Limit AM Amp

Tue Jan 24 09:43:29 EST 2012

Happy Tuesday--
    Still raining out there?  GLOOMY Here but dry so far. Gonna get colder 
again.... geez.. make up your mind, Mr.Weather!!!!

    Oh.. gotcha on the hair do.  Looks nice the way it is in the photo! 
Ever since that episode trying to cut my own bangs I do not touch scissors 
to my own hair. Bad things happen.    No tonsorial talents.

    It's the leg that doesn hurt..ha,ha... no.. it's the  L one, darn  it. 
Glad I have automatics to drive 'cause "clutching" would be ouchy....however 
the left is "inside leg" in the dog show ring so I am turning "into" it and 
that's why I had to give up on class... big time throbbing.  Hopefully it 
will just heal and no Sx and more dopping around time.  We'll see....  right 
now I gotta go put on Big Bertha and gimp out to do chores.  We may not be 
doing our Tues. trip to MV to go to Jake's for 1/2price steakburgers.. 
article on front page of CMH paper (which I saw but did not read) about new 
law that allows people with concealed carry permits to take their guns into 
bars.  For SOME reason the reporter from CMH went to MV  and interviewed the 
mgr. of Jake's so now (as B said in his harangue that met me as I came up 
the stairs 1st thing) now the whole world knows no guns in Jake's .. it's 
gonna get hit.   I won't go on about the "carloads of coons from CMH 
targeting the place" etc,etc.  I doubt that those types READ the paper 
anyway but a few dirtbags from this local area may see it and get ideas. 
Found out yesterday a house on Rd. S of here got robbed 2 wks ago. 
SIGH....   So now places on both "sides" of us have been hit since Nov. 
OY!!!!
SO... as I said to B when he paused for breath.. it's HIS choice if he 
decides not to patronize it. I am still having "aftershocks" from dining at 
Fiesta Mex. yesterday... I said "So,there's goes the last decent food in MV" 
...  we sometimes have Kennel Club meetings there so I will go then.   Looks 
like this is a good thing for Cheapfest... AmVets or Highland Pizza or 
Wendy's at Sunbury.   Before long he'll find fault with those places for 
some reason and it'll be fish heads and rice (he can cut a hole in the ice) 
or dog food. I'd opt for the dog food. Who needs Jenny Craig???  This is 
what happens when somebody doesn't have a LIFE.. all of this "incidental" 
stuff becomes the Mt. not the molehill.

    Well.. better get moving... sigh.. time to strap on Big Bertha.  It does 
feel better with that brace on... Dr said to just keep doing what I'm doing 
(except leaning against vehicles, of course..... DUH!!) and take the Tylenol 
and not Naproxin (it slows bone growth).  I'd think he could go in there 
with a little gizmo and some Crack Fix or something and speed things up a 
bit but... he's the Doc.  The clavicle, humerous, shoulder joint mess took 
about 3mos to "resolve." I did it in Oct. (still warm weather) and went to 
AZ at Christmas time and just backed away from UD and his big fat pointy 
finger.. he had a habit of poking one's L shoulder when he was "making a 
point"..OW!!! Seemed likehe'd zero in on the really tender spot where the 
side of top "knob" of humerus was pulverized and tendons bruised.  Just a 
habit of his.   Of course that was many YEARS ago so I'm sure  things healed 
faster.....    onward!!!!!

    Be back later, I hope. Depends on availability of the chair here.  May 
do a dog bath but not sure yet.  Tonight is dog school where I get to sit on 
my keester and watch the goings- on instead of "doing laps."  Good for pup 
to get out and about and get more riding experience.  She can get rabies in 
another wk. or so and then can hang out and watch and learn (I hope). 
Later, kiddo!     Gimpalong Cassidy
----- Original Message ----- 
From: "Rick Poole" <wa1rkt at arrl.net>
To: <amradio at mailman.qth.net>
Sent: Monday, January 23, 2012 11:07 PM
Subject: [AMRadio] Ongoing Quest: Legal Limit AM Amp


>
> Looking for a good design for a legal limit amplifier for my DX-100
> (looks like I'll be homebrewing it).
>
> I've pretty much narrowed down the choice to a linear amp capable of
> 375 watts carrier output or 1500 watts PEP output at 100 percent
> modulation, vs a Class C amp with high level modulator driven from
> the DX-100's audio output.
> .
> I was thinking about a pair of 3-500's in Class B push-pull.
>
> Everybody keeps telling me that I'll get maybe 30 percent efficiency
> at best during dead carrier times.  At 100 percent modulation and
> class B I should get 60 percent at worst.  I really, Really don't
> understand that at all... seems like if I can get 60 percent at 1500
> watts PEP I should be able to get 60 percent at 375 watts dead
> carrier.  But, I'm accepting it for the moment, and anyway, I digress...
>
> 375 watts unmodulated carrier output at 30 percent efficiency means
> 1250 watts input, or 875 watts dissipation or 437.5 watts per tube.
>
> 1500 watts PEP at 60 percent efficiency means 2500 watts peak input
> or 1000 watts dissipation, 500 watts per tube peak.
>
> So it seems to me like a pair of 3-500's should be able to cut it,
> especially if I give them plenty of air.
>
> I want to stick with glass tubes because I'm planning to put them
> behind a window so I can "feel the glow" during operation.  Anyway,
> it'll impress the living crap out of the XYL :-).  Hence, the
> ceramics have been ruled out for now.
>
> So, a few questions...
>
> 1.  Will a pair of 3-500's in Class B push pull really handle the
> load with no problem, assuming adequate air?
>
> 2.  This may be a rookie question, but google hasn't given me a clear
> answer... is there such a thing as class B push pull grounded grid?
>
> 3.  There are some commercial class AB pair-of-3-500 amps (e.g.
> SB-220, TL-922) that are limited in what they can do by the power
> supply.  So, I plan to make sure the power supply can easily handle
> the load.  Any suggestions on the best places to get power
> transformers that are up to the job?  So far I haven't found one
> under about $600.
>
> 4.  I'm actually not that certain that I'm competent to design
> something like this from scratch.  Any plans available on the net
> that I can use for a starting point?
>
> 5.  Current tentative plans call for the power supply to be separate
> from the RF deck, and they may be separated by as much as 6 feet
> (there are compelling reasons for that that go way beyond the scope
> of this post).  Is that practical?  Where is a good source for high
> voltage (3500 VDC) cable and connectors?
>
> 6.  As noted above, I plan to put the tubes behind a window so I can
> see them.  Is there a glass that can be used for the window that will
> maintain shielding?
>
> Thanks...
>
> Rick WA1RKT
> Londonderry, NH
> Catch me on 14.300 MHz Intercon / MMSN most days
>
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