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Re: [Amps] How to read the 3-500Z spec sheet?

Subject: Re: [Amps] How to read the 3-500Z spec sheet?
Date: Sun, 23 May 2010 17:20:05 EDT
List-post: <">>
Rob, Yes of course the 1950 volts is way too low and I suggested to him  
that he should bump up that voltage and 520 mills for 100% duty cycle is too  
high.  I think Tom W8JI changed the rating on the AL-80B over the original  
AL-80.  When I first used an AL-80B I was quite impressed on how easily it  
made power output, his claim for 70% eff. is pretty much right on.    Sorry 
you didn't stop by and have an 807 with me out at Dayton.  Many guys  
stopped by and spoke to me and was quite busy fielding questions.  All and  all 
was a great trip and I always look forward to going out there.   Perhaps 
next year.  73 Lou
In a message dated 5/23/2010 2:15:41 P.M. Eastern Daylight Time, writes:

Hi  Lou,

I saw ur setup at Dayton but I didn't have time to stop and say  hello.
Sorry about that but I'll make a point to do so next year.

A  few points:  I don't know what Rauch did or didn't do--for one
thing,  I have no idea what the original AL80 was specified to do but
I'll bet if  Rauch did design for a 1 KW output amp from a single tube
he assumed low  duty cycle and not the maximized processed super
compressed garbage SSB I  hear all over the bands now, which is not any
15 to 30% duty cycle.   Ten Tec sells some kind of nasty speech clipper
now where they claim almost  6 dB increase in average power for SSB.
With a 100 w. exciter that's taking  average 20 w. and making it almost
80 w. average.  Yikes, must sound  beautiful.

Henry's 3-500 amps all had Ep up near the 4 KV  maximum--there is a big
difference between that and the AL80B and this  guy's amp.  I think the
henry p.s. sagged to 3600 v. under load.   pair 3-500 let's say max Ip
800 ma you get 2900 w. input @ 70% efficiency  you get 2 KW out and the
tubes are under their maximum plate  dissipation.  So, you are correct
in saying this guy should have a  higher Ep.

Let's look at his situation.  I think he has 1.95  KV.  520 ma.  I get
a little over 1 KW input.  He says he  has 400 w. out. Then the tube is
dissipating 600 w.  Okay, maybe not  all the time.  If he is running
gentlemanly SSB and has a lot of fan  maybe he is okay if we follow
your thinking.

I freely confess to  being careful and conservative, perhaps to a fault.

If he is  overdriving the amp and/or has a lot of heavy processing
things may not be  so good.   If he is running his data mode which is
100% d/c then  the tube seems to be dissipating 100 w. over its limit
for the whole  transmission.



On Sun, May  23, 2010 at 9:29 AM,  <> wrote:
> Rob, You  have to remember that the tube ratings are for CCS not SSB or CW
>  service.  CCS service is 100% duty cycle, SSB is 30% duty cycle and CW  
> about 45% duty cycle.  It is not the higher plate current nor  the higher
> grid current during the cycle that kills the tube, it is  the constant 
> the top plate dissipation that kills the tube.   Running an AL-80B at 1000
> watts output on SSB will barely show much  anode color compared to the 
> anode color at CCS rating at 750  watts output.  That amp was rated by 
> designer W8JI and he  sure knows what he is doing.  I tend to agree with 
> since I  pay close attention to the tube anode color with a pair of 
>  running at 1500 watts PEP on SSB.  Although that would be in the rating  
> the tube anyway.  In fact henry I believe rated one of their  3-500 amps 
> 2000 watts output on SSB, so that is in line with  Ameritron's claim.
> In a message dated 5/23/2010 10:18:54 A.M.  Eastern Daylight Time,
> writes:
>  you say you are getting 400 w. with 520 ma Ip.  I think that's 120  ma
> over the max Ip for a single 3-500 so you're possibly in trouble  right
> there.
> you say you increase drive and get no  more suds which means the tube
> is probably saturated.
>  An AL-80B on any band putting out 900 w. is a bad idea regardless of
>  what Ameritron says.  It is a lot easier to _sell_ a "1 KW amp"  than
> it is a 700 w. amp, which is what the AL80B really is (actually  that
> power output is optimistic) unless you don't mind getting a new  3-500
> every few years.   If you consider the max rated plate  current of a
> single 3-500 (400 ma) and look at the specified power  supply v. in
> that amp (2700 v. no load as I recall) and figure it sags  down to 2400
> under load and assume 70% efficiency (giving them the  benefit of the
> doubt) you get a choice of either abusing the poor  single 3-500 or
> discovering some promotional hype license is being  taken (In ham
> radio?  You gotta be kidding me!).   That  amp is probably what is
> keeping 3-500zg rolling out of some tube plant  in China, so maybe we
> should all be glad.   Every time I  work some ham operating that amp
> and driving it over 700 w. I politely  tell him what's happening and
> get either anger or the guy never comes  back to me.   3-500 used to be
> sort of cheap for the watts  but they are getting expensive now.  Oh
> well it's not my  money.
> But, back to your point, I'd drop the drive down to  where you are
> getting < 400 ma on the plate and be happy.  How  much power does it
> take to have a QSO on 6 m. anyway.  I have  never operated that band
> but I thought the "magic band" either let you  have a QSO with 59 copy
> and 1/2 watt, or no amount of power would get  through.  Nothing in
> between.
> As for 100%  duty cycle, if the cooling is stock, you probably want to
> put in a fan  that moves more air.  No matter what you do, 520 ma is
> too much  plate current.
> 73
> Rob
> K5UJ
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