----- Original Message -----
From: "Jim Thomson" <jim.thom@telus.net>
To: <amps@contesting.com>
Sent: Wednesday, February 08, 2012 1:29 AM
Subject: [Amps] Different amp recommendations
> Date: Mon, 6 Feb 2012 11:47:42 -0600
> From: Rob Atkinson <ranchorobbo@gmail.com>
> Subject: Re: [Amps] Different amp recommendations
>
> I have doubts about the AL82 doing 1500 watts 100% duty cycle for very
> long.
>
> Knowing the p.s. in that amp you'll be right at its limit, right at
> the Ip limit of the tubes, right at or a bit above their maximum
> dissipation...
>
> It's a "legal limit" amp only because Ameritron heaped up the Ep.
>
> But you can call almost anything "legal limit" with no time factor
> considered.
>
> Your enemy is time. do you want to go for 10 minutes or more at 1500
> w. on RTTY? Do you want to be able to forget about the amp and not
> have to look at it nervously every 15 seconds to make sure it's okay?
>
> Personally, I like overbuilt stuff.
>
> you can beef up the AL-82 in some ways and settle for 1.2 or 1.3 KW,
> homebrew an amp or keep looking with more money.
>
> 73
>
> Rob
> K5UJ
>
> ## let's do the jr high school maths. The xfmr in the AL82/1200/1500 is
> rated at 1.8 kva CCS. [32 lb]. To get 1.5 kw out, we require 1500/.6eff
> = 2500w dc input.
> When those dahl xfmr's are maxed out, the temp rise is rated at 55 deg C
> over a 40 deg C
> ambient. That also factors in another 10 deg C deep inside the core..for
> 'spot heating'.
> Deep inside the core, it will be 65 deg C over the outside 40 deg C
> ambient.
> Now 40 deg C = 104 deg F. Now the hottest it will get, deep inside the
> core is 105 deg C or 221 deg F....which is hot.
> On CW, with dashes at a 3.6:1 dash to dot ratio, this
> xfmr will be fine. RTTY for hrs on end, yeah, I don't think so. A 46 lb
> dahl is only good for
> 2.7 kva CCS....and that would be the smallest size I would use in a RTTY
> contest.
>
> ## If ur eff is lousy on 10m, like 50%... now you require 3 kw dc input to
> get 1.5 kw out.
> IMO, the initial extra cost of a slightly heavier xfmr is well worth it.
> You save nothing
> in the long run by under sizing pwr supply components OR tank components
> like coils+
> bandswitch's, etc. A bigger xfmr not only runs cooler, it will also have
> way better V regulation.
> IF you burn up a xfmr, it will have to be replaced with the 46+ lb unit
> anyway, so now you
> not only didn't "save" any money....you lost money ! IMO, build it [or
> buy it] like a tank,
> then never look back.
>
> Later... Jim VE7RF
## Considering that the same transformer is used in the AL-1500 at 2200+ W
out its held up rather well over the decades.
I wonder what Ameritron uses for the custom 2 holer AL-1500's?
Carl
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