Carl & the other FB gents who replied off list,
Thanks for the explanation. The difference in temps was very
surprising to me. I never had thought to do the equivalent of a
rectal probe on an amps exhaust. We see the power on our watt meters
but the air temps aren't metered, at least not on any amp I've owned.
As to the probe, I'm using the Sunbeam electric oven probe for the
bird at Thanksgiving, it slides into the exhaust ductwork just fine).
As to the loafing, Seems like RTTY doesn't need a lot of power but
rather than run the K3 at 100 W RTTY, 300W ought to be fine using the
amp at minimal settings. The amps blower is at full RPM so I figured
it was a no brainer. Nope, needs a brain...
I run legal limit during the contests and other than taking part in
the last couple of SSB contests, I've only worked CW contests from
day one, nothing else. I was thinking this amp ought to be good for
RTTY at legal limit all day long but I see I'd surely break 200F if I
did that. Will see what comes about with the low power setting.
73,
Gary
KA1J
> Cuz the amp is not designed to be loafed in the HV position, efficiency
> sucks do to the much different plate load.
> The LV position is a bit more efficient.
>
> Why are you loafing an 8877 for anyway? Drive it with 50W and tune for max
> in the LV position and then measure.
>
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "Gary Smith" <Gary@ka1j.com>
> To: <amps@contesting.com>
> Sent: Wednesday, March 12, 2014 4:58 PM
> Subject: [Amps] HV & temps
>
>
> >I have started working RTTY for the first time in 25 years (sending
> > using the CW paddle & having the K3 convert it to RTTY). I thought
> > I'd use the amp to give me a better signal and take it very easy on
> > the K3. I have a temperature probe in the air exhaust and it tells me
> > when the tubes are heated enough to fry an egg or not.
> >
> > I had the amp set for 300 watts output using the higher volt setting
> > of 3,800V and saw the exhaust temps closing in on 180F pretty
> > quickly. After fiddling with the load plate settings I ended up with
> > pretty much the same results of high temps with low output power.
> >
> > I then tried with the voltage in the low HV setting of 2,600V and for
> > the same 300 watts out, it takes a whole lot longer to get to a
> > higher temp.
> >
> > Why would this be? With the higher V it takes less current & with the
> > lower volts it takes higher current to get the same wattage. Why does
> > using the higher voltage setting result in a hotter exhaust?
> >
> > Gary
> > KA1J
> >
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