When reducing power for rtty you need to RETUNE the amp for maximum power
out at the reduced drive level. This will bring the efficiency back to where
it should be.
If you tune up for SSB or CW, tune for max out, then reduce the drive, your
efficiency will be considerably less.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Jeff Blaine
> Sent: Friday, August 20, 2010 11:21 AM
> To: Rob Atkinson; Patrick Barthelow
> Cc: amps@contesting.com
> Subject: Re: [Amps] Can I cool too much the tubes?
>
> Gentlemen,
>
> You should take a look at the plate dissipation at the reduced power
> levels.
>
> In my amp, as the power output drops back, the efficiency drops at a
> faster
> rate on some bands. Which means that running the amp at half power, for
> example, as is the current rule of thumb for RTTY operation, may not
> actually reduce the effective plate dissipation very much.
>
> Of course, one point does not make a trend. But it's easy to make the
> calculation and then a guy can KNOW rather than just guess.
>
> And if we were perhaps talking about an SB220, that transformer is pretty
> light weight to begin with, and a guy would definitely want to check the
> efficiency there.
>
> Hope to see you in the SARTG.
>
> 73/jeff/ac0c
> www.ac0c.com
>
>
> --------------------------------------------------
> From: "Rob Atkinson" <ranchorobbo@gmail.com>
> Sent: Friday, August 20, 2010 10:09 AM
> To: "Patrick Barthelow" <apolloeme@live.com>
> Cc: <amps@contesting.com>
> Subject: Re: [Amps] Can I cool too much the tubes?
>
> > Pat,
> >
> > I have the amp, manual with schematic. There is nothing in there
> > about any sensor that throws the amp in standby if it gets too hot.
> > That's why I asked.
> >
> > It must be an aftermarket mod in your amp Rudy.
> >
> > But, I am always willing to be surprised and eat crow. Why not give
> > Ten Tec a call and ask them? There might be something in there
> > having to do with current draw I don't know about, thay may have been
> > taken out in later models. Anyway, my comment about specifiying mode
> > was not directed at you.
> >
> > It's up to you whether or not 400 w. is enough, but in my opinion a
> > new Alpha is not the answer if you want a really robust amp. If you
> > can afford a new Alpha you can afford an old one back before they
> > tried to jam everything into a teeny desk-top cabinet, or an old
> > Henry, or two, or homebrewing one in a rack....maybe an old TMC or
> > Collins commercial communications amp...
> >
> > On Thu, Aug 19, 2010 at 11:40 PM, Patrick Barthelow <apolloeme@live.com>
> > wrote:
> >>
> >> Does anyone have a schematic for the amp under discussion, or perhaps
> >> looked
> >> to see the sensor device that senses excessive heat to
> >> trigger a shutdown? I am curious what they sample for the heat trip
> >> function. And, if it is an internal sensor for the transformer core,
> >> it
> >> might not help, but perhaps some extra muffin fans, mounted external
> or
> >> internal to the amp could add enough cooling to extend its duty cycle
> on
> >> RTTY.
> >>
> >> Back in the olden days, as a kid, I used to sit a muffin fan right on
> top
> >> of my Drake TR-4 Finals Cage, drawing upward, and the whole radio
> became
> >> and
> >> ran dramatically cooler.
> >>
> >> Best Regards,
> >> 73, de Pat Barthelow AA6EG
> >>
> >>
> >>
> >>
> >>> Date: Thu, 19 Aug 2010 20:16:13 -0700
> >>> From: r_bakalov@yahoo.com
> >>> To: amps@contesting.com; ranchorobbo@gmail.com
> >>> Subject: Re: [Amps] Can I cool too much the tubes?
> >>>
> >>> Rob,
> >>> I am the second owner of this amp and don't know its age. It is the
> grey
> >>> model. I can certainly look up the serial number when I am back to VE3
> >>> where
> >>> my contesting QTH is.
> >>> As far as mode goes, my very first post noted that this is with
> respect
> >>> to
> >>> RTTY where I can't really run it longer than 30 min at full power. I
> am
> >>> not
> >>> a SSB guy; CW runs all day long at full power. Standby or not, some
> sort
> >>> of
> >>> protection kicks in when the amps gets too hot and the orange STBY LED
> >>> is
> >>> on.
> >>> So now my dilemma is if I should run low power, without the amp, or
> high
> >>> power at only 400 W during the upcoming CQWW RTTY contest :-) Or time
> >>> for an
> >>> Alpha :-)
> >>> Rudy N2WQ
> >>> --- On Thu, 8/19/10, Rob Atkinson <ranchorobbo@gmail.com> wrote:
> >>>
> >>> From: Rob Atkinson <ranchorobbo@gmail.com>
> >>> Subject: Re: [Amps] Can I cool too much the tubes?
> >>> To: amps@contesting.com
> >>> Date: Thursday, August 19, 2010, 4:28 PM
> >>>
> >>> Rudy,
> >>>
> >>> Is this automatic standby mode protection a new thing with the
> >>> Centurion? Mine is around 10 years old and it has nothing like this.
> >>>
> >>> When did you get yours?
> >>>
> >>> N.B. When you guys write about transmittion time at some power level,
> >>> it is very important that you specify the mode.
> >>>
> >>> There is a huge difference between "1.5 KW no time limit (operating
> >>> SSB) and 1.5 KW no time limit carrier.
> >>>
> >>> SSB is the "Coors Light" of transmission modes.
> >>>
> >>> 73
> >>>
> >>> Rob
> >>> K5UJ
> >>>
> >>>
> >>> On Wed, 18 Aug 2010 10:34:58 -0700 (PDT), Rudy Bakalov
> >>> <r_bakalov@yahoo.com> wrote:
> >>>
> >>> >Experience trumps specs. The amp goes into standby mode after about
> 30
> >>> > minutes
> >>> >running at full power, i.e. about 1200 W. If I run it at around
> >>> >400-500
> >>> > W it
> >>> >is fine.
> >>> _______________________________________________
> >>> Amps mailing list
> >>> Amps@contesting.com
> >>> http://lists.contesting.com/mailman/listinfo/amps
> >>> _______________________________________________
> >>> Amps mailing list
> >>> Amps@contesting.com
> >>> http://lists.contesting.com/mailman/listinfo/amps
> >>
> >>
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|