I've used the Paragon and my Omni on extensive RTTY contests without
failure of the radio. Yep, the radio does get hotter than I'm
comfortable with. However, during one evening of hot RTTY activity, the
power supply lost a bridge rectifier. It was mounted on the bottom
panel of the PSU and did not have thermal compound between the bridge
device and bottom panel. I replaced the bridge device and added a
liberal amount of white thermal compound. No problems since.
I agree that pushing the PA devices to the higher temperature limits
will shorten their lives. This is a fact of silicon devices. I've
added a 12V fan, low speed 7 blade model so it isn't noisy, to both my
Omni and my 961 PSU. Those small high speed jobs sound like a mad bee.
I've found that slow moving air is more effective than a job that tries
to blow the heat sink off the radio.
According to specs from Tentec, "the radio is rated for 100% duty cycle
for 20 minutes. Continous duty with customer supplied air cooling of
the rear panel heat sink". The PSU is rated at 22 amps for 5 minutes.
73
Bob K4TAX
Dale Martin wrote:
>
> >
> > >The inefficiency of heated air convection?
> > >
> > >My recommendation for any and all heatsinks is to have a fan
> > oriented to
> > >keep air flowing across the heatsinks at all times. An
> > acquaintance of mine
> > >lost his Omni VI+ finals while operating Field Day. He was operating
> > >outside, under a covered pavilion, in 90 degree temps, and no breeze.
> > >
> > >My Omni VI's have fans for each.
> > >
> > >Besides, the nice air flow from under and around the radios keeps the
> > >operator fresh, too.
> > >
> > >Get a 12v fan and plug it in to your Pegasus or PS aux V+
> > jack. Same goes
> > >for you VI/V/Paragon/Corsair, etc, owners, too!
> > >
> >
> > Hmm....
> > You do not have a fan if you have a good designed heatsink.
>
> That may be true, but any help you can give a heatsink, the transistors will
> appreciate by giving you long life.
>
> > But the heatsink in OMNI VI+ is not adeqaute. It is too litlle and
> > its fins (ribs) are mounted horisontaly. It means you loose
> > again lots of
> > cooling efficency. (cooling will be degradate but a factor of 60%)
> >
> I agree.
>
> > What I did was to change the whole heat sink with a propper one.
> > I did calculate the theoretical dissipated power and did
> > choose the ambient
> > temp
> > to be 30 deg Celcius. The fins are vertical which make the
> > air cool the heat
> > sink in a natural and proper way.
> >
>
> > Thanks to that design I can operate my OMNI VI+ for hours
> > (CW) in 20 deg C
> > ambient and the heatsink is mearly warm (35-40deg).
>
> 35-40 deg C seems somewhat low, actually.
>
> > No need for fan !!!! (even if I have one in my drower for
> > just in case...)
> >
> > The jobb took only two days of porting and 25$ for hardware....
> > I hate fan noise...
> >
> Real hams wear headphones. :-)
>
> Most hams have their radios in somewhat confined spaces where airflow is
> minimal.
>
> So, the fan noise is immaterial. For ten minutes work, a couple of dollars
> for parts and some parts out of the junk box, my Omni VI's have forced air
> movement across their heatsinks. The whole radio cabinet is lot cooler now,
> too.
>
> Heat is the enemy. Be cool: force air to move.
>
> 73,
> dale, kg5u
>
> --
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--
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