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LOL Well I work on a 1:400
efficiency for my Mf Ae , so to
radiate 1 watt erp , that's 400 watts
carrier power to the Ae, I can do the
same on 7 meg with 500 mW to the same Ae ....
dont forget 'we' had to change the
reported wspr power level to 'erp'
as the Ae feed powers where so big ,
until then it was Ae feed power , which
made very little sense , but this was a
long time ago, before everyone had (except me
) has class e/d amps
It all stems from the race to dB's , as
you can see now Gus has a decode at
-20 dB across the pond , where Stefan, just a
new boy to 500 has only -23 dB , but I
know Gus was building a new washing
machine size PA over the summer , looks like
its running on Half load ;--)
73 -G..
I
Sent: Tuesday, November 06, 2012 9:56 PM
Subject: Re: LF: TRANSVERTERS
Hi Graham
Thought that WSPR stuff was supposed to be ultra low
power?
How come its blowing rigs up? Could it be that the
Wisper is really a blooming great shout and we have a misnomer which is an
advertising euphemism. Just pile on the power and be heard
at all costs? Well it's an ill wind...... !
73 es GL Pete M0FMT
IO91UX
But what are you sending with the reduced
power rig ?
SSB ... Normal CW Opera
all have low duty cycles and
result in low heat build up
But if you running at 100% key
down sending qrss and the like
, then , yes the rig will heat up , in
the early days I always though wspr should
of been named Icarus , with
the number of thermal run a ways caused
by 100% duty over 120 seconds ( not
a problem at Hf where power levels are low,
but down here at 1:400 efficiency's =
a lot of heat)
The rig will have a class AB1
or similar PA with high standing
bias to reduce cross over distortion = splatter
on ssb , so standing dissipation will be
high ..not much you can do ... add a fan
to cool the heat sink , but be careful of
the thermal gradients , out side cold , wont
mean inside is also at the right temp
..may still be very hot , if parasitic
'ambient' cooling is part of the equation and
the fan is only cooling the last part of
the heat path ..
73 -G..
Sent: Tuesday, November 06, 2012 4:45 PM
Subject: LF: TRANSVERTERS
RIG/TRANSVERTER HEAT
I have noticed when running a Transceiver at low power
for Transverter or other use the Transceiver PA gets very HOT so it would
appear that this is an inefficient approach except the Transceiver has a
dedicated low power output.
I was wondering what system was used to reduce this
power. It would be better to disable the PA and take the output from the
driver stage.
It is vy noticeable on an IC-706
de G3KEV
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