Re: LF: TRANSVERTERS

[M0FMT <m0fmt@yahoo.co.uk>]

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

From: Graham <g8fzk@g8fzk.fsnet.co.uk>
To: rsgb_lf_group@blacksheep.org
Sent: Tuesday, 6 November 2012, 18:57
Subject: Re: LF: TRANSVERTERS

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..

 

 

From: mal hamilton

Sent: Tuesday, November 06, 2012 4:45 PM

To: rsgb

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