[Premium-Rx] Powering receivers away from electricity grid

[Gary Geissinger]

Guys,

I agree.  I use a little Honda generator.  I have never heard the
electrical interference and with the control system built into the
generator the power is pretty close and stable to 60 Hz with good
voltage regulation as well.

Gary



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-----Original Message-----
From: premium-rx-bounces at ml.skirrow.org
[mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of Carcia, Francis
A HS
Sent: Tuesday, September 27, 2005 6:09 AM
To: premium-rx at ml.skirrow.org
Subject: RE: [Premium-Rx] Powering receivers away from electricity grid


Why not just buy a little generator and shield the spark plug wire.

-----Original Message-----
From: Eric Gauja [mailto:e.gauja at unsw.edu.au] 
Sent: Tuesday, September 27, 2005 12:59 AM
To: premium-rx at ml.skirrow.org
Subject: [Premium-Rx] Powering receivers away from electricity grid

Dear Group Members,
                                   I would appreciate feedback on the 
subject of powering sensitive receivers away from the electricity grid, 
such as on DXpeditions. I own a WJ 8709, and have been looking at
options 
for powering it away from the mains. The 8709 (normally operated on
240/110 
VAC) has internal DC supply rails of +24V, +15V, +10V , +5V 
and  -15V.  This means that it cannot be powered from a single 12V
battery 
(although it could be done with a number of such batteries, but this
gets 
expensive and weighs a ton!) . I have experimented with using 12/240V 
inverters - the normal grid AC supply here in Australia is 240V, but the

situation would be similar for 12/110V inverters.  I first tried the 
cheaper"modified sine wave" inverters , but the problem of noise arose.
No 
problem with the stronger signals, but the weaker signals had to compete

with a low level background hash not present using mains operation. I
then 
tried a more expensive "true sine wave " inverter, expecting much better

results, but this was not to be. The backgound noise was a bit lower
than 
when using the modified sine wave inverter, but low level signals still
had 
to compete with noise from the inverter circuitry.
The inverter is in a well shielded and grounded case, and I have also 
clipped ferrite cores around the AC lead from the inverter and also on
the 
DC battery leads.  I can also pick up this noise on my portable Sangean 
ATS909 receiver, powered  independently by dry cell batteries, so the
noise 
appears not to come via the power leads or earth connections of the 
inverter to the WJ8709.  I have reached the conclusion (perhaps wrong)
that 
even the true sine wave inverter radiates noise which because of the 
sensitivity of the WJ8709 and ATS909, is annoyingly noticeable when 
receiving low level signals.  Another possible power source that I have
not 
tried is a portable petrol motor/ generator combination - the lower
power 
models are not too expensive. But there seem to be some types that are 
called generator /inverters, so I suspect that the inverter portion
could 
also generate significant RF noise. Has anyone had any experience with 
these and the subject of receiver DXpedition power in general?
 
Best 
Regards from Downunder!


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