[Premium-Rx] Powering receivers away from electricity grid

[Guy Atkins]

Hi Eric,

Last year I tried almost the identical scheme with a RA6790GM for DXpedition
use away from you. The true sine wave inverter was slightly quieter, but
still made a racket. I tried completely shielding the unit and one of my
deep-cycle batteries inside a galvanized metal box, and situated it 20
meters away from the receiver location. No luck! Still noisy. Even with the
case grounded and using shielded ("medical grade") 3-conductor cable routing
the AC between the inverter and receiver I was getting noise. No matter what
I tried I still had a good amount of radiated RFI  :^(

73,

Guy Atkins
Puyallup, WA USA


> -----Original Message-----
> From: Eric Gauja [mailto:e.gauja at unsw.edu.au]
> Sent: Monday, September 26, 2005 9:59 PM
> 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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