[Premium-Rx] Powering receivers away from electricity grid

[Steve Stutman]

Hi,

If you go the micro genset route beware the inverter type, as Eric 
already mentioned; usually have something clever like "i" in nomenclature.

Older  < 1kW  models of Honda, Yamaha, 4-stroke Mitsubishi, etc, are 
nice and quiet, acoustically.

Would check to see which, if any, are brushless. Ignition HV is one RFI 
source, given rise/fall times, but brushes/slip-rings can be worse.

Diesel and brushless is probably the way to go, but somewhat at odds 
with portable.


73,
Steve


Carcia, Francis A HS wrote:
> 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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