[Premium-Rx] Powering receivers away from electricity grid

[ToddRoberts2001 at aol.com]

In a message dated 9/27/2005 1:00:13 AM Eastern Standard Time, 
e.gauja at unsw.edu.au writes:
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. 

I have been looking into the same problem of how to power a premium RX 
offline. One approach would be to use 2 - 12V Gel Cells in series for 24V then with 
a series of 78xx regulators you could pick off the +15V, +10V and +5V rails 
then make up an extra battery pack perhaps with a set of D-Cells for the -15V. 
If you don't mind the extra weight use 2 light or medium-duty marine batteries 
for the basic 24V and that would run the receiver all day. Also you want to 
check the current draw of each voltage to factor that in with your regulator 
circuits. Sometimes minus rails like the  -15V may only draw 50-100ma or less so 
a D-Cell battery pack would be practical here. The +5V rail may draw the most 
current if the receiver uses a lot of 5 volt IC's so you may need something 
bigger than a 78xx series here.   You could tap the 5V regulator off one of the 
12V batteries for less power wasted. The 78xx regulators are not the most 
efficient but will give you the quietest power used with 24V batteries - would be 
good right down to VLF with zero noise. And of course the 12V batteries can be 
easily recharged for the next DXpedition. You would probably be the only 
person in the world with a battery-powered 8709. These are just suggestions that I 
hope may give you some ideas. Or if all this sounds like too much work then 
break down and get a Drake  R8A or R8B and all of your problems are solved for 
12VDC operation. 73 Todd WD4NGG