alternative power

>  From: Dan Jacobson <[email protected]>
>Subject: Re: alternative power sources: can't fool the R2
>
>Dave> As the radio cycles the receiver on and off in power save mode,
>Dave> current varies, and voltage drop across the meter varies, and
>Dave> this is likely the cause of the strange behaviour you saw.
>
>Does this make sense?: "Why of course, all I need to do is turn off
>power save mode, the radio will then use constant power, and I can
>then use a "3V DC" simple wall wart to power the radio.  The only
>problem would be when we initially hit the on switch[!?]..., aside
>from that, the R2 won't waver its current usage, therefore the
>wallwart won't waver its volts, therefore the R2 will think all is
>hunky dory."

I feel like I'm wasting my time answering your questions, since you don't 
seem to read the answers very carefully.  You're mixing together several 
different answers in a way that doesn't make sense, and leaping to a 
conclusion that's wrong.

The text you quote is explaining why, even with a constant-voltage source 
like a pair of batteries, you can't put meter with significant resistance in 
series with the radio and expect it to work.  You're also ignoring the 
characteristics of wall wart power supplies that I described.

Turning off power save mode just means that the current will not vary 
because of that source, but the R2 will not magically become a 
constant-current load.  Current will still vary depending on whether the 
squelch is open or closed, how high the volume control is set, whether the 
LED is on or not, and probably even the frequency being received.  In 
general, no electronic device can be expected to draw truly constant current.

This means that you can't put a significant resistance between batteries and 
the load and expect the device to work.  So you can't use many ammmeters on 
their lower ranges, and you also can't use a fixed resistor to drop the 
voltage from a 6 V or 12 V source.

Also, even if the radio's current *was* constant, you still couldn't use a 
cheap wall wart because its own output is not constant - even with constant 
load.  There is a large amount of ripple on the output.  The only way to 
properly power the R2 with a cheap wall wart is to add an electronic voltage 
regulator between the wall wart and the R2.  Then, if you use a 6 V wall 
wart, the output voltage may vary between 5 and 7 V 120 times per second, 
but the output of the regulator will be a steady 3V, regardless of the 
ripple in the wall wart output *or* changes in load current at the radio.

>Wish there was an 3v gel cell that one could substitute for the AAs,
>all I have is 6v... 

Lead-acid chemistry produces 2 V per cell.  You can get 2 V, 4 V, or 6 V, 
but 3 V is impossible.

>P.S. just got thru using delete-trailing-whitespace again here in
>emacs, removing the invisible blank that is appended to the end of
>each line by several posters here.

This is a consequence of the way many people's mailers work.  They type text 
continuously, using carriage returns only to create paragraphs.  Then the 
text is wrapped into 70 or 80-character lines just before sending, after any 
editing is done.  The wrapping process often leaves the inter-word space at 
the end of the line so things work properly if you unwrap and re-wrap a 
paragraph.  The question is: why do you care?  How do trailing spaces hurt 
anything?  They're normally invisible.

        Dave 


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