[Icom] Power Issues

[Frank A. Ellis]

>>> If you consider that a radio may well draw 10A,
then if you have 2-3 ohms of series "stuff", how much
voltage do you have for the radio? <<<


In this case, there would be no voltage available to
the radio at all, as the drops would well exceed the
supply voltage. 2-3 Ohms at 10 amperes is 20-30 volts
of drop. Bill makes a very good point, and I would
recommend that total resistance in a 10 ampere power
supply loop (including ground) does not exceed 0.2
ohms, and preferably less. In a 20 ampere circuit,
such as in a typical 100w HF/VHF installation, the
problem is twice as difficult to overcome.

73, Frank W3UHF






--- William Lambing <w0lpq9@msn.com> wrote:
> To add to what Clif so well stated:
> 
> In line components.  Those who use the cig lighter
> adapters should pay heed to the solder issue.  Also,
> these adapters sometimes have a spring that makes
> "point contact" with the lighter.  Corrosion or
> other crud on these lighters is in effect a series
> resistor.  The spring also is usually small gauge
> wire.  Look at any ARRL Handbook for wire size
> compared to current it will handle.  With time and
> current, this little wire spring becomes a series
> resistor also.
> 
> Use Ohms law and figure your own losses out. 
> Measure, as Clif stated, the voltage AT the radio. 
> You might be well surprised at how little voltage
> you do have at the radio.
> 
> If you consider that a radio may well draw 10A, then
> if you have 2-3 ohms of series "stuff", how much
> voltage do you have for the radio? That will put you
> under the recommended voltage for that radio.  Then
> you complain that your Icom or whatever sounds like
> crap.  Whose fault is it??  Certainly not those of
> Icom.
> 
> A friend of mine complained about his radio not
> working worth a darn at 50W, but was ok at 10W.  We
> measured the voltage and found under the 50W rating,
> he had less than 10V at the radio.  We looked at the
> lighter adapter spring and found out it was on the
> order of 3 ohms.  That plus the other losses in his
> system, really killed it.
> 
> Been there, seen it happen.
> 
> 73
> 
> Bill, W0LPQ
> 
> 
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