[Icom] Power Issues

Thu, 01 Apr 2004 18:39:25 +0000

Back in the hollow state (vacuum tube) days,
I used #6 gauge wire from battery to the
DC power supply to run my National NCX-3
in my 1964 1/2 Mustang.  That was for a
mere 6 foot run from battery to other side
of the engine compartment.  Total draw
at max output for that rig including filaments
was at 30A.  It never hurts to overkill on
your power conductor size.

Mac in Oklahoma City

----Original Message Follows----
From: "Frank A. Ellis" <[email protected]>
Reply-To: [email protected]
To: [email protected]
Subject: Re: [Icom] Power Issues
Date: Thu, 1 Apr 2004 10:28:00 -0800 (PST)

 >>> 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 <[email protected]> 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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 > Your Moderator: Dick Flanagan K7VC,
 > [email protected]
 > Icom Users Net: Sundays, 1700Z, 14.316 MHz
 > Icom FAQ: http://www.qsl.net/icom/

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----
Your Moderator: Dick Flanagan K7VC, [email protected]
Icom Users Net: Sundays, 1700Z, 14.316 MHz
Icom FAQ: http://www.qsl.net/icom/

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