[Antennas] Interesting article written by a ham

Mon Jun 14 15:18:44 EDT 2004

Although the discussions seems OT, the basic premise of power efficiency
is important to hams.. particularly those that operate on battery
power - whether on the go or at home during power outages.
It's good to understand that your radio needs anywhere from 2.5 to 4+
times it's output (rf watts) as DC input. Older hollow state rigs (tube
based gear) usually needs about 4+ watts of DC input to produce 1W of rf
out. Newer design solid state rigs can require 'as little' as 2.5 to 1.
An example is my Yaesu base rig. It requires 23 AMPS at 13.8 V to
create 100W rf.
That 23 amps works out to 31W DC , for an 'efficiency rating' of only
31%. So basically 2/3 of the input power is needed to run the radio
itself and/or lost as heat. And this does not yet take into account any
losses in the tuner, transmission lines or even at the antenna !
Consider what my neighbor did to allow him to operate during a power
outage (which are usually short, but common, during typical northern
winters:
 4 parallel car batteries feeding a DC-> AC inverter
 The AC output of the inverter feeding his bench top
power supply
 The DC output of his power supply running the radios
gear.
I figured out that he needed about 5 watts of DC battery power to
produce
1W of rf output.. sounds kinda sad, doesn't it. He finally rewired the
battery
to a large switch to be able to run the radios from either the PS or the
batteries,
thereby eliminating the inverter (which is only about 66% efficient).
I have a setup that allows me to switch over to battery power at home.
A bank of 14ah gel cells, constantly on a trickle charge, powers the
whole thing. I even have a small voltage regulator on the battery bank
that outputs a lead of 9V - to power the cordless phone base/charger and
the answering machine.
I do know folks who run their entire station on battery power all the
time. Planning such is a simple exercise in math, once you know all
the specs and can guesstimate your operation (talk/listen/quiet time,
hours of operation, etc. The batteries are on a slow charge all the
time with an 'intelligent charger'.
BTW, the heater looses a bit of power via magnetic field output. Other
'losses', might be 1-3% for the fan (look at the watt rating on the fan
motor) and induction from it;s external wiring. However, any infrared
(even from heater elements that do not glow) is still heat which as long
as it's directed into the room is a negligible loss. Electric heating
elements them selves (i.e.; 'calrod' elements) are typically about 97%
efficient. The loss in the house wiring (assuming it's large enough not
to get warm) might account for another 1-2% depending on length from the
meter to the appliance.
====
73, Frank
 ._._.
> ----- Original Message -----
> From: "George, W5YR" <w5yr at att.net>
> To: <holford at sympatico.ca>; <Antennas at mailman.qth.net>
> Sent: Monday, June 14, 2004 12:13 AM
> Subject: Re: [Antennas] Interesting article written by a ham
>>> > Guess it depends upon how you define the "output" of the heater. We
> can
> > measure the input, but what is the output? Heat delivered to how
much
> air in
> > what period of time? Joules out to where? Beats me . . .
> >
> > The electric heater may have a fan in it in which case there are
some
> VAR's
> > to take into account. Even if not, the heating element has a tiny
bit
> of
> > inductance so the phase angle between current and voltage is just a
> smidgen
> > off of 90 degrees. Silly, of course, but its all these little
> "gotchas" that
> > mess things up. Like the IR drop in the line cord which probably
> doesn't
> > contribute much to warming your feet.
> >
> > Gang, before the list owner chops this thread, I think I have had
all
> the
> > fun I can stand. Thanks for all the comments and thoughts.
> >
> > 73, George W5YR
> > Fairview, TX
> > w5yr at att.net
> > http://www.w5yr.com
> >
> >
> > ----- Original Message -----
> > From: "Dave Holford" <holford at sympatico.ca>
> > To: <Antennas at mailman.qth.net>
> > Sent: Sunday, June 13, 2004 8:38 PM
> > Subject: Re: [Antennas] Interesting article written by a ham
> >
> >
> > > On 12 Jun 04, at 21:29, George, W5YR wrote:
> > >
> > > > Excellent rant, Daniel, and well deserved I suppose.
> > > >
> > > > However, regardless of the physics, politics, awards, or
whatever,
> > > > NOTHING in this world is 100 % efficient compared to ANYTHING.
> > > >
> > > > 73, George W5YR
> > >
> > >
> > > I always thought that my little electric heater was 100%
efficient,
> if
> > > it ain't i'd like to know where the lost energy goes?
> > >
> > > I know the system from generation to my cold feet has losses, but
> > > I really thought the heater was lossless.
> > >
> > > Dave
> > > VE3HLU
> > > - - -
> > >
> > > Your moderator for this list is:
> > > Larry Wilson KE1HZ antennas-owner at mailman.qth.net
> > > _______________________________________________
> > > Antennas mailing list
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> >
> > - - -
> >
> > Your moderator for this list is:
> > Larry Wilson KE1HZ antennas-owner at mailman.qth.net
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