First I would like to thank all who have provided advice and comments. This is
a great reflector!Second I will fully explain my setup: Astron RS-35M to a
Samlex BBM-12100 battery backup module to a RIGrunner 4012 to the K3. The cable
between the Astron and the Samlex is #10 and about 6'6 long.
When switching my K3 from RX to TX 100W FM, I measured these voltage drops:
0.03V directly at the Astron RS-35M's output
0.25V at an unused output of a WMR RIGrunner, connected to the RS-35M by a
2ft cable
1.00V as indicated by the K3, connected to the RIGrunner by a 4ft cable
By cable I mean
@mailman.qth.net
Sent: Wed, 3 Jun 2009 17:59:42 + (UTC)
Subject: Re: [Elecraft] K3 voltage under load
When switching my K3 from RX to TX 100W FM, I measured these voltage drops:
0.03V directly at the Astron RS-35M's output
0.25V at an unused output of a WMR RIGrunner, connected to the RS-35M
On Wed, 2009-06-03 at 10:59 -0700, hb9brj wrote:
...
Guess the major problem resulting from voltage drop is a reduced efficiency
of the KPA3.
Actually, for a given power level the KPA3 probably has better
efficiency. For lowest heat in the PA, the supply voltage should be as
low as possible
I guess the most interesting thing is that we never heard back from Harris,
K9RJ, about his setup!
What se ye, Harris?
73,
Steve
NN4X
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Help:
I've made some measurements of my K3's efficiency versus DC supply
voltage, output and frequency at
http://www.cliftonlaboratories.com/elecraft_k3_efficiency.htm
Jack K8ZOA
www.cliftonlaboratories.com
Alan Bloom wrote:
On Wed, 2009-06-03 at 10:59 -0700, hb9brj wrote:
...
Guess the
The graphs show: the lower the power supply voltage, the higher the
efficiency.
The reason: When you set the K3 to, say, 100W it has to put 1.4A into
the 50-ohm dummy load (P = I^2R = 1.4^2 x 50 = 100).
The DC current through the PA transistors is pretty much directly
proportional of the RF
Alan,
Your analysis is correct - BUT --
Efficiency is one thing. but it has been previously discussed that
higher DC voltages result in improved IMD.
So the best voltage to be used is a compromise (efficiency alone is
not the only consideration). My preference is to stay with the 13.8 volt
Very true. There is a tradeoff between efficiency and distortion. The
K3 has good cooling, so for a fixed station where power consumption is
not an issue, you might as well keep the PS voltage fairly high. It
also might give you a little more power output 6 meters which tends to
run a little
I am running my K3 off an Astron RS-35M. No load voltage at the rig is 14.0V
(per the K3 display). Running approximately 100W this reading drops to 12.3V.
Is this the norm? BTW current reads just under 18 amps. The amp meter reading
on the Astron is way off.73 Harris K9RJ
I don't think that this is normal. It depends upon the voltage drop
on cable between the radio and power supply, as well as any voltage
drop inside of the radio. I actually was measuring this
yesterday. My supply reads between 13.7 and 13.8 on the K3 meter
under receive. With 100W keydown,
I own an Astron analog power supply, and there is NO fluctuation of voltage
under full load, without load, or anything in between. That's what a regulated
power supply is supposed to do. I would say you have a defective power supply.
Bill W5WVO
Harris Leck wrote:
I am running my K3 off an
At 6/2/2009 08:26 AM, Bill W5WVO wrote:
I own an Astron analog power supply, and there is NO fluctuation of voltage
under full load, without load, or anything in between. That's what a
regulated
power supply is supposed to do. I would say you have a defective power supply.
No, not necessarily.
Harris -
This is likely due to I squared * R losses in your DC cable; the voltage
is being reduced by the resistance of the cable. I had the same problem.
How long is it? What gauge is it? Are there any fuses or other items
in-line with it?
73,
Steve
NN4X
On Tue, Jun 2, 2009 at 2:07 AM,
It only takes about ** a tenth of an ohm ** between K3 and power supply to
drop 1.7 volts at 18 amps. Size of wire, bad crimp in a connector, tiny bit
of corrosion, etc., etc.
AND, the tenth of an ohm may be spread out in different places.
I have three feet of #10 to the K3, and I drop from
...@mailman.qth.net] On Behalf Of Harris Leck
Sent: Tuesday, June 02, 2009 2:08 AM
To: elecraft@mailman.qth.net
Subject: [Elecraft] K3 voltage under load
I am running my K3 off an Astron RS-35M. No load voltage at
the rig is 14.0V (per the K3 display). Running approximately
100W this reading
--- On Tue, 6/2/09, Ed K1EP k1ep.l...@gmail.com wrote:
From: Ed K1EP k1ep.l...@gmail.com
Subject: Re: [Elecraft] K3 voltage under load
To: Bill W5WVO w5...@cybermesa.net, Harris Leck
vk...@yahoo.com, elecr...@mailman.qth..net
Date: Tuesday, June 2, 2009, 12:39 PM
At 6/2/2009 08:26 AM, Bill W5WVO wrote
Maybe there's too much concern to do all the hand wringing?
It all depends on what's between the PS and the radio. In my case,
for example, my 13.8v supply feeds a West Mountain Radio battery
charger (200AH of battery), and there's a drop there (.4V). then to a
WMR distribution box and
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