key down voltage drop

[k6xr]

What is the normal voltage drop on a power supply 13.4 volts with a k2 at 15
watts output? My power supply drops to 12.1 volts. My ts570 at 100 watts
only drops .2 of a volt so I am curious.

Reggie

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[Bob Boehmer]

Reggie -

That is really dependent on two things: the power supply design and the
current you are drawing. Are you using the same power supply for both the
ts570 measurement and the k2 measurement? (Also if you have a light gauge
wire between the power supply and the k2 and are using the K2 voltage
display for your measurement you will be getting some drop across the wire.)

73,
Bob, WB3FXC



> What is the normal voltage drop on a power supply 13.4 volts
> with a k2 at 15
> watts output? My power supply drops to 12.1 volts. My ts570
> at 100 watts
> only drops .2 of a volt so I am curious.
>
> Reggie

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[Dan Barker]

That is very odd indeed.

You should measure at the other end of the wires, to see what the radio is
seeing, but I'm afraid that would make it even worse.

Can you measure the current being drawn? That would be an interesting
figure.

Are you certain RF isn't getting into the PS or the meter?

13.8 - 12.4 is more than .2 volts! 1.4 comes to mind.

A 3 volt drop in a 35 amp supply just doesn't compute. Maybe if you were
using a long 18 guage wire and measuring at the rig, but you aren't!

You mention 5x9 signal reports. Any reports of any other artifacts (other
than Strength)?

Keep us posted!

Dan / WG4S / K2 #2456


k6xr Sent: Thursday, September 16, 2004 2:44 PM

Hello Dan and thanks for your thoughts.

I installed both the 570 and the k2/qrp and k2/100 on a astron AS35a power
supply.
I connected a voltmeter across the power supply terminals and keyed each rig
on 20 meters at 1.0.1 swr at 100 watts output.
power supply voltage unloaded measures 13.8 volts.

ts-570 drops voltage down to 12.4 volts
k2/100 drops voltage down to 10.8 volts.

k2/qrp at 15 watts drops down to 12.1 volts.

the reason for all this is that I kept getting 558 557 598 signal reports
and decided to see if I had a voltage problem.


Dan Sent: Thursday, September 16, 2004 10:08 AM

Something ain't kosher.

Are you measuring the same thing on both radios? With the same PS? With the
same meter? What you describe doesn't fit in with my view of "Voltage Drop".

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[Don Wilhelm-3]

I would suggest that the problem is inside the power supply - perhaps
something as simple as a poor connection on the inside of the output
terminals.  Even the drop you are seeing with the TS-570 seems excessive to
me.

We don't know the actual current being drawn, but it may be quite different
with the 100 watt TS-570 and the K2 (the K2 may actually draw more under
these conditions).  I am not familiar with the TS-570, but many other
transceivers will simply produce less power with a lowered voltage, but the
K2 will attempt to draw more and more current with reduced voltage levels in
an attempt to produce the power output that has been requested - this is
done by the K2 internal ALC function.  That COULD explain part of the
voltage with the K2 at 100 watts, but it does not explain the 12.1 volts
with the K2 at QRP levels - something very strange is present here, and
IMHO, the 'cure' will be found in the power supply.

73,
Don W3FPR

----- Original Message -----
From: "Dan Barker" <[hidden email]>

> That is very odd indeed.
>
> You should measure at the other end of the wires, to see what the radio is
> seeing, but I'm afraid that would make it even worse.
>
> Can you measure the current being drawn? That would be an interesting
> figure.
>
> ---------------------------------------------------------------------------
>
> k6xr Sent: Thursday, September 16, 2004 2:44 PM
>
> Hello Dan and thanks for your thoughts.
>
> I installed both the 570 and the k2/qrp and k2/100 on a astron AS35a power
> supply.
> I connected a voltmeter across the power supply terminals and keyed each
> rig
> on 20 meters at 1.0.1 swr at 100 watts output.
> power supply voltage unloaded measures 13.8 volts.
>
> ts-570 drops voltage down to 12.4 volts
> k2/100 drops voltage down to 10.8 volts.
>
> k2/qrp at 15 watts drops down to 12.1 volts.
>
> the reason for all this is that I kept getting 558 557 598 signal reports
> and decided to see if I had a voltage problem.
>

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