Regarding the K3, select an antenna, be sure RF gain is at max and turn
AGC OFF. Set the display to AFV for a couple seconds. This provides a
baseline value against which the DBV display is calculated. (This means
dB in terms of voltage, not the traditional, standard dBv. Thus 2x the
voltage is shown as a 6 dB increase.)
The measurement time is either 0.5 seconds or 1.0 seconds in the DSP
code. The AFV TIME config menu item is either 500 (for 500
milliseconds, or 0.5 seconds) or 1000 (for 1.0 seconds). You'll want to
dwell on a signal for twice that period to be sure the reading is
accurate, then jot it down. Now switch antennas, wait again and then
jot it down.
The calculations in the DSP are true RMS calculations over the time
period. The previous results are not averaged. Each measurement time
is independent.
73,
Lyle KK7P
On 9/28/15 7:39 AM, Bill Conwell wrote:
I'd like to do some quick and dirty comparing of antenna output signals
using my K3 (and/or P3).
(I've got two antennas I'd like to compare using different received carrier
signals - e.g., from a neighbor's TX, W1AW RTTY bulletins, etc.)
I see that the K3 can display the RMS value of receiver AF output (mVp-p),
unaffected by AF GAIN control. And after that stabilizes, I can also get
dbV to display. (How long is the stabilization period? Does the display
sample and hold a single value, or is it averaged and continuously updated?
It seems like the former.)
Is this the way to go, or is there something I can do with the P3 that will
give a readout in dBm? (I guess I could make a rough graphical measurement
by setting the P3 display threshold to match the weaker signal, then
switching to the stronger signal, and seeing how far above that threshold it
rises - with Scaling maximized.)
I know there's also W8WWW's S-Meter Lite, with which I've also dabbled -
presenting a digital S-meter, or relative dB, output. (Or I could do a step
attenuator approach, but then I couldn't compare by simply flicking the
antenna switch, and QSB would be a problem.)
Thoughts?
Tnx,
/Bill, K2PO
Portland, OR
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