Re: [Elecraft_K3] K3/P3 video display on AM vs SSB


Joe Subich, W4TV
 

But the difference is the display is the question. WHY?
Are you using the peak hold mode for voice modulation as Al ask
and I told you how to enable? There is a significant difference
between a static display of 1 KHz modulation and the dynamic
display of voice modulation. When you enable averaging, the
sideband level will appear lower based on the length of each
dynamic element as a percentage to the total averaging time.

*USE PEAK HOLD* and see if the peaks in the sidebands aren't
close to -6dB compared to the carrier.

73,

... Joe, W4TV


On 2015-07-03 2:53 PM, Mel Farrer farrerfolks@yahoo.com [Elecraft_K3] wrote:
Yes, Joe,
But the difference is the display is the question. WHY? My 8920 show proper power distribution on the sidebands, the P 3does not!!!!!!!


Mel, K6KBE
From: "'Joe Subich, W4TV' lists@subich.com [Elecraft_K3]" <Elecraft_K3@yahoogroups.com>
To: Elecraft_K3@yahoogroups.com
Sent: Friday, July 3, 2015 11:35 AM
Subject: Re: [Elecraft_K3] K3/P3 video display on AM vs SSB


> Then I had him set up his RCA AM transmitter to monitored 1 KW
> carrier on the bird.


Which is, of course, illegal as soon as he modulates the transmitter.
A 100% modulated 1 KW AM signal is 4KW PEP ... the legal limit (in the
US) for AM is now 375 W carrier => 1500 W PEP just like every other
mode.


With the Peak averaging set to max, the side band AM signals were
> 20-25 dB down from the carrier.


You are not measuring peak audio components - you are measuring the
average audio level. Instead of average, select MENU:PEAK to turn
on "spectrum peak hold" and set averaging to the minimum.


73,


... Joe, W4TV


On 2015-07-03 1:29 PM, farrerfolks@yahoo.com [Elecraft_K3] wrote:
OK, Alan, Thanks for the input.

Here goes. I am monitoring a friend near by, 15 miles. I took care
to have him set up the 100 W SSB station and his 1KW AM station like
this.

In CW mode, send a 100 W measured carrier. I recorded the level on
the P3. Then had him transmit normal voice levels and the peak SSB
audio components reached the same level as the CW signal on the P3.

Then I had him set up his RCA AM transmitter to monitored 1 KW
carrier on the bird. I recorded the level on the P3, ~1-2 dB of 10
dB more than the CW signal. Same antenna on both.

I had him transmit a 1 KHz tone 100 % modulated and yes, the 1 KHz
was 6 db below the carrier at 1 KW on the P3.

Now I had him talk to the 100% modulation point on the AM
transmitter.

With the Peak averaging set to max, the side band AM signals were
20-25 dB down from the carrier.

If the premise is that a 100% modulated AM signal has 50% of the
power in the sidebands and 25% on each side, that is 500 watts total
audio and 250 watts on each side. So the level should be only 6 dB
down from the carrier.

The only difference is the complex audio components vs the signal
tone. So why is the SSB signal peaking at the 100 watt level and the
AM signal 10 to 15 dB lower?

Comments appreciated....

Mel, K6KBE
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