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


Mel Farrer <farrerfolks@...>
 

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@... [Elecraft_K3]"
To: Elecraft_K3@...
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@... [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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