On 4/28/2014 8:37 AM, Vic Rosenthal K2VCO wrote:
What should work is to use the spectrum display of the P3. If you want to know, for example, the bandwidth of a signal at 30 dB down, you just find the points where the 'skirts' of the signal are 30 dB below the peak. This is easy to do on the P3 which can display the signal strength in dBm.
Yes. And as N1AL recommends, use peak hold. I've done spectrum plots of various signals and conditions with the P3. I usually set the SCALE for a pretty wide range (like 72 or the full dB), and set the SPAN to about 10 kHz. I use both the Peak Hold Mode and the Average Mode. In both modes, but especially with Peak Hold, we must take care to differentiate sidebands from other stations. I try to set the reference level so that the peak of the signal is at one of the level lines and the noise level is near the bottom of the display.
With almost any rig, you'll see small signals down the sides of the slope that are intermod products, and they are usually symmetrical on a CW or RTTY signal. A clean SSB signal should be well confined by the bandpass filter limits of the audio and TX filter skirts. Anything that extends beyond that is IMD. When a rig is badly overdriven, it's common to see splatter as horizontal streaks extending above and below the signal frequency.
Last week, I was on 20M SSB trying to work a weak DX station, but what I heard was massive splatter from a QSO about 5 kHz up the band. One guy was relatively clean, but the other was not. I broke the QSO to tell him he was clobbering a weak DX station. Turns out he was an aeronautical mobile using whatever radio was onboard. He didn't know whether he was transmitting AM or SSB, but thought it was AM. I assured him that it was, indeed, USB, and that the problem was that he was likely overdriving it badly. He went QRT to figure it out.
As a percentage of transmitted signals, I don't find contesters any better or worse than non-contesters -- we contesters stand out because during a contest, there are a LOT more of us. :) I'm retired, so I have access to the ham bands during the day (when I'm not working on something else). It's not at all uncommon to tune around 30, 40, and 80 during a weekday and hear fewer than a half dozen signals on these bands (if you hear any at all), and no more than a few dozen on most of the higher bands. Compare that to a major contest, when there are several hundred workable signals on every band from any given location for the duration of the contest, and for stations with better antennas, perhaps 2-4X that number. The winners of contests like the ARRL SSB Sweepstakes make more than 2,000 QSOs, and you can work a station only once.
73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
