[CQ-Contest] excessive bandwidth limits (was:CQ WW CW 2014 Results)

[Barry N1EU]

I applaud the efforts to nail down the exact meaning of "excessive
bandwidth" going forward.

btw, it's a trivial exercise to create a minute or two video/audio clip of
the SDR panadapter as "evidence."

I welcome the eventual possibility of no longer getting clicked/splattered
off my run frequency.

73, Barry N1EU

On Tue, May 5, 2015 at 10:22 PM, Jim Brown <k9yc at audiosystemsgroup.com>
wrote:

> On Tue,5/5/2015 4:11 PM, Paul O'Kane wrote:
>
>> Therefore, to get the ball rolling, I suggest that
>> excessive bandwidth be defined, in part, as follows -
>>
>>   CW  - width greater than 500Hz at 40db down
>>   SSB - width greater than 6kHz at 40db down
>>
>
> Having studied this matter for a while, and having done some measurements
> of my own, I'll throw these thoughts onto the pile. First, some numbers.
>
> My 2008 vintage K3 driving a 1980 vintage Ten Tec Titan to 1500W is 360 Hz
> wide at -40, 470 Hz wide at -50.
>
> Before the September 2014 firmware update and set for 6 msec rise time
> (it's slowest), a neighbor's FTDX5000 was 480 Hz wide at -40, 800 Hz wide
> at -50. After the update, the numbers are 410 Hz wide at -40, 600 Hz wide
> at -50. The greatest improvement with the new firmware is below -50 -- it's
> 1.7 kHz wide at -60 before the update,
>
> I'm measuring with a P3/SVGA hooked up to a K3, and the rig under test is
> driving a 500W dummy load. I'm using dits in the range of 30-35 WPM. I'm
> measuring in peak mode, and accumulating peaks for a while, so it's a worst
> case measurement.
>
> SO -- since the FTDX5000 was the widest of the modern rigs ARRL tested,
> I'd say your 500 Hz at -40 is a pretty good limit. Setting the rise time
> faster will cause it to be wider. Being careless with amplifier tuning, or
> using AGC between amp and rig, or using a dirty amp, will all make the
> signal wider.
>
> On SSB, I'd call 6 kHz wide at -40 pretty tight. That's what a K3 does
> with strong LF rolloff driving a legal limit power amp; an FTDX5000 is
> slightly better running 50W in Class A, slightly worse running Class AB.
> I'd call 7 kHz at -40 more realistic. SSB gets real wide real fast with
> distorted audio and those same problems with power amp setup. Again, these
> numbers are for accumulated peaks. One way to tell that it's an RF problem,
> NOT an audio problem, is when the waterfall shows horizontal lines going
> both sides of the carrier on voice peaks.
>
> The really dumb part of badly distorted, overdriven audio is that it makes
> the guys that do it really hard to copy.
>
> 73, Jim K9YC
>
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