Topband: Topband Digest, Vol 117, Issue 20

[k6xt]

An additional issue for weak sig CW folks is the nature of digi 
operations. Digi operators don't always check for pre-existing activity. 
The result is the digi setup begins its 1 minute of howling, 
irrespective of some CW activity already in progress. No problem to the 
digi operator whose setup will mindlessly repeat until acknowledged. A 
deal breaker to the CW activity.

Like Tom I neither endorse nor object to digi activity, except as it 
jams existing CW. I share his opinion that the frequency choice for digi 
activity could not have been more poorly chosen.

73 Art K6XT~~
Success is going from failure to failure without a loss of enthusiasm.
ARRL, GMCC, CW OPS, NAQCC
ARRL TA

On 9/16/2012 10:00 AM, W8JI wrote:
> Message: 5
> Date: Sun, 16 Sep 2012 03:25:01 -0400
> From: "Tom W8JI"<w8ji at w8ji.com>
> To:<topband at contesting.com>
> Subject: Re: Topband: The use of digital modes on 160 metres
> Message-ID: <F86C84D7C0764E30BDE23B7F70EAC56D at tom0c1d32a93f0>
> Content-Type: text/plain; format=flowed; charset="UTF-8";
> 	reply-type=original
>
>> >While there may be many that disagree with me I love digital modes on 160.
>> >I primarily use JT65 and it has been one of the reasons that I have worked
>> >Japan and New Zealand on TB. I use it primarily when my hearing
>> >disabillity kicks in and my ears start ringing and I work CW the rest of
>> >the time. I can tell you that my ears do not like CW close to the noise
>> >floor. The frequencies and modes most used (so far as I have heard) are
>> >1.836 6 for WSPR, 1.838 for JT65 and also 1.838 for PSK31.
> I'm not endorsing or objecting to the concept of digimodes on 160 meters,
> but whatever happened to the ARRL bandplan?
>
> http://www.arrl.org/band-plan-1
>
> Our region sets digital modes as 1800-1810.
>
> 1835 up though around 1840 is used by CW as a DX CW work when the band is
> busy. I often try to stay above 1835 on CW during European propagation times
> to stay out of other people's hair when the band is very good and crowded
> with stations.
>
> The problem with digital modes, in my opinion, is they often are not
> generated and decoded properly. They are generally audio baseband signals
> converted up to RF by a normal cheap transceiver's SSB chain, and converted
> back down through the SSB receiver.
>
> This means most digital modes are subject to all the hum, noise, carrier
> suppression, opposite sideband suppression, and limited dynamic range of any
> SSB system. The limited dynamic range, caused by dumping encoded baseband
> audio into a SSB audio input and decoding through a SSB audio output, is why
> digimode people have such an affliction about power amplifiers. The
> transmitter system has all the issues of any SSB system. To "cure" the
> problem of IMD or maladies like hum, noise, or harmonic distortion inherent
> in any SSB communications system, they simply mandate making the signal
> weaker, so the inherent problems are buried in band noise.
>
> 160, because band layout is different than other bands, is a particularly
> unwise place to stick digimodes between normal SSB operations and weak
> signal CW operations. Had digimode positioning been planned by experienced
> 160 operators and people who understand SSB systems, instead of 160 novices
> or those unfamiliar with SSB system issues as they relate to dynamic range,
> digimodes would never have been placed in an existing  DX communications
> band area between 1835 and 1840.
>
> The root of this problem is inexperienced people who just decided a 100Hz
> (or whatever) wide varying amplitude audio signal into a TX SSB port always
> comes out exactly 100 Hz wide without hum, noise, carrier, harmonic
> distortion, or other inherent SSB transmitter maladies. Worse of all,
> "planning" never considered the CW area of 160 is "upside down", and the CW
> weak signal working band for the last 40 years primarily was 1825-1835+.
>
> >From a purely technical standpoint, use of 1835 to 1840 is one of the worse
> ideas ever. This puts SSB transmitters down to 1835 or less dial setting,
> right in what was a weak signal area, usually in the hands of people who
> don't have a clue how the baseband-to-RF modulation and demodulation systems
> work.
>
> This is entirely different than 80 meters on up, where there is an
> incredibly wide buffer area for digimodes and weak signal work areas. On
> 160, lack of technical planning and experience with the band has now placed
> splattering or harmonic distorted signals, or placed common wiring design
> issues where people insist on running unbalanced lines grounded at each end
> between computers and the transmitter, right against (and into) two
> traditionally weak signal areas.
>
> Eventually this might evolve into a solution, but that might take years if
> it ever happens. What will happen if digimodes stay between 1835 and 1840 is
> the DX area near 1835 will get pushed downwards by headaches with less than
> paper-perfect SSB transmitters, and SSB DX will get pushed upward away from
> 1840 or less as the lower voice channel edge.
>
> What I stated above, which is factually accurate, is why so many people
> resent audio tone software experimenters deciding they could just wiggle
> right into what were existing weak signal CW and SSB areas.
>
> Many times over the winter season, I hear harmonics of audio tones well off
> the baseband bandwidth. I have to decode the signal to see who the guy is,
> and then try to convince him he has an issue with what he thinks (because he
> read it someplace) is a 50 Hz wide signal.
>
> The entire notion of using 1835 to 1840 without proper band use and
> technical limitation investigation was either dumb as a rock, or terribly
> inconsiderate. Anyone understanding how band usage already worked and how
> **real** SSB systems work never would have used a 5 kHz slot in an area
> already used by weak signal operators.
>
> 73 Tom