Topband: TB digital

[MIKE DURKIN]

Can you copy 25 stations that are at noise level at 25 wpm at the same time? All in a 1.4khz spectrum?


Fantasy is your part of the wet noodle of an antenna ....

Mike KC7NOA 

Using psk31 ... my computer can ... 

> Date: Sun, 16 Sep 2012 20:46:19 -0700
> From: jim at audiosystemsgroup.com
> To: topband at contesting.com
> Subject: Re: Topband: TB digital
> 
> On 9/16/2012 7:16 PM, wa3mej at comcast.net wrote:
> > Finally,  you cant mean to tell me that the little bit of space being used by digital at the top of the CW window causes a hardship on anyone.. heck half of the time the SSB stations are even down there and no one growls about that.. and wait until a SSB contest you wont find an empty spot in the CW band.. so what is the beef with 5 KHz or less being used, sometimes for a sound card digital mode when much of the CW band is empty 75 percent of the time.
> 
> Right. And for the record, JT65 uses ONLY 2 kHz between 1838.5 and 
> 1840.5, and it's not unusual for there to be 6-8 signals in that bandwidth.
> 
> Another point -- most digital operators I know LISTEN to their receiver, 
> especially when running RTTY, JT65, FSK441, and ISCAT.  If you're 
> listening, of course you're going to hear if another station is there -- 
> assuming your noise level isn't too high.  AND, because you've got a 
> spectrum display in front of you tuned to that 2 kHz bandwidth, and so 
> does everyone else operating that mode in that space, any rig with hum, 
> buzz, or audio harmonics is going to stand out like a you know what in 
> the punchbowl.
> 
> AND, if all these signals were as full of hum and buzz as you imagine, 
> the combined hum and buzz resulting from all those guys transmitting at 
> once with their VFOs all set to 1838 USB would be very close to zero 
> beat, and would more or less add by 3dB for every doubling of the number 
> of dirty signals.  Reality is that it doesn't happen that way, because 
> digital operators are NOT mostly lids, they DO work on making their 
> signals as clean as they know how, and other digital operators will make 
> sure that they do because they don't want the QRM.
> 
> And since which is 1835-1840 "reserved for weak signal work?"  I've been 
> on Topband for a while, but this is news to me.  There used to be a "DX 
> window between 1830 and 1835, but that's long gone.
> 
> But all of this begs the obvious question -- if I'm here in California 
> having fun on my run frequency in a contest (CW, of course) and 2,500 
> miles away in GA Tom want's to work an S1 station who just got spotted 
> on my frequency, which I've busted my butt to find and hold..You think I 
> should QSY?  Heck no. Now tell me how that is different from some guys 
> mostly running 10-20 watts, mostly into a wet string, using about 200 Hz 
> in a 2 kHz chunk of spectrum?
> 
> 73, Jim K9YC
> 
> 
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