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Author Topic: Are wide signals + IMD on SSB more important than click on CW?  (Read 3162 times)
NO9E
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Posts: 406




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« on: February 27, 2013, 11:16:20 AM »

W8JI led a crusade against clicks on CW. He has largely won but there are still a few operators who have almost 2 KHz clicks  and do nothing against because the clicks clear frequencies around.

In recent CQ 160 SSB, a midwestern strong station was taking almost 8 KHz. The main signal was about 2.5 KHz wide. However his sidebands were as long and only 20-25 db below; -25db during the first second and -20 later. There was no way to hear 100W stations within 4 KHz of his signal. Unless one had a receive antenna back to him. He made an excellent score, partly due to excellent antennas and partly due to having clear frequency for listening.  He has no incentive to improve his TX signal.

There are two ways for narrower SSB signals. First, amps with low IMD and using 50W drive so that 100W rigs generate less IMD. For example K3/Alpha combination. Second, radios with adjustable bandwidth. Many stations use 1.8 KHz on receive, meaning the frequency response around 300-2100. Yet nearly all rigs generate 2.4k-2.7 K signals.  Should we petition the manufacturers to produce radios with sharp frequency cutoffs, like in receive?
Or, with adjustable IMD  Grin.

Ignacy, NO9E



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W8GP
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Posts: 213




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« Reply #1 on: February 27, 2013, 12:09:46 PM »

CW and SSB IMD are equally important.Sometimes splatter is caused by operator error and sometimes by operator intent.No matter how clean your rig/amp is, it won't take care of the latter. Also, some rigs can generate higher IMD when operated at reduced power due to ALC issues.
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M6GOM
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Posts: 915




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« Reply #2 on: March 02, 2013, 06:31:52 AM »

I reported one Russian station in the CQ-WW contest last October. Apparently I wasn't the only one. 7kHz either side of his center frequency he was S9 and that was narrowing my TS590 down to 1.8kHz.
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NO2A
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Posts: 786




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« Reply #3 on: March 24, 2013, 04:50:18 PM »

I`ve heard this much more on ssb then I ever have on cw. The other night I heard an am station on 75m 8khz away,but at least he was on am.
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