----- Original Message -----
From: "Roger (K8RI)" <k8ri@rogerhalstead.com>
To: <amps@contesting.com>
Sent: Wednesday, December 28, 2011 6:03 PM
Subject: Re: [Amps] Fwd: Linear Amplifier Tuning---PROPERLY!
> On 12/27/2011 11:27 AM, Jim Thomson wrote:
>> Date: Sun, 25 Dec 2011 13:34:03 -0800 (PST)
>> From: Commander John<crazytvjohn@yahoo.com>
>> Subject: Re: [Amps] Fwd: Linear Amplifier Tuning---PROPERLY!
>>
>> I fail to see how having spurious sidebands at -20, -30, -40?or whatever
>> makes the??????????????
>> Signal wider.? The sidebands are still there regardless of
>> final?suppression level.
>>
>> ### You are confusing sidebands with IMD. This is NOT FM. It's
>> SSB. IMD is caused by non linearity.
>>
>>
>>
>> It is the receiving stations receiver having the rejection ability that
>> reduces received?interference.?
>>
>> ### wrong again! IF station XXX using his ICOM on TX....is 10 khz
>> wide... then he's 10 khz wide. If you are 3 khz away, you are now
>> screwed, and there is no filter on the the planet that's gonna do any
>> good. He's Txing on your RX passband, so his TX IMD is now
>> overlapped with your RX passband.
>>
>>
>>
>>
>> Having adjacent sidebands that are stronger than necessary causes a
>> receiving station to hear these sidebands at a harmful signal?strength
>> further away from the transmitted frequency than if they had supression
>> at a highter level
>>
>> ## It's adjacent IMD, not sidebands.
>>
>>
>>
>>
>> A legal limit station would have much stronger IMD because it is stronger
>> not wider.? It only is preceived as wider because they are stronger than
>> from a 100 watt transmitter.?
>> ## That all depends on how loud his IMD is to start with. But yes, if
>> 2 x stations have the same IMD... but one is 10db louder than the other
>> [say a bigger ant or amp].... then the station with the 10db syronger
>> signal will also have IMD that's also 10db stronger. Which is all the
>> more reason to have a cleaner signal when u have a big amp, and big
>> towers' ants etc.
>>
>> ## No point in all these deluxe receiver's with 100db dynamic range.
>> It's of now use,and pointless on ssb. Not until the TX IMD gets
>> improved on these ham xcvr's. The Icom's are 10 khz wide when u stuff
>> white noise into them...and the yaesu 5000 in Class A is only 3.5 khz
>> wide [both measured at the -45db point]. The bands are NOT crowded .
>> They are just jammed full of sub standard xcvr's..which is most of
>> them.. with junk TX portions. If everybody got heir act together, you
>> could easily double the number of ssb signals on a given band. You
>> could triple that if everybody had class A, or the eq.
>
> Just think what the bands would sound like if we were still using SSB
> rigs from the 60's<:-)) Even the Collins and Hallicrafters were not all
> that great. There were exceptions, but not many.
>
> Of course it's not just crappy IM from many of today's SS rigs. Many of
> them give the operator so much control over the signal they end up
> generating garbage up and down the band quite a ways trying to find what
> they think is the perfect, tailored audio. "I think" if you find
> noise/splatter/buchshoting more on one side than the other it's probably
> related to IM as IM can be much more prevelant on one side than the
> other. OTOH over driving the amp usually ends up with buckshot and
> splatter pretty much equal on both sides. Neither is likely to result in
> a nomination for "ham of the year".
>
> 73
>
> Roger (K8RI)
>
>>
>> Jim VE7RF
If you really looked at the specs of those rigs you would see that IMD wasnt
as bad as many SS rigs are today. Most were in the -25 to -40's and the amps
were generally in the -30's. Not great but acceptable.
The transmitters, transceivers and receivers had minimal phase
noise....which is reciprocal. As one who did a lot of contesting during
those years the band crud wasnt even close to what it is today. Speech
processors were mostly in the future and optional stand alone accessories.
The huge majority ran amps at about 1200W PEP output which is ~3dB below
many that are on the market today and dont try to tell me that those are all
run at only 1500W! The QST IMD reviews are at 1500W, not where the tubes are
run into saturation.
Carl
KM1H
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