[TenTec] Scout,Omni,TS 850 transmit

[Adam Farson]

Hi Bob,

Excessive transmitter IMD unnecessarily increases the  occupied bandwidth of
the transmitted signal, and has the potential to cause harmful
adjacent-channel interference ("splatter") - particularly to weak adjacent
signals. As the intermodulation products appear on both sides of virtual
carrier, excessive IMD also effectively degrades opposite-sideband
suppression. In extreme cases, the power contained in these products can
exceed regulatory limits for spurious emissions.

An SSB signal with high 3rd- and 5th-order intermodulation (IP3 and IP5) can
also sound rough and unpleasant to the listener.

The difference between -35 dBc and -25 dBc IP3 is 10 dB, i.e. 10X power or
1.5 S-units. This can make all the difference to a station in the adjacent
channel struggling to hear a "weak one" - particularly if the station with
poor transmitter IMD is running full legal limit.



-----Original Message-----
From: tentec-admin@contesting.com [mailto:tentec-admin@contesting.com]On
Behalf Of robert k stephens
Sent: Friday, August 23, 2002 21:26
To: tentec@contesting.com
Subject: [TenTec] Scout,Omni,TS 850 transmit


I think that my favorite non Ten Tec rig is  the Kenwood TS 850/870 series,
so I thought it would be interesting to compare  the quality of its ssb
transmit audio with the Omni V and my  Scout. Since there is a review of
the Mark V Field in Aug QST I have included that rig as well.

Transmit IMD         3rd order         5th order

Omni V               -30 dB            -45dB
Mark V               -31 dB            -44dB
TS 850               -28 dB            -40dB
Scout                -25 dB            -35dB

The Omni and Mark V are virtually tied for 1st place and my Scout is last.
I have a basic understanding of what receive IMD is but I really don't
understand what transmit IMD is. What effect does good or bad transmit IMD
have?  Can you hear it on the other stations receiver e.g., does it affect
perceived audio quality?  What other effects does it have? In comparing the
Omni to my Scout how much worse is the 3rd order -25 compared to the Omni's
-30 dB and how much worse is the 5th order -35 as compared to the Omni's
-45?    What difference does it make?

73
Bob KB1CIW




p.s.
Just for the heck of it I also compared the receive IF BW

Receiver IF BW

Mark V                281 Hz   to   2771 Hz   (2490 Hz)
TS 850                160 Hz   to   2456 Hz   (2296 Hz)
Scout                 181 Hz   to   2433 Hz   (2252 Hz)
Omni V                377 Hz   to   2289 Hz   (1922 Hz)