To all those on Topband who asked...here is the results of the TS-940
tests.
73 Carl KM1H
--------- Begin forwarded message ----------
From: km1h@juno.com (km1h @ juno.com)
To: wsvhf@qth.net
Subject: [WSVHF] TS-940 Specs
To: <topband@contesting.com>
Date: Tue, 09 Sep 1997 22:35:15 EDT
Message-ID: <19970909.214104.9687.15.km1h@juno.com>
As an addition to the Sherwood receiver info, here are some specs on a
TS-940.
All tests were run on 28MHz during the past few days on a customers unit.
TS -940 late serial # with factory phase noise updates:
MDS SSB -135 dBm
MDS CW cascaded 500Hz filters -137 dBm
Sensitivity 10dB S+N/N .12uv
Phase Noise -131dBc at 10 KHz
Filter rejection CW >90 dB
2 tone dynamic range Wide 95 dB @ 20 KHz
2 tone dynamic range Narrow ( CW Filters) 77 dB @ 2 KHz
3rd Order IP +1dBm at 20 KHz
Wide Band transmitted noise -75 dB below full carrier
The same TS-940 but with PIN diode mods to RF and IF boards:
MDS SSB -137dBm
MDS CW -142 dBm
Sensitivity ~ .1uv
Phase noise -131 dBc @ 10 KHz
Filter rejection ( CW ) >90 dB
2 tone Dynamic Range Wide 102 dB @ 20 KHz
2 tone Dynamic range Narrow ( CW Filters) 83 dB @ 2 KHz
3rd Order IP +5 dBM @ 20 KHz
Wide band transmitted noise -90 dB below full carrier
A few notes and comments:
Although the PIN diode improvement is evident in the numbers the audible
difference is much greater. First of all the receiver is noticeably
quieter. The IMD performance shows an "apparent" improvement of about
10-12 dB under crowded band conditions. This follows along with
conversations I had with Dr. Ulrich Rhode several years ago when I first
started using PIN diodes. The cumulative effect of multiple strong
signals degraded IMD performance in a stock receiver a lot more than a
simple 2 tone test would indicate. The receiver is a pleasure to use in
lowband pileups now.
The improvement in wideband TX noise is due to, I believe, the use of
PIN's in those paths that were common to TX and RX on the IF board. The
stock diodes either generated noise or allowed RX path noise into the TX
path. The same appears to hold true in the opposite scenario. This TX
noise is something I was recently made aware of by a local on 6M and
bears closer examination and possible additional improvements. The noise
does not change dB levels when going from full power to the 20-30mw from
the transverter port so it can not be blamed on thermal noise in the
subsequent linear amp stages.
Magazine reviews of the TS-940 were of early production. Kenwood at first
refused to admit to phase noise problems. They then went thru two
different mods before they were satisfied. The improvement between early
and late models is about 15 dB.
Serial numbers in the mid 8 Million group and up had factory mods.
Kenwood Service Bulletin 917 may be retrofitted to the earlier radios. It
is a fairly simple mod.
Other KW radios such as the TS-850 and TS-930 could also benefit from PIN
mods. They both have transverter ports and are quite reasonably priced on
the used market.
I cant speak for other brands but a quick review of a few Service Manuals
shows an awful lot of commonality across all brands with respect to diode
switching schemes.
73....Carl KM1H
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