[TenTec] FT-2000 Webpage

[Bill Tippett]

 >I still can't understand why Yeasu and Icom don't use close in filters like
the Orion2???

         It's a problem fundamental to the design
of the rigs.  All Japanese rigs offer general
coverage and use an up-conversion IF scheme.
This puts their 1st IF at typically 40 or 70 MHz.
Most Ten-Tec rigs (excluding Paragon) are ham
band only and use IF's at a much lower frequency
(e.g. 9 MHz for Omnis and Orions).

         It's difficult and expensive to build a
600 Hz filter at 40 MHz.  A 600 Hz filter has
BW .002% wide at that frequency (600 / 40E6).
Conversely, 600 Hz at 9 MHz is 0.01% wide
(600/9E6), which is easier and less costly.

 >I'll have to wait until the testing is done on this unit in close in 2KHZ
dynamic range and where it falls in Rob's table.

         It should be very similar to the
FTdx9000 reported in ARRL's ETR tests, since
both front-ends are essentially identical.

(20 meters, 500 Hz BW, Preamp Off)

14.02 MHz 2 kHz – 87 dB* µTune
14.02 MHz 1 kHz – 70 dB* µTune
* Measurement was noise limited.

For comparison, Orion's measurements
with the stock 1 kHz filter were reported
by ARRL as:

14.02 MHz 2 kHz 92 dB
14.02 MHz 1 kHz – 84 dB

...and using the optional 600 Hz
Inrad #762, Sherwood reported:

"At 2 kHz spacing, the improvement is on the order of 6 to 7 dB.
At 1 kHz spacing the improvement is closer to 10 dB."

         The problem indicated by the *
under the Yaesu data simply means that
the measurement was limited by phase noise
rather than the IMD itself.  Also note these
measurements were using the uTune front
end accessory which is not standard in the
FT-2000.  Also notice the -17 dB change in
performance between 1 and 2 kHz above.
This is due to the fact that one of the 1 kHz
spaced interfering signals in the IMD test
fell within the 3 kHz BW, which was not
true for the 2 kHz spaced measurement.
This demonstrates why it is important to
have a roofing filter which excludes any
interfering signals, and also why there
should be little difference in Orion II using
the 300 Hz or 600 Hz filters, since either
would exclude a 1 kHz interfering signal.

 >I think the roofing filters are in the Yaesu Ft9000 and Ft2000? Not real
sure on the new Yaesu 2000 model. I believe the 
Icom 7800 does too, but both the
7800 and 9000 are out of my price range at the moment.

         The IC-7800 (latest version), FTdx9000
and FT-2000 all have 15 kHz, 6 kHz and 3 kHz
filters as standard equipment, so they should
all have similar performance for close-spaced
IMD.  Icom supposedly has improved the PLL in
the latest 7800 update so it will be interesting
to see if they have helped the phase noise
problem reported in the original units.  Rob
Sherwood has one of these now and he will
probably post some new measurements soon.

                                 73,  Bill  W4ZV

P.S.  Here are some good explanations by Inrad
and Sherwood regarding roofing filters, etc.

http://www.qth.com/inrad/roofing-filters.pdf
http://www.sherweng.com/Dayton_2004/Dayton_2004-Sherwood.pdf