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In response to Lee's question about filters and the OMNI 6 use
in a heavy rf environment:
While I'm not a full time heavy duty contestor, I have been in
quite a few and in the Multi-Multi arena, and my experience shows
the opposite of what was reported by the KH7 group.
It was always an eye opener to go from station to station of
Yeasu and Kenwood rigs with BP filters and have to dodge the
images of the other stations, until I got to the Ten Tec, where I
would only hear what I was supposed to.
Use of direct digital synthesis generates products throughout the
spectrum, albeit the modern super rigs have it well under control.
The best I've seen in controlling it was the Yeasu FT 990.
The heterodyne scheme of the OMNI-5 & 6 totally eliminate these
products and make not only for a cleaner transmitter, but a
cleaner receiver .
I have see "Filter Blow-by" in my SIX, but not of any great concern.
Local KW stations with antennas pointed at me quite often are seen
beyond the filter bandpass, so there could be a effort made there, and=20
after market filters may be better.
Now - let's look at the Yeasu FT-1000 with the mechanical filters. Much
lower total attenuation numbers than the standard TenTec filters.
Mechanical filters were never found to have a great out of bandpass
attenuation. Their advantage was in shaping, with a clean roof in the
bandpass and symmetrical front and back porches. This allowed Collins
to change sidebands merely by moving the carrier frequency from
one side to the other and maintain good quality, as opposed to
the normally used scheme of heterodyning from above or below
to switch sidebands.
All of these things would lead an engineer to believe that the OMNI 6
would inherently be better in a high rf environment than the
competition.
Why do other contestors use the JA radios? Why do some people
insist Chevies are better and others just as intelligent, insist Fords
are better? There is a human factor that just will not go away.
Don't confuse me with facts, my mind is made up!
de KL7HF
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<BODY bgColor=3D#ffffff>
<DIV><FONT color=3D#000000 size=3D2>In response to Lee's question about =
filters and=20
the OMNI 6 use</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>in a heavy rf =
environment:</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>While I'm not a full time heavy duty =
contestor,=20
I have been in</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>quite a few and in the Multi-Multi =
arena, and my=20
experience shows</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>the opposite of what was reported by =
the KH7=20
group.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>It was always an eye opener to go =
from station=20
to station of</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>Yeasu and Kenwood rigs with BP =
filters and have=20
to dodge the</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>images of the other stations, until =
I got to the=20
Ten Tec, where I</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>would only hear what I was supposed=20
to.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>Use of direct digital synthesis =
generates=20
products throughout the</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>spectrum, albeit the modern super =
rigs have it=20
well under control.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>The best I've seen in controlling it =
was the=20
Yeasu FT 990.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>The heterodyne scheme of the OMNI-5 =
& 6=20
totally eliminate these</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>products and make not only for a =
cleaner=20
transmitter, but a</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>cleaner receiver .</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>I have see "Filter =
Blow-by" in my SIX,=20
but not of any great concern.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>Local KW stations with antennas =
pointed at me=20
quite often are seen</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>beyond the filter bandpass, so there =
could be a=20
effort made there, and </FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>after market filters may be =
better.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>Now - let's look at the Yeasu =
FT-1000 with the=20
mechanical filters. Much</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>lower total attenuation numbers than =
the=20
standard TenTec filters.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>Mechanical filters were never found =
to have a=20
great out of bandpass</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>attenuation. Their advantage was in =
shaping,=20
with a clean roof in the</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>bandpass and symmetrical front and =
back porches.=20
This allowed Collins</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>to change sidebands merely by moving =
the carrier=20
frequency from</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>one side to the other and maintain =
good quality,=20
as opposed to</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>the normally used scheme of =
heterodyning from=20
above or below</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>to switch sidebands.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>All of these things would lead an =
engineer to=20
believe that the OMNI 6</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>would inherently be better in a high =
rf=20
environment than the</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>competition.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>Why do other contestors use the JA =
radios? =20
Why do some people</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>insist Chevies are better and others =
just as=20
intelligent, insist Fords</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>are better? There is a human factor =
that just=20
will not go away.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>Don't confuse me with facts, my mind =
is made=20
up!</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>de KL7HF</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV></BODY></HTML>
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