In the past on this reflector, there's been various comments
saying that the Omni D version B (model 546B) can not be put onto
30 mtrs due to its crystal mixing scheme and resultant spurious
emissions.
Two calls to Ten-Tec counter that.
The tech/repair dept says that many were modified to work on 10MHz
transmit
but that due to the age of the rig, the parts are no longer available.
The coils, etc are no longer being made and the stocks are depleted.
I was rather annoyed by their attitude when I asked if the component
values were available. Their claim was that the info was discarded, etc.
They seemed to feel, (as to the Japanese companies) that I shouldn't
expect
detailed support for a rig "that old".
In any event, I did some experiments. As originally configured in the
10 Mhz position, the low power band-pass-filter is left open in
the 10MHz position. The RF output lowpass filter is jumpered straight
thru, allowing 10MHz receive.
I jumpered the 14MHz low pass filter to the 10MHz postion and tried
using
the 7MHz BPF and then the 14MHZ BPF. RF output on 10MHz was around 5
watts using the 14MHz BPF and around 30 watts using the 7MHz BPF.
When the BPF was jumpered straight thru, output rose to 100 watts.
Thus the 14MHz LPF works well and should suppress the 2nd and higher
harmonics
of 10MHz. The only apparent problem is the BPF.
Does anyone know the component values (coil inductance or overcoupled
transformer
values, etc) for the low power Band Pass filter? Apparently a parts kit
was
sold for over 10 years.
With the proper BPF function, the 546B should meet spurious emission
specs.
Again, Ten-Tec apparently modified many of them.
Better yet, anyone have one of the old kits lying around that was never
installed??
If all else fails, I'll try to design my own band-pass filter....
I currently don't have access to a spectrum analyzer so complete testing
is
difficult.
73,
Doug/WA1TUT
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