The receive and transmit frequencies of an Omni VI are determined by
three oscillators. The oscillators are the VFO (called the 5.0 - 5.5 MHz
PLL) , the band select oscillator (called the XTAL OSC) and the BFO.
The VFO is controlled by a bunch of digital circuitry, which has various
inputs such as the main tuning knob encoder, the sidetone setting, RIT,
XIT, etc. Ultimately it's accuracy is determined by the 20 MHz reference
oscillator on the LOGIC BOARD. Some reference oscillators are TCXO and
some are ovenized crystal oscillators.
The band select oscillators are crystal oscillators, which are also
locked to the 20 MHz reference oscillator on the LOGIC BOARD.
The BFO is also a crystal oscillator which uses two crystals and various
trimmer capacitors and switching diodes to produce one of five possible
BFO frequencies, necessary for all the TX and RX modes the rig is
capable of. The BFO is NOT locked to the 20 MHz reference oscillator.
In order to get the Omni VI frequency calibration correct on all bands
and modes, the 20 MHz reference oscillator needs to be correct AND the
BFO frequencies have to be correct.
DE N6KB
K9RT@aol.com wrote:
Is there a simple adjustment to calibrate the Omni 6+.?
Mine is off about 300hz and is just annoying enough to want to try and adjust
it for more accuracy.
Thanks
Dick K9RT
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