OMNI V BFO Mod
Mod: Provides a means of varying the bfo frequency on the CW and LSB modes.
History: The Omni V has no RIT. Offset tuning is accomplished by operating constantly in the split mode. This is cumbersome. Installing a real RIT control would be overly complex. This mod provides the next best thing.
Specs: Allows frequency of bfo oscillator to vary over a 600hz range.
- To allow changing the audible pitch of incoming cw signals without engaging the "split" mode.
- Allows the operator to change the bfo offset at will for a more comfortable pitch.
- Increases convenience during NET operations allowing one to ( tune in) off channel signals and quickly QSY to another frequency without pushing the split and a=b buttons.
- 1ea. 68pf disk ceramic capacitor
- 1ea. 12k 1/4 watt resistor
Parts Cost: $2.50
- Remove C3 from the transmit audio/bfo board. If you are careful and lucky, this cap can be crushed with pliers and the remaining lead used as a connecting point for the new cap. Otherwise, you will need to remove the board. The latter makes for a neater job anyway.
- Solder the anode lead of the NTE612 to the ground lead of R21
- Solder a lead of the 68pf cap to the cathode lead of the NTE612
- Solder the other lead of the 68pf cap to the ungrounded lead of the former C3.
- Locate the IF/AF board. Locate connector 53. Pull the wire out of the center pin. This wire comes from the wiper of the notch control and provides a variable source of dc regulated and well filtered voltage. Other controls could be used but would prove more complex.
- Extend this wire up through the large hole in the back of the chassis up to the tx audio/bfo board.
- Solder the 12k resistor to the end of this wire.
- Solder the other end of this resistor to the junction of NTE612 and 68pf cap.
- Set the notch control to the center position.
- Connect the frequency counter to the hot side of R30.
- Apply power to the rig and adjust C4 for exactly 9mhz.
- While you're at it, adjust C6, C7, C10 and C9 per instructions on page 6-57.
Note: If the 250hz filter is used, the PBT may need readjusting when the bfo is varied over a wide range.
For those who like the notch function. The tone control or squelch could be used since they are all 10k pots. The regulated voltage source can be applied to the top of either pot and the bottom end grounded. The wiper can then be routed as previously outlined.
For you who like the looks of a good mod may I suggest drilling a hole and mounting a new pot right in the middle of the word Ten-Tec on the front panel. Rename the rig Omni V+. This should increase it's value at least $300. I suggest a bright red knob with BFO written on it with a Marksalot.
Need Help? Be glad to! 73