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Here's a more complete quote from that webpage, also showing the previous paragraph. ?He's got some high level diode ring mixers that want +17 dbm and +7 dbm at the local oscillator port. ?The mixers on the ubitx have schottky diodes, and should have around +3 dbm at the LO port ?The local oscillator should be much stronger than the strongest incoming signal at the RF port.

I have no idea where his -10 dbm vfo is going.

Jerry

The VFO and Crystal oscillators are fed into a double balanced diode mixer and then filtered by 10 separate relay switched 2 section Series C BPF's (bandpass filters). Some may question the wisdom of using only a 2 section filters at this stage, however the receiver input BPF's (which are also shared with the transmitter) are 3 section filters and provide adequate stop band attenuation. After filtering, further amplification increases the LO power output where it is split into three separate outputs, +17 dBm for the receiver mixer, -5 dBm to the transmitter board (later to be amplified to +7 dBm for the transmitter mixer) and a low level output for the frequency counter.?

When I first built the LO system I did not pay attention to setting the VFO output level and for reasons I can't remember, the VFO output was 0 dBm. After connecting the LO to the receiver mixer I found a number of spurs that shouldn't have been there. Wes, W7ZOI came to my rescue explaining the importance of not driving the RF port of a balanced mixer with more than -10 dBm. After decreasing the VFO output to -10 dBm the spurs disappeared. The VFO is built into a box made of PC board material. The 10 crystals oscillators and LO mixer are built into the top half of a box made of PC material. The bottom half of the box contains the 10 BPF's and an amplifier to boost the LO output power to the desired level.?