Re: 122 GHz boards

Roger Ray


I generally agree with all your points.
However as Amateurs, we need to be a lot more aware of where are spurious / unwanted emissions lie. In the past there has been very little thought of radiation from local oscillators, mixed products, and harmonics.
Now with rapidly increased commercial use of new microwave bands, it is a different situation. Has anyone measured the second harmonic of their 24 or 47GHz transverters?
However my main point, is to avoid producing signals that could effect Passive earth observation satellites (EES or EESS). These satellites looking down, can have a path loss of only 200dB. With sensitivities of a few Kelvin. The main protection generally is, that we are communicating horizontally along the earth, not pointing straight up. However with the relatively low loss of signals going straight up we need to be mindful of the harm it could do. Actually in practice at below 122.25 the most likely observation is at 118.8GHz oxygen line, just where the attenuation is the highest.
UK operation at 122.4, has been used with an LO at 122.829 (for Elcom) or 122.833.
Using CW there is not an image mixed product. Thus LO and TX signal remain within the band of 122.25 and 123.00.
The move to a second channel at 122.99x with LO low makes a lot of sense to minimise path loss, when we get to 100km paths.


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