I would like to add a couple cents worth on testing receivers for quality
based on using the third harmonic of a broadcast station on the 160 meter
band. It would be very important to know exactly where this third harmonic
is being generated. There is one scenario I can think of that would simply
invert Earls tests and make the last one on the list become the first one on
the list. Consider the fact that a third harmonic is often generated from a
clipping action resulting from nonlinearities or overload. For strong
broadcast stations a third harmonic could actually be generated right in the
receiver being tested and I have seen this happen. This signal could come
right in to the antenna input or be a large current on the outside of the
antenna coax resulting in a large signal. The resultant level of the
offending signal then would be stronger in each radio tested depending on
how weak the receiver actually was. Bingo, the poorer the receiver the
greater the signal to noise ratio on the third harmonic where the rig is
tuned. Or good radio bad SNR, bad radio good SNR. I for one certainly would
not base any rig purchasing decisions based on tests using a signal of
completely unknown origin or precise signal strength. I spent a lot of years
setting behind bench test equiptment as an RF engineer chasing just these
kind of signals and so I believe we will see a lot more about actual
performance of these different rigs as time goes by. Then we will see where
all the chips will fall. My Omni 6 beats anything I have ever used or owned
on SNR and I look forward to the day I can own or at least try an Orion
under my own test conditions and maybe a few others too.
Regards: Lee K7TJR Oregon
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