Some radios have moved forward in circuits, some backwards. Many have
moved backwards due to phase noise from local oscillators. Some like the
Yaesu FT-736 ignored the known optimum operating conditions for double
balanced mixers (broad band terminations) and perform poorly for dynamic
range. Many radios depend on a first IF roofing filter that is often
wide enough to pass FM or to allow for a few KHz tuning range on the
second oscillator for fine tuning to get lower synthesizer noise.
Trouble is that opens up the second mixer for strong signals close to
the desired signal. Which makes the intermod measurements and
performance very dependent on spacing.
73, Jerry, K0CQ
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