Sadly, C448 was not the actual culprit.? When I replaced what I thought was the defective cap, the malfunction returned.

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At this point, I suspect the 1^st IF mixer, or the amplifier post-mixer.? I am waiting on the tools to properly probe the signal path to know for sure.? Once I have the equipment to test, and have more info, I will post it here.

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-- Mike

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For what it is worth, and to give you guys an idea I have a good background servicing Motorola and other brands of LMR 2-way radio equipment for over 40 years. I use a R2001H service monitor on the bench as most of my customers with big radio fleets are still on analog. Besides the R2001H (1GHz), for tracing I do have a Fluke 85 RF probe, which has a upper -3dB limit of 500MHz, and among other scopes have a Tek 2465B with P6137 400MHz probes, and several 1.1GHz frequency counters which I check and recal as needed with a 10MHz rubidium oscillator. Plus the obligatory 3468, 3478 and several 974/975 handheld DVMs. Not sure that would stack the odds enough in my favor towards being prepared to find the RF problem in that 4411B.

But just in case I would definitively check C448 first, although I doubt will be this lucky.