sbe -33 - BoatAnchors Forum at eHam.net

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eHam.net Forum : BoatAnchors : sbe -33

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sbe -33	Reply
by KE6HXF on November 2, 2009	Mail this to a friend!
hi guys, I am working on a sbe-33 it is a early model made in rancho vista ca.this radio has a collins mech filter in it. the radio will transmit but with no audio, receive does not work, on transmit i can trace a audio signal(with my scope) thru the radio all the way to the collins filter on the other side of the filter. I all but lose the audio signal very little getting thru the filter, my question is fellas ,does the audio signal stay the same amplitude thru the filter do these filters go bad is there a simple test i can do to check out the filter? thanks in advance for any suggestions 73s rob ke6hxf

RE: sbe -33	Reply
by AA4PB on November 2, 2009	Mail this to a friend!
The signal going thru the mechanical filter is RF, probably at 455KHz, and not audio. There is some attenuation (a couple of dB) thru the filter. You don't get audio on the Rx until after the product detector extracts it from the modulated RF signal and this occurs after the IF amplifiers and mechanical filter. Do you get RF out of the transmitter but no modulation (audio) from the microphone? If so, the RF and IF stages (including the mechanical filter) are okay. You may have some common (Rx and Tx) audio stages that are defective and killing both the Tx and the Rx audio.

RE: sbe -33	Reply
by KE6HXF on November 2, 2009	Mail this to a friend!
thank you for your repley. yes, i do have output but no audio from the mic impressed on the carrier. The thing that keeps getting me that with this radio is that sbe injects the 455 carrier twice in this thing right after the detector just before it is amplified to go into the filter and then just right after the filter. What im thinking is i would think that it would look like a modulated carrier coming out of the filter would that be correct? thank you for your time take care 73s rob ke6hxf

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