Not all FT-847's are alike. A stock FT-847 has wide, low-Q ceramic IF filters. My FT-847 has INRAD CW and SSB crystal filters that give narrower IF bandwidth, with MUCH higher Q. I haven't compared them, but I suspect that a FT-847 receiver with quality IF filters performs roughly on par with an IC-910.
If shopping for a used FT-847, look for one with optional IF filters. Collins mechanical filters are an improvement over the stock ceramic filters, but crystal filters are even better.
Wayne Estes W9AE Oakland, Oregon, USA
I would also strongly recommend better filters than the stock ceramic filters to do a comparison. When I bought FT-847 in 1998, Inrad did not have compatible filters, so I bought the Collins mechanical filters which were available. I did not do extensive testing, but the HF reception was remarkably better than the stock filters.
Alan WA4SCA
To All, Once the phase noise of local oscillator has been addressed the IF filter becomes the next most important element in the receiving system for audio clarity. Having a flat amplitude response in the filter pass band gives a clear quality to the voice. Most ceramic filters and some crystal filters have poor pass band responses leaving the audio on the muddy side. Collins mechanical filters have for several decades been the benchmark for receiver IF filter technology.
SDR has eliminated the need for IF filtering at the expense of poor image responses in cases where high level signals are present in adjacent channels. SDR works best in satellite and cell phone environments where signal levels are controlled either by distance or minimum power necessary for communications.
Amateur radios of the future may emulate cell phone power control technology, but until that is widely in use, a hybrid system with a roofing filter and SDR IF currently offers the best performance.
Art, KC6UQH
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Alan P. Biddle Sent: Saturday, May 30, 2009 12:29 AM To: amsat-bb@amsat.org Subject: [amsat-bb] Re: FT-847 vs IC-910
I would also strongly recommend better filters than the stock ceramic filters to do a comparison. When I bought FT-847 in 1998, Inrad did not have compatible filters, so I bought the Collins mechanical filters which were available. I did not do extensive testing, but the HF reception was remarkably better than the stock filters.
Alan WA4SCA
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participants (3)
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Alan P. Biddle -
Art McBride -
Wayne Estes