I drug out the test gear and answered my own question. The answer is — regardless of transmit filter selected, the upper end of audio in AM transmit is a pretty hard limit at about 2.95 Khz give or take a bit where the output drops off to better than 10dB below the mid range of the audio passband. At 3 KHz there’s virtually no audio at all. So no, there is no improvement in transmit bandwidth by using the FM filter for AM transmit.
Which is a shame. The Flex radios (for example, and ignoring the rest of their faults) if properly driven and adjusted can produce very nice AM audio with a reasonable transmit passband for this mode. The K3 on the other hand generally gets a pretty bad (and perhaps deserved) rap on this in the AM community. It would seem since ESSB allows up to 4 Khz of audio bandwidth, that it might be possible to offer something in this range for AM and perhaps a bit more (adjustable to conditions) as well when using the FM filter for transmit. It would make a big difference over the 2.9+ KHz currently available. **** Please note, I am not trying to start yet another long thread on the whole bandwidth war discussion, or what the rules say or don’t or make anyone’s head explode. But it sure would be a good thing if Elecraft could see a way clear to improve the transmit fidelity in AM. Grant NQ5T > On Mar 19, 2015, at 9:24 PM, GRANT YOUNGMAN <[email protected]> wrote: > > If the FM filter is assigned to AM transmit, is there any improvement in > transmit audio bandwidth beyond 3 KHz,or does it remain DSP limited to this > relatively restricted range? > > Grant NQ5T ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
