Howard, Joe Taylor would be best qualified to answer your questions about mode timing, but I've been told that synchronization coding takes up 50% of each JT65 transmission. Obviously the clock sync issue is important and is the reason why we find it hard to decode those that are out of sync.
My understanding is that altering the mode to improve throughput would take away from it's ability to dig into the noise as well as it does. Part of why the mode works so well is it's limited message format; callsigns, grids reports. The bottom line is that the stations who benefit from JT65 the most are the ones with limited power and antennas. The consensus is that the mode truly does dig down into the noise and make the contact happen when other modes fail. It's not just a sensitivity issue either; JT65 holds together with static crashes and when the ionsphere is disturbed. I watch it decode very weak signals from Japan that had heavy auroral flutter and it didn't miss a beat decoding down to -25db. 73, Tony KT2Q ---- Original Message ----- From: "w6ids" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Tuesday, April 17, 2007 11:52 PM Subject: Re: [digitalradio] Re: JT65 -- Set your PC time before getting on the air > Tony, > > Tonight, there were a couple of messages on the > APRPACK forum > discussing the JT65A mode and tying it to > comparable MFSK possibilites > for low signal activity. > > It was also suggested that brief messages could > be sent by adding > them to one of the "TX" keys. Of course, it was > added that wider > bandwidth would be effective for this. > > Just wondering here - is that what is possibly > within the intent of any > development for HF use for JT65A? I had the > impression that the HF > activfity focused only on simply making and > confirming a weak signal > contact using the protocols established by the > EME groups. There's > no real need for a 40-character "TX" key ability > for transmission. I did > try to add words to a couple of the keys and it > seemed to louse things > up a little bit. > > That said, is it absolutely necessary to adhere > to the EME protocols > involving "TX" key content as such and the > strict compliance with > transmission timing and clock accuracy - as > pertains to HF testing? > Now, I know that EME is very stringent due to > the nature of the beast. > However, appears that there is a line of > thinking developing which > embraces the notion that EME demands are not > necessarily applicable > to HF when using JT65A and WSJT. That, despite > the nature of the > transmit/decode cycle. > > I'd be interested in your comments. > > Howard W6IDS > Richmond, IN > > ----- Original Message ----- > From: KT2Q > To: digitalradio@yahoogroups.com > Sent: Tuesday, April 17, 2007 9:56 PM > Subject: Re: [digitalradio] Re: JT65 -- Set your > PC time before getting on the air > > Jose, > > All good ideas. Hope to see you on JT65... > > >SNIP< >SNIP< > >
