Re: Topband: JT65 Power and bandwidth
On 3/18/2017 2:42 PM, Mike Waters wrote: I was wondering about just how narrow we can go on JT9, JT65, or WSPR. Below is some information on the bandwidth required for JT-65. This was copied from one of the JT-65 websites. JT65A operators use USB VFO FREQUENCY for spots. JT65A signal is about 1.3+kHz higher than the VFO frequency The JT65A Passband is about 355Hz. Bandwidth is about 200Hz. JT65A may be used in the 500Hz bandwidth segments of bandplans. Normal operation of JT65A is a sync audio frequency of 1270.5Hz. Sync tone is the reference mouse-click frequency for JT65. JT65A signal bandwidth extends about 200Hz above 1270.5Hz sync. The lowest tone of the JT65 signal is normally 1270Hz. The system allows approximately +/-600Hz auto-tuning on receive. WSPR requires that an SSB filter be used and the radio has to be set to the specified frequency for that mode. You can change the bandwidth to anything your radio will give you but you can't change the dial frequency. That will change the frequency of the tones and cause the decoding to stop. PSK31 works OK down to 50 Hz bandwidth on my radio. Although I would not recommend tuning around with that bandwidth. Radio dial frequency can be anything that gets the signal in the bandwidth. Jerry, K4SAV _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: JT65 Power and bandwidth
I was wondering about just how narrow we can go on JT9, JT65, or WSPR. I always believed that reducing it would actually degrade the RX. However, the User's Guide (first link below) doesn't say that! Apparently, the reason for a wide RX bandwith --up to 5 kHz-- is simply so that we can see more signals in the wider waterfall. physics.princeton.edu/pulsar/K1JT/wsjtx-doc/wsjtx-main-1.7.0.html Any more experiences about reducing the bandwith, even below 1300? And we should encourage using JT9 whenever possible. The reasons are well-known. Not only is JT9 significantly more sensitive on 160m, but you can fit 10 JT9 signals in the same bandwidth as one JT65 signal. See physics.princeton.edu/pulsar/K1JT/wsjtx.html 73, Mike www.w0btu.com On Mar 18, 2017 1:48 PM, "Dennis W0JX via Topband" wrote: ... Regarding bandwidth, it is not necessary to run your SSB filter wide open for JT65. On my K3, I adjust the width downward to about 1300 Hz. It really helps with noise and QRM. _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: JT65 Power and bandwidth
FCC regs say you should use the minimum power necessary to establish communications. That might require more than 100 watts, perhaps even 1500 depending on conditions, type of TX antenna, etc. Regarding bandwidth, it is not necessary to run your SSB filter wide open for JT65. On my K3, I adjust the width downward to about 1300 Hz. It really helps with noise and QRM. 73 Dennis W0JX _ Topband Reflector Archives - http://www.contesting.com/_topband
