hb9ari wrote: > > Hello, > > As i use principally JT65A (snice ~ 2years), > i've remarked transmit output power variations > depending where the audio is located in the waterfall, > as i'm not speaking English, it's difficult to explain correctly; > if i'm ~ in the middle of the waterfall (~ 1200Hz) > i get over 3dB in output power variations; for an expected > 50W output power, between some tones of the JT65A > modulation, the output level can vary from 20W > to 60W; if i'm working away from the "middle", > variations are lower and acceptable but most > of time, "central" frequencies are used... > I've always worked with this "problem" as i > expect some AGC effect by the receiving side... > I would appreciate to have an explanation > of this effect. > >
This topic has been brought up before in the context of RTTY. The reason is that there is no automatic level control in DATA A mode (or rather, there is, but it is very slow acting to avoid causing IMD on PSK31 signals) so there is no compensation for ripples in the roofing filter passband. It has been suggested that the problem is less when using the 8-pole SSB roofing filter as it has less ripple than the standard 5-pole filter. The output should not vary as much as you suggest while working within the normal passband for JT65A operation so I'm wondering if you have correctly adjusted the audio input level in DATA A to get 5 bars on the ALC scale. This will not prevent the power varying for different tones during a transmission but it should help maintain a constant average level when working at different places within the passband. ----- Julian, G4ILO. K2 #392 K3 #222. * G4ILO's Shack - http://www.g4ilo.com * KComm - http://www.g4ilo.com/kcomm.html * KTune - http://www.g4ilo.com/ktune.html -- View this message in context: http://n2.nabble.com/JT65A-output-power-variations-tp3985152p3985354.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ 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
