On Thu, Oct 20, 2011 at 8:29 AM, Guy Harris <w6...@guysfreehold.com> wrote:
> > Ed, > > Are you serious? > > Understand that JT65 is a WEAK signal mode; one the biggest problems is > people running far too much power and causing de-sensing. > Desense is overload (compression). You need a lot of signal to cause desense, even in poorly-designed older radios. A distant station running even up to 100W is not likely to be causing desense. This is not a problem. I think that what you are alluding to is people running filters that are too wide, usually rigs using SSB filters for narrow modes like CW, PSK31, and JT-65. In that case the unwanted signal is in the normal passband of the receiver and activating the AGC. The AGC cannot differentiate between the desired signal and the undesired signal in the passband. It just takes total power in the passband and uses that to modulate the AGC. There is no brain in the radio to be able to recognize which signal you want and which one you don't want. The only solution is to narrow the filter to match the desired signal and let the undesired signal fall outside the passband. Fortunately that is easy to do with the Flex radios and much harder with others. Maybe someday we will have the CODEC integrated with the rest of the radio so that the CODEC uses the level of the actual desired signal to control the AGC instead of just power in the passband. Until then, there is no choice but to narrow the filters to just pass the desired signal. > Please do a little research on this mode before proceeding; and try running > 5 Watts. > While it is always a good idea to run the minimum power necessary to make a contact, that minimum power may turn out to be 100W or even 1500W, not 5W. It is what it is and there is no arbitrary number you can place on it. OTOH, if JT65 is reporting that your signal is +10dB, then you can probably get away with dialing down the power and still maintaining the contact. The only problem with that is that you don't know what the power was until after your first exchange, at which time the contact is over! Oh well. -- Brian Lloyd, WB6RQN/J79BPL 3191 Western Dr. Cameron Park, CA 95682 br...@lloyd.com +1.767.617.1365 (Dominica) +1.916.877.5067 (USA) _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/
