Don, That makes sense too, thanks.
I still would like to have an option of a tap off the low power drive before the PA with the PA disabled when using an external transverter, so that I could have the benefit of controllable low power with low wideband transmitted noise and no heat problems at high duty cycle. 73 David Anderson GM4JJJ > On 5 Jan 2014, at 20:17, Don Wilhelm <w3...@embarqmail.com> wrote: > > David, > > I don't know about the power control characteristics of the KX3 yet, but with > the K2 without the K60XV option), more steady power control is achieved in > the 2 to 10 watt range as compared to lower power levels. It all has to do > with resolution - the power is set in 0.1 watt increments, and an uncertainty > of 1 count can double or halve the power level at very low values, but that > same uncertainty is much less at 2 watts and even less at 4 watts. > > For JT65 and other long transmission full duty cycle periods, the heat > dissipation must be considered if you want to prolong the life of the finals > - so use 2 or 3 watts. > > 73, > Don W3FPR > >> On 1/5/2014 2:42 PM, David Anderson wrote: >> David, >> >> I have a further thought about the difficulties of using the KX3 with an >> external transverter, if we reduce the maximum power output for the XVTR by >> using the XV PWR H setting to say a very low value (say the lowest which is >> 0.1 Watt), then is there a danger that the relative transmitted wideband >> amplifier noise will be higher than if we kept the power at say 4 Watts and >> then used a big attenuator on the input of the TX port on the transverter? >> >> All my previous experience with transverters have been with radios that had >> dedicated low power transverter RF out ports. Even then there were problems >> with thermal power drift, excessive drive levels due to lack of the normal >> ALC that radio normally depended on when using it on HF etc. >> >> I presume that there is no way to easily bypass the PA and driver stages >> within the KX3 to get lower drive power without reducing the TX gain. I have >> been looking at the KX3 schematics trying to work out where the as yet >> unreleased KX3 internal 2m transverter gets it drive from and at what level >> that is. >> >> Perhaps Elecraft may give us some clues or guidance. >> >> What would be neat, but it don't suppose we can expect Elecraft to do it, >> would be a board that would replace the planned internal 2m transverter, and >> would just act as a lower power transverter output from before the PA >> stages, on an SMA connector where the 2m antenna socket will be, with the >> main antenna BNC as a receive only port, (though that could be dangerous), >> perhaps a low power TX/RX on the SMA would be best. >> >> 73 >> >> David Anderson GM4JJJ > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
