There's no way to avoid some increase in SWR reading error at low power, since the bridge transformers have a low coupling ratio to avoid heating at full power. We're already using very low-drop diodes and pre-biasing them.
That said, I am going to look at a correction based on power level if possible. tnx Wayne N6KR On Nov 9, 2009, at 9:06 AM, Jack Smith wrote: > Wayne: > > There's also an SWR versus output power issue, or is that part of > the first correction factor? The SWR error increases significantly > at lower power. I have not had a chance to plot the data because it > was not part of the original question, but there is a clear power > related error seen in the raw data, which I assume is tied to the > detector diode linearity at low voltages. > > Jack K8ZOA > > > Wayne Burdick wrote: >> There are two sources of the reported SWR inaccuracies: >> >> - An SWR calculation scalar that I'll be adjusting in firmware; >> this is what's causing a 2:1 SWR to read closer to 1.8:1 on some >> K3s. >> >> - The KAT3 itself, and to a much lesser degree, the KANT3, which >> is present if the ATU is not installed. Both modules have inherent >> stray reactance, part of which is due to the 8.2 MHz first-IF >> trap. These strays slightly alter the impedance seen by the K3's >> SWR bridge. >> >> Even when the scalar correction is applied, there will still be a >> small frequency-dependent variation in SWR reading between the >> K3's bridge and an external instrument. This has no impact on K3 >> operation. >> >> 73, >> Wayne >> N6KR >> >> >> ______________________________________________________________ >> 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 >> >> ______________________________________________________________ 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
