I am aligning my new XV50, latest build using the RA30H0608M module and having issues with setting the quiescent bias of the pa as per the manual. I see others have had this same problem but I can find no answers.
The manaul calls for R39 to be adjusted for 20mV on the DMM across TP3/4 (across the 20mohm current sense resistor R17). With R39 at its maximum I get 16mV corresponding to a total current of 800mA as against the required 1A. This is confirmed by the digital current meter on the 12V psu powering it and my K2, which increases from 0.5A to 1.3A when I enable transmit on the XV50. Before anybody asks, I DO have link W1 fitted, and in fact I have the correct bias voltage on pin 2 of the output module. However there is where I suspect the problem as the maximum voltage achievable there is 4.7V. I found a datasheet of the RA30H0608M, albeit a preliminary one which has a few sheets 'in preparation'. It does not give any figures for standing bias versus the bias volts but suggests it must be somewhere between 4.5 and 5V (there is no power output below 4.5V). The voltage at the R29/R39 junction is limited by the current flowing through R28 and the module bias current (typically 1mA). So I am wondering whether some rf modules need a bit more than 4.7V to get the correct bias current of around 1A. Maybe reducing the value of R39 (56 ohms) is the answer. Or is mine near enough for good linearity? Any help welcome. 73 Dave G3YMC http://davesergeant.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 Message delivered to [email protected]
