All the suggestions about trying different cable lengths are good thoughts to help find the "sweet spot" of compatibility between the XV432 output circuit impedance and the Henry input impedance.
Folks on the repeater-builder group talk about this very issue often; Of course in their case they are concerned about the transmitter feeding a reactive duplexer assembly. Oscillations don't seem to be the issue presented, rather, the tendency of the transmitter output stage to produce "other" by-products when forced to feed a reactive load, such as a narrow band-pass duplexer, causes unhappiness in the transmitter. Spurious signals are the result. The oft touted "simple" cure proposed is "try different lengths of cable between TX and Combiner." The more professional solution is to place an Isolator between the TX and the Amp during transmit. One example is shown here... http://www.rflambda.com/pdf/isolator/RFLI101M40M50.pdf This way, the TX only ever sees a nice infinite coax assuming, of course, the third port is properly terminated into 50 ohms. Of course you need to receive as well and the isolator won't help with that by itself. So all I have done here is to propose a workable, but unwieldy and expensive solution if, in fact, the cause of the oscillations is impedance issues between the XV432 output stage and the Henry input stage. The point is impedance issues between a Source and Load can cause the source to not play nice. Let's hope your problem is just a feedback path solved with chokes. John > Good day, > > I'm working with the XV432, Flex 1500 and Henry 2004A Amp. The rig, xvrtr and amp PTTs are sequenced. Hoping somebody might have been down this path before and has a solution. > > If I connect the transverter output to the amp (or different pieces of open coax) and key the transverter, the power meter goes full scale and I see an oscillation on the spectrum analyzer. The frequency of the oscillation varies with the load. (i.e. amp connected or different lengths of coax) If I connect the XV432 to a 50 ohm load, no > oscillations and all works well. > > I ran through the alignment procedure again with the XV432 connected to a 50 Ohm load. All the voltages look right and the tuning is smooth. (e.g. 20mV Quiescent Current Adjustment, TP3/TP4) It's obvious the XV432 is happy into 50 Ohms, but not into impedances that wander from 50 Ohms. > > BTW, I have added all the mods as per the Elecraft website. > > Any ideas? > > 73's > Stu2 > W7IY > ______________________________________________________________ > 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
