Ron, Yes, that is valid justification for putting the balun at the tuner input, BUT it ignores the physics of the tuner itself. If the tuner is actually a balanced design, I have no problem, but many try to force fit an unbalanced tuner design after the balun. That latter part is the part that does not fit. There is no way that an unbalanced network no matter how well isolated can preserve the balance - just consider the phase of the signal as it passes through each tuner element if you want proof.
If you want to use a balun at the tuner input, then please follow it with a balanced tuner t maintain that balance. If you want to use the "rule of thumb" that the balun impedance should be 10 times the load impedance, then refer to K9AY's RFI and balun information and use those 5 or 6 large cores to provide the proper choking impedance for up to 500 ohms antenna impedance (5000 ohms impedance for the balun). 73, Don W3FPR On 12/8/2011 7:36 PM, Ron D'Eau Claire wrote: > Is it true that the efficiency of a balun is not affected by the impedance > of the line in which it is used? > > The justification I had seen for putting the balun at the tuner input where > it will see a load very close to 50 ohms resistive (when the tuner is > adjusted for a "match") while at the output the balun may see anything over > a huge range of impedances. > > Ron AC7AC > > ______________________________________________________________ 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
