Higher Q parts/paths MAY sometimes support unwanted/parasitic action/energies otherwise not normally sustainable when losses in lower Q circuits overcome those paths/sources.
An example... The six meter duplexer made from 1-1/4 and 1-5/8 inch hard line can also be made of common coax. The Q of the common coax is relatively low enough so the flexible coax version won't work very well, the higher Q 1-5/8 inch line being the better choice. Both the 1-1/4 and 1-5/8 inch home-brew rigid line duplexers are considered usable... graphs of both rigid line version are on the various web pages and clearly show the performance numbers. If you experience a grunge/imd problem with/through using the better 1-5/8 inch hard line duplexer... the same mix/grunge/intermod problem might not be sustained(able) through the 1-1/4 duplexer because of it's higher internal loss (lower Q). Keep in mind the 1-1/4 inch diameter hard line 6 meter duplexer is still quite usable. In common land mobile antenna combiners... we can and do increase the cavity, coax and network insertion loss to reduce problems in some specialized cases. A lot of this is just about trying to describe how sometimes a reduction in an antenna/duplexer hardware and feed-line Cable Q (quality) can attenuate unwanted energies. In my opinion the South American Telewave VHF Transmit Combiner story we saw here on the group a while back was very much about having high-Q cavities and very, very small amounts of unwanted energies fairly possibly solved with a number of modest changes including increasing the loss numbers on some of the combiner channels. The combiner was engineered by Telewave and the potential mix numbers looked pretty darn good. But the as-built hardware had mix problems no-one seemed to be able to source using the off the shelf tricks. Reducing the Q of a circuit was probably not an "off the shelf method" used or even thought about by most people. When working on/with high powered tube rf amplifiers we often use parasitic suppressors to reduce Q and make the amplifier ultra stable. Reducing the circuit Q a slight amount is enough to prevent unwanted parasitic oscillations and potential spurious energy mix generation. Fractional reduction in gain/performance traded for grunge free operation. Tis something to consider... cheers, s. > "Laryn Lohman" <[EMAIL PROTECTED]> wrote: > > I've been <trying> to follow the current thread on cable Q, > and this is a new term to me. > > My educated guess is that lower Q may mean more loss, and the > opposite. But I've never heard of cables being described this way > before. What have I missed? Please explain. Thanks. > > Laryn K8TVZ >
