> >There have been example cases where unwanted product generation > >has been "fixed" by replacing portions of the antenna system > >coaxial cables with a less or lower Q cable. Some transmit > >antenna combiner low-level generation issues have been addressed > >with lower-Q coax jumpers. > Not really a fix. "Lower Q" in transmissionlinespeak is "lossy".
If the (relative higher) Q of a coaxial transmission (in this example) line contributes toward unwanted interactions and/or product generation... Using a lower Q cable like RG-214 with more loss/ft... compare that loss value against rigid or higher Q lines (at UHF), its sometimes a much desired pad effect well worth the trade. Most folks call the described hardware trade a pretty good fix. I'd trade away a pesky grunge - gremlin or glitch problem for less than a dB additional loss most any day of the week. > Using a lossy cable to fix some interaction between, say a > TX & duplexer and/or antenna is IMO a band-aid solution. Mil-Spec (quality) RG-214 is the flexible cable used by many/most companies making antenna combiner systems and duplexers.... not the RG-400 (RG-58 sized) type Teflon cables. I don't believe they feel using RG-214 coax is a band-aid solution... Nor do I > >I have replaced higher-Q feed-lines with more resistive cable, > >which in more than one case has solved an otherwise pesky gremlin > >- grunge problem. > > Yes, attenuators can "fix" a lot of interference issues, if > you don't need optimum sensitivity or most efficient TX > power transfer out of your system. You seem to miss the point... using a lower Q cable like RG-214 is probably the first specified (non rigid) cable choice for most duplexer and combiner applications. There are cases where using higher Q cables will cause a potential train-wreck. In this original topic example Using Higher-Q cable might actually be a part of the problem. > Particularly at low-level sites, I find I need all the > performance I can get & have very little margin for any > additional loss in either the TX or RX path. You've never had a gremlin or grunge problem at a low-level site? > >One other item... pay attention to the actual RG-214 description > >aka mfgrs label as there seem to be a larger number of clone > >cables, which is not actually the mil-spec RG-214 cable "real > >deal". > > The key phrase to watch out for is "RG-214 TYPE". I've seen > copper shielded coax with this designation. cheers, s.
