That's what I thought Chuck. Thanks! I haven't yet decided whether I want to rip the heat shrink tubing off an element and disassemble it to see what coax is inside, which is why I asked.
I was sort of contemplating whether it might be possible to replace all that coax with RG-214 in an attempt to build a noise free harness. But if there's a matching section, I'm sure the return loss without it would be really ugly. Paul N1BUG Chuck Kelsey wrote: > There is a 1/4 wave impedance matching section of coax (125?) inside the > element. The matching section is stagger tuned from the element itself. > That's why it is more boadbanded and why you see two return loss dips. > > Chuck > WB2EDV > > > ----- Original Message ----- > > >> I wonder if anyone knows what (if any) gimmick Sinclair used to get >> such broad SWR bandwidth on these dipoles? The exposed portion of >> the coax on each dipole is RG-213, 50 ohms... but I'm wondering if >> they may use some quarter wavelength (or ???) of some other >> impedance on the part hidden inside the dipole, especially since >> these things exhibit a clear double dip SWR curve (one dip near the >> low end of the design range, 138 MHz, and another dip near the upper >> end, 174 MHz, with a somewhat reactive bump in between). >> >> 73, >> Paul N1BUG
