So the elements are 50 Ohms? It does help to know that. :) But you seem to be calling for some kind of magical 35 Ohm coaxial transformer.
Jeff --- In [email protected], Ron Wright <[EMAIL PROTECTED]> wrote: > > JK, > > The coaxial sections coming off each antenna element is 35 Ohm coax at odd multiples of 1/4 wave length. > > What this does with antenna element at 50 Ohms then 1/4 wl down the 35 Ohm cable it looks close to 100 Ohms looking into this cable. Then you take 2 of these ant elements/35 Ohm coax in parallel and you get 50 Ohms at this junction. If have 4 elements do the same for the other 2 and then make another to join these 2 again using 35 Ohm 1/4 wl coax. > > The length of the 50 Ohm coax going from the tx/rx to this antenna input does not matter for SWR or impedance. Only concern would be length and loss of 50 Ohm cable. > > 73, ron, n9ee/r > > > > > > >From: Jeff Kincaid <[EMAIL PROTECTED]> > >Date: 2008/03/05 Wed PM 11:24:35 CST > >To: [email protected] > >Subject: [Repeater-Builder] Re: DB 212-2 Harness info. > > > > >OK John, just making sure. I'm not familiar with the configuration of > >the antenna, but what you are saying makes sense. I'm confused by the > >idea that the length doesn't matter, because that would imply that > >everything is 50 Ohms throughout, which doesn't seem to be the case. > > > >'JK > > > >--- In [email protected], "John Everson" > ><johneverson@> wrote: > >> > >> --- In [email protected], "Jeff Kincaid" <jeffk@> > >> wrote: > >> > > >> > I think this is just sloppy word choice, rather than a lack of > >> > understanding, but I've seen it a couple of times now so let me > >> clear > >> > it up in any case. Regarding velocity factor, it's a factor, so you > >> > want to multiply it. Subtraction is not a part of the equation. > >> > > >> > Say your free space length is 100 inches, and your velocity factor > >> is > >> > 88%. Your length in cable is then 88 inches: > >> > > >> > 100 x 0.88 = 88 > >> > > >> > Regards, > >> > Jeff > >> > > >> > --- In [email protected], "John Everson" > >> > <johneverson@> wrote: > >> > > > >> > > So if I understand correctly, the length of the 50 ohm sections > >> is > >> > > irrelevant, as long as they are equal? Also, is my previous > >> > > assumption that the matching stub is just made of 35 ohm cable > >> cut to > >> > > 1/4 wavelength at the operating frequency minus the vel. factor > >> > > correct? > >> > > > >> > > Thans again for the help. > >> > > John > >> > > >> Hello Jeff. > >> > >> You are correct. It was a poor choice of words on my part. I > >> understand the theory of velocity factor. I am still not sure about > >> the lengths involved with the harness. If the 50 ohm sections from > >> the loops to the "tee" can be any length, (as long as they are the > >> same) doesn't that affect the impedance at the tee? I will assume the > >> impedance at the feedpoint of the loop is 200 ohms. If we use half > >> wavelengths of coax between the loops, the feedpoint impedance will > >> be repeated at the end of the cable to the tee. Is this correct? If > >> so, when the loops are connected to the tee, we should see 100 ohms, > >> then, the matching section brings us to about 50 ohms. > >> > >> Is this correct? Or am I out to lunch? > >> > >> Is the matching section a quarter wave? > >> > >> I need to dig out the antenna handbook and refresh. That is for > >> certain. > >> > >> Thanks. John > >> > > > > > > > Ron Wright, N9EE > 727-376-6575 > MICRO COMPUTER CONCEPTS > Owner 146.64 repeater Tampa Bay, FL > No tone, all are welcome. >
