Shannon, RG-6 coax has a characteristic impedance of 75 ohms, your radio is designed to feed an output at 50 ohms. So from your radio's perspective, it sees a 1.5:1 SWR if the antenna is perfect. The practical result of this is that unless you are feeding a tuned dipole or another resonant antenna at the resonance frequency, it may work, but will not be very efficient. There are some advantages of feeding a tuned dipole with 75-ohm coax. but they only apply to a resonant antenna, and the price you pay for those advantages is a higher Q (think of Q as the shape of the SWR graph, high Q means a sharper V, low Q means a flatter U shape), since the 75-ohm feedline is effectively a loading coil to the antenna. There is one caveat to the above, if your 75 ohm coax is exactly 1/2 wavelength long, the mismatch of the reactive and resistive components of the current will present 50 ohms at each end. The other issue with CATV coax is that the standard SO-239 PL-259 connectors won't attach to the cable without modification.
Ron On Tue, Oct 20, 2020 at 7:53 PM Shannon Tassin via BVARC <[email protected]> wrote: > Hi all, > > Working to get my first radio setup and would appreciate some advice. > > I have some existing RG-6 coax in the house that I ran when I built it > from the attic to rooms that has never been terminated or used. I just > bought the TBJ-1 antenna from Ed Fong that someone here recommended > recently. It has an SO-239 connector on it. > > Is there a specific cable spec I need to buy to connect to the antenna? Is > there a certain resistance level? > > Can I then connect that cable to my existing RG-6 coax and leverage that > existing RG-6 in the wall to the room where the radio is? > > Do I need anything besides the right cable and adapters between my antenna > and radio (have a Yaesu 991A with built in antenna tuner on the way)? > > Could I then use that setup to connect the antenna to either my 991A or my > FT3D HT (assuming the right adapters)? > > Thanks much to all who have time to respond! > > Take care, > Shannon K4SCT (previously KI5KTF) > ________________________________________________ > Brazos Valley Amateur Radio Club > > BVARC mailing list > [email protected] > http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org >
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