This weekend I built a 10m dipole which is fed by 75 ohm coax (uses 75 ohm
catv cable already in the building) .
Since the 259 is designed for a 50 ohm system I am curious to know if it is
useful when the coax is all 75 ohm. If so what would be the procedure for
adjusting for resonance?
In my case the dipole was cut for 28.5 mhz. Due to the 50/75 ohm mismatch
I would expect a swr of 1.5/1 if things were perfect. With the dipole
horizontal at about 10 feet, I found a 1.1/1 dip around 27 and a 1.8/1 dip
around 29.5. At 28.9 the impedence was 75 ohms and swr was around 1.9/1.
I also found a close to 1/1 dip at 86.6 mhz. After hooking up the antenna
in a vertical dipole configuration (bottom leg about 2 feet off the ground)
I worked a dozen stations on 100w mostly in WI and AZ around 3z-4z last
night.
Thanks, Pete ws4g
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|