This mod will LOWER the resonant frequency of these antennas
It is not hard to tune a Stationmaster down in freq. Take a number of strips of aluminum foil, starting about 2" wide and tapering down to about 1 to 1-1/2" and long enough to wrap around the antenna mast. Secure the antenna as far as possible from other objects, at least 4-6 feet. I have heard of people have success with two tall sawhorses or better yet tall step ladders to get it high enough off the ground.
Wrap the first piece around the ant and smooth it out. Start at the bottom with the widest strip and slide the strip up the antenna until you see a dip in reflected power at the freq. desired. Slide it up to about 18" above the bottom and then move in 1/2" increments until a dip is reached. Fine tune back and forth till you're happy that it's as good as it's going to get, then start the next one about 35-36" above that one. Secure each piece with electrical tape, pref. 33+, then when you're happy with the finished ant., cover all the pieces with more tape, maybe spray everything with clear enamel (not lacquer) or whatever else seems appropriate. We have used the peel-and-stick foil ground plane kits from A/S as well. Don't peel the back off until you have the piece in place. Mark it if you have to remove the foil, so you don't lose your place.
REMEMBER: Don't go near the antenna while taking a measurement! Besides a bit of a safety risk, it will have a HUGE effect on the reading. Also the antenna needs to be at least 1 wavelength above ground (abt 6'). Once you have that dipped, do the same thing again above the first one, then keep going all the way up. On a TRUE Stationmaster, the first dip will be about 1/4 wave up from the bottom and the rest will be at 1/2 wave intervals. This is the construction of the antenna. Myself and others have done this on MANY antennas that were tuned as high as 165 MHz, and it works very well! We are using one now on our 2M rptr, and with 60 watts out, it out-talks anything at the site, including the 375 watt paging tx's on 158!
The spec'd gain on a Stationblaster is 5.25 dBd, but real world, it is as good as a Hustler G-7 and MUCH better than anything Comet or Diamond or Cushcraft make, except of course yagis. In other words, the S/M is REAL 5.25 dB, the rest are fudging. By the way, this has also worked very well on the UHF 7' sticks that we have played with, too.
Copyright February 09 2000 James Barbour WD8CHL
html Copyright February 09 2000 Kevin Custer W3KKC & original author.
All Rights Reserved.