It Really Made A Difference

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masonb

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Feb 13, 2007
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I got out the old calculator, tape measure, & radio frequency wavelength chart and took the time to size the whips for the frequency's I was going to be monitoring instead of just using a ballpark setup that kinda worked. I wanted to monitor the mid 150's & 868-867Mhz. I used to use a singal whip that was cut for UHF (11.5 inches). It picked up the 800 band fine but the 150's struggled. I recently got another trunk lip mount & mounted in a UHF cut at 6.75 inches to catch half the wavelength & it works like a dream. I also went out and got a Larsen antenna that I cut at 38 inches to get 155's. I then used a bnc connector from each short cord (2 feet maybe each (cut them)) that feed into a T-junction that went through only 10 feet of cord to get to the radio. It works like a dream. I get everything from all over now & according to the 396T's signal strength meter on trunk systems it dominates the old setup. I guess the moral of the story is I actually took the time to do the research & got wonderful results!
 

mtindor

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masonb said:
I got out the old calculator, tape measure, & radio frequency wavelength chart and took the time to size the whips for the frequency's I was going to be monitoring instead of just using a ballpark setup that kinda worked. I wanted to monitor the mid 150's & 868-867Mhz. I used to use a singal whip that was cut for UHF (11.5 inches). It picked up the 800 band fine but the 150's struggled. I recently got another trunk lip mount & mounted in a UHF cut at 6.75 inches to catch half the wavelength & it works like a dream. I also went out and got a Larsen antenna that I cut at 38 inches to get 155's. I then used a bnc connector from each short cord (2 feet maybe each (cut them)) that feed into a T-junction that went through only 10 feet of cord to get to the radio. It works like a dream. I get everything from all over now & according to the 396T's signal strength meter on trunk systems it dominates the old setup. I guess the moral of the story is I actually took the time to do the research & got wonderful results!
That's great news, and the ultimate satisfaction -- doing it yourself. Good job man. Happy listening!

Mike
 

prcguy

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It looks like your using a half wavelength formula for making a dipole but using the resulting lengths for whip antennas, which should be half that length or one quarter wavelength. A half wavelength antenna will not match directly to 50 ohm coax without a complex matching network and reception will suffer. A UHF whip will be around 6 inches along and a VHF Hi band whip will be around 16 or 18 inches long. Combining two antennas with a tee adapter is a crap shoot and could give marginal to poor results. You did mention your current setup worked better than the previous but if you cut the antennas to the proper length and use a diplexer you will see a noticeable improvement.
prcguy
 
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