A friend of mine just put a 102ss on his truck and the swr on channel one is 3. If you grab the atenna it goes down to 2, so we grounded it and it was at 2.25 still not low enough but if you grab it with the ground wire on it it goes down to 1.2. Any ideas on what it could be?
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High SWR Question
- Thread starter red79
- Start date
I don't know what year it is, Or where the 102 whip is mounted. Make sure the area where the nut and warsher are on the inside are free of paint or rust. No. 2 Take a hose clamp skin the end of 14 or 12 guage wire, clamp it on the connector at the whip and run it to a good bolted clean ground. Run a ground strap from under the bed to the cab. The Bed and Cab are on rubber bushings, So extra grounds can not hurt. Let me know how it turns out. Perry
it s a 90s model ford and the whip is behind the cab i put a ground from the antenna where it screws into the mount and run it to the battery ground and it made it go down a bit but with the ground wire on it and if i grab the whip with my hand it goes down to 1.2
The Bat does nothing for reflecting power. If the Ant. does not have a good ground to the Truck Metal, You are just transmitting off the small area of the Bat. cable. If you ever get a chance to look under an old State Police Car, You will see how many ground straps they have added. Befor the new UHF Radios, They would run 100 watts or more when they were on low band and 150 mhz. Check the cable with an ohm meter to be sure it is 100%. Short heavy ground wires or straps work best. Even house wire will work. But will break from vibes over time, Thats why they use stranded wire in cars.
if you're using only a 102" whip WITHOUT the heavy duty spring and ball mount then the antenna is too short. (physically and electrically) if it's mounted right behind the cab then coupling capacitance between the cab and the antenna is shortening it (electrically) even further. there should be no body metal that rises above the base of the whip in the near field. the truck cab is in the near field.
a 102" steel whip including the heavy duty spring and ball mount measures approximately 107.5". under these conditions with a mounting location other than described above and a properly terminated image plane (the vehicle body) typical vswr is usually 1.5:1 or better. if none of the above applies then you have no ground plane for the antenna (whip, spring & ball) to image itself against. a quarter wave antenna (assuming the proper length) more often than not will present an input impedance of approximately 16 - 17 ohms at the feedpoint when no image plane is present. that input impedance would also place the voltage standing wave ratio at 3:1.
a 102" steel whip including the heavy duty spring and ball mount measures approximately 107.5". under these conditions with a mounting location other than described above and a properly terminated image plane (the vehicle body) typical vswr is usually 1.5:1 or better. if none of the above applies then you have no ground plane for the antenna (whip, spring & ball) to image itself against. a quarter wave antenna (assuming the proper length) more often than not will present an input impedance of approximately 16 - 17 ohms at the feedpoint when no image plane is present. that input impedance would also place the voltage standing wave ratio at 3:1.
agreed your grond strap should be on a metal surface not the battery.
and ya should use the h.d. 6inch spring.and ball mount.
and ya should use the h.d. 6inch spring.and ball mount.
