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MR,COILY ANTENNAS
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Vote For The Top CB Radio Site! MR,COILY ANTENNAS
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Interpreting swr readings What we would all like to see when we look at are swr meter is a perfect 1.0.1 SWR This is a possibility but only under certain conditions or with dummy loads. Actual antenna installations have higher readings. The following information below should help you understand what is going on in your coax and antenna system.
SWR EFFICIENCY INTERPRETATION
co-phased
The optimum distance for CO-phased antennas is 9
feet,18 feet,36 feet, between the antennas. This produces greater signal
forward and backward on the vehicle. If possible try and not go under 9 feet
to much as this will create a signal over lap .
basically your antenna will fight with each other.
leaning antenna(s) forward
Tilting the antennas forward to decrease the
height, changes the radiation angle of the antennas, and is not recommended.
If due to height restrictions, it is necessary, do not tilt the antennas more
than 15-25 degrees to maintain as much vertical polarization as
possible.
If the SWR will not go below 2.0:1
Not being able to go below 2.0:1 SWR after tuning
generally indicates a
impedance problem between the coax and the antenna.
This can be caused by poor ground.
but is generally attributed to reflection in the
mounting location
,stacks,mirror,bars,cab,bad grounds, hinges all
can create poor swr,
you can add a grounding strapped not ground your antenna
from mirror to
mirror as it can create a dipole affect and make
adjustment impossible.
always try and set your mounts as far out as possible
reflection test
here is a reflection test get your sir set and open your
doors see if your swr drops
or increases .If the swr drops when you open the doors
then you are getting reflection off the
cab,stacks,mirrors,aircleaners,hood,ect et. Its a good little test to try and
I have seen antennas go from 1.6.1 to 1.2.1 just by opening your doors, anyway
if you find this happening set your swr with your doors open all the way.
Close your doors and that's it if your swr jumps when you close your doors its
a reflective reading and not to worry as you have already set your swr
and its not changing just creating a false reading due to reflection off
the cab and other reflective features hope this helps .
all antennas should be mounted on the top bar of
the mirror bracket, and as far out as possible. Do not mount the antenna on
the bottom bar of the mirror, bad bad bad .As this will cause
reflection and interference from the top bar to the coil
and make it impossible to tune
length of coax cable to use
If you are using less than 500 watts and a single
antenna, use 9' 12' 15' or 18' length of RG-58/AU depends on how much
you need. its 95% shielded, stranded center, with 50 ohms impedance. If your
running up to 2000+ watts, then change to the RG-8u or 213u type the big
stuff HOW ABOUT CO PHASED YOU CAN PICK UP A CO PHASE HARNESS AT
YOUR LOCAL TRUCK STOP OR RADIO STORE
IN 12' AND 18' FOOT Lengths
ADJUSTING YOUR ANTENNA
Using a good external SWR meter, calibrate on
channel 20.
Switch back to SWR and record the readings on three
channels; 1, 20, & 40.
If the lowest SWR reading occurs on channel 1, the
antenna whip is to long and must be shortened. Loosen the two set screws and
lower the whip 1/4"-1/2" into the mast. Tighten mast set screw and
again read SWR. Repeat until lowest SWR is obtained. If the whip is fully
lowered into mast and the SWR is still high, remove the whip from mast. Using
a hacksaw, grinder, or bolt cutters, cut 1/4" from the bottom part of the
whip. Re-insert the whip into the mast and test again for SWR. Repeat the
above procedure until the SWR is below 1.5 of all channels. If the lowest SWR
reading occurs on channel 40 the antenna whip is
to short and must be raised. Loosen the mast set screws and raise the whip
1/4", re-tighten set screws and test SWR again. Repeat the above
procedure until the SWR is below 1.5 of all channels.
HIGHER ON CHANNEL 40 DROP THE STINGER HIGHER ON CHANNEL 1 RAISE THE STINGER
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