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BARRETT 4050 HF SDR TRANSCEIVER - OPERATING AND INSTALLATION MANUAL
For each frequency which will not tune correctly you will need to determine
whether the tuning is high or low in frequency. Generally any frequencies
which will not tune will always be out the same way. When the antenna is
manufactured, most frequencies are deliberately made on the low frequency
side and adjusted upwards by the placement of “tuning rings”. Tuning rings
are single short circuit rings of 20 amp fuse wire placed on the windings of an
individual part of the antenna. A tuning ring inductively raises the frequency of
the section of antenna over which it is placed.
It must be understood that the tuning of an antenna on a particular vehicle
or installation may not hold for other vehicles or installations. To determine
whether any particular frequency tap is high or low, hold the tune key down
on the relevant frequency and observe the VSWR on a suitable meter. Get an
assistant to slowly move his outstretched arm closer to the antenna tap in use.
If the VSWR gets better, then the
antenna is too high in frequency. This
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antenna to ground capacity. Usually
this happens when the antenna is
mounted too far away from the body
of a vehicle. Either re-site the antenna
closer to the vehicle or remove any
tuning rings which are already on the
antenna.
If the highest frequency on the whip
requires adjustment, initially place
the tuning ring here and slowly move
upwards until a satisfactory SWR is
obtained.
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and the highest frequency on the whip
requires adjustment, initially place
the tuning ring here and move slowly
upward until a satisfactory SWR is
obtained.
If ONLY the lowest frequency requires
adjustment, initially place the tuning
ring here and slowly move upwards
until a satisfactory SWR is obtained.
If the VSWR gets worse when fol-
lowing the above procedure ,then
too much capacity is already present.
This is frequently encountered when
mounting the antenna too low on a
vehicle bumper bar or when mount-
ing close to bodywork as in cab-over
type vehicles. In this case, either re-
site the antenna further away or add
extra tuning rings to the frequency
sections affected until a suitable
VSWR is obtained.
Note: Truck cab-over installations usually produce distorted radiation patterns even
when the VSWR looks good.
When tuning is complete, any new rings added should be coated with epoxy
resin to secure and protect the ring from damage. Five minute quick setting
type epoxy is suitable. If rings need to be removed they may be cut off using a
sharp pair of side cutters. Take care not to cut into the body of the antenna.
Summary of Contents for 4050 HF SDR
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