MFJ-1775B 80/40 Meter Dipole Instruction Manual
3
If you have followed the instructions and installed the antenna with about
one foot of the ends wrapped back on themselves, the resonant frequency
on 80 Meters should be somewhere near the bottom of the band (3.5
MHz). You can determine the resonant frequency of the antenna using an
antenna analyzer or a transmitter and SWR bridge. The amount the 80-
meter wires will need to be shortened to raise the resonant frequency a
certain amount will depend on the type of installation (level, inverted
vee, sloper) and on surrounding metal objects. A very rough rule of
thumb is one foot per side for 100 kHz. When shortening the antenna,
simply wrap more of the two wires back on themselves; do not cut them.
On 40 Meters this antenna should cover the entire 7.0 to 7.3 MHz range
with an SWR below 2:1. On 80 Meters, because it is a shortened
antenna, the 2:1 bandwidth is much less: 30 to 50 kHz, depending on
surrounding objects, etc. The usable range of the antenna on 80 Meters
can be extended by using an antenna tuner at the transmitter.
Maintenance
This antenna is constructed of heavy duty materials and should withstand
normal climates for many years. General Electric makes a pure silicone
grease called "
silicone dielectric compound
" that can be applied
sparingly
to the soldered connections at the antenna’s center insulator.
This is the same type of sealer that commercial antenna installers and
CATV companies use with great success. A less desirable but adequate
sealer is the automobile seam sealer commonly marketed as "coax seal,”
a pliable black sealing compound.
Technical Assistance
If you have any problem with this unit first check the appropriate section
of this manual. If the manual does not reference your problem or your
problem is not solved by reading the manual you may call
MFJ
Technical Service
at
662-323-0549
or the
MFJ Factory
at
662-323-5869
.
You will be best helped if you have your unit, manual and all
information on your station handy so you can answer any questions the
technicians may ask.
You can also send questions by mail to MFJ Enterprises, 300 Industrial
Park Road, MS 39759; by FAX to
662-323-6551
; or by email to
techinfo@mfjenterprises.com. Send a complete description of your
problem, an explanation of exactly how you are using your unit, and a
complete description of your station.
