MFJ-986Differential-TTuner Instruction Manual
9
WARNING:
1.
Never
operate the tuner with the top removed. Contact with the components inside the tuner while
transmitting will result in painful RF burns.
2.
Never
rotate the ANTENNA SELECTOR switch while transmitting. Doing so may permanently
damage the switch.
3. Locate the tuner so that the rear terminals
ARE NOT
accessible during operation. The single wire
and balanced line connections may have high voltage while being used.
4. Disconnect
all
antennas from the tuner during lightning storms.
5. Always tune with low power (i.e. less than 100 watts). Apply maximum power only after tuning up.
6. Be sure to adjust the SWR before transmitting at high power (above 100 watts).
Do Not
transmit
with a high SWR for extended periods of time.
In Case Of Difficulty
If the tuner fails to tune, please double check all connections and follow the tuning procedures again.
Be sure you are using enough inductance and have the capacitors open far enough.
If the tuner arcs, please double check all connections and follow the tuning procedures again. The
power rating of this tuner is 1500 watts PEP RF power. If this tuner arcs at these power levels, make
sure you are using the least amount of inductance and the greatest capacitance possible that still allows
matching the load on the operating frequency.
If you are still unsuccessful, but the tuner does adjust and operate when switched to a dummy load or
another antenna, please read the ANTENNA HINTS section.
Grounding Hints
To minimize RFI, single wire feedlines (such as used with Windom or longwire antennas) should be
kept away from other wiring. Radiation will be minimized if the single wire feeder runs parallel and
reasonably close to the wire that connects the tuner to the outdoor ground. The antenna feed wire
should be adequately insulated to prevent arcing or accidental contact.
For safety, please use good dc and RF grounds. It is particularly important to have a good RF ground
while using a single wire feeder. When using a single wire feeder, the tuner needs something to "push"
against in order to force current into the single wire feedline. If a good RF ground is not available, RF
will usually find it's way back into the power line (RFI), transmitter audio circuits (RF feedback), or the
operator (RF burns).
Water pipes and ground rods provide good dc and ac safety grounds, but they are often inadequate for
RF grounding because they are single conductors. Ground rods by themselves are almost useless for
dependable RF grounding.