1. Mount
the small flat aluminum reflector on the white plastic end of the downconverter
with the screw provided.
2. Mount
the two small L shaped brackets in the two slots in the face of the dish,
facing into the area of the focal point of the dish. Then mount the downconverter inside the two L shaped brackets,
aligning the 4 holes; only one bolt
and nut are provided. The dipole will be
parallel with the grids of the dish.
3. Mount
the 4 stove bolts into the face of the dish into the 4 holes. Put the 2 brackets on the 2 bolts on the
back side of the dish. The slots in the
brackets should be facing each other to go around the mast. The holes in the dish are such that the dish
can be mounted either vertically or horizontally on the mast. Horizontally
occupies less mast space -- the
satellite doesn’t care.
4. Connect
the female F connector on the downconverter to the supplied RG-59 cable and
loop it through the hole in the dish at the base of the downconverter. I mount my downconverter so the F connector
faces down when horizontal.
5. Connect
the other end of the RG-59 cable to the female F connector on the power
inserter, plug the wall power supply into the wall. Connect the short F cable to the 6 dB attenuator and screw that
end into the RX side of the power inserter.
Connect the other end of the short cable to the supplied F to BNC
adapter and into your radio. Radio
Shack also sells a female F to PL-259 male connector, if you want to change it.
FREQUENCY: The
middle beacon is at 2401.323 (plus or minus Doppler) and is the most common
beacon, it will be found at 145.323 MHZ
on your receiver. Remember: 2400
MHZ = 144 MHZ and 2401 MHZ = 145 MHZ.
Check with the schedule, the beacon (and translator passband) may or may
not be on and the squint angle may or may not mean that AO-40’s antenna is
pointing at you. Keep listening. The
downconverter’s frequency is set when it is warmed up, keep it on all the time and it will be on frequency when you use it. I have used closed cell polyurethane pipe
wrap my downconverter for thermal stability.
CONVERTER GAIN AND
CABLE LOSS: The downconverter was
made to feed a long run of 100’ or more of RG-59 cable into a multiset TV
coupler and into the house TV wiring – this adds up to a lot of losses. It has excess gain at the 2 meter IF
amplifier frequency to overcome these losses and the signal should be
attenuated into your communications receiver. THE GAIN OF THE DOWNCONVERTER HAS ALMOST NOTHING TO DO WITH THE SIGNAL
FROM THE SATELLITE, THE GAIN IS MAINLY FOR OVERCOMING LOSSES – ONLY THE NOISE FIGURE AND DISH GAIN WILL
AFFECT THE REAL SIGNAL TO NOISE RATIO OF THE SIGNAL FROM THE SATELLITE..
With the supplied cable, the downconverter will produce an S
- 7 to S – 9 meter reading of noise in your receiver, with no signal. I NOW
SUPPLY A 6 dB ATTENUATOR PAD (Extras are $3.00) to reduce the S meter to a
more practical S -- 3 or so. I do like
to see some S meter reading , so I know it is working. Remember, the AGC in your receiver is
treating this S – 8 noise from the
downconverter like a signal. So, along
with some other conditions, an excessively strong noise signal into your
receiver could end up masking weaker signals.
This pad also provides some
protection , should you accidentally key up into your downconverter with
your 2 meter transceiver. The smoke in
the pad costs a lot less than the smoke in the downconverter..
THE 75 OHM CABLE:
The RG-59 cable, with F connectors, provides for a cheap and easy way to
connect the downconverter. The small
mismatch from the 75 ohm cable to the 50 ohm receiver input translates to a
very small amount of loss, or attenuation, and is of no concern in this
application. Using a low loss cable here, or too little cable, will not buy you
anything, it will result in too much noise into your 2 meter receiver though.
FINDING YOUR TX IN
THE TRANSLATOR PASSBAND Tune your
receiver to hear the MB beacon, and then set your TX frequency to 435.665 MHZ
and lock the TX to the RX (reverse). DO
NOT TRANSMIT. Tune your RX up the
band away from the beacon and unlock your TX from your RX. Transmit and tune your TX to find yourself
in your RX. Lock them back and they
will be good for the session.
NOTE: THE POPPING
SOUNDS IN YOUR RECEIVER ARE PROBABLY A 2.4 GHZ WIRELESS LAN OR A 2.4 GHZ
CORDLESS PHONE. They use
spread spectrum and are actually operating on AO-40’s receive frequency. Turn the source off and it will go away. If
it is at your neighbor’s house, then work with them.