Ramsey Electronics AM25 Manual de Instruções descarregar pdf (Página 17)

AR1 • 17

ALIGNMENT AND ADJUSTMENT

Alignment of the AR1 receiver consists of simply adjusting L6 for the desired

tuning range and peaking the IF transformer (L7). If you are using a signal

generator, frequency counter or other VHF receiver for calibration, remember

that you want to set the local oscillator frequency 10.7 MHz higher than the

desired signal or range to be received.

Adjustment of the L6 oscillator coil MUST be made with a non-metallic

alignment tool. The use of a metal tool of any kind will detune the coil

drastically, making alignment almost impossible. Also, if you’re receiving FM

broadcast stations, you have the slug tuned too far down in the coil form.

Turn it until it is higher in the form and try again.One other thing that you can

do to improve the operation of your kit is to spread out the three 2 turn coils

at the antenna input, L1, L3, and L5. Stretching these out will give you

greater sensitivity.

Once you know you are receiving aircraft or airport transmissions, adjust the

IF transformer (L7) for best reception. Typically, L7 is adjusted 2-3 turns from

the top of the shield can.

If you don't have any signal reference equipment at home, and are not yet

hearing airplanes, your best bet is to pack up your AR1 and needed tools and

head for the nearest airport! If there is no control tower, don't hesitate to visit

a general aviation service center on the airport grounds. If you've never done

this before, you will probably find it to be a fun and interesting experience.

Ask which are the most active frequencies and adjust L6 and your front panel

Tuning control until you hear the action. A ground service operator or private

pilot may be willing to give you a brief test transmission on the 122.8 Unicom

frequency. Remember, also, that if your airport has ATIS transmissions, you

can get a steady test signal as soon as you are line-of-sight with its antenna.

The AR1 does not produce a loud hiss when no signal is being received

(unlike an FM receiver or expensive AM receiver); this is due to the

somewhat limited amount of IF gain. Increasing the IF gain would produce a

hiss and marginally better sensitivity (about a microvolt) but also require

much more alignment, AGC circuitry, and builder ability - far beyond the

intention of this kit.

"VOR" OR "OMNI" TRANSMISSIONS

If you know of a tall white "cone" structure at your airport or in the middle of a

big farming field, it is useful for you to know that these are VHF navigational

aids operating in the 118-135 MHz frequency range, just below the air-ground

communications range, sending a steady signal which may be helpful in initial

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 23 24

Sem comentários

Ramsey Electronics AM25 Manual de Instruções Página 17