Receiver Operation - Main Functions; First Switch-On; Filter Calibration - AOR AR7030 Operating Manual

6 Receiver operation - Main functions

It may be useful to refer to the overview and quick
reference guides in section 2 of this manual whilst working
through this section.

6-1 First switch-on

Connect an appropriate aerial to the input on the rear of
the receiver and make sure that the ANTENNA SELECT
switch is correctly set. The selection of aerial depends
upon your location and specific requirements but may
include a dipole or long wire.
Plug the d.c. cable of the supplied mains adapter into the
power socket on the rear of the AR7030 and then plug
the adapter into the mains supply. Never connect the
receiver directly to the a.c. mains.
Press and release the power button
will turn on and the LCD back light will illuminate.
Firstly, check the clock time - it should be displayed at the
top left corner of the display. If it has started from 00:00:00
instead of reading a sensible time then it is likely that the
small rechargeable battery in the receiver has run down.
This battery operates the clock and retains some
calibration data in memory, so you should work through
sections 6-2 and 6-3 to restore this data before using the
receiver. To re-charge the battery leave the receiver
connected to its mains adapter for about 48 hours (it
doesn't matter whether the receiver is switched on or off).
The charge should last for many months.
If the clock looks OK then you can skip sections 6-2 and
6-3 for the time being, but have a look at them later.

6-2 Filter calibration

If the data retention battery is discharged, or you have
added extra filters, or you have just got bored with listening
to your radio then you can run through the filter calibration
procedure. This is an automatic process once started and
takes about half a minute. Choose the SETUP menu by
pressing the button and then choose CONFIGURE
by pressing (the soft-key function shown on the
display above the
one click anti-clockwise to display Filter calibrate: and
press .
The receiver will display the filter number currently being
calibrated, signal level, -20dB and -6dB frequency offsets
PAGE 14 AR7030 OPERATING MANUAL
, the receiver
button). Rotate the spin-wheel
for high-side and low-side calibration. The AR7030
generates and injects a variable frequency signal from
the DDS and uses the AGC system to measure the filter
passband characteristics. In the process, the -6dB
bandwidth, centre frequency and USB and LSB carrier
insertion frequencies are determined. A list of filters is then
generated in ascending bandwidth order, regardless of
the physical position in which any filter has been fitted.
Ideally the calibration should be made when the set is at
its normal operating temperature (i.e. after about 30
minutes of use). You may carry out the calibration as often
as you like... it will not affect the performance of the
receiver if run more than once but it is interesting to watch!
The displayed bandwidth is rounded to the nearest 0.1kHz
so there may be slight variations in the results between
different calibration runs. Some filters are quite sensitive
to temperature changes.
Note: Most filter manufacturers usually quote a minimum
pass-band bandwidth (and a maximum stop-band
bandwidth) so in practice filters often measure wider than
their specification. The receiver, of course, doesn't know
the spec - it can only measure what's fitted. In fact the
standard 5.5kHz filter fitted to the AR7030 has a specified
bandwidth of 4kHz, so be careful when comparing the
filter calibrate results with bandwidths specified for optional
filters or other receivers.
Ceramic filters, such as the Murata ones fitted to the
AR7030, have very rounded filter characteristics. Many
people like the AM audio sound produced by this type of
filter, however such a filter is very difficult to accurately
measure. Collins mechanical filters can be fitted to the
AR7030 and have much sharper shoulders making them
easier to measure. Collins produces a 4.0 kHz AM
mechanical filter which will provide excellent results, the
optional 500 Hz CW mechanical filter and 2.5 kHz
mechanical filter are also very good. The displayed
bandwidth is not important for the receiver's performance
- it is only used by the receiver to build its filter table in
ascending order and as identification of which filter is
selected at any time.
Typical displayed bandwidths for the standard filters are:-
Filter 1 Displays as 1.8 to 2.3 kHz
(Spec. nominal 2.2 kHz)
Filter 2 Displays as 5.4 to 5.9 kHz
(Spec. minimum 4kHz)
Filter 3 Displays as 6.3 to 7.0 kHz
(Spec. minimum 6kHz)
Filter 4 Displays as 9.5 kHz
(Spec. minimum 9kHz)