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4-5. Function SWR-CHK
Before giving an SWR-CHK command, you have to stop any transmission and put
the amplifier (when available) to bypass (STBY mode). Never apply more than
100W tuning power in order not to trip either AATU protection!
When you select the function SWR-CHK between the square brackets in the main menu and then press Enter, you
will see the function inscription:
The operation principle is the same as when using the AUTO TUNE function (see S.4-1). After you have applied RF
power, the SWR is measured at the AATU input and then you have to stop the power:
At last, you get the measurement result:
or:
You can start the AUTO TUNE procedure while using SWR-CHK function and
return back to the SWR-CHK by pressing the button Enter.
The function can be restarted via the button Enter. To exit, press the button Esc until the main menu appears.
4-6. Using STATUS and SWR-CHK Functions for RF Path Diagnostics
Using both functions efficiently, you can estimate the status of the antenna and especially of the
feeder.
a) If you select BYPASS and check the SWR for a given frequency where you certainly know the
antenna has a bad SWR, but you can measure a good SWR instead, this is a symptom about high
losses in the feeder.
For instance, moisture could be present below the cable sheath, the insulation could be soaked with
water (unless it is dense) or shielding-braid corrosion could be present. Such a coaxial cable should
be replaced since it will cause much power loss and instability in both transmission and reception
modes.
b) If an * OK * is indicated after an AUTO TUNE but you find a bad SWR at the station end of the
cable (for instance looking at the transceiver or the amplifier indication), the antenna and the AATU
are OK but the coaxial cable has a problem (bad contact or short-circuiting at either connector is
likely). Check the antenna switch if any.
c) If you frequently get a message "Timeout Expired" (although above 50W tuning power applied)
and during the 20s-timeout period the SWR is OK at the station side, check the following:
the coaxial cable losses might be so high that the RF power reaching the remote unit is
-
insufficient to operate the AUTO TUNE function (below 10W);
in the remote unit, the fuse F2 at the RF-impedance sensor output has blown for some reason.
-
To replace it, see S.5-2(c) and fig.5-2.
d) If you frequently get a message "Timeout Expired" (although above 50W tuning power applied)
and during the 20s-timeout period the SWR is very high at the station side, check the following:
the coaxial cable could be torn or has a short circuit (most likely in either coaxial connector);
-
in the remote unit, the fuse F1 at the RF-impedance sensor input has blown for some reason
-
(then check F2 too). To replace them S.5-2(c) and fig.5-2.
C A U T I O N
Mode: SWR Check
.
Apply 10-100W RF ( )
Mode: SWR Check
.
Stop RF ...
.
Mode: SWR Check
.
SWR > 1.5 No Good
Mode: SWR Check
.
SWR < 1.5
* ОК *
N O T E
17
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