MFJ-926B HF Automatic Remote Antenna Tuner
Instruction Manual
2010 MFJ Enterprises, Inc.
8
If not enough power is applied for tuning (less than two watts); “QRO” (dah-dah-di-dah di-dah-dit dah-
dah-dah) will be sent on CW as indicated on the green LED. Increasing the input power above two watts
ends this message.
When input power is too high, the tuner enters a self-protection mode by bypassing the tuner. The tuner
will not allow any of its relays to change. This feature prevents damage to your tuner.
If too much power is applied when tuning, the tuner will cease the tuning routine and send “QRP” (dah-
dah-di-dah di-dah-dit di-dah-dah-dit) on CW. This occurs when the forward power exceeds 75 watts and
the SWR is greater than 3.0, or when the forward power exceeds 125 watts regardless of the SWR.
If more than 200 watts is applied to the tuner, the tuner will go into bypass mode and send “QRT” (dah-
dah-di-dah di-dah-dit dah) on CW.
If the tuning process is activated under these conditions, the tuner will not start the tuning. It will send
the appropriate code on CW.
The following table shows the various tuner Flashes:
Function
Indicates By
One Flash
Indicates By
Two Flashes
By Pressing
Antenna
1
2*
[ANT] < 1
second
Memory Bank
Bank A
(1 Flash)
Bank B*
(2 Flashes)
Bank C*
(3 Flashes)
Bank D*
(4 Flashes)
Off
(5 Flashes)
[ANT] > 1
second
Bypass Toggle
Bypass Mode
(L = 0 and C = 0)
Restore Last L/C Setting
[TUNE] < 0.5
sec.
Tuned SWR
SWR
≤
1.5
(1 Flash)
SWR
≤
2.0
(2 Flashes)
SWR
≤
2.5
(3 Flashes)
SWR
≤
3.0
(4 Flashes)
SWR >3.0
(“SWR”)
[TUNE] for
0.5 to 2
seconds
StickyTune
On
Off
[TUNE] > 2
seconds
Tuning Mode
Automatic
Semi-Automatic
[TUNE] +
[ANT]
* Not available on the MFJ-926B Table 2. Tuner Flashes.
Foldback Circuit
Modern transceivers with solid-state finals usually have a foldback circuit to protect the final transistors
from high SWR. A foldback circuit detects the SWR during transmit and reduces the output power as the
SWR rises above a preset threshold, usually 2:1. The higher the SWR the lower the power is set to
prevent damage.
If your transceiver has a foldback circuit, you can simply key down and tune at any power level from 2 to
100 watts. If your transceiver does not have a foldback circuit, you must manually set the power level to
20 watts or less for tuning (2-10 watts recommended). At higher power levels, the reflected power
occurring during tuning can damage your transceiver and causes component arcing which can damage the
relays in the tuner.
Check your transceiver owner's manual to see if your transceiver has a foldback circuit.