IC-R20 Duplex, AFC, Noise Functions & Antennas

Summary: How to use the IC-R20’s duplex monitoring, AFC, noise blanker, noise limiter, AF filter, and the bar and earphone antennas.

Duplex Operation

Repeaters receive on one frequency and transmit on another. The IC-R20 receives the repeater output, but can shift to the input frequency while you hold [SQL]. Repeater information (offset and direction) can be stored in memory channels.

1. Set the receive frequency (the repeater output).
2. Hold [8 SET], choose SET EXPAND and turn it ON.
3. Choose OFFSET FREQ and set the offset (0.00000-159.99999 MHz; the VFO tuning step is used; hold [VFO MHz] and rotate for 1 MHz or 10 MHz steps).
4. Choose DUPLEX and select -DUP or +DUP.
5. Push [DUALWATCH] to exit. Push and hold [SQL] to monitor the input frequency.

The offset is set for each band independently and its default depends on the band and version. “-DUP” shifts down and “+DUP” shifts up during monitoring.

AFC (Automatic Frequency Control)

Tunes the displayed frequency automatically when an off-centre signal is received. FM and WFM only, single band only. Hold [0 AFC] for 1 second to toggle it.

Noise Blanker (NB)

Removes pulse noise such as car ignition. LSB, USB and CW only. Set mode, NOISE BLANKER (default OFF). The “NB” indicator shows. It isn’t effective for non-pulse noise.

Automatic Noise Limiter (ANL)

Reduces noise in AM mode. Set mode, ANL (default OFF).

AF Filter

Suppresses high-pitched audio. Set mode, AF FILTER (default OFF). It isn’t effective in FM mode.

Internal Bar Antenna and Earphone Antenna

• AM ANTENNA: for the AM broadcast band (0.495-1.620 MHz) choose BAR to use the internal bar antenna (default EXT: the connected antenna). Aim the receiver for the best audio.
• FM ANTENNA: for the FM broadcast band (76.000-107.995 MHz) choose EARPHONE to use the earphone cable (default EXT).

Some noise or spurious signals may be received on the bar or earphone antennas, the attenuator can’t be used with them, and the supplied or a third-party antenna must be connected to receive anything except AM or FM broadcast. See IC-R20 Set Mode Reference.