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Hardware Recommended for Use With PCALE
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PCALE functions as an ALE controller with almost any popular amateur or commercial HF radio.

How PCALE Controls the Transceiver
For rapid channel scanning, PCALE uses the computer- to- radio CAT interface to control the transceiver frequency.
Most of the usual computer - radio interface boxes that are commonly used for ham radio digital modes or transceiver computer control work fine with PCALE. Generally speaking, if you are already set up with ham radio digital mode and CAT control, then it is likely you can get basic ALE running with PCALE using your present system*.

PCALE sends PTT control via the RS-232 serial port, normally using the RTS (or DTR) pins of DB9 or DB25 connector of the computer (or a USB-to-Serial adapter).  The RTS line goes high when transmitting. Hardware PTT is recommended.
*Note: Software PTT (also known as CAT PTT) is also available for most radios, and it will generally work for basic ALE operation, but it is not nearly as fast as hardware PTT via a dedicated hardware RTS transmit signal. Depending on your radio and the serial port speed, Software PTT may not be able to keep up with the rapid handshaking and ARQ transmissions that ALE requires. It is best to use Hardware PTT via RTS.

Homebrew Interface
For the hardware control of your radio, it is also possible to construct your own interface. Schematics for homebrew interfaces are on the HFLINK Interface page here, and some of these provide speaker muting that un-mutes the station external speaker whenever another station calls you. This feature can also be adapted to ham radio interface boxes that have a "CW keying" feature, by the addition of a relay in the speaker line.
Click to zoom on interfaces:

Simple Hardware Interface for ALE

Selecting a Transceiver for ALE service with PCALE

While almost any HF transceiver is suitable for ALE work, some transceivers are better suited to continuous 24/7/365 ALE service than others.
The following recommende transceivers have internal receiver bandpass switching circuitry that is optimum for fast Quiet Relay Scanning and Sounding with PCALE.
(These radios use diode bandpass switching for receive scanning, and only use relays when transmitting)
The following Icom radios are compatible with PCALE Quiet Relay Scanning, and are recommended: IC746, IC746PRO, IC7400, IC756PRO (Milspec 1030E-DSP), IC756PRO2, IC756PRO3, IC765, IC775, IC781, IC7800. They have diode switched filters, and are capable of up to 2 ch/sec scan rate. Newer models running with CAT at 9600 baud can scan up to 5 channels/second. The IC756pro series and more recent models can run at 19,200 baud and are capable of 10 channels/second scan rate. (Note: the IC7800 has diode switched filters but has mechanical relays in the mixer, so some acoustic noise will be heard.)

Quiet Relay Scan Mods (hardware modifications) are documented for several popular Icom radios. These may provide the most cost effective solution for a scanning ALE radio system.
Icom IC-718 Quiet Relay Scan Mod
Icom IC-7200 Quiet Relay Scan Mod
The following Kenwood radios are compatible with PCALE Quiet Relay Scanning, and are recommended: All Kenwood models after TS-440 (but excluding the TS-440). They have diode switched filters. The oldest models are capable of up to 2 channels/second scan rate. The more recent models work at CAT rates of 9600 baud for up to 5 channels/second, and newest models work at 19,200 baud at 10 channels/second scan rate.
The following Yaesu radios are compatible with PCALE Quiet Relay Scanning, and are recommended: FT-920, FT-990. They have diode switched filters, and are capable of up to 2 ch/sec scan rate.
(It is also possible to modify the FT-890 with a special QS/S mod that enables solid-state scanning; you can ask about this mod on the HFLINK forum)
The following Harris radios are compatible with PCALE Quiet Relay Scanning, and are recommended: Harris RF-350 family: RF-350, RF-350K, RT-1446 URC, AN/URC-119, AN/URC-121(V) The quiet relay scanning is handled by the BYPASS command, supporting up to 2 ch/sec scan rate.
Most other radios that are not on the above lists will still function fine with PCALE. Radios that don't have diode switched filters use mechanical relays. Even though they are not Quiet Relay Scanning compatible, they will scan in Simplex on a single VFO, rather than using the Split VFO method. The bandpass relays will be clicking every few seconds during scanning. This isn't technical a problem (unless the clicking in the background bothers you). Some radios have relays that are barely audible, while others are acoustically noticeable. By limiting the number of channels in the scan group to less than 11 channels, it is possible to be compatible at a scan rate of 1 channel/second. This effectively lessens the number of relay switching cycles. Even though Quiet Relay Scanning transceivers are recommended for long term continuous 24/7/365 ALE use, many operators are currently using normal relay switched transceivers that have been running perfectly in ALE service for years. All operators are encouraged to use whatever transceiver they have, to get on the air with ALE.



Homebrew Interface

Selecting a Transceiver for Use with PCALE

Quiet Relay Scan





Other Radios

Scanning of Radios Without CAT

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It is best to use a good internal PC soundcard or the laptop built-in audio. Cheap USB soundcard dongles or inexpensive USB radio interface devices that have built-in soundcards may be OK for some ham radio digital modes, but they are generally not capable of decoding ALE with PCALE because they do not have real 48kHz sampling. It is also necessary for the soundcard to have an accurate clock, within 15Hz when the audio is measured at 2500Hz. Off-frequency soundcards often show up as a problem  decoding the ALE signal. Be sure to calibrate your radio and your soundcard before setting up ALE.

How Quiet Relay Scanning Works
PCALE uses the SPLIT VFO feature of the transceiver, and commands the radio to set the TRANSMIT VFO on a fixed frequency. Then PCALE command the radio to scan only the RECEIVE VFO. Certain models of transceivers are compatible with Quiet Relay Scanning. Other transceivers that don't have this feature will work OK for ALE, but PCALE scans them in single VFO mode, instead of Split VFO.

Quiet Relay Scan Functional Block Diagram

Typical Relay Switched Filters:

Typical Relay Filters

Typical Diode Switched Filters:
Typical Diode Switched Filters

Scanning of Radios Without CAT
PCALE can also control radios that do not have CAT, but have channel memory. The special PCALE software for this "hardware pulse scanning" is available by inquiring on the HFLINK forum. Select Hardware Pulse from the radio type menu. Connect the RS-232 port TXD line via a transistor interface to the radio's "Up Channel" mic button line.

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