A few notes on Icom's CI-V interface
Almost every Icom rig made since the mid 80s incorporates their CI-V computer interface. It allows multiple radios to be connected together and computer controlled via a CT-17, or two to be directly connected for purposes of synchronized operation.
I recently dragged one each IC-751A and R-71A out of storage to place in my main floor shack/home office. The aim was to use the -751A as my FT8 rig and the -71A as a second receiver, for monitoring other parts of the shortwave spectrum. In a future implementation, multiple receivers (a mix of R-71As and R-7000s) may see duty with each transceiver - all capable of being controlled via one CT-17.
Icom offered a CI-V accessory for the R-71, IC-751 and other rigs...the UX-14. It supports communication baud rates of 300, 1200 and 9600. We're going to take advantage of this.
The interface (in face, most CI-V hardware) also supports something called "transceive mode". That is if it's configured to use this mode, a change in operating parameters will result in a data stream being transmitted out the port so that other devices configured with "transceive" will automatically sync to the "master" (whichever radio initiated the change). Handy in true diversity-reception scenarios, or if your secondary receiver is a better performer than the one in your transceiver. A special bus address (corresponding to "all") makes this possible and is automatically set if "Transceive" is enabled on a given interface.
Conversely, if this isn't set nothing happens. A change to the radio's operating parameters won't be broadcast, and the radio won't act upon any received updates. Changing the interface mode requires removing the radios from the lineup and pulling the covers off. Not an ideal way of doing things.
While I had the -751A apart to install its interface, I decided to do a little playing around. Both receiver and transceiver had their UX-14s set to "transceive" and 9600 baud speed. Any changes made on the -751A immediately propagated to the -71A, and vice versa.
Except for changes made by WSJTX. I could change bands on either transceiver or receiver via the program and the other device stayed put. Until the VFO, Memory or Mode switches were touched, that is. I also experimented with baud rates of the UX-14s and found that if they're different, no synchronization occurs.
Some contemplation led me to the following:
- In a multi-rig Icom station with one station controller PC available, leverage a CT-17 for connection of up to four different radios.
- All radios connected to one of these can "see" each other if "transceive" is set and the baud rates are the same
- Several communications control programs (e.g., ScanCAT Gold, Spectrum Commander) offer the ability to control the R-71 and R-7000 receivers (and others) in either independent mode or as a "range pair". That is, the R-71 handles frequencies below 30MHz and the R-7000, those above. Handoff is done automatically as the programs scan or search.
- A fully equipped station with radios of this era could include the -751A, a pair of R-71As and an R-7000.
- The IC-751A and one R-71A have their UX-14s set to 1200 baud
- The other R-71A and the R-7000 are configured for 9600 baud
- Each radio is configured for a different CI-V address
- All radios have the "transceive" option set
- The IC-751A feeds signals to its companion R-71A via a Mini Circuits 50-ohm power divider, connected to the Rec Ant Out/In ports on the transceiver's rear panel
- The second R-71A is either fed from the "active" station antenna (use a 4-port divider) or via a separate receive antenna (use a receiver protector at the antenna input).
- The R-7000 is fed from a wideband scanner antenna. Use a high-pass filter if 10M operation of the transceiver is contemplated.
- An IC-EX1 handles muting of all the receivers and acts as an I/O interface to things like a SignaLink or KAM.
- Note: An R-7000 "Ext Mute" scheme is being devised. Why didn't Icom think to include this...
- To use the station, one does the following:
- Dial up a favorite frequency to monitor with the first R-71A. Set mode, memory, what have you - then hit the Tuning Lock button.
- Use WSJTX, HRD, etc. to control the transceiver. Its Tuning Lock button should also be pressed.
- Use Spectrum Commander, ScanCAT, etc. to control the R-71A/R-7000 pair. Ditto the Tuning Locks.
- Note that only one program at a time can access the serial port used to connect the CT-17. Simultaneous operation requires two of these adapters, one per "pair". You can control up to four rigs through each and I've tested this with Spectrum Commander.
- R-71 and R-7000 require a special "Squelch Detect" cable to stop on a busy signal. In the Groups.io "R7000RX" group I detailed how to build a multi-radio cable. This has been tested with three concurrently operating R-7000s.
- When you wish to sync two radios, stop the controller program which is interacting with the desired "pair" then make a parameter change to one or the other. Its companion will track.
It's important to relinquish PC control of the transceiver before changing parameters if you have accessories connected which automatically track band changes. I have an AT-150 at my FT8 position. IC-2KL/AT-500 pairs can also be pressed into service and you don't want them jumping between bands in response to a receiver-commanded change if you're actively using the transceiver.
Granted, this was a rather long post - but may spur a few ideas. Later CI-V implementations may support more choices of baud rate, and I'll look into this as yet another possibility for multi-rig operation.
