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Icom appears to delight in charging outrageous prices for all transceiver accessories, so many Hams improvise instead. A few circuits have been published for CI-V interfaces, most of which use the MAX232 IC.  Here is a very simple CI-V interface, originally described by OK2WY.  I’ve made small changes to the modem control signals connections. Although the circuit doesn’t conform exactly to the RS-232 specification, it does work well and has the advantage of being easily constructed inside a 9 pin D-type shell. Please note that the resistor value 4K7 means 4700 ohms.  The transistor types are not critical, I just happen to have plenty of 2N2222As.I’ve used this interface on various PC’s and also Dell Latitude Notebooks with both an IC735 and IC706MkIIG. No problems have been experienced even at 19200 baud with the IC706. It has also worked successfully when using a USB/Serial adapter from a notebook.  If a PTT function is required from the COM port, pin 7 (RTS) can be used to provide this facility.The circuit is powered by DTR (pin4).  I experienced some problems with YPLog using this power source. If YPLog is configured to use PTT from either the Parallel port or a different serial port from the one used by the CI-V Interface, the program drops the DTR signal, resulting in no power to the interface.   This is easily resolved by powering the circuit from RTS (pin 7) instead of DTR (pin4). To test and/or debug the interface, I would strongly recommend using AA6YQ’s CI-V Commander program.

Although I have successfully used the interface with a serial-USB adapter, I have seen

USB CI-V cables from China at very cheap prices on eBay. Consequently, it’s hardly worth

the effort of using the alternative.

Disclaimer: Although I have tested and used the above circuit on my own IC735 and

IC706mkIIG with no problems, I do not make any representation or guarantee that this

circuit will function, nor do I accept any responsibility whatsoever for any damage or

malfunction arising from the use of this circuit.

Here are some links to software for use with CI-V controlled Icom rigs:
CI-V Test by DF4OR - Freeware program to test CI-V bus
CI-V Commander by AA6YQ - Freeware program to control Icom rigs and monitor CI-V bus
RadioComm by KE7ZZ - Careware program to control and load memories of Icom rigs
YPLOG by VE6YP - Shareware Icom Rig control and logging program
Ham Radio Deluxe by HB9DRV - Bloatware Icom control program

ICOM CI-V interface to RS232 using transistors, fits in DB9 case

pro: No external power needed.
pro: Very small, fits in DB9 connector case (with SMD components)
con: Requires standard compliant serial port, may not work on all notebooks.

Alexander from Russia writes:

Concernig scematic for CI-V adapter. I drew down it from real pcb so I specified part value for readable components only. They all are smd.
C1 – ceramic (looks strange but it’s true),
R5 – at least 0.5W
Q1 and Q2 I guess can be any switch transistors.
I checked this adapter with CI-V Explorer software, everything’s ok.

Backyard Universe: Solar activity firing up
Story Photo
Staff photo by Johnny Horne
[+] click to enlarge
A large sunspot group appearing on the sun in July 2004 is shown in the overall image of the sun at left and close-up in the photo at right. Both photos were made using a telescope fitted with a solar filter. Sunspots can spawn solar flares that can trigger displays of the aurora borealis or Northern lights.

You may not have even noticed, but the sun has recently become more active.

This has nothing to do with the 90-degree days we’ve had this week, which is a seasonal effect. I’m talking about activity on the sun 93 million miles away. View full article »

Tune Your Metal Tubing Slim Jim to Perfection!

If you are reading this you most likely have built the Slim Jim antenna for the 2 meter band using either copper or aluminum tubing. After your final tuning, you may not have seen that “perfect” swr reading of 1:1 that many look for and could not get any lower to reach “perfection”. View full article »

The 4 Element Hentenna Beam for 2 Meters

by N5NNS


Having been a ham for 27 years and knowing that the most important part of any station is the antenna, I have built, designed, and redesigned antennas for over two decades. View full article »