View Full Version : IC-745 - the '751's ugly twin?

08-12-2011, 06:38 PM
Recently bought a very clean example of this transceiver from an eBay seller. It had the internal keyer but no other options installed.

So...I set off in search of.

EX-242 FM board - new old stock - $200 (Owch!)
FL-54 - 9MHz 250Hz CW filter - used - $80
FL-52 - 455KHz 250Hz CW filter - new - $133 (not as bad as Universal's $209 asking price, but still...)

Am currently looking for an FL-44A. Here's the lowdown regarding the rig:

Cosmetically, the IC-745 sits somewhere between the IC-720, R-71A and IC-751. Its greenish frequency readout is reminiscent of the unit used in the R-70 receiver but the controls and switches are a couple years more modern. Icom's only real faux pax (in my opinion) is the choice of a slide-type potentiometer for the IF Shift/PBT and Notch Filter controls but so far they've held up well.

That IF Shift/PBT control is unique...in that a front-panel switch selects its function. My '751As don't do that, nor do my R-71As. Or my TS-940s, R-5000s...R7/TR7...why does it matter, you ask? It's the only rig in my shack whose interference-fighting controls have been able to clean up a persistent (external) carrier which masks signals in an area of the spectrum which I like to monitor.

You switch modes by repetitively pressing the "Mode" key. Or by using one of the 16 Memory Channels to store an in-band frequency and mode then selecting the memory via rotary switch. You can tune the memory channel frequency via the VFO knob but you cannot work "split" while in memory mode - nor can you exchange VFO and memory data as you can with similar Icom radios.

The rig comes with an RF preamp but no attenuator (a la 751/R71's multi-position switch). Hardly a deal breaker for me as I use it on 17M and above - where an attenuator is normally not needed. Low-band operators may find the lack of an attenuator to be a drawback.

A crystal calibrator is optional but not included. You calibrate the rig's frequency readout by setting it to ".000.0" via the tuning knob then activating the calibrator accessory and adjusting a top-panel "Calibrator" control for zero beat. You can also do it via WWV or another frequency standard. Being able to externally adjust the reference oscillator is a huge convenience - you don't have to disassemble the transceiver to do so, as is the case with a number of other rigs of this era.

On-air reports indicate that the speech processor muddies up the audio quality a bit. It does increase average power by a noticeable amount.

The 745 receives but does not transmit AM. There is a mod for this.

All in all, I like the rig. It's currently slaved to an R-71A and AT-100 auto tuner and will be the 10-17M 'go-to' radio. I am eventually going to mount an AH-2 random-wire tuner controller to the case. It can then be used at our Field Day site with a wire vertical.

08-14-2011, 12:40 PM
I just scored some interesting goodies over the weekend:

An FL-44A filter;
An EX-309 Interface (parallel I/O; more on this later);
Two (count 'em) IC-EX1 "expansion terminals".

Icom incorporated a method of controlling its transceivers via PC serial port and CI-V interface starting with the IC-751...but a parallel data exchange mechanism existed within their architecture as far back as the IC-720/R70 line. To that end, an IC-7072 'transceive controller' was offered as an option. It allowed the R70's VFO to control the 720 by virtue of data lines present in the 24p accessory connector which resides on the back panel of each rig.

Examining the EX-309 / IC-7072 / IC-720 / R70 schematics, I think that I can adapt the '309 and the IC-745's accessory connector to accommodate a '7072 and an attendant R70 in master-slave mode...:chin:

12-13-2017, 05:35 PM
I know this thread is old as the hills, but was wondering if you ever found any use of the EX-309.
A few of us are working on the 745/751 projects dealing with the ram board. Yes we know you can purchase the replacement ram boards that do not fail but this is an experiment we are working on.

I really like the old 745 style radios. Looking for modern ways to interface with the original ram board. There was a few programmers designed that would do this via LPT port years ago.

12-18-2017, 12:09 PM
I have not...although I'm going to revisit that radio soon. It's currently paired with an R-70 and the previously mentioned AT-100 in my 10M spot. Plans are to mod it for AM transmit then have a look at a data converter that would allow it to transceive with the R70 - as the R-70/IC-7072 and IC-720 pairing did.

12-19-2017, 05:06 PM
I liked the variable AGC control on the IC-745.

12-21-2017, 04:23 PM
I liked the variable AGC control on the IC-745.
The other rig which offered this is the Swan/Cubic Astro 102/103.

Though they were ham-bands only and single conversion to boot, they're very good performers.

01-08-2018, 01:40 PM
Thanks for the information. I had a chance to pick one up recently but decided against it. Been really swamped here. So busy cannot get anything done.
I have been playing with the 745 ram board for a while now. I had just about forgot about this thread.

Anyway I now have the software and hardware to program those EX-314 boards for the 745/751 rigs. I know we can get the new made boards from PIEXX and the guy over seas but it is also nice to have this option on keeping the stock board alive. Did a couple of YouTube videos on it.