ICOM IC-751A and Kenwood TS-440S/AT

[w8cbc]

For the longest time I wanted a TS-440. I almost bought one but it got away while I was dithering over whether to spend the money. The next day I picked up a 751A for a bit less. That was in September. I've been happy as anything with the 751A since.

Last month (November), I went looking for a HF mobile rig. I considered several, came across a TS-440S/AT, decided it was just small enough to fit, and bought it. I've operated it both mobile and stationary for several weeks now.

The comparison begins...

First, receiving.

Sensitivity - both are excellent, I can't really tell them apart.

Selectivity - The IC-751A comes with five bandwidths stock: 500Hz CW, 2k3 SSB, 2k6 SSB/AM, 8k AM, and 15k FM. The TS-440 has two choices for CW/SSB/AM: 2k2 and 6k. FM is 12k. For what they are, all the filters have good response. The IC-751A wins in this department because of its greater filter selection. * Note: figures for the 440 were corrected 2 Jan 06.

Notch filtering: The 751A does it in the IF, the notch is very deep and helps with background noise as well as heterodynes. The 440 does it in audio, the notch is shallower and much too sharp. Major advantage: 751A.

Passband tuning (called IF Shift in the TS-440): Both operate the same and work well. The TS-440 has actual PBT. No difference.

Dynamic range: Both are excellent though the 751A's noise blanker can overload when cranked to the max. Minimal advantage to the TS-440.

Noise blanker: The TS-440 has one setting: on/off. It deals nicely with ignition noise. It makes no difference at all with power-line buzz. The IC-751A has two settings (narrow/wide) and a variable threshold level. It can eliminate power-line buzz in some but not all cases. It has to be backed off in the presence of strong signals. Advantage: 751A.

Audio quality: The TS-440 sounds thin, it has practically no bass and there's no tone control. The 751A is rich and warm in comparison and has a tone control. Advantage: 751A.

Frequency stability: The 751A, recalibrated to WWV, is a bit drifty, +/- about 20 Hz over time. The TS-440 has been bang-on since I got it despite the temperature extremes to which it has been subjected. Advantage: TS-440.

Frequency readout: The TS-440 reads to 10 Hz, the 751A to 100 Hz. Advantage: TS-440.

Frequency coverage: The 751A tunes 97-30003kc stock, the TS-440 30-30000kc stock. The 440 receives WWVB well but is rather noisy and insensitive below 50kc. Advantage: TS-440.

Overall receiving: the 751A wins mainly because of the filter selection and its superior notch filter and noise blanker.

Now, transmitting.

Frequency stability: covered in receiving, above. Advantage: TS-440.

Audio quality: I've been told the 751A sounds rich and warm. Having heard it myself via LDE, I concur. The TS-440 is "average". Advantage: 751A.

CW operation: Both are smooth and crisp. The 440 clatters relays in QSK, the 751A doesn't. As far as I'm concerned, not a big deal. Minimal advantage to the 751A. * revised 3 February 2006

Modes: Both have CW, AM, SSB, FM, and RTTY. No difference.

Power output: Both do 100 watts PEP in all but AM. The 751A does 50 watts carrier AM, the TS-440 can run the carrier to 100 watts but for good modulation quality you have to back it off to 25 watts. Advantage: 751A.

Metering: The 751A reads power, SWR, ALC level, Ec, Ic, and compression. The TS-440 reads power, SWR, and ALC. I find Ec and Ic important enough to check in some circumstances so the advantage goes to the 751A.

Antenna matching: The TS-440S/AT has an autotuner that works well with a nine-ft. whip in all bands from 80 to 10 metres. The 751A doesn't have a tuner; I use a home-built T network with it. Advantage, big: TS-440S/AT.

Power consumption: Both draw about the same current on receive and transmit. No difference.

Overall transmit: Leaving out the autotuner, the 751A would win. With it, the TS-440 wins.

General operation:

The TS-440 has a keypad, the 751A doesn't. The TS-440 is a little easier to operate otherwise because the mode buttons are separate (no "shift" functions) and changing MHz is easier with the up/down buttons than with a step switch and the VFO knob.

The TS-440 has 100 memories for frequency and mode and can store "splits", the 751A has 32 and cannot store "splits".

The TS-440 wins in the general operation category.

Overall - each has its strengths and weaknesses. If I could keep only one, I'd keep the 751A and forgo mobile operation.

But the 440 would be adequate for home operation if I had to let go of the 751A. To be better than adequate, it would need the optional CW filter - and, in my circumstances, I'd have to work on the noise blanker because power-line buzz is an unfortunate fact of life here.

[AB8UG]

Keep an eye out for an Icom RC-10 Frequency controller. #It plugs into the bottom front of the 751A and gives you the keypad function except for the up-down tune. #The up-down tune is available with the SM-8 microphone. #I get great audio reports with this mike hooked to my 751A.

[w8cbc]

Thanks for the tip - a keypad isn't a big item for me but it would be nice to have.

That Willco memory module just got here in the mail and works nice. The 751A's rx coverage is now 10-31000 kc. It hears WWVB on the zigzag so I know that's working well. I'll to have to run out the 90-foot wire again Thursday night just to find out what I can hear under 100kc and see if it's really better in that respect than the TS-440 (it seems to be so far - there's much less internal noise).

The module's 1024 memories will be welcome when I get around to hooking up the bank-switching.

Another thing to get around to will be building a jig to reprogramme the 751A's stock memory module. I'm given to understand that with a fair bit of work this thing can R and T right on up to 55MC. I would really like to get some 6-metre action going here.

---edit---

With the 90-ft. wire the two rigs are about equal from 50-100 kc. The 751A loses some sensitivity below 40 and there are a number of birdies from 31 on down. The 440 has the aforementioned synth noise below 50 and doesn't hear very well down there on account of that. I'd give the 751A the nod for longwave reception but only by a little bit.

---another edit---

I finally got 'round to hooking up the bank-switching on the Willco module. Its operation is awkward but I'll get used to it. I cannot imagine ever filling the thing up.

[N1ESE]

I wonder how much different the A version is of the 751 is.

[w8cbc]

By my understanding of it, the "A" is the cleaned-up-and-fixed version. There were some (admitted by ICOM) design problems in the 751. I think they were mostly in the transmit side.

---edit---

I got a RC-10 today at R&L. Finding it was a complete surprise; I was after other stuff. Plugged it in. Operation is simple and straightforward. I like it.

This 751A is becoming "loaded". I won't get the internal power supply as I hear there are often problems with it. Am not interested in the speech option. The only other thing I can add to it that I'd be interested in is the narrow (250-cycle) CW filter. I saw one in eBay not long ago; they're out there...

[w8cbc]

More random gumph about these two, some months on.


The TS-440 is sensitive to humidity. It'll totally lose VCO lock and just wander someplace off-frequency if it's been raining steadily for a few hours. Apparently the goop in its VCO section absorbs and holds moisture. As the thing dries out, the VCO will close in toward where it should be and then the radio will quit operating at all until it can capture and hold. Keep in mind that it resides in my car - thus no climate control.

It popped a 20A line fuse on low-power tune-up a couple of weeks ago. After I replaced the fuse, it drew excessive current again for about a second and then settled down. I suspect an intermittent in the final biasing.

I'll have to lay this thing out and give it a good going-over some time soon. It's not holding up too well in mobile service.


The IC-751A lost a trimmer cap in VCO3 (shorted) during my trip in mid-April. It was a bit of a chore to replace but that fixed it fine. I will eventually replace the other three with ceramics as well.

There've been no other problems with this rig at all.

I ran some tests on it tonight with some fairly sophisticated equipment borrowed from work.

S meter is dead-on at S9 (50uV) and +40 (5mV). It reads just a shade low (2dB at most) between those values - much more accurate than I expected for any radio, and it's quite surprising that it's held its calibration for the 15 years since it was made.

Power output is 130 watts max below 21 MC, scaling back to 110 watts at 29.6 MC. Its meter switched to "Po" reads 15% low. Icom state that it's supposed to be approximate at best. The next time I have the 751A apart I'll scale the power output back a bit and adjust its meter to give a better indication.

There's mild synthesiser (phase) noise on transmit. It's -70dBc worst case. I'd read it wrong at first and thought I had -30dBc. THAT was worrisome.

The receive section appears to be somewhat better than spec. 0.1uV in gives a CW signal of 409 RST (probably 3dB S/N) without the preamp, using the SSB filter. It's specced at 10dB S/N at 0.15uV in with the 9dB preamp on and using the 500-cycle CW filter. Had I thought to look at the specs while I had it all hooked up, I'd have done a direct comparison. In any event, it's plenty sensitive enough that it's not limited by internal noise.

I didn't do any IM tests. No need - I've never heard the thing overload except with the noise blanker cranked to max (as stated in the initial review).

The preamp adds 9dB, the attenuator cuts 18dB. Aside from that, I didn't test them. I know the preamp adds a little noise. It does help some with very weak signals above 21 MC; I don't use it otherwise.


Anyway. The IC-751A is a keeper. I'll have to find some way to keep the TS-440 good and dry. It gets quite humid around here in the summer.

---edit---

I forgot to mention, I measured the 751A's the notch filter. It attenuates its centre frequency by 57dB. It's specced at 45dB. Very nice.

---another edit---

The TS-440 popped another fuse yesterday (2 June) so I brought it upstairs and attempted to get into the PA unit. That was difficult. I couldn't get at the trace side of the board without detaching everything from the heat sinks so I resoldered the accessible end of the bias reference diode (D3, to ground, atop the board) hoping to re-establish its connection. I hope it was that end and not the other. I also applied some heat to the VCO section, hoping to dry it out and thus deal with the PLL wobble.

I worked a couple of fellows in 10 metres on the way home so it works for now.

Build philosophies appear different between Kenwood and ICOM. Kenwood made things compact, stuffing them into as small and solid a box as practical. ICOM laid things out more openly, in a larger, lighter box.

The ICOMs of that era (late 80s-early 90s) are much easier to work on and tinker with. The Kenwoods were designed to just install and operate.

[VK5MRD]

I can not comment on the TS-440 as I have neither used one or heard one in use but I can comment on the Icom 751A. #I have owned my Icom 751A now for around 5 years and I could not be more happier. #I have since added a Icom SP-3 and an Icom SM-2 mic. #I had an alignment done to mine a few years back and it works like a dream. #The RX audio is pleasant and the filters work a dream too. #TX audio is very nice with the Icom SM-2. #In my opinion a very clean well regarded radio and a solid performer in my shack.

Best 73 de Dave VK5FDMR #qrz.com/vk5fdmr http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

[w8cbc]

Update:

I finally got off me lazy bum and into the TS-440 in detail. From the way the PLLs were losing lock, and from everything I had read on the subject, I figured I had that problem with the goop becoming conductive.

It turned out that there were several deteriorated solder joints in VCO5. After fixing them and doing some realignment, the 440 runs just fine under conditions (hot and humid) that before would make it flake out.

I dragged it out for field day. Not a twitch as far as the PLLs went. Auto-tuning was a little flaky though - there was no output for a few seconds a couple of times. I don't think it was the final bias as it popped no fuses and didn't appear to be drawing excessive current but it's something to look into next.

I've just bought an IC-751 (not A) in ebay to keep in northeastern VE3. It has the ICM-1024 memory module already installed. There'll be more on this one after it gets here and I've checked it over.

---edit 3 July---

The IC-751 got here Friday. It works but has many small problems. I've fixed a few and given it an alignment per the maintenance manual but there's more to do.

It has the 6kc AM filter and no CW filter. Design is rather different from the 751A in many respects.

There'll be a review once I have it sorted out and working to spec.

---edit---

I've fixed the main problems in the 751. Some of what I found in there was... interesting. I'll run it on-air awhile before writing a separate review for it.

The TS-440 is definitely fixed now. I've left it out in the Polara for quite some time now baking in the sun. It fired right up this afternoon, no problems.

Everything I've dealt with in all this other gear makes me realise what a lucky find the 751A was. It's been perfectly reliable aside from that VCO trimmer and it is comfortably beyond spec in both transmit and receive. For what it is, I couldn't ask for better.

[KC8PX]

i have had my Icom IC-751-A for 20 years and it has been a terrific radio. As to the comparisons; it says a lot for the Icom, comparing a two decade old radio with a modern "now" built rig

KC8PX