I was operating my Icom IC-746PRO recently doing some A/B tests between it and my old Heathkit HW-16. Sounds like a bad joke, doesn't it?
Well, they don't really compare, bare rig to bare rig. With my Datong FL-2 filter, the HW-16 is much more ccmpetitive with the PRO. The Heathkit, even with filter, is prone to hearing artifacts of strong adjacent (even not-so-adjacent) signals. For example, I was on 3579 kHz for the KSN and was getting a lot of hash from a very strong station 5 or 6 kHz away. The Datong did a good job, but the strong adjacent signal's artifacts were still there. The filter minimized them to a great degree.
The problem with cranking the filter down that tight is that some nights (as was the case that night), not all the stations were zero beat. The NCS was about 80 cycles high, and some stations were zero beat and some where fairly far away (as audio filters go). A couple of stations furthest away from the net frequency were on the edge of the audio filter's passband. Opening it up naturally let in splatter with the signal.
The IC-746PRO has a similar issue with strong nearby signals. It's not bad, but noticeable. While tuning the band and operating I usually use the widest filtering I can get by with. On the 746PRO, I typically run 1.2 kHz, simply because I prefer the audio quality. When there's QRM/QRN, I crank the filtering down as required. This morning I was copying the mail on a 40 M CW QSO and was hearing artifacts of a nearby signal some 15 kHz away. I cranked down the filtering, which helped, but you could still tell there was a little “shh-sh-shhh-sh shh-shh-sh-shh” faintly audible. Not a problem, of course, but it makes me wonder how other rigs compare.
I've unintentionally turned the 746PRO into my main HF rig. I bought the rig after I bought the PROIII, and got it dirt cheap. It was a bit of a gamble (like anything on eBay, I suppose) — the seller was upfront about the rig's history. It was a low serial number, one of the early models with the “dead transmit” problem. He had it properly repaired, but replaced the rig in the interim and never used it again.
With that history, I figured I should run the rig long and hard to see if the transmitter would fail again. I've done just that since the day I unpacked it. I quit expecting it to die many, many months ago. Used 746PROs are selling on eBay for hundreds more than the price I paid … heck, even the plain IC-746s are selling for more. If the rig died today, I wouldn't hesitate to ship it off for repair, its really a great radio. I'm delighted with the bargain, and wouldn't hesitate to recommend it.
SPEAKING OF CW … My comments on CW filtering fired a neuron in my brain, triggering a memory of my early CW contacts, which were pretty much sans filtering.
My first HF rig was my Hallicrafters SR-150, nicknamed by its previous owner as “Old Ironsides.” The rig is a great SSB rig, but as I discovered, it lacked a few things for CW operation.
The first thing it did not have was a sidetone. I tried to hook up the Heathkit tone oscillator with my key, but the voltages on the key weren't very friendly to the oscillator. I sent slowly enough that I could watch the output meter of the SR-150 and judge my character spacing that way (I shudder to think of how bad my fist must have sounded). The SR-150 also had no CW filtering to speak of, nor did it have any options for adding filters. This was a major oversight in my book. The Halli SX-117 (part of the Hallicrafter “Twins”, coupled with the matching HT-44 txmtr) offered four levels of filter, right down to 500 Hz. I guess at the time, the market for the SR-150 was the mobile SSB market, and leaving off the filtering saved a few bucks.
The transceiver was designed so the crystal lattice filters and IFs were shared by the rigs receiver and transmit circuitry, so perhaps adding CW filtering would have complicated the rig. To its credit, the SR-150 has pretty good selectivity on SSB, but on a busy night or contest, working CW required the old “brain filter” to copy while you tried to ignore other signals in the passband.
My next HF rig was the Heathkit SB-102, and that rig was a big improvement for my CW efforts. I worked a lot of CW with the 102. I have wanted to re-acquire an SB-102 station for nostalgia's sake, but I'll admit I have reservations about doing so. I suspect my recollections of my SB-102 have been sweetened over time by my selective memory … perhaps its better to remember my old Benton Harbor rig in a favorable light than to get another one and discover how mediocre it really may have been …
The HW-16 is probably enough Hot Water for any shack, though I do have a DX-60 transmitter I've never put on the air yet. Hmmm…