ICOM 703 PLUS

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Hi, Donald,

W4RT doesn't sell the narrow filter so they don't recommend it.  Seriously.

The narrower the passband the less you hear on either side of the signal you are copying.  If, like me, you need to concentrate on a relatively fast CW signal, eliminating the adjacent interference and any background noise (the DSP does the latter) makes copying much easier and much less fatiguing.  That's why I like the narrowest filter I can get that still allows me to hear a nice crisp, clear signal.

The only disadvantage of a narrower filter in some older rigs was ringing and a hollow sound to the signal.  IME the Icom and Inrad filters are very good and I am pleased with the way the 250Hz filter sounds in the IC-703.

One thing an inexperienced operator can do with a very narrow filter:  if you use it in conjunction with passband tuning (PBT, not available on the IC-703) or IF shift you can effectively shift the IF passband of the radio completely outside the passband of the filter, in effect shutting down the receiver (with PBT) or moving it off the signal you are copying.  Simply putting back the IF Shift to a nearer normal, center position corrects this.

I can wholeheartedly recommend a 250Hz filter on an IC-703 based on actual use and experience.

Oh, and I would hardly call myself an "expert" CW operator.  More a casual CW op.  On a QRP rig there are times SSB just won't get through on a given band and yet you can work tons of people on CW.  Heck, on 40 at night with the broadcasters booming in that's true at almost any legal power level sometimes.

73,
Caity
K7VO

:
WA3JJH wrote:

> The IC-703 does have one non-removable 2.4-kHz SSB
> filter.

Yes, but the stock Murata ceramic filter isn't very good.  That's why W4RT offer to remove that one and replace it with a Collins mechanical filter.  If they'd do that and offer a good 250Hz CW filter as well I would have jumped at their One Board Filter.  It's a good deal for the price.  

> I normally use a 500-Hz IF filter and use DSP for
> narrower response.

That makes sense on a rig that offers DSP bandwidth filters.  Sadly the IC-703 doesn't.  Heck, on the Ten Tec Argonaut V the IF DSP bandwidth filters are so good you don't need anything else.  This is one of the reasons I consider the Argonaut V superior to the IC-703.  Overall receiver performance is a bit better on the Ten Tec as well, at least to my ears.  Both are very good radios, though, and the smaller size, the DSP noise reduction, and especially 6m argue in favor of the Icom.

> I don't think you'll find anyone who thinks
> the 703 makes a good CW rig with only the
> standard SSB filter in place.

Thank you.  That was the main point.  If you are at all serious about CW then some sort of CW filter becomes essential.  With five or six different choices on the market you can choose the one that best fits your taste and your style of operating, but one of some sort is pretty much a must.  Of course, if you don't do CW at all (or very little) an SSB filter may make more sense.

72/73,
Caity
K7VO

Phil Salas:
I second Caity's recommendation for a 250 hz cw filter.  I normally leave the menu setting up that lets me switch the narrow filter in and out.  So I tune around with the SSB fitler, then select the 250 hz filter when I'm "ready to go".  The 250 hz filter really works well.  As an added bonus, you are prettyy much zero beat when you tune in a signal with this filter in-line.

Check my website for a way I used to mount a battery on the side of the IC-703.

Phil - AD5X
www.ad5x.com
ad5x@arrl.net

Nathan Houck:
I'd follow Caity and Phil's advice.  You can't find two better Elmers to guide you on your journey.  There are people out there willing to pay for their advice.

72 de Nate

Chuck Guenther:
AE6RF wrote: "W4RT seems to think that the narrower CW filter requires a "warning." (Don't get this filter unless you know what you're getting, we don't recommend one this narrow, etc.)

Can you give a brief description as to why this might be the case and what the trade-offs are?"

One thing not yet mentioned in this thread was the possibility of excessive insertion loss that is a design tradeoff in narrow crystal filters.  Filter insertion loss has the effect of lowering the IF gain, and is not a problem if there is enough gain in the first place.  Ten Tec "warned" me about this when I purchased my used Omni 6 from them.  

73,
Chuck  NI0C
 

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