[TenTec] what is "quiet"?
Wed, 03 Apr 2002 07:06:52 -0500
I'm curious Tom. What modern receiver do you use or recommend for those
weak cw signals?
From: "Tom Rauch" <firstname.lastname@example.org>
To: N1EU <email@example.com>, firstname.lastname@example.org
Date: Wed, 3 Apr 2002 05:47:28 -0500
Subject: Re: [TenTec] what is "quiet"?
> > it's single conversion. The thing that has really surprized me is
> > that, at least for me, I don't find all this hash or whatever one
> > might call it on the 756 PRO - I have used the PRO for hours and do
> > not get the listener's fatigue I hear people talk about.
> One problem with comparing things is many of the effects are
> subjective, like "fatigue". One person might be bothered by
> something that won't bother another person at all.
> The other major problem is our locations and operating habits vary.
> If we live in a quiet location, use narrow filters, have directional
> receiving antennas, and work weak signal DX receivers that might
> make someone else very happy can "fall apart" and be useless.
> For example, I can't (and MANY others can't) use receivers with
> low gain much of the year when working weak-signal CW on my
> receiving antennas, even with a 10dB gain distribution system
> ahead of the receivers. A low-gain receiver, like an Omni-6 or an
> Elecraft, can not get down into the external noise floor. The AGC
> won't do anything, and I have to crank the volume wide open.
> On wider bandwidth, like 2 kHz or wider, most receivers are OK
> because the noise power is 10dB more than with 200Hz selectivity.
> On my TX antennas, even so-called "quiet antennas", lower gain
> receivers are OK because the noise power summed from all
> directions is higher and the antennas provide a bit more signal
> Bottom line for gain is you should be able to hear the noise
> increase a noticeable and clear amount when you connect the
> antenna on the quietest day using the narrowest filter. If you can
> not do that, then your system is gain limited under those
> As for ringing and other flaws, the number of conversions is not the
> problem. The problem is how well everything is designed and how
> well the system actually works.
> Most receivers seem to be planned for SSB bandwidths, urban or
> suburban locations with modest or high local noise, and TX
> antenna noise levels. Most important, few of them are better than
> around 80dB for close-spaced blocking and dynamic range...and
> many are worse. 80dB DR is very marginal in quiet locations on
> low bands.
> I'd bet most receiver filters are never tested for group delay errors,
> or ringing.
> If the filters ring (for whatever reason) sharp rough noise pulses are
> stretched into longer pulses that are more destructive to
> readability. Some similar filtering systems are better, some are
> worse. The IC751A's 250Hz crystal filters are useless with any
> sharp noise, because they ring. The "Drake" 250 Hz crystal filters
> in my solid-state modified R4C's are useful under almost any
> condition, even though the stock R4C receiver is a VERY poor
> 73, Tom W8JI
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