[TenTec] what is "quiet"?

n4lq@iglou.com n4lq@iglou.com
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? 

-----Original Message-----
From: "Tom Rauch" <w8ji@contesting.com>
To: N1EU <n1eu@yahoo.com>, cyr999@extremezone.com
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 
> level. 
> 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 
> conditions.
> 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 
> performer.
> 73, Tom W8JI
> W8JI@contesting.com 
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