[Elecraft] SWL with KX1

Fri Dec 5 12:08:16 2003

Your points are well-taken, Scott.

True .. not exactly the same.  But it still works well at rejecting 
interference from a nearby station on one side by choosing the other 
sideband.

I have  three Sonys with that feature and find the KX1 to do a better 
job of interference rejection, even if it is not perhaps so 
sophisticated in its approach.  Likely this is due to a better xtal 
filter in the KX1 (not intended for as high a fidelity in audio as a 
consumer SWL receiver).  And I seldom listen to music on SWBC; there are 
far better sources.

73, Phil

Scott Prather wrote:

>Just as a correction, synchronous detection doesn't imply receiving only the
>upper or lower sideband.  Synchronous detection means that the receiver
>generates it own constant-amplitude carrier which is phase-coherent with the
>incoming signal's carrier.  This locally-generated carrier is used to feed
>one input of a product detector, with the second product detector input
>being the received signal.
>
>During selective fading of  AM signals, it's common for the carrier to fade
>but at least one sideband remains strong. The advantage of synchronous
>detection is that it eliminates the severe distortion caused by selective
>fading (which results in a received modulation index greater than 1.0)
>because the received carrier amplitude is constant.
>
>Many receivers that employ synchronous detection also allow you to select
>the sideband, which can substantially minimize interference in some cases.
>An SSB receiver can serve as a pseudo-synchronous detector by carefully
>tuning for zero beat.  But the SSB receiver's BFO and the incoming carrier
>can never maintain phase coherence, so you'll always have some distortion
>(worse with music where the IMD really shows up).
>
>Scott
>N7NB
>
>-----Original Message-----
>From: [email protected]
>[mailto:[email protected]]On Behalf Of Phil Wheeler
>Sent: Thursday, 04 December, 2003 20:41
>Cc: [email protected]
>Subject: [Elecraft] SWL with KX1
>
>
>First, I appologize for not having as yet any quantitative comparisons
>to my SWL receivers.  A minor point, but none of them have BNC
>connectors.  So my assessment is pretty qualitative.  More will follow.
>
>I've spent three evenings listening (casually, while doing other things)
>to a variety of stations on 31 meters using my 30 m dipole.  Lots of
>audio (no surprise).  Audio quality is very nice with filter set to full
>width .. better than I expected.  Both usb and lsb are good.  And that
>brings up a major point: One of the high-end features of pricy SWL
>receivers is "synchronous detection" which simply means you can listen
>to ether the upper or lower sideband.  This feature is inherent in the
>KX1 design.
>
>When I get more serious with this comparison, I expect the following:
>
>o SWL receivers will be more sensitive with very short antennas (4-6 ft)
>o The KX1 will hold its own on any antenna capable of ham ops (e.g. 20
>ft wire)
>o SWL receivers will overload on such antennas (all but the best of them)
>o The KX1 will show much better selectivity (e.g., rejection of that
>station 5 KHz away)
>o SWL receivers will work much better on LW/MW/FM bands (not tunable
>with the KX1)
>
>Soon I will test the KX1 and several SWL receivers (Sony ICF SW-100,
>Sangean ATS-909, etc.) and the KX1 with the sort of antenna I use when
>backpacking and in European hotels: Reel-type antennas in the 8-16 ft
>range.  Whatever the results, the KX1 will be with me in the Sierras
>(Yosemite and Mammoth) in Feb and in Greece in May.  The very best SWL
>receivers are not great for making CW contacts :-)
>
>73, Phil
>
>
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