[Kenwood] RE: Receiver question

[MJ Venter]

Hi All

The explanation given is correct.  More stages, better
selectivity, more noise.  An interesting one is the reason
for fitting an amplifier at the antenna at the mast and not
down below, because then you amplify noise picked up by the
coax as well.

Happy hamming.

Martin.
ZS6AZV


On Mon, 15 Aug 2005 17:02:17 -0700
 "Hsu, Aaron (NBC Universal)" <aaron.hsu at nbcuni.com> wrote:
> Kurt,
> 
> I'm not a receiver guru, but this is the way I understand
> it (after reading
> quite a few messages over the years about the subject).
> 
> The ideal receiver will have one conversion...straight to
> audio.  This
> should result in the "cleanest" received signal
> relatively free of local
> mixer artifacts (such as noise and harmonics).  The
> difficulty is designing
> circuits (such as amplifiers and bandpass filters) that
> operate at the
> received frequency using typical component
> values/tolerances (esp at VHF and
> higher).  Converting to a lower IF resolves this issue.
> 
> Multiple conversions also allows designers to add
> additional filtering to
> the receiver making it more *selective*.  At each
> conversion, you can add a
> bandpass filter (to boost selectivity) and an amplifier
> (to recover filter
> losses and maybe add some sensitivity).  However, each
> conversion introduces
> mixer artifacts and the additional amplifiers introduce
> noise of their own.
> So what you end up with is a receiver that is (or almost
> is) as sensitive as
> a single-conversion receiver with much better
> *selectivity*, but at the cost
> of locally induced noise and harmonics (birdies) that may
> mask the desired
> signal.
> 
> So, "daisy-chaining" your '830 to your '850 would
> probably make for better
> selectivity, but possibly at the cost of increased noise
> and birdies.  On
> top of that, the '850 has one of the best receivers ever
> made by Kenwood
> (some say the *best*).  I don't think you could make it
> any better by adding
> an '830 to the front end.
> 
> Again, I'm no guru...someone please correct me if I
> misstated or
> misunderstood something.
> 
> 73,
> 
>   - Aaron Hsu, NN6O (ex-KD6DAE)
>     {nn6o}@arrl.net
>     {athsu}@nbcuni.com
>     No-QRO Int'l #1,000,006
>     . -..- - .-. .-   ".... . .- ...- -.--"
>  
> 
> -----Original Message-----
> Sent: Monday, August 15, 2005 11:54 AM
> Subject: [Kenwood] Receiver question
> 
> Here's a question for you receiver gurus. I own a Kenwood
> TS-830S and a
> TS-850S/AT. The '830 is dual conversion and the '850 is
> triple conversion.
> The '830 has a 455kHz I.F. output and the '850 can
> receive 455kHz. If I
> attenuated the '830's I.F. output down to, say, 50
> microvolts with a source
> impedance of about 50 ohms, would there be anything to be
> gained (pun
> intended) by connecting the I.F. output of the '830 to
> the input of the
> '850?
> 
> Wouldn't this result in a quintuple conversion receiver?
> Would it be a
> better receiver than either one alone? (Transmitting, of
> course, would be
> out of the question!) What do you think?
> 
> 73, Curt, K4TL
> 
>
______________________________________________________________
> Kenwood mailing list
> Home: http://mailman.qth.net/mailman/listinfo/kenwood
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:Kenwood at mailman.qth.net