[Kenwood] RE: Receiver question

[Hsu, Aaron (NBC Universal)]

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