[ARC5] Inspired hack job

[Dennis Monticelli]

Dave,

I have experienced your listening observations on LF also.  In fact this
effect can be observed on any noisy band.  When one is trying to pick out a
weak signal among a noisy background that features a high peak to average
ratio (such as atmospheric, man-made, and even internal white noise sources
to a lesser degree), the signal chain needs to be very linear in the manner
in which it processes those peaks.  If there is any distortion, many the
products of that distortion will manifest right in the passband.  I think
non-linear phase is probably a bigger deal than non-linear amplitude when
it comes to what the ear doesn't like.  Further, hi-Q circuit elements
(like the resonators in an IF filter) can store the energy peaks and then
release the energy more slowly and nt a way that is unpleasant to the ears.
  An AGC is a non-linear circuit and it can add to the ear fatigue also.
 Anyway, minimizing those effects that translates into simple linear
circuits with low Q paths and no AGC.  What a minute....I just described a
BC-453!

As an aside, I recently received a high-rice box for Christmas/B-Day.  It
replaced a TS-820 as the main rig (Yes, I threw in the towel, but I
featured that Kenwood in the shack since 1979 so I don't feel too guilty).
 Anyway, the maker paid much attention to a highly linear signal path
throughout the chain.  For example, the IF DSP used the latest algorithms
for maintaining linear phase, even when set for tight bandwidths.  After
using this radio on various lower bands for a couple of months I can
definitely say that Yaesu succeeded in getting back to where we were with
the ARC-5 :-)

Dennis AE6C

On Thu, Mar 7, 2013 at 1:45 AM, David Stinson <arc5 at ix.netcom.com> wrote:

> I cannot say why a BC-453 performs so well on LF
> compared to some other sets; Mike is certainly right about the technical
> details.  But I understand the assertion that the 453 et al. is "better".
> In my experiance, the 453 is better "listening" than many
> because the signals I receive are "cleaner."
> When receiving LF signals, noise floor and IF bandpass shape are more
> important than is sensitivity; learned that first-hand during my years
> DXing on the 160-190 "Lowfer" band.  Perhaps the fewer stages contribute
> less noise?
> Maybe it's the tuning ratio and/or IF design.... Maybe it's just my own
> personal prejudices coloring what I hear.
> I dunno.
>
> But if I'm listening to LF between my 348 and my 453, the 348 has a higher
> noise floor and less-pleasing audio.  The audio from a stock 453 is "silkly
> smooth."
> I pull-out more and cleaner signals with the 453
> and they just sound better to my ear.
> If you have both in good working order,
> try tuning freq-for-freq with the same antenna
> and you'll see what I mean.
> I've heard smatterings of European LF broadcasters
> on one of my 453s.  I've never heard that on a 348.
> The only way I know to make sense of that technically
> is noise floor.
>
> 73 Dave S.
>
>
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