Sony ICF-SW100 & Stephan's notes


Giampiero Bernardini
 

Dear Stephan,
Thanks a lot for your observations about sensitivity and other technical tips about these pocket rx, really interesting.

About Sony ICF-SW100: yes it is not an Ultralight according to "standard" (DX.ca) definition. It is an "Ultralight not Ultracheap" rx... HI

Anyway, I was interested in some test and in comparing this receiver with two other "standard" Ultralight. I think that in future it will be possible to get better and better performances with new DSP and not only DSP technologies.

Other note: in North America the Ultralight rxs are mostly intended for MW use, but they can give us satisfactions also on other bands.

Good DXing to everybody
Giampiero

Giampiero Bernardini
Milano, Italy

-----Messaggio originale-----
Da: ultralightdx@... [mailto:ultralightdx@...] Per conto di sgrossklass
Inviato: venerdì 27 novembre 2009 22.55
A: ultralightdx@...
Oggetto: [ultralightdx] Re: Old Ultralight test: Sony ICF-SW100

--- In ultralightdx@..., "Giampiero Bernardini" <g.bernardini@...> wrote:

Ciao,

I tested, after many years I forgot it in a box, an old
ultralight, the Sony ICF-SW100 with my outdoor antenna T2FD 15
meters long. It is nice to observe that it doesn't need on SW the
preselector, as Tecsun PL-310 and Grundig G6 Aviator.
On the other hand, people never were particularly excited about
sensitivity straight off the whip, especially on old (pre-1997)
samples. That is likely to be related, at least in part, to the
external antenna supply (RF sees 220 ohms and 100 µH to supply,
quite a low impedance at low frequencies, not whip friendly),
lately I had a resistor swapped in my ICF-SW7600G to correct the
same issue. (The same wouldn't be possible for the SW100 though,
as that resistor is a series resistor going to the external
antenna input. On the 7600G it merely is in series with the
choke.)
I think I found the reason for the good strong-signal handling
that you observed. The RF preamp seems to be cleverly included
in the AGC system (as is the external antenna supply). That is
not the case for most such designs, plus something like the G6
is quite hot on the whip antenna already so was probably
designed to work well that way. The SW100 was clearly designed
to work with the AN-100 that came with the S model.

BTW, I don't think the SW100 really qualifies as an ultralight
per the "standard" definition - it is small indeed, but
certainly /not/ inexpensive (US$360 for the S model back then).

Sony SW100 is a nice receiver with Synchro AM (upper and lower)and
good SSB too.
It does have its share of warble on stronger stations though,
doesn't it? All the Sony sets which achieve 100 Hz steps by
fine-tuning the 2nd LO seem to be affected by that.

On LW, for NDB, it shows more sensitivity with its internal
ferrite than PL-310 and G6.
The ferrite materials used in the Chinese sets do not seem to
be very suitable for longwave. Ferrite rod size should be
about the same for all of them.

Stephan

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