[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [IRCA] Sony ICF-SW7600GR Hot-Rodding
Hey Gary:
Thanks for venturing into yet another unknown receiver - your habitual
experimentation is much appreciated by many of us!
I have a 7600GR, which is an excellent DX portable. One issue - in the
urban RF jungle in which I live, daytime images (910 khz from a strong
local) can be substantial, so I will wait with great interest how your
unit fairs with a much larger ferrite.
For those of you who may be interested in the 7600GR, it has selectable
sideband reception in both syncronous AM and SSB mode. According to one
afficianado (http://stephan.win31.de/sony76-1.htm), the AM mode uses a
wide filter of around 7.3 khz (I think it sounds more like 6), while the
SSB mode uses a narrower 3.2 khz filter.
Unfortunately, one cannot mix and match the filters and modes: the narrow
filter is not available in AM-Synch. If you want to use the 3.2 khz
filter for AM DXing, you must go ECSS, and the BFO is very warbly and
nearly impossible to use...at first. However, I have found that after a
15 minute or so warm-up period in SSB mode, the BFO becomes quite stable,
and I can zero-beat in ECSS mode while DXing the AM band with the 3.2 khz
filter, switching between sidebands as I wish, and the zero-beat stays
put! Plus, as Gary intimates below, purposely setting the BFO to produce
a het when tuned on-frequency means it can be used as a spotter for
split-freq targets.
Additionally, a form of passband tuning is possible is either mode, and
can make a very noticeable difference. In AM mode, the synch detector
will generally stay locked on a decent signal when I tune a khz or two
away from an adjacent pest, which can make a difference when using the
wide filter. In SSB mode, the BFO clarifier can go plus/minus one or two
khz as well. So, if I want to tune in 620 underneath strong local 630, I
can tune to 618 and either let the synch detector lock in (AM mode) or
spin the BFO thumbwheel back to zero beat (SSB mode).
For us mere mortals who don't tear into these units like Gary does, the
stock ferrite is not too shabby, and resting the unit in the loving cradle
of a Terk loop or similar makes it a pretty mean DXing machine.
73 - Kevin S
Bainbridge Island, WA
> Hello All,
>
> After several requests to develop an alignment system for the
> popular,
> compact Sony ICF-SW7600GR portable, I finally decided to dig in to the
circuitry, and investigate the stock loopstick thoroughly. Perhaps the
fact that
> an upcoming family vacation (during which our compact vehicle would not
accommodate the 30" or 19" loopstick modified ICF-2010's) had something
to do with
> my motivation.
>
> The SW7600GR loopstick is in fact a smaller version of that used
in
> the
> ICF-2010, i.e. a large, fixed center coil and a much smaller end coil,
used
> (in Sony's design) for adjusting the spurious signal rejection of the
loopstick. Like the ICF-2010 system, there is no way to align the fixed
> coils on
> this antenna. The only way to significantly improve AM-DX performance
is
> to
> remove the entire 4 3/4" x 3/8" stock loopstick, and replace it with a
longer
> externally-mounted looptick having comparable coil inductances.
Fortunately,
> the ICF-2010 "Supercharging" file (currently posted in dxer.ca's
Ultralight
> File section) tells exactly how to accomplish this, in an electrical
manner.
>
> For the ICF-SW7600GR, a hobbyist will need to measure the stock
> inductances of the two coils, and either recycle the stock loopstick in
a
> larger
> composite bar augmented by blank 3/8" ferrite bars on the ends, or
create
> a
> self-wound loopstick on 1/2" diameter Amidon ferrite bars (my probable
choice).
> Practically speaking, the external loopstick should be limited to a
length of
> about 15", since it is unlikely that this hot-rodded SW7600GR would
have
> a
> performance surpassing that of a hot-rodded ICF-2010, even with a
longer
> loopstick.
>
> It will be interesting to see how this "supercharged" ICF-SW7600GR
> performs in the real world. Although not really close to being an
"Ultralight"
> radio, it might be useful as a barebones SSB "spotting receiver" for
those
> travelers unable to accommodate a more capable SSB unit.
>
> 73, Gary DeBock
>
>
>
> **************Get the scoop on last night's hottest shows and the live
music
> scene in your area - Check out TourTracker.com!
> (http://www.tourtracker.com?NCID=aolmus00050000000112)
> _______________________________________________
> IRCA mailing list
> IRCA@xxxxxxxxxxxxxxxx
> http://montreal.kotalampi.com/mailman/listinfo/irca
>
> Opinions expressed in messages on this mailing list are those of the
original contributors and do not necessarily reflect the opinion of the
IRCA, its editors, publishing staff, or officers
>
> For more information: http://www.ircaonline.org
>
> To Post a message: irca@xxxxxxxxxxxxxxxx
>
>
_______________________________________________
IRCA mailing list
IRCA@xxxxxxxxxxxxxxxx
http://montreal.kotalampi.com/mailman/listinfo/irca
Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers
For more information: http://www.ircaonline.org
To Post a message: irca@xxxxxxxxxxxxxxxx