Hello Laurie (and Byron),

Congratulations on your simple and highly effective modification of
rewiring the PL-310's external antenna plug-in jack, to allow highly sensitive MW
and LW antennas of all types to be used in boosting the PL-310's
performance, Laurie. That's one of the best ULR modification ideas I've seen
recently, and certainly one that should prove extremely popular!

Because most of my own LW and MW 7.5" loopstick experimentation has been
concentrated on the PL-380 model, I had no option but to design a similar
plug-in "docking port" for the top of the PL-380 cabinet, which would accept
the 7.5" plug-in MW loopsticks already sent out to 22 DXers using the PL-360
model. This is certainly a more involved process than rewiring an existing
plug-in jack, as in your PL-310 modification. For those DXers wishing to
use the PL-310 with any type of external LW or MW plug-in antenna, your
modification is certainly the way to go!

Regarding the avoidance of high AM-band varactor lockup (in the Si4734
chip) when transplanting loopsticks, I did run extensive tests with various
coil inductances and orientations in the 7.5" loopstick PL-380 model, using a
signal generator under controlled conditions. The results may be of
interest to you in your PL-310 loopstick experimentation, Laurie, and are posted
at _http://www.mediafire.com/?jwdqmdzmi0j_
(http://www.mediafire.com/?jwdqmdzmi0j) . Thanks again for sharing the details of your highly effective
modification, and we all appreciate your experimental success in
transforming the PL-310 into a very effective DX receiver.

73 and Best Wishes,
Gary DeBock (in Puyallup, WA, USA)


In a message dated 8/14/2010 9:32:05 A.M. Pacific Daylight Time,
lmann98@... writes:




Hello All,
My apologies if this mod has already appeared in the forum.

I recently purchased the PL-310 and, eager to try out some of Gary
DeBock's ferrite loopstick ideas, I popped the back off and I noticed, happily,
that the 3.5 mm socket for the ext SW/FM antenna is actually a stereo
switched socket and that the SW-FM switched connection for the whip antenna is
directed to go to the tip of a 3.5 mm stereo plug. The other pair of switched
terminals in the socket are for the ring connection to a stereo plug and are
conveniently left unconnected on the PCB. Hence I routed the internal loop
stick hot connection through these unused terminals so that with no plug
in the socket the internal ferrite rod is connected as normal and, when a
3.5 mm stereo plug is connected, the internal ferrite rod is disconnected and
the MW/LW input circuit of the radio is available on the ring connection
of the plug. The only thing to watch for is potential shorts between the
whip antenna base and these pads on the PCB as they are almost coincident with
one anoth er when the back of the radio is in place; I put insulating tape
over the base of the whip where it overlaps these pads and there has been
no shorting problems thus far.

Via this plug connection made with a short length (few inches) of RG-174
coax, I tried large external loop sticks around 2,000 uH and they work very
well on LW being tuned by the radio's internal cap up to about 400 kHz. For
an external MW ferrite rod it is necessary to avoid too much stray
capacitance for the upper end of the band if you want the radio's internal cap to
tune the ferrite coil, or else optimise with a lower coil inductance than
you might otherwise use. A switched inductance coil on the external ferrite
rod will doubtlessly be the way to go but the stray C in the interconnect
to the radio will be an issue and I may end up going with short open leads
to the 3.5 mm plug to allow minimum stray capacitance.

The mod also allows for the direct connection of external tuned loops and
my external amplified tuned MW/LW ferrite rods work very well through this
interface.

Regards from Perth, Western Australia
Laurie Mann