Hello. I'm out of my depth here, but I'll try to be coherent in my question..

I had bought a Tecsun PL-390 after seeing several good reviews by radio
amateurs as well as general public. It's awesome, but crash-prone (and if
anyone can guide me to a means of immediately resetting to regain full
control instead of being made to wait 20 munites for power to fade, I'm all
eyes... I like it enough to be willing to risk some effort to modify it,
given some guidance).

I rapidly became aware of the IC inside it when looking for info about its
bad habits, and having already got an AOR AR-3000 recently set up for RS-232
control decided that this might be a way to go with those IC's, because they
can take commands to do many things already, but by means I'm probably not
familiar with.

I Googled "Si4734 OR Si4735 OR Si4735D60 OR Si4770A20 ttl serial" (minus
quotes) and the results are not promising, I already know that there are many
more experimenters out there with better systems than the commercial
offerings than Google has any clue about, so I decided to ask here. The
Elektor project is one way to go but maybe hard to get, a tad large, and
likely improved on by now, too.

Has anyone come up with a SMALL circuit board, some neat rectangular FR4 PCB
easily mounted to some custom-built conditions, containing the IC, ideally
Si4734 or Si4735 (but I don't need RDS, but do want LW and VHF FM stereo as
well as SW. I am looking for ttl serial at 4800 baud, 8N1 standard setup if
possible, so I can turn an old Psion Organiser II XP into the controller, as
those are cheap, easily found, etc.. So in the same spirit, I'm hoping to
find a small board to use this method to make a radio, so I can ecomonically
make more than one, so I have backup and some future-proofing.

I'd love it if the Tecsun PL-390 worked reliably, I'm all for an easy life if
I can get one, but apparently it is not to be...

Most interesting to me is that the AR-3000 returns signal strength allowing a
programmer to build something like the ETS tuning method of the Tecsun radios
easily! Scan, measure, store if it looks good... A similar method for these
new DSP radio chips complete with TTL on a tiny board is what I'm looking
for.

On Sat, 26 Jul 2014, Lostgallifreyan wrote:

Hello. I'm out of my depth here, but I'll try to be coherent in my question..

I had bought a Tecsun PL-390 after seeing several good reviews by radio
amateurs as well as general public. It's awesome, but crash-prone (and if
anyone can guide me to a means of immediately resetting to regain full
control instead of being made to wait 20 munites for power to fade, I'm all
eyes... I like it enough to be willing to risk some effort to modify it,
given some guidance).

I rapidly became aware of the IC inside it when looking for info about its
bad habits, and having already got an AOR AR-3000 recently set up for RS-232
control decided that this might be a way to go with those IC's, because they
can take commands to do many things already, but by means I'm probably not
familiar with.

I Googled "Si4734 OR Si4735 OR Si4735D60 OR Si4770A20 ttl serial" (minus
quotes) and the results are not promising, I already know that there are many
more experimenters out there with better systems than the commercial
offerings than Google has any clue about, so I decided to ask here. The
Elektor project is one way to go but maybe hard to get, a tad large, and
likely improved on by now, too.

Has anyone come up with a SMALL circuit board, some neat rectangular FR4 PCB
easily mounted to some custom-built conditions, containing the IC, ideally
Si4734 or Si4735 (but I don't need RDS, but do want LW and VHF FM stereo as
well as SW. I am looking for ttl serial at 4800 baud, 8N1 standard setup if
possible, so I can turn an old Psion Organiser II XP into the controller, as
those are cheap, easily found, etc.. So in the same spirit, I'm hoping to
find a small board to use this method to make a radio, so I can ecomonically
make more than one, so I have backup and some future-proofing.

The manufacturer was selling boards intended for prototyping, but I'm not
sure if they've done it for all their ICs.

Some of these radios are so cheap, they may be worth buying second one and
using that as a development board. It's an intersting thing, the same IC
being used in multiple radios, the features varying from one to one,
because each has decided what to include. So you get a Grundig G8, and it
has no means of changing selectivity, even if the IC has multiple
bandwidths. The G8 gets good marks for FM reception, but not so much for
shortwave, yet I bet adding a bit of front end selectivity would improve
things. Of course, they can't handle CW or SSB.

The one place I've seen a lot about these ICs is
http://home.comcast.net/~phils_radio_designs/
so poke around there, you may find something of value.

Michael


I'd love it if the Tecsun PL-390 worked reliably, I'm all for an easy life if
I can get one, but apparently it is not to be...

Most interesting to me is that the AR-3000 returns signal strength allowing a
programmer to build something like the ETS tuning method of the Tecsun radios
easily! Scan, measure, store if it looks good... A similar method for these
new DSP radio chips complete with TTL on a tiny board is what I'm looking
for.

Michael Black wrote in
news:alpine.LNX.2.02.1407261848390.22322@darkstar. example.org:

The one place I've seen a lot about these ICs is
http://home.comcast.net/~phils_radio_designs/
so poke around there, you may find something of value.


Nice one. Thanks. Already found two docs there I hadn't seen yet. There is a
possibility that one of the cheapest radios might be simple enough as a base
for extensive modification and addition, but I doubt that TTL level serial is
in any of them, but if I can get that it solves so many things, leaving only
experimentation with ferrite rods and coils and long wires to do, hence the
attraction...

Above all else I must avoid having the thing turn into a brick for the twenty
minutes it takes for power to fade, allowing it to be reset. That looks like
a big weakness ripe for modification in many if not all products based on
these IC's, though it may well be Tecsun's control methods that borked in the
case of the PL-390.

Michael Black wrote in
news:alpine.LNX.2.02.1407261848390.22322@darkstar. example.org:

Of course, they can't handle CW or SSB.


I found a circuit online that puts a local IF oscillation inductively into a
radio to allow some sort of USB mode tuning. I might try makign one to feed
into the ring connector of the PL-390 I modifed with a 100-turn coil. It does
wonders with a longwire, and hopefully a magnetic loop soon as well. If
feeding it with this IF frquency method will allow SSB that small
modification would be an extremely good thing to do with a PL-390 and likely
other radios that use this IC. On the other hand if the DSP means the same IF
frequency method of analog systems is not used at all, then I guess the AM to
SSB trick isn't going to work at all...

On Sat, 13 Sep 2014, Lostgallifreyan wrote:

Michael Black wrote in
news:alpine.LNX.2.02.1407261848390.22322@darkstar. example.org:

Of course, they can't handle CW or SSB.


I found a circuit online that puts a local IF oscillation inductively
into a radio to allow some sort of USB mode tuning. I might try makign
one to feed into the ring connector of the PL-390 I modifed with a
100-turn coil. It does wonders with a longwire, and hopefully a magnetic
loop soon as well. If feeding it with this IF frquency method will allow
SSB that small modification would be an extremely good thing to do with
a PL-390 and likely other radios that use this IC. On the other hand if
the DSP means the same IF frequency method of analog systems is not used
at all, then I guess the AM to SSB trick isn't going to work at all...

I forget the block diagram, I recall the receiver converts to a low IF and
then hits the DSP. The problem is, is there an easy way to get a BFO
signal into that thing, when it's mostly one IC? ANd if it's a low IF
(traditionally the IF was 455KHz and I think this receiver has a lower
IF), any harmonics of the BFO that get into the antenna will be that more
frequent.

Also, doing it this way will be inferior to using a DSP to detect the SSB
signal. It has all the disadvantages of feeding a BFO through the IF
chain of any old receiver.

In the old days, one scheme for adapting old receivers for SSB was to use
a local signal generator of some kind on the signal frequency, coupling it
into the antenna input of the receiver. There, it only needed a weak
signal (while by the time an incoming signal reaches the detector in a
receiver, it can be quite strong, and the BFO needs to be stronger unless
there's a product detector in there), and you can adjust injection with a
simple level control on the output of the local signal generator. Another
advantage is that for receivers not meant for SSB, they would tend to
drift, while you could build a decent VFO or something that would be
stable. So the "bfo" would stay in tune with the incoming signal, even if
the old receiver would drift off. So you'd need to retune the receiver
every so often as it faded into the skirt of the selectivity, but the
"bfo" and the incoming signal would remain the same, so none of that oddly
sounding voices.

Michael

Michael Black wrote in
news:alpine.LNX.2.02.1409131746360.24400@darkstar. example.org:

In the old days, one scheme for adapting old receivers for SSB was to use
a local signal generator of some kind on the signal frequency, coupling it
into the antenna input of the receiver. There, it only needed a weak
signal (while by the time an incoming signal reaches the detector in a
receiver, it can be quite strong, and the BFO needs to be stronger unless
there's a product detector in there), and you can adjust injection with a
simple level control on the output of the local signal generator. Another
advantage is that for receivers not meant for SSB, they would tend to
drift, while you could build a decent VFO or something that would be
stable. So the "bfo" would stay in tune with the incoming signal, even if
the old receiver would drift off. So you'd need to retune the receiver
every so often as it faded into the skirt of the selectivity, but the
"bfo" and the incoming signal would remain the same, so none of that oddly
sounding voices.


Thankyou, I like that analysis. I had already wondered about drift, and this
is the way to go, removing any relation to the IF frequency or its stability
(I looked at the datasheet, but it's big, I stopped after a crude search for
uppercase IF, and found no mention of exactly how low...). Avoiding a need
for a strong emission and risk of harmonics getting back to the RF input is
good too. It does mean I have to make some small signal generator with fine
accuracy good for up to 23 MHz, but that is doable. I suspect the Maxim
version of the old 8038 can do at least 20MHz, and maybe some versions of the
4046 PLL oscillator can do it too (but not sine so not as convenient).

All worth doing though, the low cost, small size, the DSP, and the AM filters
in the PL-390 make it very tempting to improve on its all-rounder capability.

One thing I discovered was that while the HF and VHF inputs do not use the
ferrite rod's original coil, I did find that shortwave seemed to benefit from
the 50m length of wire I tested recently, when fed to the 100 turns I added
on the rod's end, instead of to the intended input on the RF jack's tip. So
coupling a small signal to the ring terminal and its extra coil at same
frequency for CW and SSB seems very likely to work with no further internal
modification.