On a sunny day (Fri, 12 Dec 2014 13:07:27 +1100) it happened Clifford Heath
<no.spam@please.net> wrote in <25siw.309932$ZT5.40650@fx07.iad>:

>If I can get the patch I'm sure you can too.
>It's a encrypted data file to program the internal
>DSP, so knowing the registers is not enough; you
>need to be able to produce the DSP code and encrypt
>it.
>
>We got the SSB patch because for DF use, you tune to
>maybe 1KHz off the fundamental CW signal to get a
>heterodyne whistle.


I did receive SSB with it,
used my Raspberry Pi as signal generator
 http://panteltje.com/panteltje/newsflex/download.html#freq_pi
to beat against the station,
so say if station is at 14 MHz, set raspi signal to 14 MHz,
and keep it close to the radio.


That other Tecsun I have with SSB has no USB LSB selector,
took a bit getting used to it.

On Wed, 10 Dec 2014 09:47:56 GMT, Jan Panteltje <panteltje@yahoo.com>
wrote:

>One or 2 years ago I bought a Tecsun radio:
> http://www.ebay.com/itm/111288607108

It's a very good radio (due to the SiLabs chipset) for a different
reason.  The IF bandwidth is sufficiently narrow, and DSP demodulator
sufficiently noise immune, to remove the overlapping HD Radio
sidebands from the receive signal.  Most other non-DSP receivers will
pickup the HD Radio junk, and all you hear is distorted garbage.  With
these receivers, it's clean.

-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

On Wed, 10 Dec 2014 15:33:54 -0500 (EST), bitrex
<bitrex@de.lete.earthlink.net> wrote:

> I'm still curious how in these later
> designs the input filter was tuned to be offset from the LO by
> the IF frequency; I don't think they're using variable caps or
> diodes. I think I'm missing something - when you have have a PLL
> synthesized LO is there a way that the need to tune the front end
> filter can be eliminated

Which later designs?  I guess you mean PLL design.  The front end was
always broadbanded from 88 to 108 MHz.  With a 10.7 MHz IF frequency,
the 20 Mhz band pass is just a little smaller than 2 * 10.7 MHz, which
would be the frequency range most like to produce receiver image
reception.  A tracking filter front end would be nice in high signal
strength areas, where some additional off frequency rejection would be
useful to reduce intermod.  However, with FM capture effect, it
doesn't buy much for consumer FM listeners, who rarely listens to weak
signals, where it would most beneficial.

On the other foot, it's not that difficult to build a tracking filter
RF amplifier, that tracks the LO frequency.  All that's needed is a
lookup table that relates the RF tuning frequency with the varactor
tuning voltage.  If I had surplus CPU cycles, I can do it by sweeping
across the approximate receive frequency, stopping at the varactor
voltage with the best SNR, and storing the voltage in RAM or FLASH.
Extrapolated to its logical extreme, I helped with the design of a
fairly conventional VHF/UHF NBFM receiver and PLL LO, that had no
tuning adjustments.  However, it never went into production because
the savings in production tuning labor and lower component costs were
negated by the increased cost and complexity of the design.

-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

On Wed, 10 Dec 2014 15:33:54 -0500 (EST), bitrex
<bitrex@de.lete.earthlink.net> wrote:

>
>> During the 1990's, most of the RF, IF, demod, and audio circuitry was
>> crammed into a single IC, surrounded by a few discrete components, and
>> run by a micro.  However, the receiver was still fundamentally an
>> analog design full of LC and ceramic filters.
>>=20
>
>Thanks for the reply.  I'm still curious how in these later
> designs the input filter was tuned to be offset from the LO by
> the IF frequency; I don't think they're using variable caps or
> diodes. I think I'm missing something - when you have have a PLL
> synthesized LO is there a way that the need to tune the front end
> filter can be eliminated

If you use a much higher than usual IF you can get image rejection quite =
a
bit easier.  Thus (little or) no RF side tuning at all.

?-)
=20

On 11/12/14 22:02, Jan Panteltje wrote:
> On a sunny day (Thu, 11 Dec 2014 12:38:08 +1100) it happened Clifford Heath
> <no.spam@please.net> wrote in <Cz6iw.1066865$yK.1035193@fx14.iad>:
>> Do you know what CPU drives the Si4734 chip?
> Well, as you asked I tried to have a look:
>   http://panteltje.com/pub/Tecsun_inside_1_IMG_4685.JPG
> The CPU (or FPGA??) is under the metal cover that is soldered,
> did not want to rip that apart.
>   http://panteltje.com/pub/Tecsun_inside_2_IMG_4684.JPG
> Seems like it could be a PIC:

That seems fairly likely. thanks for looking. A friend has
used a PIC32 for his, which does triangulation from GPS
measurements.

>> Asking because I have a couple of Si4735 chips here, including a
>> software patch from the manufacturer for SSB reception (under NDA),
> Yes, for sure it is a pity this radio does not have an SSB mode.

If I can get the patch I'm sure you can too.
It's a encrypted data file to program the internal
DSP, so knowing the registers is not enough; you
need to be able to produce the DSP code and encrypt
it.

We got the SSB patch because for DF use, you tune to
maybe 1KHz off the fundamental CW signal to get a
heterodyne whistle.

The DSP uses a very low IF; 45KHz I believe. Keeps the
power consumption down :)

> Anyways, you could control the Si4730 with a PIC I think,

Yes. I have several possibilities I'm thinking of:
MSP430 (cheapest/low-power), STM32 ARM7 (to implement IMU
and drive a colour LCD), or an FT245 USB chip in bit-bang mode
(for prototyping from the desktop computer). I was thinking of
trying the last one first, because I have a couple of alternate
front-ends to try.

> What I do not see in the Si4730-31-34-35-D60.pdf data sheet is the registers to program the chip.
> Without that data it will be next to impossible to program it from some micro.
> (Well almost impossible, we have ways of finding out).
> Do you have that register data under non-NDA?

Also under NDA I believe, but just ask, they're pretty helpful.
As I said, not useful without the DSP and encryption data anyhow.
It would be excellent if they opened that up.

Clifford Heath.

On a sunny day (Thu, 11 Dec 2014 12:38:08 +1100) it happened Clifford Heath
<no.spam@please.net> wrote in <Cz6iw.1066865$yK.1035193@fx14.iad>:

>On 10/12/14 20:47, Jan Panteltje wrote:
>> One or 2 years ago I bought a Tecsun radio:
>>   http://www.ebay.com/itm/111288607108
>> It is based on the Silabs S-4730 chip,
>> BROADCAST AM/FM/SW/LW RADIO RECEIVER
>> dataheet here:
>>   https://www.silabs.com/.../TechnicalDocs/Si4730-31-34-35-D60.pdf
>> It is an amazing receiver, use it everyday.
>> Look at the block diagram.
>
>Jan,
>
>Do you know what CPU drives the Si4734 chip?

Well, as you asked I tried to have a look:
 http://panteltje.com/pub/Tecsun_inside_1_IMG_4685.JPG
The CPU (or FPGA??) is under the metal cover that is soldered,
did not want to rip that apart.
 http://panteltje.com/pub/Tecsun_inside_2_IMG_4684.JPG
Seems like it could be a PIC:

>Asking because I have a couple of Si4735 chips here, including a 
>software patch from the manufacturer for SSB reception (under NDA), with 
>the intention of building an 80m direction-finding receiver with them. 
>I'm not sure that the RSSI/AGC steps will be small enough. Even 0.1dB is 
>a big enough step to be annoying for DF when using "whoopee" mode, so 
>I'll probably have to rectify the audio and produce my own RSSI. Luckily 
>the AGC limits, step size, and delays are software-settable, so I could 
>just use that for auto-ranging, and the post-AGC RSSI for whoopee. 
>Otherwise the AGC can be put under full software control anyhow.
>
>The PL360 is a nice format, and with a modified antenna would suit DF 
>use very well, as long as the CPU is reprogrammable/replaceable and 
>there's room to add the whoopee circuit. Whoopee is essential, no-one 
>wants to be looking at RSSI numbers while waving an antenna around in 
>the scrub.
>
>Clifford Heath.

Yes, for sure it is a pity this radio does not have an SSB mode.
For that I have an Tecsun PL600 (longwave through shortwave + FM).
I have the circuit diagram for that, but quite different, does not use the Si4730 chip:
 http://elektrotanya.com/tecsun_pl-600.pdf/download.html

Anyways, you could control the Si4730 with a PIC I think,
you can even make PWM audio with a PIC:
 http://panteltje.com/panteltje/pic/audio_pic/
But the PL360 has an analog volume control, some DA must be in it somewhere.
What I do not see in the Si4730-31-34-35-D60.pdf data sheet is the registers to program the chip.
Without that data it will be next to impossible to program it from some micro.
(Well almost impossible, we have ways of finding out).
Do you have that register data under non-NDA?

Thats easy
You use the same control voltage that the pll creates to drive the vco varicaps, to tune the front end filter varicaps.
With proper design you can use the exact same voltage, the tuned circuits are scaled such that it all tracks pretty well.

Mark

On 10/12/14 20:47, Jan Panteltje wrote:
> One or 2 years ago I bought a Tecsun radio:
>   http://www.ebay.com/itm/111288607108
> It is based on the Silabs S-4730 chip,
> BROADCAST AM/FM/SW/LW RADIO RECEIVER
> dataheet here:
>   https://www.silabs.com/.../TechnicalDocs/Si4730-31-34-35-D60.pdf
> It is an amazing receiver, use it everyday.
> Look at the block diagram.

Jan,

Do you know what CPU drives the Si4734 chip?

Asking because I have a couple of Si4735 chips here, including a 
software patch from the manufacturer for SSB reception (under NDA), with 
the intention of building an 80m direction-finding receiver with them. 
I'm not sure that the RSSI/AGC steps will be small enough. Even 0.1dB is 
a big enough step to be annoying for DF when using "whoopee" mode, so 
I'll probably have to rectify the audio and produce my own RSSI. Luckily 
the AGC limits, step size, and delays are software-settable, so I could 
just use that for auto-ranging, and the post-AGC RSSI for whoopee. 
Otherwise the AGC can be put under full software control anyhow.

The PL360 is a nice format, and with a modified antenna would suit DF 
use very well, as long as the CPU is reprogrammable/replaceable and 
there's room to add the whoopee circuit. Whoopee is essential, no-one 
wants to be looking at RSSI numbers while waving an antenna around in 
the scrub.

Clifford Heath.

Jeff Liebermann <jeffl@cruzio.com> Wrote in message:
> On Tue, 9 Dec 2014 20:18:01 -0500 (EST), bitrex
> <bitrex@de.lete.earthlink.net> wrote:
> 
>> I'm interested in how the design of consumer AM/FM radios has
>> evolved over time, particularly since digital tuning/ PLL
>> synthesizers came on the scene.  Some early (1980?) PLL receiver
>> schematics I've seen show the LC front end tank being tuned by a
>> varactor diode.  I'd imagine for several reasons one would want
>> to eliminate the complexity of this kind of front end setup if at
>> all possible.  
> 
> In the 1980's, we had synthesized local oscillators and digitally
> tuned stereo receivers.  Progress for most of the 1970's was getting
> rid of mechanical parts involved in the receiver tuning.  That meant
> microprocessor push button control of the PLL.  However, the IF and
> discriminator circuits were largely unchanged throughout the 1970's
> and 1980's.  What also changed was the inexorable drift from discrete
> to integrated designs.  Large sections of the circuitry were size and
> cost reduced down to individual IC's.  
> 
> During the 1990's, most of the RF, IF, demod, and audio circuitry was
> crammed into a single IC, surrounded by a few discrete components, and
> run by a micro.  However, the receiver was still fundamentally an
> analog design full of LC and ceramic filters.
> 

Thanks for the reply.  I'm still curious how in these later
 designs the input filter was tuned to be offset from the LO by
 the IF frequency; I don't think they're using variable caps or
 diodes. I think I'm missing something - when you have have a PLL
 synthesized LO is there a way that the need to tune the front end
 filter can be eliminated

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