BD3SC-588 board

[max-arnold]

Got a BD3SC-588 "kit". The stock fw didn't run past the "Si4735 not detected" message (likely due to missing battery), but I managed to dump it and flash into my main receiver. The fw looks like a Chinese one (authored by zooc), but the menu is in English.

fw-bd3sc.zip

[max-arnold]

Some links (easily googleable using the bd3cs-588 si4732 search term):

• ozon.ru
• aliexpress.ru
• amazon.co.uk
• amazon.de
• newegg.com

[vegos]

I can see the High-Z circuit, but no headphones amplifier...

[Yuradol1972]

@DB9JG Here is a better photo for you

I think the input part diagram is taken from here

[vegos]

This radio is capable to receive up to 600MHz, not only 30MHz.

[DB9JG]

Thank you for that info. That additional settop flexible PCB enabled additional ssb and WBFM reception at those radios. It has a 50 ohm coax input on the right.
.
Your PCB foto still hides the interesting trace under the BGA427.
But it is most likely this with the BLUE trace added :

[max-arnold]

I did some continuity probing with a multimeter, and the above diagram seems to be correct (the blue path does exist). Happy to do additional probing if you want

[DB9JG]

This seems to be the origin circuit

[max-arnold]

The board seems to be DoA - even with a battery it still shows "Si4735 not detected". LDO is ok (I see 3.3V on pins 10 & 14), RST is low. Also I traced SCL/SDA/RST lines and at first glance these are also ok. I do not have an oscilloscope, will try to do some I2C/RST tests in software.

The ESP32-S3 works, but is misaligned against the soldering pads:

[DB9JG]

The two I2C traces leading to the Si4732 on the other side of the ESP32 may be affected by this misalignment.
Did you make a continuity test (or neighboring pin shortcut) between the ESP32 pins and the two I2C pins at the Si4732?
Give it a second life;-)

[max-arnold]

Yep, I tested the continuity of SCL and SDA lines and also measured the 10k pullups.

[DB9JG]

Well - that are the drawbacks of the slow boats to China. They are even selling the devices that should habe failed the quality test - if there were such test at all

[vegos]

I would check pin by pin on the misaligned side if there is continuity to confirm the problem...

[DXKolpino]

My board arrived from the same store as max-arnold's.
At first glance, without connecting a speaker or battery, it works fine. I need to experiment further.

[max-arnold]

Got another board (can't fix the broken one because it is too small for me). Installed it into the following case https://www.thingiverse.com/thing:7057083. It almost fits a Bourns PEC11R encoder - the space is about 6mm but the encoder height is 6.5 mm (I think it is possible to print a different plastic divider part to get the required 6.5mm).

Do not plan to do thorough measurements, but in a simple test the BD3SC shows higher RSSI compared to V1.

[G8PTN]

Do not plan to do thorough measurements, but in a simple test the BD3SC shows higher RSSI compared to V1.

Hi Max,
The higher RSSI reading will be because of the LNA on the front end. This will of course amplify both signal and noise, so the S/N is actually slightly worse compared to V1. The LNA will cause some S/N degradation, specified Noise figure NF = 2.2 dB at 1.8 GHz.

The S-Meter could be recalibrated taking account of the LNA, which may allow measurements of signals below S4 (<30MHz) and S7 (VHF).

The sensitivity will be better with the LNA, but it may also cause more overload in some cases. Ideally there should be an option to switch the LNA in or out, but that is not provisioned on the hardware.

73, Dave

[DB9JG]

Hi Dave and Max,

I agree with Dave. This LNA IC is even unspecified for frequencies below 100MHz. The internal circuitry suggests an impedance of 7kΩ||1pF.

Advantage: No more theremin effect:

However, practice counts!

[EmEiBee]

...if you're already using a custom enclosure, why not install an optical encoder like an HRPG-AD32 (Agilent), M101C20 (Megatron), or similar? They occasionally pop up for a song at online auctions (if I haven't snapped them up first ;) ).

[DB9JG]

Are those compatible encoders?
I understand that Max wants to stay within the given HW and SW conditions

[EmEiBee]

Compatibility mainly depends on the steps. Fewer steps = more turns.
Another point is the question of whether you need the button in the encoder or whether an external one makes more sense. The encoders mentioned do not have buttons; were right here in front of my eyes...
I mainly use these encoders to convert laboratory power supplies and low-cost radio devices, which usually have a junk encoder installed like this boards.

Edit say: One disadvantage of an optical encoder is obvious... It naturally requires a power supply for the internal LEDs. This is usually only 3-5mA, but it's something to keep in mind...

[DB9JG]

A compatible encoder should give A/B signaling with CW/CCW direction coded in the phase shift. The mentioned decoder are likely to use an other method, if I read correctly.

EDIT: on the second view: compatible regarding CW/CCW signaling

[EmEiBee]

... all encoder like this working this way. Ok, there are some special ones (i.e. A/B/C-20° shift), but this special ones you rarely find on eBay & Co...