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Interface

G4FBZ wrote:

Hello All,
Have just built the interface and am using RDS Spy for the first time today. I am just getting used to the "Logging" via the MS option.

The PI grabbing seems quite sensitive. I have three Sony tuners so will build two more interfaces to fit inside each tuner as I prefer to use the COM Port rather than Sound Card.

Thanks for a great Program and look forward to future updates.

William Kitching. IO82SQ, U.K.

G4FBZ wrote:

Hello All,
I have now built 7 interfaces and have had a few issues along the way. The first one I built worked first time. However the second & third did not work at all.
I could not find the fault to start with, however whilst fault finding I just happened to touch the 10nf Capacitor from Pin 6 of the 555 chip to Earth and the interface burst into life. If I let go it stopped working again.
I removed the 10nF cap and it measured fine on the Multi Meter. However I replaced it with another one and the interface worked fine.

It would appear I had a funny batch of these capacitors from Maplin. I have had the same problem on two of the other interfaces, even though the capacitors measure OK. I also checked the 22K resistor in the timing chain and that was OK.
So I can only assume the tolerrance of the 10nF is quite critical.

Finally I tried two USB to RS232 converters using the Prolific Chipset. THEY DO NOT WORK.
Use the ones with a FTDI Chipset for trouble free operation.

For my main PC I purchased a PCI Com Card to give me 2 COM Ports in addition to the one on the Motherboard.

You can run more than one instance of RDS SPY if you install each in a different directory/folder and use different COM Ports. Using this method I have three receivers on one PC all running under 3 versions of RDS SPY. Great for DX'ing.
By using COM Ports and not the sound card means I can record audio from one of the tuners on the PC also.

admin wrote:

That's an interesting experience with the 10 nF capacitor. However the capacitance is not so critical as it may look like. I think it is a ceramic type which causes this problem. Use 10 nF plastic film capacitor rather. They usually have better capacity precision and what's the most important, the capacitance practically does not change with the voltage applied. Ceramic capacitors may look OK on multimeter but they have different capacitance in real circuits, depending on frequency, voltage and temperature. Only NP0 and COG ceramic capacitors are good quality and precision but they are hard to find and expensive for values greater than 1 nF.

Prolific chip based USB converters should work too, I have tried one with good result. What's the real problem of these converters, the driver supplied sometimes does not work. A bit of luck is necessary when choosing one. The FTDI is much better solution.

G4FBZ wrote:

Thanks for the information on the type of capacitor. I have used dipped ceramics. I will have to get some film types. I have mounted the circuit board inside the tuners, (all Sony SB920), so far without any temperature issues.

Thanks again.

G4FBZ wrote:

My FTDI USB to serial adaptor arrived today. Windows 7 recognised it instantly. RDS SPY works straight away with no fuss at all.
I purchased mine from USB NOW: http://www.usbnow.co.uk, well worth the extra £5 compared to Prolific versions.

Good DX!!!

William.

Bob wrote:

Any chance you will support this "USB radio", very nice thing for small money: http://www.silabs.com/products/mcu/Pages/USBFMRadioRD.aspx