Flip Side Racing has been kind enough to provide a test version of their timing and scoring software that supports the Cano decoder. We are now debugging the software, but I'll let everyone know when the final version is available.

Here's a big "THANK YOU!" to Flip Side Racing for these efforts!

The loop amplifier boards finally arrived. It only took six weeks! I sure won't be using that supplier again!

Looking excellent on a PCB! I am going to build at the weekend if I get some time.

Did anybody try the LM319 version by Paypalneg? I made one up last night as it was a more simple circuit. Need to do some testing to see if I can make it work nicely.

You'll want to investigate re-biasing the inputs on the LM319. The circuit shown has the inputs operating out of the acceptable voltage range (1V to 3V on a 5V supply). Also, the gain is not well-controlled, since it is operating open-loop; this may cause erratic operation. And the spec sheets I checked listed a minimum supply voltage of 5V.

Howardcano,
Do I have to understand that the circuit with the LM319 not works properly with your decoder ?

Payalneg,
Have you modify something in the decoder to use the amplifier with the LM319 ?

The circuit might operate with the rest of my design, but there are no guarantees. I have not tested it. It's quite likely that Payalneg is using it with different circuitry. Hopefully he will let us know.

The loop amplifier I presented has all of the attributes that I required. If I thought it could have been simpler, I would have made it simpler-- but not at the expense of my design goals. One of those goals was (and always is, for me) maintaining operation within the published specifications of the components used. That's one way to increase the chances of success for the average builder.

No, its nothing to modifite in decoder schematics. Working pretty good with 5m loop.

Hi!

Impressive work described in this thread!

Ive read through it and tried to figure out if the detection loop/amplifier would work with a AMB rc3/rc4 decoder.

Im looking for an alternative for the "connection-box-with-coax" cable that is present in mylaps store. My local club has more tracks than cables and mylaps price for the cable is a little bit high.

Would that be the amplifier + a loop?

Best regards
eslin

Not sure how your COAX is run, but if you can move it around, you can run multiple loops off the same COAX. I put banana jacks on mine to plug into the loops... loops are cheap & easy to make... just a wire and resistor. Heres one I have the bananas in the wall.

http://www.rctech.net/forum/attachme...d-wgrii-1-.jpg

I also have had several loops made over the years. The RC2 Decoder manual gave instructions on how to make the loop. I even made mine out of 14 gauge copper house wire, just to see what kind of results I would get. It worked fine...

Here is the document from the manual. I made it big so you can read it. When it says the resistor needs to be opposite from the box, it really means, whatever your length of wire is, the resistor needs to be in the middle. So if its 20ft long, the resistor needs to be at the 10ft mark to separate the two pieces of wire. Then you solder them together.

This also works on the new RC4 box as well.

Thanks! but I know about the loops, we have used a selection of different cables for those, and also differing connectors.

Im looking for more "black boxes", for permanent installs on the tracks.
Thats why Im wondering if these "amplifiers", or this decoder systems loop/setup whatever components required in the end of the COAX would work with rc3/rc4 (which are really the same decoder, with just differing firmware).

(also I really do not want to hijack this thread and make it into one of those other threads with what kind of loop is used), just focus on "will this amplifier/loop work with rc3/rc4".)

Best regards
eslin

Try this site for the box.

Transponder Services

I understand your concern with the AMB/Mylaps balun box, as they are quite pricey for what I understand is just a passive transformer! I also appreciate your concern about hijacking the thread, but I can't find any threads dedicated to the AMB/Mylaps decoder to suggest to you. When in doubt, you can always create a new thread. In any case, I hope you have received the information you needed.

The loop amplifier presented in this thread is not compatible with AMB/Mylaps decoders. It is certainly possible to design an active or passive replacement for the AMB/Mylaps balun, but I personally don't have sufficient knowledge of those systems to create one.

Ed and Jimmy, thanks for helping eslin!

I should remind casual readers that the loop Jimmy showed in post #265 is for AMB/Mylaps systems. The loop for the Cano decoder is a little simpler (it's just wire; no resistor is used), and details can be found here:

http://www.rctech.net/forum/12222187-post251.html

Thanks again Howard for all your excellent design in this thread. I have built the two amplifiers now, pictures attached. I get different voltages to your measurements at some points in the loop amplifier, need to investigate this further.

Two quick questions if I may, firstly what output is expected from the phase detector input amp during a phase reversal? At the moment I seem to get a "missing" pulse (in fact I seem to miss two cycles). Output from scope is attached, yellow is logic output and blue is sniffed with a scope probe.

Secondly did you add any filtering into the design? With no TX unit nearby I get spurious logic output at Khz frequencies. This does not occur when the loop is disconnected, so I am fairly certain it is other RF interference. I suspect this is because I have not yet tuned the loop to 5Mhz. I built revB but have not added the three extra jumpers at this time, only the single capacitor.

That's some very pretty prototype work!

Some variation in voltages is inevitable. If the parts values check out okay in the loop amp, then another step to take is either verify that the Vbe of the input pair (Q1 and Q2) match to within a few mV, using the diode check function on a multimeter. You can also use the optional input offset adjust pot to set the voltage at the junction of R8/R9. The voltage can vary a little, perhaps +/-0.1V. I'll update the schematic with an acceptable range when I get the chance. I've constructed several loop amplifiers now, always using transistors from the same production batch, and all have been functional with no adjustments.

Depending on the tuning of the transponder tank (and, to a lesser extent, the timing loop) you may see a missing pulse, or double pulses for a phase inversion. I believe that two missing pulses is also acceptable to the digital phase detector. In any case, please decrease the Q of the transponder tank so that it will return to its original amplitude quicker on a phase inversion.

Filtering is via the loop tuning (and for higher frequencies, the natural rolloff of the transistors). Spurious outputs are not unusual, as many noise sources contain energy in the frequency band we are using. During my experimenting, I located one particularly offensive source: the switching power supply on my laptop computer. Similar noise can result from the ESC and motor in the car. The preamble detector weeds out almost all of this, so the microprocessor can spend its time doing more important things.