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Simulator signal levels (Phoenix v4)

PostPosted: Mon Jul 22, 2013 6:46 am
by LeaUK
Hi All

I'm trying to locate a suitable simulator signal in my Venom 35MHz 4 channel TX and although it has what appears to be a trainer port I can't find an appropriate output on any of the 4-way mini-din pins. I've unfortunately only got a PC based Oscilloscope and as it uses the mic input (AC coupled) can't see DC levels.

I've tapped off one side of the xtal (see link: and using SmartPropoplus+Vjoy have FMS operating well, but the 650mV (I think) signal level is not suitable for the Phoenix USB input box - it can't see the transmitter. It could have a significant DC component, in fact it does as my DVM indicates on average 2.5V.


what signal level is required by the USB device; I suspect CMOS (5v) or it could be TTL (0-2.4V), perhaps the input is already AC coupled in the USB interface?

what signal level is traditionally output from training ports/Simulator outputs of training port?

Options: assuming TTL/CMOS requirements for USB interface, I could use a DC restoration circuit (diode, resistor, small cap & op-amp (gain 10ish) or simply find a compatible PPM output on the IC - maybe that's easier!?

Your advice would be greatly appreciated.


Re: Simulator signal levels (Phoenix v4)

PostPosted: Mon Jul 22, 2013 9:21 am
by LeaUK
Putting voltage levels aside, just had an obvious thought why the Phoenix USB interface can't decipher the PPM signal, it's probably swamped by the 35MHz carrier (if it doesn't have any input filtering, which I've seen posts suggest when trying to resolve Walaker 2401 interface issues)! I'd almost forgotten that my 'scope' naturally rejects/doesn't display the carrier as it's so far outside the audio band.

So even for a DC restoration /clipper cct, I will need to filter out the high frequency component.

Uhm, it's even more compelling to look up the PPM IC used and hopefully tap off some CMOS/TTL voltage levels, rather than use the xtal as the source!

I'll update later tonight after stripping the radio down (again!).


Re: Simulator signal levels (Phoenix v4)

PostPosted: Mon Jul 22, 2013 9:19 pm
by LeaUK

Tapped directly off the PPM IC and get far cleaner signal (see ) - note it's now around 1V. Phoenix Sim v4 detects handset nicely now :-) clearly it's OK with 1V.