Oracle and Fatshark problem

[npole 1]

I'm having problems with the Oracle Diversity and my fatshark goggles. As soon i connect the audio output to the oudio-in of my fatshark, the image goes "black and white" and starts to flicker.

The goggles works OK if only connected to one of the receivers (then bypassing the oracle).

I'm using two "standard" (PLL) 1.3ghz receivers (those ones that comes with a channel LCD display).

Apparently the same output works fine with other devices (ie: i use it to record the videos with a digital recorder) so the problem is only about the fatshark in combination with oracle.

Is there anything i may try? Maybe it's a matter of impedence on the output... i would like to try a resistor there, but i'm not sure. Any advice?

[Mr.RC-Cam 121]

The audio output of the Oracle is just a simple buffered signal that is the same amplitude as what is provided to Oracle. It is DC coupled, so maybe your Fatsharks have an odd design that requires a capacitor coupling (to do that just add a 10uF to 47uF cap in series with the FatShark audio-in signal). The only other thing I can think of is that the FatShark audio signal is being shorted when it is plugged in (perhaps due to the wrong cable or a defective cable) and that is causing havoc elsewhere.

[npole 1]

Thank you Mister, i've tought it was the cable initially.. so i've checked it with a tester (and verified the pinouts), the cable is ok, but definitively the cable (and the fatshark) works OK with other video/audio sources (as i said above, if i connect it directly yo the receiver it works OK; i've also tried to connect it to a DVR and it works good as well), so there must be something "different" with the Oracle... i'll try with the capacitor. Do i've to add it in serie with the signal pin (RCA center pin)? What about the polarity? Do the negative pin of the capacitor has to face the Oracle or the Fatshark?

Thanks.

[Mr.RC-Cam 121]

You didn't say, but despite the loss of color, does the audio work when installed on Oracle? If not, then there must be something wrong in the cable connections.

so there must be something "different" with the Oracle.

It is very unusual that you lose color when you plug in the audio cables. I just can't imagine what it could be. The functions are not related.

Here is what I recommend you do to isolate this:

1) Cut the audio cable that goes to Oracle. Connect only the shield (ground). Is the video OK (has color)?

2) If step 1 is Ok, then add the AC coupling cap in series with the signal wire. Plus side goes to FatShark Rx.

[npole 1]

I've added a capacitor (20uf) in serie with the audio signal (positive is poiting to the receiver) and the problem has gone, i didn't verified the video quality since i tested it only on the ground (very near) ..but the image now is "stable", i'll check it tomorrow while flying... hoping it doesn't affect the video (the audio seems ok).

[Mr.RC-Cam 121]

That is good to hear. Common video display devices will already have the AC coupling caps built into them, so I'm not sure why the FatSharks omitted it. It is even stranger that it affects the color. But, fortunately the fix is simple.