Opera Digital Data Mode Performance

Due to the effects propagation it is difficult to evaluate the parameters of a mode, particularly with detectability around the noise level.
PA0A has done Lab Tests on the ROS OPERA digtal radio data mode and found the following results.

Op1 decode @ -24dB Average from many test
Op2 decode @ -27dB Average from many test
Op4 decode @ -30dB Average from many test
Op8 decode @ -33dB Average from many test
Op32 decode @ -37dB Average from many test

This is nice to know as it agrees closely with the expected theoretical values. Odd readings are obviously the result of propagation.

Loss of Data in the signal will give abnormal S/N results. I tried removing 1/3 of the bits throughout the message, the act of doing this looks like sabotage of the correct message coding, it is, the result was just one decode from many tests of a bogus call with a marginal S/N ratio.

13:35 500 8N3CSZ de G3ZJO Op4 -30 dB in Northampton

Removing the complete mid 1/3 of the Data in the message does degrade the S/N as does removing the first 1/3, anyone can try removing the last 1/3 by stopping the transmission.

Readings with complete Data:-

14:21 500 G3ZJO de G8HUH Op4 181 km -26 dB in Somerset.
14:21 500 G3ZJO de M0BMU Op4 -15 dB in nr Hatfield
14:21 500 G3ZJO de G3ZJO Op4 0 km +6 dB in Northampton

Readings with 1/3 blocks of Data loss.

14:47 500 G3ZJO de M0BMU Op4 76 km -17 dB in nr Hatfield
14:47 500 G3ZJO de G3ZJO Op4 0 km +3 dB in Northampton

Next 1/3 of the Data was removed in blocks of 8 bits in a random fashion throughout the message again OPERA decodes successfully:-

14:53 500 G3ZJO de G8HUH Op4 181 km -28 dB in Somerset. test4
14:53 500 G3ZJO de M0BMU Op4 76 km -17 dB in nr Hatfield
14:52 500 G3ZJO de G3ZJO Op4 +0 dB in Northampton

In further tests I may try removing 50% of Data bits.

Aircraft Reflections on 50MHz OPERA Mode

We had our first de-codes via Aircraft Reflections yesterday using ROS OPERA digital radio data mode. As expected Op1 produced the best results, From past experience Opera gives many more decode-able spots than WSPR.
I calculated a hot spot in the North Sea Corridor and G6AVK and I both beamed there. It was some time before we got our first well placed Aircraft but just as I was considering trying another route, just like buses came a reflection followed by another which we could not see on the Capture even when blown up several times.

With Beams round to the Irish Sea Corridor there is no chance of G6AVK receiving me direct with 5 Watts of Op1 every minute under normal conditions. The first de-code came at 17.40UTC followed by another at 17:49UTC.

17:40 50700 G3ZJO de G6AVK Op1 127 km -20 dB in Essex with 5w + 4element
at 5.5m agl
17:49 50700 G3ZJO de G6AVK Op1 127 km -23 dB in Essex with 5w + 4element
at 5.5m agl

It’s interesting to see the Capture taken from G6AVK’s on line Grabber, there are 5 visible transmissions here most likely from the Aircraft approaching the hot spot and passing it,the one that decoded is not the straightest it does look stronger. So
Op1 doesn’t have to be dead straight to decode.

To view images full screen Right Click and Select View Image.

Unfortunately using Opera Software for TX means that the TX frequency changes for each period, there is no direct signal visible so no chance of calculating the Aircraft speed. There is some super shifting in this Capture but again no reference signal.

Some of the reflections were also received by G4DMH at the same time as G6AVK but there did seem to develop a pattern of G4DMH receiving a decode of the next transmission when the Aircraft reached his hot spot possibly.

18:10 50700 G3ZJO de G4MDH Op1 104 km -23 dB in Wootton Bassett with 5w
+ 4element at 5.5m a
18:10 50700 G3ZJO de G6AVK Op1 127 km -16 dB in Essex with 5w + 4element
at 5.5m agl
18:13 50700 G3ZJO de G6AVK Op1 127 km -22 dB in Essex with 5w + 4element
at 5.5m agl

Some decodes look quite weak 18.17UTC at G6AVK for instance, the only one out of the 5 in the capture that decoded for G6AVK,18.19UTC decoded at G4DMH but not G6AVK.

18:17 50700 G3ZJO de G4MDH Op1 104 km -23 dB in Wootton Bassett with 5w+ 4element at 5.5m a
18:17 50700 G3ZJO de G6AVK Op1 127 km -22 dB in Essex with 5w + 4elementat 5.5m agl
18:19 50700 G3ZJO de G4MDH Op1 104 km -22 dB in Wootton Bassett with 5w+ 4element at 5.5m a

There is a screen full of Op1 and Op2 mangled by Doppler which didn’t decode here.

Aircraft Scatter causes problems on 6m WSPR for many stations it seems that Opera may well give them many more spots.

Opera Mode on 500kHz

Opera mode continues to be updated not daily now which is nice. I am still trying to evaluate the mode on 500kHz, Op4 and Op8 are used on the band Op4 carries a call sign only, QRS3 can carry a call in around the same time, WSPR does the same in half the time.

In my tests QRS can perhaps hold its own if an operator can be bothered to spot the signal wait for a full ident then respond in some way. Unfortunately many on 500kHz sit and moan about the lack of QRS but cant be bothered to use the mode they love to the exception of all others.

Last week I tested WSPR against Op4 with G0KTN, WSPR won hands down on our path. Now Op8 should give 3dB advantage, never have I seen this advantage on 500kHz the modes should perform the same down into the noise when Op4 drops out and Op8 should decode at higher S/N ratios. On tests they both dropped out at the same time and Op8 produced false looking higher S/N reports. Clearly propagation causes more signal loss on longer modes.

I had to prove my TX stability and that of the G0KTN RX.

Then I asked PA0AM for some signals on Op4 and Op8, with the same results.

14:22 500 PA0AM Op4 -29 dB 322 km 10Watts
14:18 500 PA0AM Op4 -30 dB 10Watts
14:14 500 PA0AM Op8 -29 dB 322 km 10Watts
14:05 500 PA0AM Op8 -31 dB 322 km 10Watts
13:52 500 PA0A Op8 -22 dB 493 km 100Watts
13:44 500 PA0A Op4 -21 dB 493 km 100Watts

So if Op4 outperforms Op8 on 500kHz how low can we go, I did the test with G0KTN and repeated with PA0AM, where is the advantage of slower modes?

18:52 18105 PA0AM Op1 -22 dB 322 km on 500kHz
18:50 18105 PA0AM Op2 -25 dB 322 km on 500kHz
18:41 18105 PA0AM Op2 -18 dB 322 km on 500kHz

Last night the Transatlantic tests were done on OP2 and numerous spots reported, I think we may soon have Op2 and Op4 for 500kHz or even OP1 Op2.