31 Dec 2014

Tuner test: DM vs. VU+ vs. CST

Submitted by drhans

I decided to compare the tuners of these three popular satellite receivers. The models tested were

 

Dreambox 820 HD, DVB-S2 tuner BCM4505

Vu+ Solo2, DVB-S2 tuner BCM7356

Coolstream Trinity HD2, DVB-S2 tuner AVL6211

 

The tests I was about to perform were just a simple tests, consisting of the following:

1) Fringe reception performance

2) feed locking

3) High/Low SR reception

 

TEST 1 - FRINGE RECEPTION

All receivers performed quite similarly. All receivers could lock the same signals from the weakest Astra 2E transponders. Whatever TP was not lockable, was not lockable on all 3 boxes. However, even though the picture starts breaking up at the same time on all receivers, the SNR values shown differ, which means the tuner quality in both receivers is about the same, just the values shown by the GUI tend to be different. Especially the difference between Dreambox / Vu+ Solo2 and Coolstream is quite remarkable, strongly in favor of Vu+ and Dreambox. There's even a gap between the 2 Broadcom tuners in Dreambox and Vu+.

For example, the lowest SNR value for a signal which just started to break up is different on all boxes. Since Coolstream shows the SNR value as percentage, I will also use percentage shown by Vu+ and Dreambox. The measurements were done at the same time, using the same dish and LNB.

Astra 2E/F fringe reception tuner comparison
Freq. Standard SNR
    Vu+Solo2 DM820HD CST Trinity
10714 DVB-S 36 % (5.9dB) 40 % (6.4dB) 31%
10994 DVB-S 56 % (9.1dB) 56 % (9.1dB) 43%
11097 DVB-S2 61 % (9.9dB) 61 % (9.9dB) 43%

 

The images below show SNR measures for another frequency. Even here, the differences are noticable.

Apparently, the Vu+ tuner appears to perform better, compared to Dreambox, in low signals, where the SNR appears to be well below the DVB standard minimum, yet the picture starts breaking up at the same time it does on the Dreambox, which is getting better SNR. In this case, the Dreambox appears to be closer to reality than Vu+Solo2. One could argue Vu+ do this on purpose, to appear as being capable of receiving weaker signals, which is not the case.

The situation is completely different when looking at Coolstream SNR values. The SNR, as reported by the AVL tuner, seems to be much worse, yet there's no difference in terms of signal locking. This means the SNR values of AVL and BCM tuners can't be compared since they seem to measure the SNR differently.

 

TEST 2 - FEEDS

What other feeds should we test than the all-time favorites from NBC at 15W! The Coolstream was very cumbersome during scans because the menu was freezing. The Coolstream even failed to scan one of the two tested transponders. Both Dreambox and Vu+ did very well but the Coolstream did not prove to be usable for feed reception. The table below summarizes the results.

Feed lock test
Freq. Standard Lock Scan result
15 West   Vu+Solo2 DM820HD CST Trinity Vu+Solo2 DM820HD CST Trinity
12506H/3198 DVB-S OK OK OK OK OK FAIL
12512H/3400 DVB-S2/8PSK OK OK OK OK OK OK

 

TEST 3 - EXTREME SR TESTS

The last test consisted in tuning in transponders with low and high symbol rate. None of the receivers was able to lock in any SR below 1 Msym/s. However, that is fine since such capability was never advertised by the manufacturers of these boxes. On the other hand, all receivers were able to lock high SR in DVB-S2 8PSK as well as SR lower than 2 Msym/s. In this test, all of the tested receivers perform equally.

SR lock test
Freq. Standard Lock + Scan
    Vu+Solo2 DM820HD CST Trinity
30W/11651V/ SR 1010 DVB-S OK OK OK
23E/11676V/ SR 1410 DVB-S2/QPSK OK OK OK
75E/11913V/ SR 45000 DVB-S2/8PSK OK OK OK

 

CONCLUSION

Out of all these wonderful satellite receivers, the Dreambox 820 HD is probably the winner. It managed to pass all tuner tests and the SNR values reported by the BCM4505 tuner are the ones closest to the reality. 

Read the Vu+ Solo2 review here: http://drhans.tv/?q=review_solo2

and the DM820HD review here: http://drhans.tv/?q=dreambox820hd