Max SNR as Indicator of RX Performance?

[df9rb]

Hello Rene,

I have the 40 db vision since I started dreaming. To reach this goal I modified the AGC of my TS850 (but still the best SNR with AGC OFF), modified the mixer, tried several filters (between 30 kHz and 6 kHz), used attenuators different soundcards and antennas - but without success until now. So my congratulation for your best result so close to the 40 dB.
I would like to add to all of the factors you mentioned one additonal:
- the SNR at the transmitters antenna

Did anyone receive DRM close to a transmitter and what was the SNR there?


73 de Bernd, DF9RB

[Rene Schmitz]

Hi Bernd and all,

Thanks!

It would be very interesting to get results from the nearfield of a TX. I am a couple km away from the AM TX of WDR here in Bonn, 774kHz, maybe some day they'll start using DRM. :-)

It would be interesting to know what the reference receivers at the various sites acheive in SNR. Anyone?

Cheers,
René

[VE3MEO]

Max SNR table - the ascent to 40dB

Highest SNR's over 30 dB achieved with DRMRX/DReaM

This is a listing in descending SNR of reported Max DRM SNR as logged by DRMRX and Dream software, and analysed by Carknue's DRMcalc. It's for fun but might yield some useful tips for better reception. If you have results that leap the 30 dB hurdle, e-mail me with the details and I'll add it to the list. 40 dB off-air SNR has been surpassed!

73, Tom
<table align=LEFT border="1">
<tr><th>Max SNR
<th>By
<th>Receiver
<th>Converter
<th>App
<th>Antenna
<th>Service
<th>Freq(kHz)
<th>Date</th>
<tr><td>42.1 dB
<td>René Schmitz, Bonn, Germany
<td>Elektor custom IF, ADA831 2nd mxr, TUF-1,1st mxr preselector
<td>
<td>DReaM 1.1.6c
<td>5m wire
<td>DW Sines
<td>11830
<td>2005-02-05
<tr><td>41.2 dB
<td>Bernd DF9RB 150 km n. of Munich, Germany
<td>TS850 AGC inactive
<td>SA612 ceramic resonator
<td>DReaM 1.1.7c
<td>3-el ham Yagi, ALA1530, 30m wire
<td>Voice of Russia
<td>15780
<td>2005-01-31
<tr><td>37.9 dB
<td>simone, Bad Salzschlirf, Germany
<td>FRG100 AGC off
<td>Sat-Schneider
<td>DRMSWR 2.0.34
<td>whip
<td>DW Sines
<td>11830
<td>2005-02-08
<tr><td>36.7 dB
<td>df8uo, Karlsruhe, Germany
<td>FT757GX
<td>Sat-Schneider xtal
<td>Dream 1.1.1c
<td>dipole
<td>DW
<td>11830
<td>2005-03-20
<tr><td>36.5 dB
<td>CT1ADT, Sines, Portugal
<td>TS-870 unmodified
<td>11,3 kHz out
<td>DRM 2.0.34
<td>8m vert or 24m dipole
<td>VOR
<td>15780
<td>2004-01-07
<tr><td>35.7 dB
<td>hsseppo, Helsinki, Finland
<td>AD8099, AD9834 DDS TUF-3 mxr
<td>?
<td>DReaM 1.1.4c
<td>5m wire
<td>DW Sines
<td>17800
<td>2004-11-07
<tr><td>35.6 dB
<td>arniek, Muenster, Germany
<td>FRG-100
<td>Sat-Schneider
<td>DReaM 1.1.1c
<td>homemade loop
<td>DW Sines
<td>5980
<td>2004-10-08
<tr><td>35.4 dB
<td>Han, Netherlands
<td>AOR AR 7030 unmodified
<td>Sat-Schneider
<td>DReaM 1.1.7c
<td>?
<td>DW Sines
<td>11830
<td>2005-02-09
<tr><td>35.0 dB
<td>carknue, Frankfurt, Germany
<td>AOR-7030
<td>Sat-Schneider xtal
<td>DRMSWR 2.0.34
<td>Wellbrook ALA1530P
<td>VoR
<td>15780
<td>2004-01-10
<tr><td>34.9 dB
<td>dn0758
<td>elektor
<td>
<td>DRMSWR 2.0.34
<td>Sony AN-1
<td>DW Sines
<td>17800
<td>2004-11-20
<tr><td>34.4 dB
<td>chemclouds, Richmond, Va, USA
<td>Icom IC-R75 AGC off
<td>
<td>DRMSWR 2.0.34
<td>30m inverted-L
<td>CBC Sackville
<td>9800
<td>2004-11-27
<tr><td>34.3 dB
<td>FritzWue DK6QI 52N 07E
<td>FT840
<td>Sat-Schneider
<td>DReaM 1.1.6c
<td>2x 40m LW
<td>DW-Sines
<td>17800
<td>2004-12-18
<tr><td>34.3 dB
<td>Kjell Holen LA6XJ Bergen, Norway
<td>Sat-Schneider DRT1
<td>
<td>DReaM 1.1.7c
<td>70 cm indoor loop
<td>Voice of Russia
<td>12060
<td>2005-01-15 e-mail
<tr><td>34.2 dB
<td>Werner DK8FT
<td>IC R71 AGC off
<td>Sat-Schneider xtal
<td>Dream 1.1.6
<td>4m wire
<td>DW-Sines
<td>17710
<td>2005-02-20 not posted
<tr><td>33.2 dB
<td>G3VRF, Warwickshire , UK
<td>AD9852 DDS, AD831 Mixer, 2x AD603 IF
<td>12kHz DRM xtal ctld
<td>DReaM 1.1.6c
<td>35cm tuned loop in attic 11m a.g.
<td>DW Sines
<td>11830
<td>2004-11-24
<tr><td>31.8 dB
<td>Tom VE3MEO Toronto, Canada
<td>Radio Shack DX-394A no AGC nor 2nd IF fltr
<td>LF-D6 filter/NE612 protoboard
<td>DReaM 1.1.1c
<td>G5RV
<td>CBC Sackville
<td>6140
<td>2004-10-19
<tr><td>30.7 dB
<td>simone
<td>FRG8800
<td>Sat-Schneider
<td>DRMSWR 2.0.34
<td>whip
<td>DW Sines
<td>15435
<td>2004-10-10
<tr><td>30.4 dB
<td>TimoHannes, Petäjävesi, Finland
<td>elektor
<td>?
<td>DRMSWR 2.0.34
<td>active
<td>DW Sines
<td>17800
<td>2004-11-14
<tr><td>30.0 dB
<td>Bob, St Albans UK
<td>AR88D (60 yrs young!)
<td>Sat-Schneider LC
<td>DRMSWR 2.0.34
<td>long wire
<td>DW Sines
<td>13790
<td>2004-09-10</td></tr>
</table>

[VE3MEO]

Re: Max SNR table - the ascent to 40dB

Here are the latest changes to the table.

73, Tom

Jan 16: Bernd, DF9RB scores a 39.2 dB max SNR from VoR on 15780 and moves into 1st place!

Jan 15: Kjell Holen, LA6XJ, makes his first appearance on the list with 34.3 dB on a Sat-Schneider DRT1 from VoR on 12060. That's the 1st appearance of that receiver on the list, too; it's supposed to be capable of >40 dB SNR, according to the manufacturer, so look for Kjell to climb.

Jan 14:
Daniel, DF8UO, climbed a few spots to #7 today with a 1.7dB improvement in his personal best. He writes:

I am following the race to 40 dB in the forum. My configuration is nothing special, just a slight modification of my amateur equipment FT757GX and the non XTAL version of the SAT Schneider modul. I did not change any filters, just soldered a small coax before the 455 kHz IF and connected to the module.

However i noticed that the soundcard is very important. Since i use an external Creative Soundblaster Audigy, results are much better compared to the internal AC97 onboard sound.

[VE3MEO]

40 dB barrier broken!

Once thought to be unattainable in over-the-air reception, in the last couple of days, not one, but two DRM pioneers broke the 40 dB DRM SNR barrier! And not by a hair but a wide margin.

First it was Rene Schmitz and DW-Sines on Jan 30 and then, one day later, Bernd, DF9RB, pulling in Voice of Russia. With but 0.1 dB separating their results, these two are vying for first place. For details on their systems and links to their reports, click on table.

Congratulations, Rene and Bernd, on such great success in the propagation lottery. Conditions over there must have been so good that it was like having a tap on the transmitter's transmission line. And it's a testament to the quality and alignment of the transmitters and the receivers that such results might be achieved, if only momentarily. Well done!

73, Tom

[VE3MEO]

42.1 dB!

Rene hit 42.1 dB today - from DW Sines on 11830. Wow!

Originally posted by VE3MEO
SNIP

First it was Rene Schmitz and DW-Sines on Jan 30 and then, one day later, Bernd, DF9RB, pulling in Voice of Russia. ... For details on their systems and links to their reports, click on table.

SNIP

[df9rb]

Hi all,

here a link to a describtion of an DRM-Receiver with optimized performance. SNR 47.4 dB!

http://www.iis.fraunhofer.de/dab/products/drmmonitoringreceiver/Paper_5th_Workshop_Digital_Broadcasting_04.pdf

Bernd, DF9RB

[VE3MEO]

Re: Max SNR table - the ascent to 40dB

Here are the latest changes to the table.

73, Tom

Feb 8: simone inched closer to the 40 dB hurdle, now within 2.1 dB at 37.9dB.

Feb 13:
Daniel, DF8UO, climbed into a tie for 5th place with hseppo at 35.7dB.

[hsseppo]

Hi Tom and all,

I am back again with a new home made receiver. I am using now AD9951 14Bit DDS and AD831 mixer. I don't have problems of spurious or image frequencies any more. Also noise level is lower than my old AD9834 + TUF-3 receiver. I think that AD831 mixer performance is very good, low noice level, good IP3.

Here is my first test of Dream -t transmitter.

>>>>
Dream
Software Version 1.1.7cvs
Starttime (UTC) 2005-02-16 20:21:19
Frequency 10012 kHz
Latitude
Longitude
Label Dream Test
Bitrate 20.96 kbps
Mode B
Bandwidth 10 kHz

MINUTE SNR SYNC AUDIO TYPE
0000 44 150 0/10 0
0001 45 150 0/10 0
0002 45 150 0/10 0
0003 45 150 0/10 0
0004 45 150 0/10 0
0005 45 150 0/10 0
0006 45 150 0/10 0
0007 45 150 0/10 0
0008 44 150 0/10 0
0009 45 150 0/10 0

SNR min: 41.4, max: 45.8


45.8 db SNR I just can't believe it is true!
Well, the real an air signal testing is just starting.

73, Seppo

[VE3MEO]

That's impressive Seppo. What is your test transmitter system or upconverter?

It would be interesting if one could compare the % audio decoded between two receivers whose performance was identical in every respect except the max DRM SNR, so we could tell if it is worth the effort to strive for the highest max SNR in receiver design. If it turned out that the difference between a 25 dB max and a 45 dB max receiver was only 0.1% when success is over 99.5%, then it would not be worthwhile if the cost difference was significant. If it made a difference of 20% when the success rate is below 50%, who cares! The success rate is so low that we would give up trying to listen on either one.

73, Tom

Originally posted by hsseppo
Hi Tom and all,

I am back again with a new home made receiver. [snip]
45.8 db SNR I just can't believe it is true!
Well, the real an air signal testing is just starting.

73, Seppo

[hsseppo]

Hello Tom,

My test transmitter upconverter is a SA612 mixer. I am using HP Omnibook 6000 notebook computer and Dream software (linux version drm -t) to feed the mixer. Local oscillator is 10 MHz crystal oscillator. So it is very simple transmitter, just mixer and oscillator. The output of mixer is attenuated to the right level, so that receiving input level is about -10 dB.

I believe that a good SNR is not so important. My experience is that a good DRM radio must be free of interferencies. My Sony ICF-2001D receiver has very clean signal, but the PLL phase noise limits the maximum SNR to 28 dB. Clearly the new DDS receiver (AD9951+AD831, 45dB SNR) is working better. The old DDS-receiver (AD9834+TUF-3, 43dB) was sometimes much worse than Sony, beacause of DDS spurious. I even used preselector, but was not able to filter mirror and spurious frequencies. The SNR spectrum is a very good option in the Dream software. Using this option it is easy to see that a good receiver must be free of interferencies.

I think that the only usable DDS is 14 Bit AD9951. The IF must be reasonable high, I am using 21.4MHz, 15kHz 6 pole crystal filter (I would use 55 MHz, if they were easier available). Also mixer should have good third-order intermodulation and low distortion. So AD831 is a good mixer. As a bonus you get also high SNR.

At last I like to encourage to build homebrew receivers. Earlier I was afraid of small smd components, but they are really nice components and easy to use. Only a microscope (8 x) and soldering flux is needed.

Seppo

[VE3MEO]

Hi Seppo,

You did a very impressive job with the surface-mount devices.

I made a NE612 upconverter for testing at 455kHz (loopthrough the downconverter) and at 10MHz for testing the whole receiver system but did not achieve such great results.

73, Tom

Originally posted by hsseppo
Hello Tom,

My test transmitter upconverter is a SA612 mixer.
{snip}
At last I like to encourage to build homebrew receivers. Earlier I was afraid of small smd components, but they are really nice components and easy to use. Only a microscope (8 x) and soldering flux is needed.

Seppo

[Rene Schmitz]

Hi all,

First of all: Congrats Seppo! Well done!

It shows that with care, you can get on par with commercial gear.

I've made similar measurements on my modded elektor:

>>>>
Dream
Software Version 1.1.6cvs
Starttime (UTC) 2005-02-22 23:11:10
Frequency 9992 kHz
Latitude
Longitude
Label Dream Test
Bitrate 20.96 kbps
Mode B
Bandwidth 10 kHz

MINUTE SNR SYNC AUDIO TYPE
0000 45 150 1500/10 0

SNR min: 44.0, max: 45.9

CRC:
<<<<

I had made a similar test in January, but I can't reproduce its result of over 47dB.

Bear in mind that this RX uses the AD9835 DDS, which is only 10Bit. My upconverter is a RMS11-X DBM with a 10Mhz Xtal osc.
RF and IF port of the DBM were swapped. The levels have to be very carefully adjusted to get the maximum SNR. I used the lower sideband, since then the carrier which isn't fully suppressed end up on the high frequency side, where I get a better attenuation in the IF stage, by shifting the signal of the upconverter arround (IF of dream -t). On the lower side it eventually folds to negative frequencies once it gets past 0kHz. Somehow this carrier seems to affect the SNR.

So in all, I can't fully agree that the 14Bit DDS is a must. :-)

I use that AD831 as the second mixer, and I can also say that its a very good mixer. I think over time I will make all this into a fully fledged double conversion RX, using what I have now as the IF stage. The mirror supression of 450kHz IF is way to little.

Cheers,
René

[Han]

Hello everyone

Here is my max SNR reached

I use a unmodified AOR AR 7030. On the 455 kHz AUX output i have a sat schneider converter and this is the result.
For a better result i often put the AGC at Off. I can give a 5 dB better result then when on slow

Greetings Han

[VE3MEO]

Re: Re: Max SNR table - the ascent to 40dB

Here are the latest changes to the table.

73, Tom

Feb 9:
Han's 35.4 dB report of this date puts him onto the list in 8th place.

Mar 20:
Daniel, DF8UO, climbed 1 dB to 36.7 and 4th place.