Max SNR as Indicator of RX Performance?

[df9rb]

Hi all,

some posts earlier Tom asked if there would be a difference in the reception results between a receiver which can achieve very high SNR compared to another achieving only lower maximum SNR. I bought a Sangean ATS 909 some days ago to try portable DRM reception on business tripps. Today I modified this radio for DRM and did the first comparing tests between my TS850 (maximum SNR better than 40 dB) and the Sangean.
Here the first results (all tests with the same antenna):
Maximum SNR Sangean approx. 28 dB (DW from Sines 15440)
On BBCWS on 7320 there is only a little difference between both
receivers and 100% audio with both (see attachment)
The next evenings I will do some further test on more crowded frequencies and higher demands on filters and strong signal bahavior.

Bernd , DF9RB

[df9rb]

Hello,

I compared between the TS850 and the Sangean. The first screenshot shows the SNR and audio of DW from Taldom on 5830 the second BBCWS on 1296. On the 5830 there are some dropouts with the Sangean, on 1296 is only a very short dropout with the Sangean.

Bernd, DF9RB

[VE3MEO]

Comparative Decoding Success

Originally posted by df9rb
I compared between the TS850 and the Sangean.

Hi Bernd,

I think it's a great test you're doing. Are the receivers logging at the same time or are the logs showing several minutes on one radio then several minutes on the other?

Ideally, they should be simultaneous because of changing propagation and interference. Dream allows two independent instances with one decoding from the left audio channel and the second decoding from the right.

73, Tom VE3MEO

[df9rb]

Hi Tom,

the records are done one after the other at the moment. I know that Dream can use two independent inputs but I do not have the necessary cable for two channels between the computer and the radios. Next weekend I will use my laptop from the QRL to log
simultaneous. These reports are much better comparable then.


Bernd, DF9RB

[dk8cb]

Hi Bernd,

please make sure that the RF Gain on the Sangean is not turned up too high during your tests. It is preferable to us a lower gain setting since the capability to handle large signals is usually not very good on portable receivers such as the Sangean.
On my Sangean ATS-803A, which is an older model, I set the gain (set by an attenuating potentiometer) mostly to a very low value (30%) since signal strength on 'real antennas' is usually no problem.

Roland

[df9rb]

Hi Roland,

this was the first behavior I observed when adjusting the mixer for the 12 kHz IF. I tried to adjust both equipments to the same
IF level. The AGC of the TS850 has a much higher dynamic range than the Sangean ATS909. If a signal comes out of noise a little the TS850 delivers the same input signal to the soundcard as a 9+60 signal. Using the ATS909 I have to use the the RF-Gain most of the time to adjust for correct input levels to the soundcard.
I adjusted the mixer for the Sangean to a level where the input to the soundcard reaches the optimum level receiving a weak signal and AGC ON. On stronger stations I reduce the RF-Gain of the ATS909, on very strong signals I have to reduce the sondcard mixer additionally.

I observed an other influence on the SNR of the Sangean!
With batteries the SNR is approx 3 dB higher compared to operation with the original power supply. I have wound up the 6 V cable through ferrites but this did not help too much, using a regulated power supply improves the SNR a little but the best is batteries.

Bernd, DF9RB

[dk8cb]

Hi Bernd,

have you checked that the rectifier diodes inside your Sangean power supply are shorted for RF by small capacitors, usually of 10 nF each?
This is the first modification one should apply to any power supply used with a shortwave receiver regardless which mode, DRM or AM, it will be used with. But normally, the original power supply supplied with the set should already contain such capacitors.

Roland

[df9rb]

Hi all,

here as promised the first comparison log recorded at the same time between my TS850 and the Sangean ATS 909. Both radios shared the same antenna and manually adjusted RF-gain.
The 2nd graph is the Sangean.
Interesting is the parallel characteristics of the SNR graphs.


Bernd, DF9RB

[df9rb]

Hi,

here two reports TS850-Sangean for VoR on 7390 and RTL 6095.
At the beginning of the log on 7390 I used the same antenna splitting the signal with a T-connector. I was surprised about the unexpected low SNR from VoR. At 20:40 I connected a separate antenna to every radio and the SNR increased. That means that a simple T-connector is really not the correct antenna splitter even with very strong signals. I will solder a resitive splitter the next days.

Bernd, DF9RB

[df9rb]

Hi all,

my comparative test between a receiver achieving high SNR (greater 40 dB) and a receiver achieving only 15 db lower maximum SNR is very definite: The percentage of correctly decoded audio is nearly the same! Strong stations on clear frequencies give 100 % on both. For stations with strong adjacent stations or mulitpath reception the high SNR receiver has approx. 4 % more decoded audio. If the band closes both receivers stop decoding at the same time (see attachment). Because of this "go - no go" behavior of DRM I would propose a new thread which sould be named "DRM with selectable quality by the listener " as even with better receivers the listener has no chance to follow the broadcasting then with lowered quality if the signal falls beneath the "go-level".

Bernd, DF9RB

[VE3MEO]

Originally posted by df9rb
The percentage of correctly decoded audio is nearly the same! (snip) For stations with strong adjacent stations or mulitpath reception the high SNR receiver has approx. 4 % more decoded audio.

Hi Bernd,

Great reports! In my books, 4% is not nearly the same - it's a huge difference. I think that, for the average listener, the successful audio decoding must be well above 99% to be satisfying, or to avoid driving them away. A 0.5% dropout rate is significant and may be excessive for many.

I would say that your tests do demonstrate that there is merit in seeking the higher DRM SNR performance because it does make a difference where it matters - in the 99% region. I don't think anybody cares about the difference in performance when both are well below the 99% level - they will have stopped listening!

73, Tom

[VE3MEO]

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

It's been quiet as far as new entries or advancements in the table since Mar 20! What gives? Has nobody had a better result? Are there no new members hitting 30+dB SNR? Or is this a subject that has run its course?

73, Tom

Originally posted by VE3MEO
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.

[df9rb]

Hi all,

today I did two more comparative tests between the TS850 and the Sangean ATS 909 on the same antenna and both radios with
optimized RF gain. One log is BR5akt, the other RTL Radio. BR5akt does not suffer from interference so badly as RTL Radio and on this frequency the TS850 is better. On the 6095 3 stations are interfering and there is no differnece between the two radios.
In the attachment alway the 2nd graph is the Sangean.

73s de Bernd, DF9RB

[Bob]

Hi Tom,

I know this thread is just a bit of fun really but I hit a new high (for me anyway) today. My trusty AR-88D with a Wellbrook LA5030 loop antenna hit 32.5 dB this afternoon on a DW transmission on 13790KHz . I was logging simultaneously using Dream 1.2.4 and DRM 2.034. The latter showed the max SNR as only 31.2 dB so I have attached the Dream log in preference !

I hope this lifts me off the bottom of the league table (don't want to be shown up by all those solid-state receivers) !

regards
Bob

[VE3MEO]

Re: 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!

Most recent entries have dB in bold.

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>51.4 dB
<td>hsseppo, Helsinki, Finland
<td>AD8099, AD9551, AD831, 21.4 IF
<td>AD831
<td>DReaM 1.2.5c
<td>Direct from Tx
<td>Dream Test
<td>10012
<td>2005-06-30
<tr><td>45.1 dB
<td>Bernd DF9RB 150 km n. of Munich, Germany
<td>Sat-Schneider DRT1
<td>
<td>DReaM 1.3.1cvs
<td>3-el ham Yagi, ALA1530, 30m wire or EWE
<td>Voice of Russia
<td>15780
<td>2005-10-16
<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>41.9 dB
<td>FritzWue DK6QI 52N 07E
<td>Sat-Schneider DRT1
<td>
<td>DReaM 1.2.4
<td>2x 40m T up 22m
<td>DW
<td>7265
<td>2005-09-06
<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>40.0 dB
<td>df8uo, Karlsruhe, Germany
<td>FT757GX
<td>Sat-Schneider xtal
<td>Dream 1.3c
<td>dipole
<td>VOR
<td>15780<td>2005-10-03
<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>37.6 dB
<td>hsseppo, Helsinki, Finland
<td>AD8099, AD9551, AD831, 21.4 IF
<td>AD831
<td>DReaM 1.2.5c
<td>5m wire
<td>VoR
<td>15780
<td>2005-06-30
<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>36.3 dB
<td>carknue, Frankfurt, Germany
<td>AOR-7030 AGC off
<td>Sat-Schneider xtal
<td>DRMSWR 2.0.34
<td>Wellbrook ALA1530P
<td>DW
<td>5980
<td>2005-10-14
<tr><td>35.9 dB
<td>johnn, Scunthorpe, N.Lincs, UK
<td>DRT-1
<td>
<td>DReaM 1.5cvs
<td>AL1530 loop
<td>DW Sines
<td>17700
<td>2005-12-31
<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>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>33.5 dB
<td>johnn, Scunthorpe, N.Lincs, UK
<td>AOR 7030
<td>
<td>DReaM 1.2.4
<td>AL1530 loop
<td>Radio Luxembourg
<td>7145
<td>2005-10-29
<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>33.2 dB
<td>simone
<td>Coding Tech DWT
<td>
<td>Dream 1.2.3cvs
<td>long wire
<td>Bouquet Flevo NL
<td>7240
<td>2005-07-24
<tr><td>33.0 dB
<td>Digger, CH-5023 Biberstein
<td>FRG7700
<td>SO42P xtal
<td>Dream 1.2.4
<td>12m long wire
<td>DW
<td>17800
<td>2005-11-02
<tr><td>32.5 dB
<td>Bob, St Albans UK
<td>AR88D (60 yrs young!)
<td>Sat-Schneider LC
<td>Dream 1.2.4
<td>Wellbrook LA5030 indoor loop
<td>DW
<td>13790
<td>2005-05-22</td></tr>
<tr><td>32.5 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>32 dB
<td>carknue, Frankfurt, Germany
<td>Coding Tech DWT
<td>
<td>Dream 1.3.1cvs
<td>Degen DE31 Active Loop
<td>DW
<td>5980
<td>2005-10-07
<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
</table> [/B][/QUOTE]