Discriminator Forum

Data Slicers and Interfaces => Data Slicers and Interfaces => Topic started by: VidarParry on 06 Aug 2013, 19:22:06

Title: More than one interface on a single PC
Post by: VidarParry on 06 Aug 2013, 19:22:06
Thanks Rene,
The restriction that the USB interface only monitors one bit rate is an issue for me because I need to monitor two bit rates on each of the two frequencies. I suppose I could have 4 scanners and 4 PCs running PDW, but that's getting a bit cumbersome:-)
Cheers
...Steve
Title: Re: More than one interface on a PC
Post by: ttp on 18 Aug 2013, 08:59:26
Hi Steve,

Can't help you with 4 scanners but if you need 4 PCs maybe you should consider running virtual machines. Virtual Box from Oracle is free and very good, there are some other free products around.
Title: Re: More than one interface on a PC
Post by: Discriminator on 18 Aug 2013, 09:06:06
The restriction that the USB interface only monitors one bit rate is an issue for me because I need to monitor two bit rates on each of the two frequencies. I suppose I could have 4 scanners and 4 PCs running PDW, but that's getting a bit cumbersome:-)

You only need 2 scanners but 4 RS232/USB interfaces. You can split the discriminator audio for both scanners and feed two interfaces per scanner, each with a dedicated bitrate. You can have 4 instances of PDW on a single computer. Maximum number reported is 11  ;)

-Rene
Title: Re: More than one interface on a single PC
Post by: VidarParry on 29 Aug 2013, 10:48:51
@Rene
Sorry - I forgot I'd asked this question on this thread, and hadn't turned notify on:-(

So I can run 4 instances of PDW on a single PC with 4x USB interfaces each on different frequencies and baud rates fed from 2 scanners with the discriminator taps split 2 ways?

Any additional componentry for splitting the discriminator taps (eg to match impedances)?

Any minimum spec for CPU speed, RAM etc to ensure no data loss due to resource conflict?

@TTP
Hadn't thought of using VMs. Again, maybe need a higher spec CPU and RAM, but certainly worth considering.

Thanks!

Cheers
..Steve
Title: Re: More than one interface on a single PC
Post by: Discriminator on 29 Aug 2013, 11:55:43
So I can run 4 instances of PDW on a single PC with 4x USB interfaces each on different frequencies and baud rates fed from 2 scanners with the discriminator taps split 2 ways?

That's the idea. You need to have separate folders for each instance.

Quote
Any additional componentry for splitting the discriminator taps (eg to match impedances)?

The input impedance of the RS232 interface is about 20 kOhm. If you use a 10 k resistor in your receiver's discriminator path, you may have to lower it to 2.2 kOhm if you connect 4 parallel interfaces.

Quote
Any minimum spec for CPU speed, RAM etc to ensure no data loss due to resource conflict?

Not that I'm aware of. YMMV.

Regards,
Rene
Title: Re: More than one interface on a single PC
Post by: VidarParry on 29 Aug 2013, 19:48:41
Thanks Rene.

Just looking at another option - how about a single scanner discriminator input into a real serial interface, and using a serial port splitter into 4 instances of PDW?

I'm guessing this won't work because of the direct control PDW needs of the interface, but I see it is suggested in the description of the USB interface, so maybe it can with these virtual ports.

Any recommended serial port splitter? as there are many available.

Cheers
...Steve
Title: Re: More than one interface on a single PC
Post by: Discriminator on 29 Aug 2013, 20:59:29
Just looking at another option - how about a single scanner discriminator input into a real serial interface, and using a serial port splitter into 4 instances of PDW?

I'm guessing this won't work because of the direct control PDW needs of the interface, but I see it is suggested in the description of the USB interface, so maybe it can with these virtual ports.

Only if you connect the RS232 interface to the real serial port, as it observes the RS232 protocol. A 2 or 4 level slicer won't work.

Quote
Any recommended serial port splitter? as there are many available.

http://www.eterlogic.com/Products.VSPE.html


Title: Re: More than one interface on a single PC
Post by: VidarParry on 30 Aug 2013, 05:52:06
Thanks Rene.
Just downloaded and installed the VSPE, and did a quick test to see if I could get two PDWs off the same physical port and as you suggested, it didn't work (actually neither the real port or the virtual port worked!). Back to normal after uninstalling VSPE.

Looks like I might have to bite the bullet and splash out on some USB interfaces.

I'll go and investigate now....:-)

Cheers
...Steve
Title: Re: More than one interface on a single PC
Post by: VidarParry on 30 Aug 2013, 08:53:01
Hi Rene,
Just another question before I commit to the USB interfaces.

Currently, my setup shows PDW at 100% most of the time, however watching the meter, display and listening to the scanners it's clear that the PDW's are missing a number of messages - I estimate (very subjectively) 10-20% are not decoded.

Will the USB interfaces improve this to full decoding success?

(A reminder that my config is two PCs monitoring two POCSAG frequencies via 2-level discriminators from the discriminator taps on two scanners. Both are decoding 512 and 1200 baud transmissions. External antenna is a Yagi directed at the transmitter which is about 6km away line of sight, with the antenna feed going through a splitter.)

Cheers
...Steve
Title: Re: More than one interface on a single PC
Post by: Discriminator on 30 Aug 2013, 16:03:20
Will the USB interfaces improve this to full decoding success?
There's no guarantee. However, it usally performs better than a 2 level interface. Less PC processing power is required, and the USB enabled interface is set to a fixed bit rate, while PDW needs to guess the bit rate when using a 2 level slicer.

Why don't you start with one USB enabled interface to give it a try? ;)

-Rene

Title: Re: More than one interface on a single PC
Post by: VidarParry on 15 Sep 2013, 08:55:50
Hi Rene,
(For other readers of this topic, I've ordered 4 USB interfaces from Rene and eagerly await arrival!).

Can all the USB interfaces run through a 4 port USB hub into a single USB port, and the 4 instances of PDW run on the same PC (XP SP3 likely, but could go to W7)?

Cheers
...Steve
Title: Re: More than one interface on a single PC
Post by: Torquetube on 15 Sep 2013, 09:15:53
I'm looking forward to seeing how this thread progresses. I have an interface here but I can't seem to get a very good decode of pocsag both via the serial port and usb. The problem is probably with my setup rather than the interface itself.
Title: Re: More than one interface on a single PC
Post by: VidarParry on 15 Sep 2013, 10:00:12
I'm looking forward to seeing how this thread progresses. I have an interface here but I can't seem to get a very good decode of pocsag both via the serial port and usb. The problem is probably with my setup rather than the interface itself.
Hi TorqueTube,
What do you think is wrong with your setup that could be causing your problem?
Cheers
...Steve
Title: Re: More than one interface on a single PC
Post by: Torquetube on 15 Sep 2013, 10:06:02
I've been testing using the earphone socket of my scanner instead of a dedicated discriminator tap so the audio probably isn't the best of quality. I am going to hook up my interface to my Motorola GM radio that has a Discriminator output on the rear plug and see what happens. I'll keep you posted. My new laptop just will not decode pocsag via the soundcard, I've spent hours tinkering with the audio levels and it just won't do it, my sold laptop worked faultlessly at decoding.
Title: Re: More than one interface on a single PC
Post by: Discriminator on 15 Sep 2013, 10:09:27
I've been testing using the earphone socket of my scanner instead of a dedicated discriminator tap so the audio probably isn't the best of quality.

No further questions, your honor  ;)
Title: Re: More than one interface on a single PC
Post by: Discriminator on 15 Sep 2013, 10:11:00
Can all the USB interfaces run through a 4 port USB hub into a single USB port, and the 4 instances of PDW run on the same PC (XP SP3 likely, but could go to W7)?

I haven't tried a USB hub. Please keep me posted on your results.
Title: Re: More than one interface on a single PC
Post by: VidarParry on 15 Sep 2013, 10:12:08
I've been testing using the earphone socket of my scanner instead of a dedicated discriminator tap so the audio probably isn't the best of quality. I am going to hook up my interface to my Motorola GM radio that has a Discriminator output on the rear plug and see what happens. I'll keep you posted. My new laptop just will not decode pocsag via the soundcard, I've spent hours tinkering with the audio levels and it just won't do it, my sold laptop worked faultlessly at decoding.

In my experience, discriminator tap will always give a better result with PDW than soundcard - although I've never achieved "perfect" POCSAG decoding on either.....yet! Hopefully, the new interfaces will bring me closer to the perfect decoder:-)

Cheers
...Steve
Title: Re: More than one interface on a single PC
Post by: Torquetube on 22 Sep 2013, 11:22:08
Have you received your new interfaces yet Steve? I'm hoping to test out my Motorola Pmr radio later to see if it will work for Pocsag decoding.
Title: Re: More than one interface on a single PC
Post by: VidarParry on 22 Sep 2013, 19:12:48
Hi Rene,
No - not arrived yet. Did the package have a tracking number? If so, please email me it off list.
Cheers
..Steve
Title: Re: More than one interface on a single PC - HIGHLY RECOMMENDED
Post by: VidarParry on 26 Sep 2013, 21:01:09
WOW!!!

The RS232/USB interfaces arrived earlier this week. Couldn't wait till the weekend to play, so after an initial test to make sure they worked (which they did of course!), I constructed a power arrangement using an old Notebook 12v PSU feeding six power cords (4 for the interfaces and 2 for the scanners). Then connected up the 4 USB connections into a cheap ($4 on ebay) 4 port USB hub into my old IBM Pentium PC running XP SP3.

Rene had earlier suggested that the discriminator tap resistor should be reduced to facilitate 2 outputs per scanner (remember I'm monitoring two frequencies each with 512 and 1200 messages). I went for the easy option and made two discriminator leads that went from one tap to two outputs - in parallel. No impedance matching or protection.

I then plugged in the scanners to the interfaces, ran up 4 instances of PDW, configured them to match the ports, and hey presto - 100% decoding straight away!

They've now had a full 24 hours operation and just going on logfile sizes they are decoding about 25-30% more than my previous 2-level slicer configuration (adding the new 512 and 1200 logfiles together and compare with the previous combined log sizes).

Two small problems I'm working on:

For the first time in nearly 18 years of decoding, I'm pretty confident that this is now picking up 100% of messages, where I knew that the 2-level slicer was missing loads (just by hearing the message on the scanner and seeing PDW -not- detecting it.)

I highly recommend the RS232/USB interface for serious decoding - well worth the money, and it helps Rene support this great site as well as a little thank you to Peter Hunt.
 
Thanks for all your help and advice Rene:-)

Cheers
...Happy Steve :)
Title: Re: More than one interface on a single PC
Post by: Discriminator on 27 Sep 2013, 15:07:55
Excellent! Thank you for your comprehensive report. I'm happy too  :D

-Rene
Title: Re: More than one interface on a single PC
Post by: Torquetube on 04 Oct 2013, 16:42:02
I'm also pleased to say that I have got my RS232 interface working nicely now, I didn't realise that my Alinco DJ-X11 scanner already had a discriminator feature built in so I have made a lead and just tried it and it's working. I too would highly recommend the interface. I just need to find a nice case to put it in now.