Author Topic: More than one interface on a single PC  (Read 25387 times)

VidarParry

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More than one interface on a single PC
« 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

ttp

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Re: More than one interface on a PC
« Reply #1 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.

Discriminator

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Re: More than one interface on a PC
« Reply #2 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

VidarParry

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Re: More than one interface on a single PC
« Reply #3 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

Discriminator

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Re: More than one interface on a single PC
« Reply #4 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.

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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.

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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

VidarParry

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Re: More than one interface on a single PC
« Reply #5 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

Discriminator

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Re: More than one interface on a single PC
« Reply #6 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.

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

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



VidarParry

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Re: More than one interface on a single PC
« Reply #7 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

VidarParry

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Re: More than one interface on a single PC
« Reply #8 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

Discriminator

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Re: More than one interface on a single PC
« Reply #9 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


VidarParry

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Re: More than one interface on a single PC
« Reply #10 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

Torquetube

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Re: More than one interface on a single PC
« Reply #11 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.

VidarParry

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Re: More than one interface on a single PC
« Reply #12 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

Torquetube

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Re: More than one interface on a single PC
« Reply #13 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.

Discriminator

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Re: More than one interface on a single PC
« Reply #14 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  ;)