DSDPlus How Do You Make The Bandwidth Stay Put?

BM82557

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From the Notes.txt file --

-b-<bw> bandwidth locking command line option added

Example: -b-12.5

When this option is used, FMP24 ignores bandwidth hints from DSD+;
use this option to manually control bandwidth in -rc and -rv modes
 

BM82557

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Berkeley Co WV
From the Notes.txt file --

-b-<bw> bandwidth locking command line option added

Example: -b-12.5

When this option is used, FMP24 ignores bandwidth hints from DSD+;
use this option to manually control bandwidth in -rc and -rv modes

Not valid to use with FMPA
 

wgbecks

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Not valid to use with FMPA
Yes! But it need to work for Airspy and SDRPlay as well. Without out it DSD+ keeps setting to a narrower bandwidth that causes bit errors and loss of frame sync upon modest multipath. This has been observed primarily on P25 Phase-1 whereby DSD+ switches to LSM causing loss of frame sync then realizes that it's not simulcast and switches back to C4FM. Not good and I have emailed the development group twice in this regard and have been ignored!!!

I am far from a DSP expert, but forcing the signal through the narrower filter causes group delay that aggravates/triggers the above state condition that otherwise is not a problem on the same system and same identical conditions if you give up your Airspy or SDRPlay and just use an RTL SDR.
 
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That's a bummer that it doesn't work on an AirSpy. I wonder why on Earth they would do that? I've already been using -b12.5, but every new transmission, the bandwidth changes and I want it to stay put.
 

Forts

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I haven't noticed that with my Airspy.. I'll have to try it later. What if you drop the -b from the command line and just set the bandwidth manually from within DSD+?
 
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If I type b or B, it'll change the bandwidth, but it'll just keep going back to something else. It won't stay put.
 

moonbounce

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^ Is that whole post a quote?

-b-12.5 doesn't work (see above).
I don't know how the post ended up as a quote, it was supposed to be a reply, just like this one.
So if I take out the minus in front of the 12.5 my BW will switch between 9.5 and 12.5, I use an RTL2838u v3.
 

moonbounce

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One other thing I forgot to mention is that after you make the change you have to exit out of the program and restart it for the change to take effect.
 

rmosier

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The OP is absolutely correct. I have the SDRplay RSP1A with up to date DSD+ Fastlane files and I have the same issue. I applied the "-b12.5" command to FMPP-CC and later to FMPP-VC. And as the OP stated, after a short time, it changes to 9.5 I too used the b/B function from both the wave form display as well as the FMPP DOS command window. The program responds with " 12.50 Khz RF bandpass filter selected" but it still changes back to 9.5 . The problem is real.
 
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