[App_rpt-users] MASTR III

[Tim Sawyer]

It’s been a long time ago but I had a MSTR II base connected to IRLP which really sounded good. GE generally has good audio so it should work well if nothing is wrong with the radio. 

Of course you have to match the filtering to your radio. If using discriminator audio then deemphasis must be enabled. This could likely be your missing low end on RX. Sometimes you can tell if the RX filtering is correct just by making sure all the touch tones decode properly. Bring up the *CLI> with verbose 3 and play each tone to see if it’s decoded. Be sure you have good CTCSS filtering (in your radio or voter.conf or even both) because that will cause TT decode problems without. 

For TX feeding to a non-mic type input will require preemphasis.  If you are using a mic input, which I recommend, make sure there is not a DC bias on the mic. An easy way to tell if the TX filter is right is to connect to a known correctly setup node and listen to the squelch tail and user audio. The squelch tail will be obviously high frequency sounding if doubled preemphasized or muddy if emphasis is needed. 

Okay, so much for general audio filtering information. Now on to RTCM specifics.

The filter settings in the RTCM are a bit obscure. It tries to automatically do the right thing but it isn’t always what you want. The RX filter is controlled by the COR Type (menu 13). 13 = 0 assumes discriminator and thus deemphasizes. 13 = 1 assumes non-discriminator and thus has no deempahis. There is also a nodeemp setting in voter.conf which may be needed in unusual situations. 

The hidden filter trick on TX is setting a CTCSS tone. If you set a TX tone the RTCM assumes a CTCSS input and thus will preemphasize. With no CTCSS tone  there will be no preempashis. Generally I think the radio should do the preempashis (and tone encoding) as the manufacture knows best what their radio should do. But for simulcast or if you just want AllStar to sent the CTCSS tone then you must feed the radio at a point where it will not emphasis. You can fake it out if you want emphasis without a CTCSS tone by setting the txctcsslevel=1 (or other very low level) in voter.conf.  

Hope that helps.
--
Tim
:wq

> On May 8, 2015, at 10:44 AM, Jeff Carrier <k0jsc.jeff at gmail.com> wrote:
> 
> Both TX and RX more or less.  The RX path lacks a lot of the low end but is clean.  I'm having more trouble with the TX path.  I tried DPLX Line A/B as indicated in the how to but the transmitted audio lacks fidelity and is missing the low end (both from local and network audio).  It's also slightly raspy and seems to distort if the remote user has a hotter mic and the deviation exceeds 3 kHz.  I know the RTCM can sound really nice I've got a few paired with motorolas.  I had this same issue with the MASTR II and I would up giving up on that.
> 
> On Fri, May 8, 2015 at 10:14 AM, Tim Sawyer <tim.sawyer at mac.com <mailto:tim.sawyer at mac.com>> wrote:
> Please elaborate on ‘really nasty’. Is it the RX side or the TX side?
> --
> Tim
> :wq
> 
>> On May 7, 2015, at 8:42 PM, Jeff Carrier <k0jsc.jeff at gmail.com <mailto:k0jsc.jeff at gmail.com>> wrote:
>> 
>> I don't want this to sound like a dumb question and I've searched all over with really no luck.  I've also tried several things but I'm looking for "clean" audio.  I've done this a million times on Motorolas so why doesn't this work on a GE?  Does anyone have experience with an RTCM and a MASTR III?  I have tried to inject audio into every point I can find in the manual and can't make it sound "right."  There is a good write up on repeater builder about interfacing a controller with an M III but when I follow that it sound REAL NASTY.  Any tips would be greatly appreciated.
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