[App_rpt-users] Mastr II and usbradio

David McGough kb4fxc at inttek.net
Sun Sep 20 03:26:44 EDT 2015


Yes, this info is correct--I've got several Mastr II setups.

I haven't carefully followed this whole thread, but, as mentioned, for
many combinations the exciter is phase modulated. There are some direct-FM
versions, however. In particular, this is the case if you've got a PLL
exciter, which was found in many VHF Hi-band setups. For any combination,
if a PLL exciter is available, that is by far the preferred hardware
flavor since it has significantly lower spurious noise (more ideal for
repeater use). Note that the ICOMs for the PLL exciters were larger and
included the varactor diode (for direct FM) internally.

Another caveat I've found is that, depending on the exciter combination,
you will likely need a lot of audio drive to obtain the proper level of
deviation. So, be prepared to use the internal op-amp on the URI's to
obtain a higher output level. The Repeater Builder RIM adapter is likely
even a better alternative--it can provide gobs of drive, if needed. In
fact, the RIM is probably the preferred "plug and play" solution.

Also, I'll mention that you've got to be careful what audio source is used
for modulation. This is a case where a USB audio FOB, without a audio
low-pass filter, should -NOT- be used! Mastr II exciters will happily
generate a very wideband signal, if modulated by high-frequency audio,
such as is found directly at the output of a CM108/CM119 chip, etc.

Anyhow, have fun and good luck. I've found Mastr II's to be some of 
the best radio hardware available, even though it's 30+ years old! On a 
different side-note, if you've not already replaced the various tantalum 
capacitors found in the exciter and/or receiver modules, go ahead and do 
so before putting the system on-line. After letting a fair amount of 
"smoke out" due to shorting tantalum caps, I go ahead and replace them all 
and a standard maintenance item. After working on a lot of these rigs, I 
-highly- recommend this!!! ...This will save many headaches down the road!

73, David KB4FXC

On Sat, 19 Sep 2015, Jim Duuuude wrote:

> I dont have any GE equipment. I just asked the "Guru" on your behalf.
> >From my VERY limited experience with other people's GE "stuff", the transmitter,
> being phase modulated, has 2 inputs. One for "program audio" (amplified audio from
> the MIC) and one from the CTCSS ("Channel Guard" as it's known in the GE world, I believe)
> encoder. This requires you a use, say, the 'A' output for program audio and the 'B' output for
> CTCSS. In fact it was GE transmitting equipment that "inspired" us (me/Steve Henke) to 
> implement the 2 independent outputs the way in which we did. Of course, the 'other' output
> (usually 'B') can also be used to drive a 'local speaker' or something 
of the sort, in a case where the 'main' (usually 'A') output is 
generating directly-modulate-able audio (pre-emphasized audio
> along with CTCSS).
> That's about all I know. Sorry.
> Jim
> Date: Sat, 19 Sep 2015 21:42:55 -0400
> Subject: RE: [App_rpt-users] Mastr II and usbradio
> From: N1XBM at amsat.org
> To: telesistant at hotmail.com
> When you say feeding "program audio" and PL seperate, do you mean on the A and B lines to the same input. Or A going to one input and B going to a different input. 
How would you say your audio quality is. I get this strange intermittent. Clicking or popping sound. Almost like a heaphone or microphone being plugged into a board. It's soft but noticeable. Usually at the beginning of keyup or at the end of transmission. 
I noticed this one one repeater I setup. I then setup a second repeater also a mastr ii at a differnt location also using usbradio and I hear the exact same sound. 
I was wondering if you would be willing to share how you interfaced your equipment and possibly a copy of your usbradio.conf file. I'd like to rule out what is going on.
Also maybe do you notice how clean your repeater audio is. Not many people compain about or even notice it but I do.
Apparare Scientor
Paratus Communicare
Allstar Node # 27086, 41540, 41812
On Sep 19, 2015 8:56 PM, "Jim Duuuude" <telesistant at hotmail.com> wrote:

I just spoke with the "Mastr II Guru", and he said that if you take the discriminator audio
> (off of volume/squelch high), it should work with chan_usbradio quite well.
> Remember, for transmit, you need to feed it SEPARATE "program audio" and CTCSS
> (you will need to use BOTH outputs of the USB device separately).
> Jim, WB6NIL
> Date: Sat, 19 Sep 2015 15:53:16 -0400
> From: N1XBM at amsat.org
> To: app_rpt-users at ohnosec.org
> Subject: [App_rpt-users] Mastr II and usbradio
> Anyone on here running a mastr ii with usbradio? I'd like to talk to you directly to ask a few questions on your setup. I have a strange problem and would like to make sure I'm setup right. 
Apparare Scientor
Paratus Communicare
Allstar Node # 27086, 41540, 41812, 42086

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