[App_rpt-users] Small audio amp needed

RED BUTTON MICRO jrorke at cogeco.ca
Sat May 18 21:42:51 EDT 2013


The uri can put out up t o1 V p-p. so it should be enough.
Are you connected to an out put on the URI that has a cap in line?

The mic circuits might have some dc bias that is fighting with the URI. 
So put a cap in line and see if you get tx audio. Dont know which pin 
you are using but I m using tx audio in the 20 ish range on the URI. 
Cant remember which but it has a cap in line.

Jon VA3RQ
On 5/18/2013 9:26 PM, Bryan D. Boyle wrote:
> Figured I'd throw this out...
>
> I'm interfacing a batwing Systel repeater for 440...basically 2 GP300
> HTs stripped out of their cases, mounted on a headsink in a box with
> interface circuits (which I'm not using, lifted the necessary signal
> resistors so that the signals don't use the onboard controller,
> etc)...well, gone through the schematic, and have the proper pickoff for
> rx, can get it to recognize (using the PL detect pin going high +5v to
> give me a COR), asterisk recognizes carrier (faking it out by using the
> PL detect), keys up the xmt side...however, no matter HOW high I set the
> audio into the transmitter in radio-tune-menu, it is barely deviating.
>
> Now, I can take an audio generator from my streaming studio, and,
> injecting a 1K @+4dBm tone, I can get non-distorted deviation at 3.2K by
> hanging on the tx input pin.
>
> So..wondering what the audio level out of the URI is?  I'm thinking it's
> lower level then that, maybe -10?.  And based on the low level
> deviation...I'm thinking that even the +6dB amp onboard won't do much...
>
> I know that RB had to build an amp to get enough drive to modulate the
> 220 Micor using direct FM injection when they built my rig; does anyone
> have a simple schematic of a 5534 or some such op-amp that can give me a
> reasonable amount of gain so I can try and get decent (well, how about
> understandable) deviation out of this thing?
>
> Thanks, all.
>
> BB
>
> _______________________________________________
> App_rpt-users mailing list
> App_rpt-users at ohnosec.org
> http://ohnosec.org/cgi-bin/mailman/listinfo/app_rpt-users
>




More information about the App_rpt-users mailing list