[App_rpt-users] Small audio amp needed

Bryan D. Boyle bdboyle at bdboyle.com
Sat May 18 22:01:15 EDT 2013


using the ac coupled line, not the direct...iirc it has a 10 uf @16v from the schematic.  



--
Bryan
Sent from my iPhone 5...small
keyboard, big fingers...please
forgive misspellings...



On May 18, 2013, at 21:42, RED BUTTON MICRO <jrorke at cogeco.ca> wrote:

> 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
>> 
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