[App_rpt-users] RTCM/Voter pulse noise

Sam Skolfield kj6qfs at gmail.com
Wed May 17 21:56:40 EDT 2017


Try 2200pF bypass on the +12v, shunting to the shell of the dsub.
On Wed, May 17, 2017 at 6:09 PM Hayden Honeywood <haydenph91 at gmail.com>
wrote:

> Thanks Chuck,
> I'll have a play around. I have tested with two separate boards on
> separate systems with different cables and it does the same.
>
> Maybe I'll try some ferrite beads on the audio cables.
>
> I built the boards with all the specified components from digikey except
> the following which were not available anymore -
>
> *IC14* - 74HC4053N
> *C25* - 0.015uF
> *C78, C79* - 1uF
> *C75, C80* - 4.7uF
> *E1-E11* - Ferrites
> *IC5 *- 74HC139N
>
>
> The ferrites have an impedance of about 65 ohms at 100MHz as compared to
> the ones specified in the original listing which are 50 ohms at 100MHz.
> This is probably the most likely reason this noise is breaking through.
>
> Hayden
>
>
>
>
>> Date: Wed, 17 May 2017 04:11:51 -0500
>> From: Chuck Henderson <rpt2 at chuck.midlandsnetworking.com>
>> To: Users of Asterisk app_rpt <app_rpt-users at lists.allstarlink.org>
>> Subject: Re: [App_rpt-users] RTCM/Voter pulse noise
>> Message-ID:
>>         <
>> CADEYVwi5LNafXXuzaZ-zS3FgQt5578TH-jz5YGJdvPMrR-FA7w at mail.gmail.com>
>> Content-Type: text/plain; charset="UTF-8"
>
>
>>
>> I don't have any noise like that with voter boards or RTCMs.  My first
>> thought is that you may have a ground issue, or may not have your
>> audio wires shielded from your power/logic wires that are running in
>> the same cable.  Have you tried other boards or RTCMs with the same
>> cables?  Did you use the exact components to build the boards or did
>> you substitute any components, such as the regulators or capacitors?
>> I always use 2 separate cables into the common connector, one cable
>> carries shielded audio and audio ground and the other carries power,
>> logic levels (cor, ptt, etc) and power/logic ground.  If you have this
>> issue with both the boards and the RTCMs then IMHO, it must be a cable
>> issue.  (or a nut loose behind the control panel, just kidding :-)
>>  Chuck
>>
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-- 
KJ6QFS
Sam Skolfield
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