[HATS] Answer to Question about Dracom 300VMF+

[MacAllister, Andrew [EPM/HOU]]

Difficult situation with the audio subcarrier in our modulator!  We need to
investigate "Plan B" (whatever that is...) to address this.

If anyone else has any experience with the audio subcarrier in Dracom
modulators, please let me know.

Andy W5ACM

-----Original Message-----
From: Bill Frost [mailto:BFrost@rldrake.com] 
Sent: Wednesday, December 08, 2004 3:27 PM
To: 'MacAllister, Andrew [EPM/HOU]'
Subject: RE: Question about Dracom 300VMF+

Hello Andy,

Thanks for the e-mail.  Please excuse the delay in responding, as I needed
to consult the Engineering Department.

The 300 VMF+ uses a TDA8822 modulator chip. The sound carrier is generated
and summed inside the chip.  The only way to turned off the 4.5 MHz audio is
via software.  The software has no provision for disabling the 4.5 carrier.

Regards,

Bill Frost
Service Manager
-----Original Message-----
From: MacAllister, Andrew [EPM/HOU]
[mailto:Andrew.MacAllister@EmersonProcess.com]
Sent: Wednesday, December 08, 2004 11:51 AM
To: 'TechSupport@rldrake.com'
Cc: 'n5rpq@earthlink.net'
Subject: Question about Dracom 300VMF+


Hi Drake Tech Support,

We are using a Dracom 300VMF+ modulator (Ch 57) for our ATV repeater.  We
need to eliminate the 4.5 MHz audio subcarrier.  The simplistic user manual
doesn't have sufficient detail to provide clues about the actual circuit.

How can I easily remove the 4.5 MHz audio subcarrier?

Thanks!

Andy MacAllister W5ACM
Technical Projects Lead
Houston Amateur Television Society


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