[HATS] RE: RE: Question about Dracom 300VMF+

[MacAllister, Andrew [EPM/HOU]]

Hi Bill,

Thanks for the response.  We have been studying the specs on the chip.  It
appears that RF0 (RF Output) is typically set to "1" and TPSG (Test Pattern
Signal Generator) is set to "0" for RF on and TPSG off.  If we could set RF0
= "0" and TPSG = "1", the result would be RF on, TPSG off and sound
oscillator off.  Unfortunately we do not have a schematic or the specs on
how the unit boots up and subsequently sets up the operating parameters.  We
also noted that the labels on the ICs have been removed.

Is there any possibility that Drake could help out, or are we stuck?

Thanks,

Andy MacAllister W5ACM
First Drake Purchase = TR4 in 1969

-----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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