MFJ MFJ-1708 User Manual
MFJ-1708 Instruction Manual |
RF Sense Transmit/Receive Switch |
INTRODUCTION
The MFJ-1708 RF Sense T/R switch senses transmitted RF and switches your antenna from receive to transmit using a relay. It shorts your receiver antenna input to ground to protect your receiver. It provides an auxiliary contact closure to ground during receive (opened in transmit) for an "On-the-Air" sign or other use. It also has a control line input, which lets your key/keyer or PTT line switch the antenna.
An adjustable time delay circuit gives you delayed switching. This prevents your antenna from switching between dots and dashes or between syllable and words.
TECHNICAL DESCRIPTION
The MFJ-1708 RF Sense T/R switch uses a relay, which switches from transmit to receive mode. When no power is applied to the unit, it is in the transmit mode. Once power is applied the relay switches on and the unit is in receive mode. When the unit senses RF or the control line is grounded from a keyer or PTT switch, it switches the relay off and the unit is in transmit mode.
The delay adjustment allows you to change how fast the relay switches back to the receive mode. It is adjustable from 0 to 2 seconds.
The auxiliary jack provides a contact closure to ground during receive (opened in transmit) for an "On-the-Air" sign or other use.
The MFJ-1708 RF Sense T/R switch requires 12 VDC or 110 VAC with MFJ-
MFJ-1708 Instruction Manual |
RF Sense Transmit/Receive Switch |
TECHNICAL ASSISTANCE
If you have any problem with this unit first check the appropriate section of this manual. If the manual does not reference your problem or your problem is not solved by reading the manual you may call MFJ Technical Service at 662-323- 0549 or the MFJ Factory at 662-323-5869. You will be best helped if you have your unit, manual and all information on your station handy so you can answer any questions the technicians may ask.
You can also send questions by mail to MFJ Enterprises, Inc., 300 Industrial Park Road, Starkville, MS 39759; by Facsimile to 662-323-6551; or by email to techinfo@mfjenterprises.com. Send a complete description of your problem, an explanation of exactly how you are using your unit, and a complete description of your station.
SCHEMATIC
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