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Re: Topband: Relay switching at the base on antenna

Subject: Re: Topband: Relay switching at the base on antenna
From: "Augie \"Gus\" Hansen" <>
Date: Sat, 23 Sep 2017 11:31:38 -0600
List-post: <>

On 9/23/2017 6:39 AM, MR TREVOR DUNNE wrote:
Can Anyone tell me a simple way to switch a 12v relay at the base of an antenna 
using the rigs ptt as the trigger??

If you're using a coaxial feed line, you could use a pair of "bias tee" devices, one on each end of the coax, to put 12 VDC on the line during transmit and 0 VDC during receive. Here is some info on bias tees. They are available commercially and can be home-brewed using readily available components.

If your rig has a key out connector it is likely providing a contact closure to ground during TX and open circuit during RX. Use that to switch 12 volts from the rig or a separate supply on during TX using an auxiliary relay or solid state switch, and feed that to the bias tee. Pick off that DC control voltage to activate the relay at the antenna end.

NOTES: 1) The series capacitors go toward the transceiver and antenna respectively to pass RF while blocking the DC. The RFCs block RF but pass the DC control signal. 2) If you are going to use both positive and negative voltages as control signals for more complex switching over the coax be sure to use an isolated, separate power supply.

Gus Hansen

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