Remote audio feed
Posted: Sun Mar 20, 2011 7:44 am
As only one of my scanners is now still capable of GRN monitoring and digital police transmissions (in this area there are three channels of UNencrypted digital, along with two analog), and that scanner (996T) is confined to the PC room for PC control, programming, and recording, I needed some way to listen at my leisure with a coldie, to such transmissions in such locations as another room or out the back. Cable length for an extension speaker would be excessive, require plugging and unplugging, and need an 8 ohm L pad at the speaker for remote volume control. I sought a more elegant solution. Here's what I settled upon.
At the scanner, an adaptor, 3.5mm plug to two 3.5mm sockets, has been plugged into the earphone socket. I actually made a small jumper, 3.5mm plug-short cable-3.5mm line socket, to plug the adaptor into, keeping its bulk away from the earphone socket. Into one of the sockets of the adaptor I plugged a small amplified speaker (stereo) from Jaycar, fed via a stereo earphone extension cable with volume control (L pad), also from Jaycar. I modified the speaker assembly to run from a small plugpack supply to obviate the need of battery replacements. Now I had the audio from the speakers, with volume control via the L pad.
Now for the second socket of the adaptor. Into this I plugged a screened cable, running out to the "shadecloth room" outside. On the outside end of the cable is a 3.5mm line socket. The "shadecloth room" has a 12VDC supply I set up long ago, with car cigarette lighter socket outlets, fed by a 12VDC supply in the outside laundry. Into one of the 12VDC sockets I plugged one of those small FM-band transmitters meant to allow listening to mp3 players in the car via the FM radio. The transmitter was tuned to a quiet unused frequency. The 3.5mm plug on the transmitter was plugged into the 3.5mm line socket on the screened cable from the scanner.
Now, with the scanner's volume set midway and not again adjusted, I have speaker audio at all times in the PC room, volume easily adjusted by the L pad in the lead to the amplified speakers, and also I have the audio available from anywhere in the house and (small) yard, from any handy FM band radio. One point that could have sunk the whole scheme is that the car FM transmitters are designed to switch off, and need to be manually restarted, if there is a silence on the input of ten seconds or more. At first glance, this would make them useless for scanner audio input. But ah, it so happens that a tiny bit of hash from the scanner's electronics is impressed on the cable, and although not audible except at no-signal high volume, it does serve to fool the transmitter into staying on.
It all works a treat!
73 de heathen_dan
At the scanner, an adaptor, 3.5mm plug to two 3.5mm sockets, has been plugged into the earphone socket. I actually made a small jumper, 3.5mm plug-short cable-3.5mm line socket, to plug the adaptor into, keeping its bulk away from the earphone socket. Into one of the sockets of the adaptor I plugged a small amplified speaker (stereo) from Jaycar, fed via a stereo earphone extension cable with volume control (L pad), also from Jaycar. I modified the speaker assembly to run from a small plugpack supply to obviate the need of battery replacements. Now I had the audio from the speakers, with volume control via the L pad.
Now for the second socket of the adaptor. Into this I plugged a screened cable, running out to the "shadecloth room" outside. On the outside end of the cable is a 3.5mm line socket. The "shadecloth room" has a 12VDC supply I set up long ago, with car cigarette lighter socket outlets, fed by a 12VDC supply in the outside laundry. Into one of the 12VDC sockets I plugged one of those small FM-band transmitters meant to allow listening to mp3 players in the car via the FM radio. The transmitter was tuned to a quiet unused frequency. The 3.5mm plug on the transmitter was plugged into the 3.5mm line socket on the screened cable from the scanner.
Now, with the scanner's volume set midway and not again adjusted, I have speaker audio at all times in the PC room, volume easily adjusted by the L pad in the lead to the amplified speakers, and also I have the audio available from anywhere in the house and (small) yard, from any handy FM band radio. One point that could have sunk the whole scheme is that the car FM transmitters are designed to switch off, and need to be manually restarted, if there is a silence on the input of ten seconds or more. At first glance, this would make them useless for scanner audio input. But ah, it so happens that a tiny bit of hash from the scanner's electronics is impressed on the cable, and although not audible except at no-signal high volume, it does serve to fool the transmitter into staying on.
It all works a treat!
73 de heathen_dan
