I have had inquiries on the radio system I use in my truck. So, I thought I'd write a description..
Here is a block diagram of the setup:
The switch is a 4-position Alpha Delta 4B, center disconnects and grounds the feed. The lightning protector is an Alpha Delta ATT3G50U. It's bolted directly to the truck floorboard. The paint was scraped to bare metal to ensure a ground. One side benefit was a significant reduction in ignition noise.
A notch filter was necessary as much of my listening is done at or near transmitter sites. This was homebuilt in a Hammond cast aluminum box. The schematic is below.
The overall receiver gain is good, but the antennas have a low output. A DX Engineering RPA-1 preamplifier is part of the installation.
Audio is fed from the headphone output of the R30CC through a Radio Shack 270-054 Ground Loop Isolator. It goes to the dashboard radio auxiliary input. And, the power to the receiver and preamp goes through a Radio Shack 270-051B 10A noise filter. These filters do help keep the truck electrical noise down.The antennas are the copper tube loop units described elsewhere on the site. I have two of the single feed versions mounted in the back of my Chevy Blazer at 90 degrees to each other. One goes lengthwise, the other sideways. Noise pickup is significantly lower than the common vertical. Being able to select antennas easily while driving provides some interesting choices in stations heard, or external noise reduction. The sideways loop picks up far less street side AC line noise than the lengthwise loop, for example. The fiberglass bed cover of the Blazer makes this work. A steel roof would attenuate the signal below useability. The whip is a roof mounted stainless steel CB antenna cut down to 68". This length is set for FM band reception on the dash radio. The signal is split between the switch and dashboard radio with a Diamond MX62M duplexer. Low pass side is LW to 56MHz, high pass is 76-470MHz. The external input is often used with a phaser and long wire antennas while parked at various sites.
I will be doing further development on this as time, money and ideas allow. Hopefully some pieces of this will be useful to you.
|Last update: 12 August 2007|