AM Reception on the Jensen AWM968

Fergie · September 2016

With other preparation modifications and concerns in our first extended usage of our 2015 T@B SMax that we bought last fall (this summer we took a 3600 mile trip from MN to the east coast and back in two weeks) that ended up as a great first real experience with the T@B, I haven't paid much attention to the Jensen AWM968 system that came with the unit. We have used the DVD, but haven't been anywhere that the external TV signal is available. I found that the FM seems to work very well everywhere for our purposes, but the AM doesn't seem to work at all, even on our one local station that is receivable everywhere in our region. This is when we are on shore power at the campsite or in my driveway. I even took a portable radio we use for camping into the trailer with me and placed it right under the Jensen and it worked fine.

Reading some of the entries here on the T@B users blogs I noticed that one mentioned that the inverter in the WFCO Power Center might be causing enough interference to block the output of the Jensen amplifier. From my own radio experience this could happen if the interference overpowered the station signal and in turn activated the avc (automatic volume control/limiter) circuits in the Jensen causing it to block the audio output. So for an experiment I tuned into the local station, heard a low hiss or hum, then went to the inverter and flipped all the breakers to "off". The local station then came in loud and clear, not as sharp as my portable camping radio, but still very usable! This says to me: 1) The Jensen AM circuitry has very poor noise rejection and 2) the WFCO Power Center Inverter generates enough noise to drown out any AM reception and manages to transmit it on the 12volt lines.

For the short term we will take our trusty camping radio along (a Grundig S350DL) on our trips. Unless someone has figured out a fix for the Jensen/WFCO problem, in the long run I will be looking at a replacement for the Jensen.

I would be curious if any other "radio oriented" T@B owners have found a solution to this problem.

Fergie in MN

Photomom · September 2016

One thing you can try is a ferrite core. If you have a Radio Shack store they may have it. https://www.radioshack.com/products/radioshack-snap-choke-core-1?variant=5717356421 Otherwise you can order it from any electronics parts source.

Snap it around the Jensen power cord close to where it connects to the radio.

Most places I've been AM radio is nothing but political rants or religious rants, so we bring our own music on an iPod or iPhone. Jensen works great over Bluetooth.

Fergie · September 2016

"Photomom Posts: 1,241Member

7:16AM

One thing you can try is a ferrite core. If you have a Radio Shack store they may have it. https://www.radioshack.com/products/radioshack-snap-choke-core-1?variant=5717356421 Otherwise you can order it from any electronics parts source."

They shut the only Radio Shack store in our town a year or so ago, but I ordered a set from the web. It's been a while since my ham radio days and I had forgotten about ferrite filters and such things. Thanks for reminding me. We will try it and see. I may also put one on the 12volt output of the WFCO unit also.

Fergie

Photomom · September 2016

Can't hurt. I remember when you could go in Radio Shack and buy most of the stuff you needed to build a project!

Fergie · September 2016

Well I ordered a package of ferrite cores from Amazon:

https://www.amazon.com/gp/product/B007Q94DBK/ref=od_aui_detailpages00?ie=UTF8&psc=1

I placed them on the 12volt power line of the Jensen, the 12volt output and ground lines of the WFCO converter unit and the power line of the CO2 unit (not knowing if it generated a noise frequency). I had already inserted a ground isolation transformer in the TV audio output lines as someone else had recommended. The net result of all this was enough improvement to finally hear our local AM station, but nothing to write home about. My conclusion remains: 1) The Jensen AM circuitry has very poor noise rejection and 2) the WFCO Power Center Inverter generates enough noise to drown out any but the strongest AM reception and manages to transmit it on the 12volt lines.

Fergie

The pictures show where the cores were placed:

AM Reception on the Jensen AWM968

Comments

Categories