RF getting into computer/serial cable

jmr061 · Post by **jmr061** » Tue Apr 15, 2003 3:48 pm

Ok we go. I have a 50 watt astro vhf and a 100 watt ge delta radio (used for aprs) in my 97 Lumina. The astro ant is in the roof. The delta ant is on the left rear 1/4 panel. I have a Toughbook Cf-28 mounted in the car and am running a serial cable from the docking station to the trunk where a metal enclosed relay controller is mounted. The computer is used to activate the relays for whatever you have hooked up to them.

My problem is that RF apparently getting into the computer/serial cable when I transmit either radio. This "resets" the relay unit and shuts all relays off. So if something was turned on it isn't anymore. I have used shielded and non-shielded three conductor cable and moved up to cat5 twisted pairs but nothing seems to be eliminating the problem. I also put on a ferrite and it doesn't help either.

I am using 1/4 wave vhf antennas. I tried a gain ant (i think 5db) and the problem seems to went away.

I prefer to stay low profile with the 1/4 wave ant. Anyone got any suggestions.

Jason

jmr061 · Post by **jmr061** » Tue Apr 15, 2003 6:05 pm

Think I may have gotten it. NMO mounts for the ant. were not dug in enough for a proper ground when TXing. Tightened them up and seems to work fine now.

Jason

007 · Post by **007** » Tue Apr 15, 2003 8:40 pm

Good call.....I was wondering what the issue was, because the WSP cars have an almost indentical setup and no obscene RFI issues.

Good to know.

jmr061 · Post by **jmr061** » Sun Apr 20, 2003 10:07 am

Well the problem is back. APRS is screwing with this setup. I use 1/4 wave antennas but when I put the 3db gain ant on the APRS radio then it doesn't interfer. Any suggestions or do I just stay with the 3db gain ant.

Jason

elkbow · Post by **elkbow** » Sun Apr 20, 2003 1:22 pm

My guess is that you still don't have a good ground on your antenna mount causing RF to 'leak' all over. Have you hooked up an SWR meter? My guess is that you are still not making a good connection on the roof. You need to scrape the inside of the roof well, I use rough sandpaper, then make sure you are torqueing down the nut good. You can also check your connection at the radio to find out if you have a good crimp on your connector. Be careful, you could burn up your radio if you antenna cable/connection is not up to spec.

jmr061 · Post by **jmr061** » Tue Apr 22, 2003 8:40 am

The connector is a PL259 and checks fine. I have now used different coax ( I did sand the underneath as well), different radios, different cable for the serial cable, different laptops, even used shielded power cable for the relay controller run from the battery. NONE OF IT HELPS.

Does anyone have any suggestions. The only piece I haven't been able to switch out is the docking station as it has two serial port outputs and the laptop only has one so I need to use it to run aprs and the relay controller at the same time. Oh I haven't swapped relay controllers either, I don't want to spend another 170 bucks just to test it out.

Jason

jmr061 · Post by **jmr061** » Tue Apr 22, 2003 5:03 pm

Did some more testing with the setup per the company's request (the ones that make the relay controller). It appears RF is getting into the microp on the board and rebooting it.

Is anyone out there aware of some sort of RF shielding I can get for hte microp. I was thinking non-conductive RFshield tape would be neat if they even make anything like that.

Any thoughts?

Jason

jmr061 · Post by **jmr061** » Sun Apr 27, 2003 10:19 am

The company sent me their R810 board and used that and the setup works fine!!!!!!!!!!!!!!!!!!! NO RF PROBLEMS.

Anyone else interested in this let me know. My brother says he won't charge for the software but a small donation would be appreciated.

Jason