Radio clashing with GPS

[Spikepretorius]

Not sure if this should be in the radio section or the GPS section.

I have an Icom F110 and an Oregon 550 gps in my vehicle, amongst other things. When keying my mic the 12v power to the gps switches off. This is intermittent so when I want to do tests I can't replicate it. It's usually when I'm using the radio a lot. When the gps is powered by AA battery it's fine.

When fitting the gps 12v power supply I decided to go the whole hog and fit a Blue Sea fusebox inside the cab. The fusebox has common pos and neg buses.I now have multiple power points connected to this fusebox and also opted to wire my radios to this fusebox thinking that common + and - could save me groundloop hassles. The fusebox is connect to the battery via 16mm cable.

I've rechecked all the wiring and checked for voltage drop etc. It all seems kosher.

Nothing else is plugged into the other spare power points at the moment and no other accessories are connected to the fuse boz yet. Only the VHF radio and the GPS were being used. On one day the 29mhz radio was also on but it did not cause the same problem.

Any ideas here please? Anybody ever experienced this?

Extra voltage drop as the radio heats up under heavy use??
Teeny voltage drop detected by the GPS power supply and causing it to fail??
RF causing problems with the GPS power supply cable??
Take the radios off the common fusebox and connect directly to the battery again??

 

[HenryJ]

Take the radios off the common fusebox and connect directly to the battery again??

That sounds like a good solution. The battery acts like a shock absorber. It will cushion and filter the load.
It sounds like the problem you are having is the GPS sensing the small amperage drop and signaling it to shut down. Our Crossover does a similar thing when is senses changes. It will power down, or up.

 

[mrlocksmith]

It could be responding poorly to the RF radiation from your radio. You did say it only happens when you transmit.

You can put an RF choke (Google: Ferrite Core) on the power supply chord to the GPS and if that does not work try to make a metal shield out of several layers of tin foil to cover the GPS as a test to see it it needs further shielding. I guess you will have to peek under the shield to see if your GPS has turned off.

You could also find and connect a 12V/24V device with a similar amp load as your radio during transmit and see if the GPS drops out then. Or you could use a dummy load on your antenna to contain the RF radiation.

HTH

Mark Weiss
K7VQU

 

[SunTzuNephew]

+1 on the ferrite beads - like these (or whatever size is appropriate): [ame="http://www.amazon.com/Ferrite-Core-Cord-Noise-Suppressor/dp/B0002MQGE0/ref=sr_1_1?ie=UTF8&s=electronics&qid=1278591630&sr=8-1"]Amazon.com: Ferrite Core 1/4" Cord Noise Suppressor: Electronics[/ame]

And the fusebox is connected with 16mm cable? The wire is 16mm in diameter? Thats huge (like AWG 00000000). What is the diameter of the conductor, and how far is it running to the battery (and back)? If you're getting a sufficient voltage drop when you transmit the GPS could drop off, but it would be odd (the GPS runs on nearly nothing).

 

[Spikepretorius]

That's 16 mm/2
I don't know gauge that is. The rest of the world doesn't use gauge any more
It's like thin battery cable. Probably about 8mm diameter
Voltage drop on transmit is tiny. A fraction of a volt.

 

[SunTzuNephew]

That's 16 mm/2
I don't know gauge that is. The rest of the world doesn't use gauge any more
It's like thin battery cable. Probably about 8mm diameter
Voltage drop on transmit is tiny. A fraction of a volt.

The rest of the world doesn't have your problem, either An 8mm conductor would be like spark plug cable in the US, or AWG 0....should be adequate.

Try the ferrite beads...I tend to just put them on power leads when I install anything. They're cheap, don't hurt anything and seem to fix a lot of problems.

 

[TangoBlue]

The rest of the world doesn't use gauge any more

The rest of the world doesn't have your problem, either

:coffeedrink:

 

[rusty_tlc]

I kind of doubt it is an RF problem. My guess would be that you get a power droop when you key the mic. I'd go back to a direct connection to the battery for the radio and add a 1000uF electrolytic cap near the power connection for the GPSr.

 

[Herbie]

I don't know gauge that is.

OK, I get to indulge my EE and Manufacturing history geek self:

In the earliest days of metal wire (solid copper, etc.), wires were made by literally pulling the material through a progressively smaller set of dies. Each pull through the die would stretch the wire longer, and to a slightly smaller diameter. The 'gauge' of a wire was an indicator of how many times (or dies) it had been pulled through. Thus a 22-gauge wire is quite small and a 4-gauge wire is much larger. When technology finally made it cheap enough to make wire braided from many much smaller gauge wires, the resulting wire's gauge number was set to either the equivalent physical size (for wire rope) or to the equivalent electrically conductive size for electrical wire. Thus a braided 16-gauge wire is often noticeably different in diameter to a solid conductor 16-gauge wire.

A similar grading system was used for the rolling of sheet metal, except counting the number of passes through the rolling mill.

 

[PhulesAU]

Mine does the same thing. I blame it on the charger plug, picking up on Rf at random.

 

[gary in ohio]

A quick test.. Power the GPS from a different battery, jump box, 12v lantern battery,etc.. Now key the radio. If it shuts off its most likley RF, if not its
the radio pulling down voltage and the gps is resetting. Its only a 25 watt radio, but if your wire is undersized then you could have a pretty good voltage drop.

If its RF, a snap on "interference" filter around each end of the power cord.

 

[Saratoga]

Similar to what Gary in Ohio says but with the Yaesu 8800 I've found that if you are pulling too much power that the battery can give the radio will restart. For example, when the voltage drops below a certain level of charge.

This could be related to the GPS in that the battery is too low or the cable providing power is too thin to supply and therefore one shuts down?

You could try running a seperate power cable from the battery to the GPS (even temporarily) and, as suggested above, using a different power source for either the radio or GPS.

 

[UK4X4]

You already guessed the issue, when you transmit, the extra power the radio needs, means you drop the voltage in the shared supply to a point where the GPS decides batteries are fine.

Up the size of the cable or run seperate lines for the GPS and the Radio

Don't work...start messing with silver foil hats !


PS

if its 16/0.2 your core is less than 1mm

if its 16/2 you are using speaker wire ! and not power cable, although it will still supply power it was not designed for it

 

[Saratoga]

Although my radio only puts out a max of 50w, from 12v that's 5amps. The power cable from my battery for my GPS and Radio is 16a and goes via a 15a fuse, so the fuse will go before the wire burns/melts/overloads.

I don't know how much 16 gauge would allow through it but I guess it would be lower than 5amps