Odd Reception Scenario

[JimmyJet727]

New ham here. Yesterday I was out running errands with a 2M handheld and stock antenna. The radio was not connected to a power source or anything else. My area has a daily 2M Net at 11am on a local repeater. So about that time I pulled into a parking lot and tuned into the net.

Sitting in the car the signal was pretty good and I could understand each transmission. But it was time to go so I shut the engine off, at which point the signal dropped and I could hear nothing. Thinking that was odd, I restarted the engine and the signal returned. So I shut the engine off again, twice actually, and each time the result was the same.

It's common knowledge that cars can cause RFI from multiple sources so this has me really puzzled. I would have expected the exact *opposite* result. The car is a 2011 Genesis and does have XM Satellite Radio which was turned off at the time.

So, any ideas why this happened?

 

[KB4MSZ]

Would you be interested in selling that car?

 

[RFI-EMI-GUY]

Very odd! Try this, put the radio volume loud enough to hear it while outside the car.

1) Turn the car off, get out and 2) lock it. Did the signal come back after locking? 3) Now wait 5 minutes. Did the signal come back? 4) Do you have a key fob? Move it far from the car. Did the signal come back? Failing these, 5) Try disconnecting the negative battery cable. Did the signal come back?

Most new cars have circuitry that activates either to sense the key fob, and/or to keep electronics in the vehicle alive for a short period of time.

 

[JimmyJet727]

Would you be interested in selling that car?

Yes. After I figure out why, and get a patent.

 

[KQ4ZVY]

Pure speculation: I have heard about (usually, cheaper or less well made) handhelds being effectively desense'd by being too close to a very strong signal source. Something about the signal being so strong the amplifier can't produce good signal for later stages? Could it be possible you're too close to the transmitter, but the EM noise from the running car is just right to reduce the apparent signal enough for the handheld's processing to pick out signal?

 

[MIMTBR]

Multipath attenuated by the running car?
Did you exit the car and walk around a bit with the HT?

 

[RichardKramer]

Did you try tuning other freqs to see if the same thing was happening; for example the wx freqs?

 

[JimmyJet727]

Did you try tuning other freqs to see if the same thing was happening; for example the wx freqs?

No but that's an excellent suggestion. Thanks guys, these are all good suggestions and good info. For now I'm just putting this in the category of... "sometimes radios just do weird things". I'll get back to troubleshooting when I have more time.