[ale] ot - FM transmitter makes good GPS jammer
Ron Frazier (ALE)
atllinuxenthinfo at techstarship.com
Mon May 7 15:47:42 EDT 2012
Hi Jim,
OK, I did one more test. This time, I tested both my tablet GPS and my
TomTom GPS. Both devices were running on battery power and had no
connection to the car at all. I plugged the fm transmitter into the
headphone output of my boombox. I started the test with 10 - 11
satellites being tracked by the TomTom and about 7 being tracked by the
tablet. The moment I plugged the fm transmitter into the cigarette
lighter, the TomTom went down to tracking only 3 satellites and the
signal levels on those decreased substantially, so it would sometimes
lose the fix. The tablet went down to tracking no satellites. Once I
remove the fm transmitter from the outlet, both units return to normal.
I do think the GPS receiver in the tablet is weak, for whatever reason,
but this problem is not the tablet. It's definitely the fm transmitter
and it's definitely RADIO based. This thing is SO fired from my
collection of gadgets.
Sincerely,
Ron
On 5/6/2012 7:13 PM, Jim Kinney wrote:
>
> Last tast: plug the transmitter into a different sound source like the
> boom box. I'm betting the fault is with the tablet.
>
> On May 6, 2012 10:37 AM, "Ron Frazier (ALE)"
> <atllinuxenthinfo at techstarship.com
> <mailto:atllinuxenthinfo at techstarship.com>> wrote:
>
> Hi Jim,
>
> I think I'm just giving up on that particular product / project.
> I now have a wire running from the tablet's headphone jack into a
> small boom box sitting on the seat. It works, and I don't have to
> fret with it. It's a shame, because, with the FM transmitter, I
> could use one less piece of relatively large equipment and clear
> the seat up if the tablet is on the dash. There's no easy way to
> test the FM transmitter without plugging into the cigarette
> lighter as that's where it gets its power.
>
> Sincerely,
>
> Ron
>
>
> On 5/4/2012 4:51 PM, Jim Kinney wrote:
>>
>> Ron,
>>
>> That test doesn't isolate power drop on audio output from signal
>> overlap.
>>
>> to test that the FM transmitter is overlapping the GPS signal,
>> you need a secondary GPS receiver other than the tablet.
>>
>> It really sounds (ha!) like the tablet has a bad headphone jack
>> or the FM transmitter has a fault and is pulling power down the
>> audio line.
>>
>>
>> Try your test again but with the transmitter NOT plugged into the
>> car power jack.
>>
>> On Fri, May 4, 2012 at 3:21 PM, Ron Frazier (ALE)
>> <atllinuxenthinfo at techstarship.com
>> <mailto:atllinuxenthinfo at techstarship.com>> wrote:
>>
>> Hi Jim, and all,
>>
>> I've tested this several times and confirmed the behavior.
>> It's definitely not power. Today I tested this as follows
>> with the tablet running on battery power.
>>
>> I start the tablet on battery power and run a program called
>> GPS test. I get a nice clean fix on 5 - 6 satellites, a
>> positional accuracy of 15 ft or so, and SNR values in the 26
>> - 31 range (this program doesn't specify the units). Those
>> satellites are color coded in yellow by this program. I have
>> a podcast playing in the background on the tablet's internal
>> speakers. I have the fm transmitter plugged into the
>> cigarette lighter but the AUDIO cable is not plugged into the
>> tablet. So, sound is coming from the tablet's speakers, and
>> nothing is coming from the car's speakers. Everything is
>> fine. GPS works.
>>
>> I plug the AUDIO cable in from the FM transmitter into the
>> tablet's headphone jack. Sound starts coming out of the
>> car's speakers, as it should. Immediately, SNR's for the
>> satellites drop below 20, satellites with a fix drop to 0 -
>> 1, and the position fix is lost. I've confirmed this several
>> times. It is exceedingly strange.
>>
>> I've officially fired the FM transmitter. I don't think I
>> have the packaging to take it back to Fry's. It's a NAXA
>> NA-3029 if anyone's interested. I'd recommend avoiding this
>> unit.
>>
>> I've gone back to my old method. I have a boom box with aux
>> input sitting in the seat, and I run a wire from the tablet
>> to the boom box. Messy, but it works.
>>
>> Sincerely,
>>
>> Ron
>>
>>
>>
>>
>> On 5/1/2012 8:19 AM, Jim Kinney wrote:
>>> that sounds more like an internal power issue. The device
>>> draws more power on a bus that is available for both the gps
>>> and it to run to gps falls down.
>>>
>>> To see if it's actually radio interference, check you cell
>>> phone gps next to it and see if it also chokes.
>>>
>>> On Tue, May 1, 2012 at 12:20 AM, Ron Frazier (ALE)
>>> <atllinuxenthinfo at techstarship.com
>>> <mailto:atllinuxenthinfo at techstarship.com>> wrote:
>>>
>>> I have one of those cheap fm transmitters that
>>> broadcasts audio from a
>>> portable device to the car stereo. It works great to
>>> send sound from my
>>> tablet to the car. However, it also jams the tablet's
>>> GPS system. When
>>> I plug in the transmitter, the number of satellites the
>>> tablet has a fix
>>> on goes from 6 or more to 1 or zero immediately. The
>>> GPS fails to
>>> work. If I unplug the fm transmitter, the GPS works
>>> again. Anyone ever
>>> seen that happen?
>>>
>>> Ron
>>>
>>
>>
>> --
>> --
>> James P. Kinney III
>>
>> As long as the general population is passive, apathetic, diverted
>> to consumerism or hatred of the vulnerable, then the powerful can
>> do as they please, and those who survive will be left to
>> contemplate the outcome.
>> - ////2011 Noam Chomsky
>>
>> http://heretothereideas.blogspot.com/////
>
--
(To whom it may concern. My email address has changed. Replying to former
messages prior to 03/31/12 with my personal address will go to the wrong
address. Please send all personal correspondence to the new address.)
(PS - If you email me and don't get a quick response, you might want to
call on the phone. I get about 300 emails per day from alternate energy
mailing lists and such. I don't always see new messages very quickly.)
Ron Frazier
770-205-9422 (O) Leave a message.
linuxdude AT techstarship.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.ale.org/pipermail/ale/attachments/20120507/aa22c979/attachment-0001.html
More information about the Ale
mailing list