[ale] ot - FM transmitter makes good GPS jammer

Mon May 7 16:19:56 EDT 2012

That is a clear test of a BAD transmitter.

unless you _want_ to own a GPS jammer....

On Mon, May 7, 2012 at 3:47 PM, Ron Frazier (ALE) <
atllinuxenthinfo at techstarship.com> wrote:

> **
> 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> 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> 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> 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
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>
> Ron Frazier
> 770-205-9422 (O)   Leave a message.
> linuxdude AT techstarship.com
>
>
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-- 
-- 
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/
*
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