[ale] ot - FM transmitter makes good GPS jammer
Ron Frazier (ALE)
atllinuxenthinfo at techstarship.com
Tue May 8 10:41:01 EDT 2012
Geoffrey Myers <lists at serioustechnology.com> wrote:
>On 05/06/2012 10:37 AM, Ron Frazier (ALE) 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.
>
>I've had two different such FM transmitters and both really provided
>lousy sound. You might consider replacing your auto sound system with
>one that has an input jack. That's what I did with my truck.
Hi Geoffrey,
That's a good idea to keep in mind. However, it's really not worth the trouble for me. I guess I'll just use the boom box for now. I have to choose carefully where I spend my money.
>
>>
>> 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
>>
>>
>>
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>
>
>--
>Until later, Geoffrey
>
>"I predict future happiness for America if they can prevent
>the government from wasting the labors of the people under
>the pretense of taking care of them."
>- Thomas Jefferson
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--
Sent from my Android Acer A500 tablet with bluetooth keyboard and K-9 Mail.
Please excuse my potential brevity.
(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 email messages very quickly.)
Ron Frazier
770-205-9422
linuxdude AT techstarship.com
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