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TMC Mod

 
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blackwellgraham
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Joined: Apr 12, 2007
Posts: 22
Location: GO710 from Leicester, UK

PostPosted: Tue Apr 17, 2007 8:50 am    Post subject: TMC Mod Reply with quote

Just to let you know, I took my TMC apart and modded it as per the PDF article; I've bought a magmount 50-1300MHz aerial which is now in the centre of the roof on my mondeo. I've connected both the outer braid and the inner conductor of the coaxial cable to the PCB in the end of the TMC antenna, and its still not working.

Tonight I'll unsolder the braid from the pad on the PCB and try again.

Fingers crossed.

The input impedance of the two pads on the PCB appears to be < 1.0 Ohm. Is that what you'd expect ? (with nothing connected to the gold pads)
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mikealder
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Joined: Jan 14, 2005
Posts: 19638
Location: Blackpool , Lancs

PostPosted: Tue Apr 17, 2007 8:57 am    Post subject: Reply with quote

Yes 1 ohm is about right, there appears to be an inductor strapped across the pads. Where are you located in the UK? - Mike
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blackwellgraham
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Joined: Apr 12, 2007
Posts: 22
Location: GO710 from Leicester, UK

PostPosted: Tue Apr 17, 2007 10:52 am    Post subject: Reply with quote

Leicester. I could only get coverage on the M40 between J8 and 9 in either direction. I travel a fair bet between Leics and Crawley (M1-A43-M40-M25-M23) and its never worked anywhere else.
Went up to Doncaster the other week, nothing along the M1 either.
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mikealder
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Location: Blackpool , Lancs

PostPosted: Tue Apr 17, 2007 12:17 pm    Post subject: Reply with quote

I have found limited reception with the mini-scan mag mount, it does improve signal strength but an amplified aerial is a much better option. Some people have reported the later build RDS-TMC units don't work as well as the earlier supplied ones when modified due to components that have been changed, the theory bei the older devices allow more RF to leak into the device from the external aerial.
I will send you a POI file when I get home so you can work out the nearest transmitter and applicable frequency to you position when traveling, this might help a little - Mike
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blackwellgraham
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Joined: Apr 12, 2007
Posts: 22
Location: GO710 from Leicester, UK

PostPosted: Tue Apr 17, 2007 1:14 pm    Post subject: Reply with quote

Thanks Mike

Just sat in the car over lunch time and tried to programme in 100.1MHz which is the same frequency that the RDS stereo in the car shows for Classic FM, and the GO710 cant pick anything up.

Wheres the article on using an AMP?

My PCB has the same revision as the one shown in the photographs in the PDF document on modding the TMC.

Should I bother disconnecting the braided earth from the coax? Doesn't sound like its going to make a difference.

I have access to scopes etc. Do you know what I can check on the PCB to show what the signal being received looks like? ie pk-pk voltage etc.
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blackwellgraham
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Joined: Apr 12, 2007
Posts: 22
Location: GO710 from Leicester, UK

PostPosted: Wed Apr 18, 2007 9:26 pm    Post subject: Reply with quote

Pleased to report that the TMC still works, despite my modification.

I've now extended the range from J9-8 to J9-J5 on the M40. Will see if it picks up Classic FM from J5-J9 on the way home tomorrow evening. It was tuned in to 101.3MHz FM

Still doesn't pick up anything outside of this corridor, so TMC is still useless, but at least I've made it a little less useless Laughing
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Tim Buxton
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Location: Surrey, United Kingdom

PostPosted: Wed Apr 18, 2007 9:41 pm    Post subject: Reply with quote

From the M25/A24 junction down to Crawley I get TMC on 101.9MHz, most of the time.
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blackwellgraham
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Joined: Apr 12, 2007
Posts: 22
Location: GO710 from Leicester, UK

PostPosted: Tue Apr 24, 2007 11:13 am    Post subject: Reply with quote

I had partial coverage on the M18 and southbound on the M1 yesterday morning. I had good coverage on the M69, M6, M42 and A50 back in to Leicester on Saturday and Sunday.

Having the green icon on for more than 20 minutes is becoming a bit of a novelty. And the warning yesterday about the accident on the M1 at J22 allowed me to dive off at J24 and head down the A6 to Loughborough to avoid the delays.

When it works, its great! However, its still not working on my trips down the M40/M25/M23 other than the short section along the M40 nr Oxford, so I'm still not happy.

Trips to Manchester tonight, and Doncaster again tomorrow night, so I'll see how the reception is again with the new aerial.
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Tim Buxton
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PostPosted: Tue Apr 24, 2007 11:52 am    Post subject: Reply with quote

Tim Buxton wrote:
From the M25/A24 junction down to Crawley I get TMC on 101.9MHz, most of the time.


Sorry, this should be 100.9MHz. Embarassed
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