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Wiglet
Occasional Visitor
Joined: May 14, 2007
Posts: 6
Location: Cranage, Cheshire
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 Posted: Fri Sep 21, 2007 11:18 am Post subject: |
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| philpugh wrote: | At home (2 miles south of Jn 10 M56) I get about 27-30 in-car for channel 145 (Galaxy FM) and I am a little further away than you. I get a lock with the car parked in an old 'tin' barn. Before the connection to the aerial I was only getting 15-20 and failed to get any TMC data until I got to Jn 6 M56 or closer.
As you can get it working in your home it would suggest that there is something else going on here. It could be that you are getting electrical interference on the aerial lead. This would have adverse effects on the ability to decode the TMC info at low signal levels.
With the Volvo diversity aerial. Do the two aerials feed the radio separately (i.e. a 'special' Volvo unit) or do they go into a 'box', presenting one aerial feed to the radio? I was wondering if you can connect directly to one of the aerials and disconnect it from the diversity system entirely. |
I am pretty shaw the aerial amplifier is in the back of the car and it feeds two coax to indivdual sockets on the back of the radio. Both aerials give the same signal strength so I have borrowed one for the GTM and the radio is quite happy with the other.
I also thought it might be the diversity setup causing the problen so I have tried running coax from the newly fitted Shark fin but with a long length of coax signal strength falls away to 0. |
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philpugh
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Joined: Dec 28, 2005
Posts: 2003
Location: Antrobus, Cheshire
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| Posted: Fri Sep 21, 2007 1:05 pm Post subject: |
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| Wiglet wrote: | | I also thought it might be the diversity setup causing the problen so I have tried running coax from the newly fitted Shark fin but with a long length of coax signal strength falls away to 0. |
The sharkfin aerial will almost certainly require some sort of amplification due to the low inherent signal levels they pick up. Do you know if it has an in-built amplifier? If so then something will need to feed 12v up the coax to it. You can buy adapters to do this for you. A few manufacturers' 'own label' radios provide this facility and if you fit an alternative radio (as I did in my VW) you need to buy the adaptor (~£10) to do this.
Even with longish co-ax runs (and you will probably be talking about 4-5 metres max) you should not get enough loss to drop signal to 0 - unless it is very small to start with.
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Phil |
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Wiglet
Occasional Visitor
Joined: May 14, 2007
Posts: 6
Location: Cranage, Cheshire
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| Posted: Fri Sep 21, 2007 2:28 pm Post subject: |
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[quote="philpugh"] | Wiglet wrote: | | I also thought it might be the diversity setup causing the problen so I have tried running coax from the newly fitted Shark fin but with a long length of coax signal strength falls away to 0. |
The sharkfin aerial will almost certainly require some sort of amplification due to the low inherent signal levels they pick up. Do you know if it has an in-built amplifier?
The Shark fin I installed has a built in amplifier. As I said above connecting directly to the GTM shows reasonable signal strength but any length of coax kills the signal. |
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philpugh
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Joined: Dec 28, 2005
Posts: 2003
Location: Antrobus, Cheshire
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| Posted: Fri Sep 21, 2007 3:27 pm Post subject: |
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| Wiglet wrote: | | The Shark fin I installed has a built in amplifier. As I said above connecting directly to the GTM shows reasonable signal strength but any length of coax kills the signal. |
So how is it being powered (the shark fins amp)?
The symptoms you describe are consistent with a very low level of output from the sharksfin/amplifier - which could point to a problem in the unit itself.
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Wiglet
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Joined: May 14, 2007
Posts: 6
Location: Cranage, Cheshire
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| Posted: Mon Sep 24, 2007 9:53 pm Post subject: |
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The Shark fin is a waist of time, as soon as there is any coax connected the signal strength dies. (This Shark fin has an amplifier built in with its own dedicated power supply).
I have now permanently connected the GTM-21 to the V70 aerials (one of the two gives a better signal than the other). At home south of Manchester by 25 mile CH145 comes in at a steady 30 but never recieves data until within about 10 miles of the city with signal strength 33 or above. However I noticed Ch136 booms in at 40 but the GTM never locks on until I select the "Test" function then the messages pile in by the hundreds but ! but they never get displayed what going on? |
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philpugh
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Joined: Dec 28, 2005
Posts: 2003
Location: Antrobus, Cheshire
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| Posted: Mon Oct 01, 2007 2:55 pm Post subject: |
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| Wiglet wrote: | The Shark fin is a waist of time, as soon as there is any coax connected the signal strength dies. (This Shark fin has an amplifier built in with its own dedicated power supply).
I have now permanently connected the GTM-21 to the V70 aerials (one of the two gives a better signal than the other). At home south of Manchester by 25 mile CH145 comes in at a steady 30 but never recieves data until within about 10 miles of the city with signal strength 33 or above. However I noticed Ch136 booms in at 40 but the GTM never locks on until I select the "Test" function then the messages pile in by the hundreds but ! but they never get displayed what going on? |
Sounds like your Sharksfin should be returned!
Ch136 = 101.1MHz - which is Classic FM - transmits TMC for iTIS and therefore won't be decoded on the Garmin's TrafficMaster system.
I get a lock on Ch145 with signal strength of 27+ quite reliably.
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Phil |
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Wiglet
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Joined: May 14, 2007
Posts: 6
Location: Cranage, Cheshire
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| Posted: Mon Oct 01, 2007 11:08 pm Post subject: |
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| ch136 and ch126 both show as receiving data (mode 5) when the GTM is in test mode, however the data doesn’t get displayed obviously because its not from traffic master; but none the less its interesting the GTM recognises it. |
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