Reply With QuoteAre you running straight to your battery? Other electrical devices eg sounders can cause interference. You can also try an inline filter
I have a problem where when i scan my unit gets stuck on chanel 8 consistently. Any ideas as to why this is happening? Navman 7200 is the brand, and when it happens it sounds like a slow machine gun. Cheers
Are you running straight to your battery? Other electrical devices eg sounders can cause interference. You can also try an inline filter
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I'm no electrician by a long shot Horse so wouldn't know ( theres a bloody maze of wires behind dash ). I know that when i start my motor my sounder has to be restarted if that helps. When i put the unit on a single chanel like 16 it works, but on scan it goes through the chanels until 8 and then i have this droning slow machine gun like sound where i want to throw the F#$##*& thing overboard.
Cheers
Does this model have 3 channel scan? If so tag the emergency channel and 2 others you might regularly chat on, and see if that helps when you put the 3 channel scan on.
Mike
Pretty sure it does Mike, i'll give it a go.
Cheers
Might want to get that looked at...Originally Posted by paul251
If scanning and it sticks on a channel, usually means there is enough signal on that channel to stop the scan and stay on that channel. Someone on the channel may have a mic button stuck on etc.
Mike
Based on your comments it appears that you have two separate issues.
The first is that the voltage drop when you start the engine is sufficient to require the sounder to be "rebooted". This suggests that your battery is nearing the end of its life. Get the battery tested, replace if necessary.
The second is the generation of electrical "noise" which is being picked up by your VHF. This could be due to a number of things, including worn bushes in an alternator, a poor connection that is subject to vibration, a dodgy plug lead or leads, worn bushes in an accessory motor such as a bait pump or deckwash. Radio noise is usually the result of "arcing" due to vibration or wear. The droning machine gun sound you refer to is the radio picking up a regular arc
Try the following steps to isolate your problem.
Adjust the squelch on the VHF, it could be that simple.
Check battery terminals for clean and tight, especially the earth and the alternator wire from the engine. Also check connections to the bus bars.
Switch on your radio with no other accessories running and the motor not running and see if it is still finding noise on Ch8. If it is, then the next step would be to try another aerial.
Switch on the accessories one at a time with the radio in scan mode and see if there is a specific accessory generating the noise. If there is one, check all connections on that circuit for clean & tight, pay attention to crimped or soldered joints.
Turn all accessories off except the radio and start the engine, still with the radio in scan. If noise is picked up, try switching the engine off and removing a plug lead, start the engine and repeat the test (it will run rough as), and check to see if the noise is till occurring. Repeat for each lead, replacing the previous one each time. This will help isolate a dodgy plug lead.
If the noise is present all of the time, it is unlikley to be leads.
If you are able to do so, try running the engine after sunset in as close to complete darkness as you can get, and look for your own personal little lightning show, it is amazing what this can show up, pay particular attention to the coils when doing this, a bit of dirt or grease can act as a conductor for HT current. Spray everything electrical with WD40 or similar and wipe down.
Try replacing the plugs with "resistor" type plugs of the same configuration and heat range. This is a common cause of radio interference in older vehicles.
If all of that fails, given your comment about "a maze of wires", try taking to your local car audio tech, they do this kind of trouble shooting for a living.
A question, doe the "machine gun" get faster when the engine revs? If so this indicates either the ignition of charging system is the cause.
Another question, does your cabling for your transducer wrap around the aerial cable? Induction, the energy produced as the result of a fluctuation in the magnetic field, can also cause noise, cables wrapped aroudn cables act like a transformer.
Another dodgy way to track down this kind of noise is with a handheld VHF radio, see if you can tune it to the noise and then listen for variation in volume as you move it around the electrics, starting at the alternator and coils. IF you can't tune to the noise on Ch8 then your VHF may be the source.
Hope this helps
Cheers
Thy
Thanks for writing such a big post Thy, i will try the above but some i know such as batteries as had them tested a few weeks back and are ok. I should have said that since using batteries on both my sounder dosn't turn off, but on 1 battery it does, and i'm lead to believe that Raymarine are very sensitive to volyage drop. The noise dosn't ( slow machine gun ) get faster with higher engine revs. I will try some of the other things as well.
Cheers
Another question, does the "machine gun" sound happen when the engine is not running?
If it does, this should discount the engine electricals as the source of the noise.
As for post length, I do a lot of documentation so typing is no real drama. The logical thinking takes a bit more effort
Cheers
Thy
Yeah it does it when the motor is turned off, which is why it drives me nuts and makes me want to piff it over the side..Strange thing is that it doesn't do it at all when i lock in a single channel. I was thinking along the same lines as Mike as it stops because it picks up something faint, but i have never heard anything apart from the slow machine gun noise. It's just annoying as i like to scan sometimes.
Cheers
If every other channel scans and only one keeps locking, it's picking up scatter from something broadcasting in your area at similar mhz. Either turn up the squelch and see if that knocks it out, or deselect channel 8 from your scanning channels.
My experience with Raymarine is they are sensitive to voltage dips. Especially the DSM250 and 300 which drop off line around 11.5V depending on the transducer used.
From your post above... when on CH8 but not scanning, is the machine gun noise present?
Which brand of radio is it?
When on CH8 (not scanning) does the squelch have to be set higher than other channels in order to mute the background noise?
Has this always happened or just recently?
Sometimes its better to look like an idiot than to open ones mouth and remove all doubt.
Its a Navman 7200 Testlab and when i do a full scan it consitently get caught on ch 8 and it makes the noise ( machine gun ) once it stops on ch 8, and yes i have tried all squelch settings but still happens. It has been doing it for 6 months or so at a guess, but the unit works in every other way which is annoying. Think i will just do a 3 chanel scan and be done with it. Cheers for all the help guys especially you Thy for your post.
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