Antenna noise filters - diyAudio
Go Back   Home > Forums > General Interest > Car Audio

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 12th July 2008, 01:01 AM   #1
diyAudio Member
 
Join Date: Jun 2007
Default Antenna noise filters

Does anyone know what kind of circuit is in an antenna noise filter ( eg - http://www.crutchfieldcanada.com/Pro...AS100&CartID=2 )?

Spraiski
  Reply With Quote
Old 12th July 2008, 02:33 AM   #2
diyAudio Member
 
Join Date: Dec 2005
Location: Northern California
I built my own by separating the shield of the antenna coax and inserting a ceramic disk capacitor in between the two side after I cut the shield in two. A piece of black plastic tape or shrink sleeve later and VIOLA! a Antenna noise filter.

The big deal is to isolate the ground so to prevent ground loops.

Another way would be to add a RF balanced transformer to do the same thing, but if this is done a signal amplifier might be a good idea to compensate for the loss the transformer will cause in the RF signal strength. And these amplifiers themselves can cause noise issues.

The only possible purpose for doing any of the above is if you have found that the antenna is the source of you engine noise issue because of a ground loop condition it may be causing...Hope this helps
  Reply With Quote
Old 12th July 2008, 08:18 AM   #3
diyAudio Member
 
Join Date: Jun 2007
Well maybe a bit more background to my particular situation is in order. I have a 2001 Honda Civic LX Coupe. It uses the grid on the rear window as an antenna for the radio.

FM reception is acceptable. AM reception is the problem - with the engine off the reception is marginally acceptable, but with the engine running, or when anywhere near another vehicle that is running AM stations are almost completely wiped out. I know that adding an external antenna would cure the problem, but I would like to see if I can get better performance with the window grid.

I'm trying to get together several different solutions so that I can try different things in the same afternoon (avoiding possible placebo effects).

1. First off will be a thorough check for breaks in the grid.

2. Redo the grounds from the battery to the engine and to the body ensuring that I have good metal to metal contact (with a dab of copper antiseize to prevent any future corrosion of the mating surfaces).

3. Add a low pass RC filter to the power leads going into the radio/cd player.

4. Add an antenna filter of some sort...but I'm not sure what sort of ciruit is in there - is it just a high pass RC filter (and if so, what sort of cut-off frequency do I want to aim for)?

5. There is an 'antenna module' at the rear of the vehicle right next to the window - I think this is an amplifier, but I'll have to investigate further before doing anything with it.

Any thoughts?
  Reply With Quote
Old 12th July 2008, 06:51 PM   #4
diyAudio Member
 
Join Date: Dec 2005
Location: Northern California
Well your planned approach sounds valid in this case. Most unwanted noise is created under the hood of the radios host vehicle.
Everything from bad spark plug wires to bad grounds etc.. can be the main reason for most of the issues you mentioned.

But please bear in mind that the radio itself can also be a weak link in the scheme of things. Some stock radios are just so poorly designed that the issues your dealing with may be unavoidable.
  Reply With Quote
Old 12th July 2008, 07:52 PM   #5
Banned
 
Join Date: Jan 2008
Blog Entries: 2
I wouldn't expect a radio in any modern car (especially a Honda) to exibit these problems unless there is a fault. Car radios are, after all, designed to work in cars.

It's a bit complicated in this case 'cause of the screen antenna and the amplifier.

First I'd be looking for obvious faults. Is the antenna cable connected to the radio? In some cases you can still get reception without one. Is there any possibility of ingress of water (condensation) into the antenna cable or amplifier? Is there power to the amplifier?

Then check the radio for obviously faulty capacitors - blown cases or cracks. Also check for dry joints. These can manifest as almost invisible cracks in the solder. If you can, operate the radio in the dark, you can sometimes see tiny sparking in a dry joint. Otherwise you can remake every joint in sight... Most car radios operate in a pretty hostile environment, hot and with high vibration, the failure rate reflects this.

You should be looking for a fault to fix, rather than seeking to bolt on something that will correct it.

w
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
car antenna coki Car Audio 3 11th August 2007 11:35 AM
DIY antenna Fry-kun Analog Line Level 3 24th May 2007 08:52 PM
FS: Capacitors/ Opamps/ Power Transistors/Noise Filters & Other Interesting Stuff dtm1962 Swap Meet 1 8th February 2006 04:21 PM
What do you think about this antenna ? darkm4n Parts 0 6th March 2004 09:47 PM
Ultra low noise filters tiroth Solid State 14 21st May 2002 10:19 PM


New To Site? Need Help?

All times are GMT. The time now is 03:02 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2