On 11/16/2011 06:52 AM, Tim wrote: > On Wed, 2011-11-16 at 10:19 +1100, Roger wrote: >> Apologies for being a light year OT but I do not know who else to ask. >> Way back when car radios were first installed in cars there used to be >> a plug in filter that went between the arial connection and the radio >> input, it cut the RF static from overhead SEC wires. > > Dunno about filtering outside interference, but filtering out noise from > the ignition system has needed doing ever since cars had radios put into > them, and still does. It can be done it two ways; ignition noise > suppressors in the power line to the radio, and noise suppressing leads > on the spark plugs. And some use both methods. > > Go to a general electronics shop, or a place that fits car radios. --- you do not mention am, fm, long wave, or short wave, but i will mention about am broadcast and 2 meter fm. i have a 1970 ford f100 truck with a 429 high performance block, that had a bad case of ignition pop and alternator whine in am broadcast radio. when i got my amateur ticket, i was kidded a lot about drive a ford with out other operators even asking what i was driving. and this was with 2 meter fm. after 3 days, i had enough and decided to 'roll my own'. i broke off the long side of a tv high voltage transformer core, about 4" long. i wrapped it with 2 - 10 turn layers of dual 10 gauge stranded instrument wire, 1 for battery positive, other for battery negative. i then mounted choke in a 'bud box', shielded power leads out thru a short length of 'water tight greenlee flex' to inside of truck cab, then unshielded to radio. next day i heard one of the hams who had kidded me about driving a ford, talking to another ham. i broke in and asked him how radio was sounding. he laughed and said clear and clean and asked if i had radio hooked up in house or was i sitting with engine turned off and started laughing again. i told him that i was driving on street and his reply was that i must be driving a chevy and again laughed. i replied that i was still driving my ford and he told me that was impossible because no ford was that clean. i turned into a parking lot of some stores, pulled in between 2 building, rolled down window, held mike outside and keyed. i revved up engine and 'wrap the pipes', and honked the horn. i then asked him what he heard. his reply was "a sweet sounding engine and cleanest signal i have ever heard coming from a ford." he asked what i had done, so i told him. shortly after, another operator broke in and asked where he could find a core because he had a ford and he was always getting complaints about his electrical noise. i told him he should be able to find one at any tv repair shop and if they did not, ask them to save one for him. a few weeks later, i was driving around town and heard my call sign and replied. it was same op that i had talked to before. he told me he had built choke as i had described and he want to thank me for suggestion. he told me that because he did not have any 'greenlee', he mounted the 'bud box' on firewall and ran wire thru bottom of box and thru firewall. as for the am broadcast, i seldom use it now because i mounted an fm broadcast in overhead console with 2 meter fm and use same supply for it. moral for op, he might try same, but mount box on back of his neck. lol -- peace out. tc.hago, g . *please reply "plain text" only. "html text" are deleted* **** in a free world without fences, who needs gates. ** help microsoft stamp out piracy - give linux to a friend today. ** to mess up a linux box, you need to work at it. to mess up an ms windows box, you just need to *look* at it. ** The installation instructions stated to install Windows 2000 or better. So I installed Linux. ** learn linux: 'Rute User's Tutorial and Exposition' http://rute.2038bug.com/index.html 'The Linux Documentation Project' http://www.tldp.org/ 'LDP HOWTO-index' http://www.tldp.org/HOWTO/HOWTO-INDEX/index.html 'HowtoForge' http://howtoforge.com/ ****
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