|
New to Ham Radio?
My Profile
Community
Articles
Forums
News
Reviews
Friends Remembered
Speak Out
Strays
Survey Question
Operating
Contesting
DX Cluster Spots
Propagation
Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers
Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net
|
|
1-7 of 7 messages
|
Page 1 of 1
|
|
Help identifying RFI
|
Reply
|
|
by JAKK on August 21, 2009
|
Mail this to a friend!
|
Hi. I just set up my shack last weekend. It consists of a Ft-450, Samlex SEC1235M, LDG Z100 plus, and an Alpha Delta DX-EE. While I am pretty much RFI free I do have this annoying interference that I am having a hard time identifying. It seems to occupy all bands and has no pattern as to spacing. It sounds like someone is tuning (a steady tone) and the signal itself occupies a few khz. I have made a recording of the sound which can be downloaded from the link below. The part of the recording where the tone changes pitch is me tuning around the noise.
Last night I hooked up the 450 to a battery and shut off all power to my house. The noise still remained so it's not something in my house. The noise seems to almost dissappear when I remove the antenna as well. Another odd thing is that the noise seems to go away if I switch to AM and is only audible on lsb/usb. Thanks for taking a look at this. The mp3 is located at:
http://drop.io/ncx4gnv/asset/rfi-mp3
|
| |
|
RE: Help identifying RFI
|
Reply
|
|
by WB5JEO on August 21, 2009
|
Mail this to a friend!
|
A couple of questions. When you say it's on all bands, does that mean it comes and goes on all bands? Same times everywhere or appears one place once and one place another time? And I assume the change in audio frequency was you tuning and not the source changing frequency. Is it always in those short key-down periods as in the recording? And, if it appears on several widely separated frequencies at once, do you have any idea what a set of those frequencies might be?
As an unmodulated carrier, I would expect it to appear to go away on AM as it does.
|
| |
|
RE: Help identifying RFI
|
Reply
|
|
by JAKK on August 21, 2009
|
Mail this to a friend!
|
|
Hi. The noise is pretty much on all bands, although it does change locations a bit. For example, one tone may be on 7.234. A few hours later, that tone will not be there but there will be a tone on 7.265. The tones are not just for the period. I probably should've mentioned that I was tuning around a band during that whole recording. The tones themselves last for an indefinite amount of time. The change in pitch is me tuning around the noise, not the noise itself.The tones seem to be spaced in no particular order at all. There will be a bunch clustered together and then nothing for a few hundred khz.
|
| |
|
RE: Help identifying RFI
|
Reply
|
|
by WB5JEO on August 21, 2009
|
Mail this to a friend!
|
RFI from a computer network can sound like many unmodulated carriers spread out but are most often above 17 mHz. But I'm still suspicious of some part of a neighbor's computer system. You may have to work up a loop and do some direction finding with a portable. Now the fix, if it turns out to be a network switcher or something, may be tricky an isn't always entirely successful. It has involved buying new gear for the network, like devices in metal housings instead of plastic to at least drop the signal down some.
Most larger clubs have one or more members who are experienced at hunting down local interference, and you'd sure want to try to ask first if anyone else nearby has that problem. That might save you hunting the neighborhood for something that farther away. But somehow I doubt the source is very far off.
I suppose that if your property isn't too big and the neighboring houses are close, it might be worth rigging a simple inefficient antenna, like a piece of wire soldered to the center conductor of a long coax, and dragging it around to the areas near each neighbor while someone listens. I'd want to begin with enough of a wire that I heard the thing on and cut at it until it's not hearing it in the shack and does hear it as you move around to one area. Of course, a temporary loop isn't that hard to construct. Or borrow a portable and see if it can differentiate as the antenna is telescoped down.
Let's see if anyone else has ideas now that they know more about it. Whatever, if you work it out, come back and post the results. There's a lot of new sources we all need to share information about.
|
| |
|
RE: Help identifying RFI
|
Reply
|
|
by K6RF on September 9, 2009
|
Mail this to a friend!
|
|
I had a similiar problem a few months back and turned out to be neighbors wireless Linksys router. Fortunately I had a portable rig to use and walked up and down the block using my battery operated FT-817 with the watched the S meter. Two houses down was the culprit. I told the home owner I would buy him a new router (Netgear) to rid myself of the problem. It was a end to a problem that was driving me nuts. Unfortunately, I don't remember what model of Linksys router it was, it was the newer style without the protruding antennas. Good luck in your problem solving.
|
| |
|
RE: Help identifying RFI
|
Reply
|
|
by K6RF on September 9, 2009
|
Mail this to a friend!
|
|
I had a similiar problem a few months back and turned out to be neighbors wireless Linksys router. Fortunately I had a portable rig to use and walked up and down the block using my battery operated FT-817 and watched the S meter. Two houses down was the culprit. I told the home owner I would buy him a new router (Netgear) to rid myself of the problem. It was a end to a problem that was driving me nuts. Unfortunately, I don't remember what model of Linksys router it was, it was the newer style without the protruding antennas. Good luck in your problem solving.
|
| |
|
RE: Help identifying RFI
|
Reply
|
|
by WB4BYQ on September 10, 2009
|
Mail this to a friend!
|
Most of the time the tones or birdies that you hear are comiing from network equipment, computer equipment. I have seen these carriers come from switching power supplies. I had a neighbor that was
using a Linksys router with the antenna, cable modem, and dell pc. i traced the birdies to that system in their room that was next to my house. I live close to most of my neighbors within 30 to 100 feet. i fixed the problem with shielded cat 5 cable between all the equipment. CRT computer monitors will generate these birdies as well. switching power supplies usually make a buzzing noise up and down the band. Now is the time to learn a little about fox-hunting. you will have to do some looking around, listing, testing. a lot of the rfi that i hear comes from the power line leaving the house if is above ground. a sniffer ant at the power meter will find the noise and correct location, using a small radio, hf radio. look at these sites for help.
http://www.olympixcorp.com/rfchoke/ferrite.htm
http://atnm.mcars.us/HomeBrew/WB4BYQ/CommonModeChokes/
richard
|
| |
|
Email Subscription
You are not subscribed to this topic.
Subscribe!
My Subscriptions
Subscriptions Help
Check our help page for help using
Forum, or send questions, comments, or suggestions to the
Forum Manager.
|
|
|
