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Author Topic: AM Radio qrm  (Read 488 times)
KE7LJO
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Posts: 5




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« on: April 11, 2008, 11:40:31 AM »

thanks for your time. i live in slc ut and my house is close (1 mile) to 3 am transmiters and one is bloting out most of the hf bands and bleading in to my phone, computer audio, xtal set and it is just 1 station that is giveing me problims what can i try???
thanks ke7ljo

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K8KAS
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« Reply #1 on: April 11, 2008, 12:00:55 PM »

I would suggest you move and or purchase a very good receiver/transciever with great front end spec's, as well some front end filters/ tuned to the offending frequencys such as contesters use when operating a multi-op station.
You don't mention your radio, I lived 3 miles from a couple of 5 KW AM broadcast stations and had no trouble with my Kenwood TS850S or my Yasue FT1000D
rigs. You might have a dog of a radio?
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KF9XK
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« Reply #2 on: April 11, 2008, 12:09:46 PM »

Look up AM Brick-Wall filter.  this should kill everything below 160 meters
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KB1LKR
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« Reply #3 on: April 11, 2008, 12:17:05 PM »

... or a 50kW vs. 5kW station at a third the distance -- could be 90x the field strength!

AM phone line filters can be bought/built, ferrites on speaker wires should help, a notch filter for HF receiver, etc.

X-tal receivers may be a lost cause -- I recall as a kid triing to use them at a couple miles from 50 kW WHDH 850 -- it dominated everything.
Likewise, as I recall, my Heathkit GR-81 superegenerative MW/SW receiver had trouble w/ it on the low (~300-600 kc) band, though not (IIRC) on the other bands 600 kc to 18 mc).
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KE7LJO
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« Reply #4 on: April 11, 2008, 12:17:40 PM »

my rig is an kenwood 440 in good shape.
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WA3SKN
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« Reply #5 on: April 11, 2008, 12:23:47 PM »

The phone should not be susceptable to RF.  You can try shielding the phone or installing filters to clear the problem. The company that made the phone might supply them.
The computer should not be susceptable to RF.  Try ferrite filters on the speaker leads near the speakers. I doubt the company that made it will supply any.
A xtal set is a radio receiver, and one with poor selectivity... easily overloaded, it should pick up strong signals.  Nothing suprising there.
Transmitters have high standards they must meet, receivers have had none to very poor standards... I.E. cheaply designed.
In amateur radio you might be working with very low signal levels.  You might consider moving a little farther away from the stations.
73s.

-Mike.
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KE7LJO
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« Reply #6 on: April 11, 2008, 01:26:10 PM »

I dont think i will be moving any time soon my dirt shack is allmost payed off but thanks for the input!!
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W3LK
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« Reply #7 on: April 11, 2008, 01:38:08 PM »

That's interesting, as I lived for two years a little over a hundred yards from a 5kW AM/50kW FM station and had nothing from either of them in  my phones, computer or anything else.

Something basic is wrong if everything in your house is affected. I'd check ALL your grounds: phone line where it comes into the house, shack grounds and your electrical ground where the AC comes into your house.

73,

Lon - W3LK
Naugatuck, Connecticut
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W4VR
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« Reply #8 on: April 11, 2008, 01:47:11 PM »

There are at least two 50 kW AM broadcast stations in Salt Lake City and some 10 kilowatt stations as well.  You must be located near one of the 50 kilowatt stations to be experiencing overwhelming interference.  Probably would be a good idea to call the station that's interfering with your equipment and ask to speak with their chief engineer about the problem.
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WB2WIK
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« Reply #9 on: April 11, 2008, 01:49:30 PM »

A high-pass filter installed at the coax connector on the TS-440S should easily take care of any problems you have with that rig.  Actually, a high-pass L-match or T-match network (antenna tuner) tuned for the band you're actually using will probably help a lot (a pi-network or low-pass L-network probably won't help).

However, that won't help your telephones or computer speakers!

Some phones are much better than others, you might experiment with this since phones are so cheap nowadays they're throw-aways.  We just picked up some "Panasonic" (branded) 6 GHz cordless phones that are the most bulletproof I've ever used so far -- I can run 1500W output power on any band and the phones are completely immune to it, while previously most phones I've used required some filters to be usable.  Just got lucky in this case, my XYL bought the phones and I didn't know about them until she brought them home.

Amplified computer speakers are notorious receptors of RFI from almost anything, so I'm not surprised they're screwing up with a BC station less than a mile away.  Best solution I've ever found for this is to take the amplified speakers and its little "cube" power supply and it wires, bundle them up and toss them all in the nearest trash can; then, buy a PCI sound card and *passive* (non-amplified) speakers.  Install the card, plug in the speakers, and that's the end of that problem!

WB2WIK/6
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WB2WIK
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« Reply #10 on: April 11, 2008, 01:53:13 PM »

>RE: AM Radio qrm  Reply  
by W4VR on April 11, 2008  Mail this to a friend!  
There are at least two 50 kW AM broadcast stations in Salt Lake City and some 10 kilowatt stations as well. You must be located near one of the 50 kilowatt stations to be experiencing overwhelming interference. Probably would be a good idea to call the station that's interfering with your equipment and ask to speak with their chief engineer about the problem.<

::Might be helpful, but usually they tell you to call 1-800-DIALAPRAYER because this really isn't their problem!  The chief engineer might be familiar with what other local residents have used to resolve the interference, though, so a call couldn't hurt.  
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N6AJR
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« Reply #11 on: April 11, 2008, 02:19:35 PM »

look for an ICE broadcast band filter.
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KE7LJO
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« Reply #12 on: April 11, 2008, 02:26:12 PM »

good ideas to try! i do not want to sound bias but it is the mex radio that is the problim. ksop has 2 of the tsansmiters and they do not give me any problims?
and i have a hard time getting info in the spanish station I don't understand what they say??
i have a hard time with english LOL.

and my phone line has 2 panasonic corless phones one is 2.6 gig and a 900 Mhz. in the shack i have a old western electric hard line phone all of them get the radio?

but my bud told me to try a DSL filter on the line it helped!

my computer audio is the 1/8 mini out(not balanced xlr) going to a crown D75 amp with marshal 14 gage wire. and jbl centry L100 studio monators.

shack grounding cood be better work in progress.weather permiting.
the probim is getting worse as i get more in to it.
thank to all!!

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W7ETA
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« Reply #13 on: April 11, 2008, 05:46:48 PM »

Are you using a resonant antenna for HF bands?

Bob
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KE7LJO
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Posts: 5




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« Reply #14 on: April 11, 2008, 06:46:01 PM »

no. it is a 80 foot long (random) wire in to the mfj versa tuner II for the low Mhz bands(receve only) and the radio station is at 1640 Kc. I have a dipole on the 10m that works good.
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