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Author Topic: I NEED HELP! When I transmit I hear my voice into AM broadcast station program.  (Read 7307 times)
KC2SKM
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Posts: 7




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« on: November 15, 2012, 12:59:19 PM »

Hello! everyone

My problem is when I transmit my voice go into the AM radio broadcast programs but FM its all ok. Also testing in the same device using CD player and no radio and no problems speakers are all clear. So, problem is just with AM radio. my station is FT-950 Yaesu,Cushcraft MA5B on the top of the 3 floor building about 6-7 ft high from the roof level (no permission from the owner to put up more high my antenna), Heil PR-781 mic,bencher low pass filter,toroid core in the mic both ends, balun choke homemade close to the antenna using the same RG-213 feed line I have running for my station.

So, this is the story... I find out some information for ham to have problems but vice verse of my problem, when AM broadcast station is very near from HAM station and then signal go into our radios(yaesu,icom,etc). and making a rejection-filter you can fix the almost all signal from the broadcast to your HF radio. So I was think why not something similar in vice verse way as my case. Really, I don't know how many people have this same problem as TVI,etc but when you don't know what you need to do, I think is better make the questions even is your question sound stupid or funny, but maybe from the all people 1 or 2 will know your problem and have the solution. Smiley

So, I hope someone who read my lines can help me to fix this problem. I will very appreciate all your opinions,solutions..I'm not expert in electronic area but no afraid to try it. I have my small multimeter and iron solder Smiley so small things its no problem for me also my father know so much about electronic as fixing TV,VCR,stereos radios,etc.

Well, so again I hope receive your help.. THANK YOU SO MUCH FOR READ ME. 73s

Billy KC2SKM
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AA4PB
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Posts: 12841




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« Reply #1 on: November 15, 2012, 03:15:02 PM »

We need more information in order make a recommendation. What type of antenna does the AM receiver have? Is the receiver an AM broadcast band receiver or is it some other band, using the AM mode? How far away is the AM receiver antenna from your ham antenna? What bands are you transmitting on when you cause the interferrence?

Probably your transmitter is not transmitting any signals in the AM broadcast band. It is probably RF overload of the AM receiver or being picked up by the power lead or interconnecting audio cables. The solution in that case will always be filtering at the AM receiver rather than anything you can do at the transmitter, other that reducing power or separating the antennas.
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KC2SKM
Member

Posts: 7




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« Reply #2 on: November 16, 2012, 09:10:35 PM »

Hello! Thank you for read my lines

Ok, here is the answers...
What type of antenna does the AM receiver have?
  No,antenna on the domestic AM/FM radio I install one wire directly as antenna taking 1 pin of the main dial inside (no sure how say that in english sorry) and add a toroid in the wire but the funny thing was the station I listening was cover up for another station come more stronger Smiley when I add the wire as antenna for AM and then of course! when transmit the RFI still.

Is the receiver an AM broadcast band receiver or is it some other band, using the AM mode?
  Is a regular radio you can bay and any electronic store have AM,FW with digital display,CD player and cassette.

How far away is the AM receiver antenna from your ham antenna?
  Well, no sure how far because the antenna I have is on the top of the roof in 3 floor building and the receiver can be in the 1th floor and the RFI still there, so maybe 33 ft between AM receiver and my antenna.

 What bands are you transmitting on when you cause the interferrence?
In all of them 10,12,15,17,20 but more stronger when I use 12 and 15M. (I dont have 80,160m)

I forget tell about, I add toroid in the speaker wires, also un the power cord in both ends even I grounding the speakers and the transformer but the RFI still there. Just one thing I discovering when I use my short wave sony radio the RFI still on but...if I use batteries the RFI gone. So, why the toroid in the power cord not help? also I was thinking... whats exactly is causing this RFI? my antenna? bad domestic recever manufacture? because even if I fix the problem with 1 radio maybe more people around me have the same problem and will be very hard fixing all++ radios Smiley jejeje

Well, its all...I wait your help. Thank you! for your time.

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K1ZJH
Member

Posts: 978




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« Reply #3 on: November 16, 2012, 09:26:39 PM »

When I was a kid, my 25 watt AM 2-Meter transmitter would get into the neighbors' AM radios. It was the result of the radios being in close proximity to my 2 meter beams... maybe 75 feet at most. AM radios have a diode detector to demodulate the audio information. If your transmitter RF level is strong enough, the radio will act like an amplified crystal receiver and your audio will be heard on its speaker.

Pete
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WX7G
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Posts: 6043




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« Reply #4 on: November 20, 2012, 07:20:23 PM »

The easy fix is to use a different AM radio.
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AA4HA
Member

Posts: 1434




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« Reply #5 on: November 23, 2012, 06:28:35 PM »

 Grin That was how I learned morse code, listening to my father transmit da dit da dit  da da dit da, da dit da dit  da da dit da... It came through the AM radio, the television, the cassette deck. I think it came through my fillings in my sleep. Being anywhere near an SB-200 doing code all night long was a sure-fire way to be forced to learn morse.

You just may not be able to eliminate the interference. Your station can be in compliance, the AM radio can be in compliance, if things are too close then you are going to hear it.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
K1CJS
Member

Posts: 6034




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« Reply #6 on: November 24, 2012, 07:36:20 AM »

The simple answer is that the AM receiver that you're hearing yourself over has a front end that is way too loose--that is it lets in and does not filter out the off frequency strong local signals that are present.

The only fix is to get a different AM radio just as WX7G suggested.
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KC2SKM
Member

Posts: 7




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« Reply #7 on: November 26, 2012, 04:01:05 PM »

Hello! everyone

Ok, I understand is no easy and also about my antenna and domestic radio AM are to close but I trying to eliminate, the sugges for use different radio I tested already with 3 differents radios 1) SONY stereo 12 bands FM/SW/MW/LW, 2) PIONER audio/video receiver, and 3) the device I start with the problem.(neighbor radio).

With sony potable radio the RFI voice is a bit low, if I use batteries RFI almost gone but still there in the background just need pay attention carefully, using toroidal FT-240-77 with 27 turns in the thin adapter cord the RFI come down almos disappear just you can hear if move dial to frequency where thera are no station or holding cw key you could hear noise like when power supply need filtering to move the noise they make.
Over the Pioner receiver the RFI is similar as the Sony using toroidal, no testing add toroidal in the power cord yet because the pioner is not the device I need fix the problem is the AM radio of my neighbor. Smiley hi hi

Also experimenting already using toroidal in the transformer wires 1 test in DC wires 2th over the AC wires in both cases the RFI no disappear just come down but no gone; better results attach the toroidal in the wires the transformer give power to the device but no eliminate, another test... removing the transformer of factory and use my AC/DC adapter to turn one the AM radio using toroidal and RFI still there but more low but no eliminate the RFI.

So, as all of you see I pased my free time weekend trying as test-error to find out the cure to my problem Smiley but still no lucky Sad at all. I did severals modifications to the AM radio but I need more informations and experince about electronic and electricity area; my father help me a lot but also he dont know all to solve this hadche hi hi!

If someone have more ideas are very welcome Smiley also need asking about who know about MFJ-1164B? will be higher % to fix this problem? anyone can speak about it....

Thank you! to all of you guys to try help me. I appreciate so much your support.

73s and I hope all had a great thanksgiving day.
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