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Author Topic: Noise reduction- HELP  (Read 6083 times)
KB8ZF
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Posts: 25




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« on: March 03, 2012, 06:09:54 PM »

After being off the air for several years (10) I have managed to get some equipment back. We live on the second floor of an apartment complex and I am going to put up a stealth antenna of some sort on the balcony. However I have been listening on an old Icom 730 transceiver with just a make shift antenna. I have purchased a Yaesu FT-1000mp Mark V Field for the main rig along with a Palstar tuner, but when I listen on the 730 (haven't had a chance to hook up the Yaesu yet) I am getting all kinds of noise here sometimes worse than others. Just wondering if I can do anything to eliminate some of this interference or am I just stuck with it. Really frustrating, but hopefully somehow I can reduce it to a lower level. Hopefully some of you have some suggestions. Been a ham since 1977 and have an advanced class and just hate to see it go to waste! Thanks in advance.
« Last Edit: May 06, 2012, 06:41:42 PM by KB8ZF » Logged
ONAIR
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Posts: 1735




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« Reply #1 on: March 03, 2012, 08:59:52 PM »

After being off the air for several years (7) I have managed to get some equipment back. We live on the second floor of an apartment complex and I am going to put up a stealth antenna of some sort on the balcony. However I have been listening on an old Icom 730 transceiver with just a make shift antenna. I have purchased a Yaesu FT-1000mp Mark V Field for the main rig along with a Palstar tuner, but when I listen on the 730 (haven't had a chance to hook up the Yaesu yet) I am getting all kinds of noise here sometimes worse than others. Just wondering if I can do anything to eliminate some of this interference or am I just stuck with it. Really frustrating, but hopefully somehow I can reduce it to a lower level. Hopefully some of you have some suggestions. Been a ham since 1977 and have an advanced class and just hate to see it go to waste! Thanks in advance.
  Depends on the type of noise and its point(s) of origin.  Before you become too worried, get your antenna set up outside on the balcony, and see if the noise level changes.
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WX7G
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« Reply #2 on: March 04, 2012, 05:00:18 PM »

One thing to do is to run a balanced antenna that has the coaxial feedline decoupled from the rig via a current balun (choke).

Using your make shift antenna the other half of the antenna is the apartment AC ground (unless you are running the radio on batteries) and it is not 'grounded' to the apartment AC wiring. The apartment AC wiring can be "hot" with RF noise from the hundreds of wall warts and other devices connected.

What balanced apartment antennas can you use? An MJF-933 loop tuner will do it. Likewise with a Buddipole or a full size dipole inside the apartment. Each of these needs a 1:1 current balun installed in the feedline between the tuner, or antenna, and the rig.
« Last Edit: March 26, 2012, 06:41:15 AM by WX7G » Logged
KB8ZF
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Posts: 25




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« Reply #3 on: March 04, 2012, 06:05:03 PM »

WX7G what kind of currrent balun do you recommend? I am going to a hamfest here this coming weekend maybe I can pick one up. Thanks
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W6RMK
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« Reply #4 on: March 04, 2012, 09:04:11 PM »

Get yourself some 2.4" toroids with #31 mix and use those to make a choke for your feedline.  5 or 6 turns of the coax works just fine.
(Fairrite 2631803802)
Works better than almost anything else: a heck of a lot better than any of the air core coil o'coax things, and generally better than the W2DU string o'beads (just because you get almost N^2 the effect from N turns through a core).

31 mix is relatively new (10-15 years?) and is almost ideal for HF chokes.

Check out K9YC's writeup on RFI and chokes: http://www.audiosystemsgroup.com/RFI-Ham.pdf

Test data for all kinds of different baluns and chokes. Part numbers to order from FairRite or stocking distributors like Arrow, Mouser, Newark.  I wouldn't get them from Amidon.. they tend to be higher priced than the big mailorder places.

Mouser part #623-2631803802 $7/each in qty 1..  They're NOT in the catalog page, but they are online.

There are other sizes that are smaller, and snap on varieties, etc. 
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WX7G
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« Reply #5 on: March 05, 2012, 06:16:41 AM »

WX7G what kind of currrent balun do you recommend? I am going to a hamfest here this coming weekend maybe I can pick one up. Thanks

I recommend a current balun having an impedance of 1000 ohms or more at the lowest frequency you will use. But, amateur baluns are not specfied this way. So what do we do? I'd just order one and try it out. Or build the balun recommended by W6RMK.

The balun I would not use is the 'ugly' balun that is coax wrapped on a PVC form. This makes a high-Q choke while what we want is a low-Q choke. Ferrite is lossy and the choking impedance is R and X.
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KB8ZF
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« Reply #6 on: March 09, 2012, 06:18:16 PM »

Well I have found part of my noise problem, seems like the plasma tv's are causing some of my noise but when I turned on my wife's desktop pc it gets really bad. Seems like it is generating a lot of noise, it is located in the same room of the shack. I just went a bought her a new laptop (trying to get her out of the ham shack) Cheesy LOL. Has anyone else had to deal with this kind of noise and if so, what did you do to reduce it or help it at any level. I can also operate late at night or early in the mornings when noise is at a lower level. Thanks in advance.
« Last Edit: April 08, 2012, 05:33:25 AM by KB8ZF » Logged
WB0UQD
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Posts: 44




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« Reply #7 on: March 25, 2012, 06:27:55 PM »

That is such a good idea WX7G.  I am in a condo and had a HUGE problem with RF getting into the wiring, then entering my power supply and giving me a good shock.  Using the battery like you said completely eliminates the AC feedback loop. I am going to try this!!!
Thanks!!!
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NU9J
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Posts: 109




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« Reply #8 on: April 09, 2012, 08:31:54 AM »

Well I have found part of my noise problem, seems like the plasma tv's are causing some of my noise but when I turned on my wife's desktop pc it gets really bad. Seems like it is generating a lot of noise, it is located in the same room of the shack. I just went a bought her a new laptop (trying to get her out of the ham shack) Cheesy LOL. Has anyone else had to deal with this kind of noise and if so, what did you do to reduce it or help it at any level. I can also operate late at night or early in the mornings when noise is at a lower level. Thanks in advance.

Yes. HDMI/DVI monitors cause lots of noise. You will probably notice that the cable has ferrite chokes at both the monitor and computer end (or should), but that tends to not be enough with so many bits flying through the wire. Choke the crap out of that wire, or it will continue to act like an antenna. Also, the monitors themselves tend to be made like crap, so noise still leaks out of the monitor itself sometimes.
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~Philip
K2ZS
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« Reply #9 on: May 06, 2012, 04:35:30 PM »

I also live in a 2nd floor apartment and was plagued with high noise levels on my indoor loop. What I found was that the new CFL light bulbs are a huge source of noise, is yours as high during the day as it is at night?

I wend back to incandescent bulbs inside my apartment and was able to reduce the noise level by about 2-3 s units. I can't control what my neighbors use and the complex has converted over to 100% CFL so I'm happy with my 3 s unit reduction...

Just a thought...
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Antenna restricted?
http://www.k2zs.com
K2ZS
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« Reply #10 on: May 06, 2012, 04:37:18 PM »

BTW... I found my closed loop antenna to be quieter than anything else I have tried so far
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Antenna restricted?
http://www.k2zs.com
KB8ZF
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« Reply #11 on: May 07, 2012, 03:26:51 PM »

BTW... I found my closed loop antenna to be quieter than anything else I have tried so far

Ok thanks for the suggestions, I will give it a try on the CFL bulbs, and also I plan on trying to get up a closed loop somehow on the balcony also, see my post in Antenna Restrictions on Bent Dipole or Loop.
Thanks
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