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  #21 (permalink)  
Old 05-05-2016, 5:45 PM
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What would be the alternative?
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  #22 (permalink)  
Old 05-05-2016, 6:16 PM
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I noticed from your photo that you have a wireless mouse/keyboard and are using wi fi for networking. You might try disabling those or going wired temporarily to see if the interference gets better. Also, the monitor itself could be causing you trouble. After your computer is up and running, try powering down the monitor and disconnecting the power cord to the monitor and the video cable from the computer. Test your scanner and connect your monitor back up in the reverse order. (To get your computer back up and running.) The video cables usually come with ferrites on them but they are minimal. You can continue to add them until additional ones no longer improve things.
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Old 05-07-2016, 2:58 AM
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Ferrite cores and isolator installed. One Union Pacific channel that comes in now, sometimes clearer than other times, but it does work, even with everything plugged in. Put a new system on the Uniden limited to local metro RR freqs only. The ground loop isolator started malfunctioning within hours (only provided left channel)--good thing it was cheap; a review online described the same thing. The ferrite cores do seem like they make a difference. 5 on aux 5 on usb. It worked well enough to hear clearly the details of a car stuck on the tracks thus a section of the railroad blocked off. Very exciting. Have seriously heard a lot of transmissions today. The next move might be to add a Traintenna Blade to the setup.

Last edited by briskattivo; 05-07-2016 at 3:10 AM..
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Old 05-10-2016, 2:04 AM
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After experimenting with this for a couple of weeks, I'm regressing in that I now believe the majority problem has to do with my attempt to listen to a wider distance with a simple VHF tuned duckie or an RH77CA more than it does my computer. I found a couple of streams of local radio bands I had been trying to listen to, including rail, and the amount transmissions I picked up on my radio compared to stream was minute. My scanner does, however, work great for police/fire/ems and other trunked systems, which is good because I love listening to those. I will invest into a more serious antenna in the future. And it wasn't all in vain as I got this sweet Lian Li 7B-Plus II case out of the experimenting. It was very interesting to try and troubleshoot, so thank you!

Last edited by briskattivo; 05-10-2016 at 2:18 AM..
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Old 05-17-2016, 8:29 PM
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Quote:
Originally Posted by briskattivo View Post
After experimenting with this for a couple of weeks, I'm regressing in that I now believe the majority problem has to do with my attempt to listen to a wider distance with a simple VHF tuned duckie or an RH77CA more than it does my computer. I found a couple of streams of local radio bands I had been trying to listen to, including rail, and the amount transmissions I picked up on my radio compared to stream was minute. My scanner does, however, work great for police/fire/ems and other trunked systems, which is good because I love listening to those. I will invest into a more serious antenna in the future. And it wasn't all in vain as I got this sweet Lian Li 7B-Plus II case out of the experimenting. It was very interesting to try and troubleshoot, so thank you!
Here is one more thing to try that may improve your situation. Make a simple BALANCED antenna to minimize conducted noise from the cabling and ineffective grounding from entering your antenna system. This is like the twin lead antenna provided with home stereo receivers, but will be electrically shortened and need to be matched to your 50 ohm receiver with a BALUN transformer like used on TV sets. It will also need to be installed vertically, and the feed line (also 300 ohm twinlead 4 to 6 feet) should be strung horizontally away from the dipole to minimize interaction and coupling.

For materials you can simply buy a commercial FM dipole and cut it length.

http://www.amazon.com/Parts-Express-...CVMHZ7QFXRV5B8

1. Make a 1/2 wave dipole antenna from 300 ohm twinlead.

The formula for a center fed one-half wavelength (in inches) is 5,616 divided by the frequency (in megahertz) x the velocity factor of the twin lead 0.82. so 5,616/160.8375 = 34.92 inches X 0.82 = 28.63 inches.

http://www.avsforum.com/forum/attach...3&d=1428579867

Start with the length of 35 inches center fed at 17.5 inches and once you have it installed (vertically) shorten the arms by up to 3 inches each to improve reception if necessary. Having an antenna analyzer would help. Personally, w/out the analyzer I would try it out "long" and see how it works out.

2) Connect to your receiver via a 300 ohm to 75 ohm BALUN transformer:

http://www.amazon.com/300-Ohm-UHF-Ma.../dp/B0002ZPIOG

3) And a BNC to F adapter of the appropriate sex for your cabling:

BNC F Adapters - Monoprice.com

Last edited by RFI-EMI-GUY; 05-17-2016 at 8:42 PM..
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  #26 (permalink)  
Old 06-08-2016, 9:08 PM
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Quote:
Originally Posted by RFI-EMI-GUY View Post
Here is one more thing to try that may improve your situation. Make a simple BALANCED antenna to minimize conducted noise from the cabling and ineffective grounding from entering your antenna system. This is like the twin lead antenna provided with home stereo receivers, but will be electrically shortened and need to be matched to your 50 ohm receiver with a BALUN transformer like used on TV sets. It will also need to be installed vertically, and the feed line (also 300 ohm twinlead 4 to 6 feet) should be strung horizontally away from the dipole to minimize interaction and coupling.

For materials you can simply buy a commercial FM dipole and cut it length.

http://www.amazon.com/Parts-Express-...CVMHZ7QFXRV5B8

1. Make a 1/2 wave dipole antenna from 300 ohm twinlead.

The formula for a center fed one-half wavelength (in inches) is 5,616 divided by the frequency (in megahertz) x the velocity factor of the twin lead 0.82. so 5,616/160.8375 = 34.92 inches X 0.82 = 28.63 inches.

http://www.avsforum.com/forum/attach...3&d=1428579867

Start with the length of 35 inches center fed at 17.5 inches and once you have it installed (vertically) shorten the arms by up to 3 inches each to improve reception if necessary. Having an antenna analyzer would help. Personally, w/out the analyzer I would try it out "long" and see how it works out.

2) Connect to your receiver via a 300 ohm to 75 ohm BALUN transformer:

http://www.amazon.com/300-Ohm-UHF-Ma.../dp/B0002ZPIOG

3) And a BNC to F adapter of the appropriate sex for your cabling:

BNC F Adapters - Monoprice.com
Hey RFI-EMI-GUY. I ordered the parts, I have had a chance to take a look at the FM dipole and the transformer. The adapter from Monoprice is on the way, went with BNC male to F connector male, two for measure. I have plenty of room for the dipole as is, so I'll test it that way first. Don't have an antenna analyzer, that would be nice. Just had a quick question. The dipole and the transformer both terminate at little U shaped hooks (like on an old TV or stereo). I was wondering what you would suggest for connecting them. I was thinking electrical tape. Thanks for your help.

P.S. I have become a bit more interested in air traffic control signals recently. What is this thing's wide-band capability?
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Old 06-08-2016, 9:47 PM
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The antenna as-is is cut for 88-108 MHz, probably optimized for about 98 MHz so you will need to cut to dimensions calculated for the rail-road band. As far as VHF air band, you could try it as is, but would be best cut to a frequency midway up the air band. These dipoles are cheap so you could make two and use a cheap TV coax switch.

To connect the transformer to the dipole, you could use small nuts and bolts, but be sure to keep them separated close to the the width of the 300 ohm twin lead. Another way are those barrier strips used for electrical connection that have screws already in place.

When you get it up, make sure the dipole is vertical and the twin lead feed line extends to the side at a right angle on the wall as much as possible so as not to influence the dipole.
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Old 06-09-2016, 4:05 PM
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Quote:
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The antenna as-is is cut for 88-108 MHz, probably optimized for about 98 MHz so you will need to cut to dimensions calculated for the rail-road band. As far as VHF air band, you could try it as is, but would be best cut to a frequency midway up the air band. These dipoles are cheap so you could make two and use a cheap TV coax switch.

To connect the transformer to the dipole, you could use small nuts and bolts, but be sure to keep them separated close to the the width of the 300 ohm twin lead. Another way are those barrier strips used for electrical connection that have screws already in place.

When you get it up, make sure the dipole is vertical and the twin lead feed line extends to the side at a right angle on the wall as much as possible so as not to influence the dipole.


Received all parts today. Assembled, and yeah! Airband is like the difference between night and day. That is as is. I'm talking constant stream of readable transmissions. RFI-EMI-GUY you are the best! I suppose I will order some more duplicate orders so I can experiment on railband and airband with measured dipoles. I'm serious though, this is really cool. For the record I ended up using a combination of motherboard landing nuts and bolts and electrical tape on the hook connectors. Seems to have worked. I'll reply with an update when I try a railband dipole. Feeling a bit cautious to try and cut down my only dipole down to a measured length for airband when it already seems to be working so well, so I'll wait until I get one more for that too.
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Old 06-09-2016, 10:24 PM
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Oh btw, misspoke the motherboard nuts and bolts were standoffs not landings.
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Old 06-09-2016, 10:49 PM
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Quote:
Originally Posted by briskattivo View Post
Received all parts today. Assembled, and yeah! Airband is like the difference between night and day. That is as is. I'm talking constant stream of readable transmissions. RFI-EMI-GUY you are the best! I suppose I will order some more duplicate orders so I can experiment on railband and airband with measured dipoles. I'm serious though, this is really cool. For the record I ended up using a combination of motherboard landing nuts and bolts and electrical tape on the hook connectors. Seems to have worked. I'll reply with an update when I try a railband dipole. Feeling a bit cautious to try and cut down my only dipole down to a measured length for airband when it already seems to be working so well, so I'll wait until I get one more for that too.
Glad that's working out. Let me know if the rail band cleans up!
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Old 06-10-2016, 1:17 AM
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Glad that's working out. Let me know if the rail band cleans up!

Well, I got antsy and decided to cut the dipole for the airband I meant to cut to 19 for each arm to reflect the formula for 122.5 MHz. I guess it ended up being more of a 17.5 inches than the 19. I might try another uncut version for the airband again becaues I honestly can't tell if this is much different. Interesting note though, I guess that did end up being the measurements for the railband dipole you described. I tuned into the railband and believe it or not, (well maybe it's easy to believe) it worked! I can hear several railroad channels. Unfortunately the railroad band around here spawns some pretty crude/rude humor and most of the time I can only hear one end of the conversation so it was sort of anticlimactic. Good to be able to listen though. Might try the airband dipole trimmed again. It is worth the wait. Will provide more updates as this occurs. I hope that's allowed. Thanks.

Last edited by briskattivo; 06-10-2016 at 1:29 AM..
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Old 06-10-2016, 1:58 PM
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Wait, a minute. That's wrong, isn't it? Should be about 14 inches for the railband. And this near 17.5 is just short for the airband, hence why it seems to be working. Okay. Very clear air traffic contro.l this morning. Sorry, I'm not very good at math/numbers, more experimentation to come though.

Last edited by briskattivo; 06-10-2016 at 2:05 PM..
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Old 06-10-2016, 2:11 PM
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I am not sure the bandwidth of these antennas, +/- 10% probably on the safe side. If you had an antenna analyzer you could dial it in. Otherwise cut and try. You might, for the sake of experimentation, leave it long and cut out a window every 1/2 inch or so and solder a shorting bar and try it that way. Heck, you could make it long, put some slide switches at 1 inch intervals and tune it that way.
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Old 06-10-2016, 2:51 PM
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Yes, there certainly are a lot of ways to experiment with this. I noticed differences even based on where I put it on the wall. Btw, thumbtacks are pretty useful for this experiment. Goes right through the plastic ribbon and easy to remove. I've destroyed pretty much everything I've tried to solder before. These are new times though, so maybe I could do it using video instruction.

I was reading a little bit about folding dipole arms in a loop, and that actually there are antenna manufactured this way like a oval. I'm not sure I totally understand it though or if it would benefit me. One trouble is, I cannot know if I need to make adjustments because I'm not sure if I can improve the signal more than I have, particularly airband which again is really great (hearing everything). The police band is actually pretty clear too, although that has worked with pretty much every antenna I have used. I would like to get a few more of these to experiment with. Airband, police, and railband are all fun and games but like I said, numbers, not good at them, and despite them being a different type I have no idea what the numbers on these bands mean half of the time.
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Old 06-10-2016, 10:00 PM
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19" is right for 2M ham. Railroad will be a little under 18" - 17.5" sounds about right.
Airband will be around 19" or maybe a little more depending on the part of the band you want to target.
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Old 06-10-2016, 10:10 PM
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19" is right for 2M ham. Railroad will be a little under 18" - 17.5" sounds about right.
Airband will be around 19" or maybe a little more depending on the part of the band you want to target.

Hmm, well due to my sloppy measuring the top arm is about 19" and bottom arm is about 18". Now what? That ATC is very good, it does sound a bit weird though at times, there is better reception but I feel like the audio quality was better when I left it long. jOverall it is better though. I guess I'll have to be a bit more precise next time and compare.
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Old 06-10-2016, 10:32 PM
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You should be fine. Some antenna designs actually mismatch the elements slightly to get more bandwidth.
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Old 06-10-2016, 10:44 PM
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You should be fine. Some antenna designs actually mismatch the elements slightly to get more bandwidth.
Brilliant! So glad I stuck with this thread. It's been very fruitful.
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Old 06-11-2016, 12:28 AM
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It seems that you have tried about everything while also keeping your good video card.
One thing I may have missed seeing in your posts is the video cable itself.
Have you tried a better quality video cable?
Or simply switching from DVI to VGA or the reverse just as a test to rule out the video cable as a noise source?

I've had the same issues as you and if not from the video card itself, I've found both the type and quality of the video cable to be the source of noise.
As several have also mentioned, the power supply itself but it seems you have tested that very well using different supplies.
I once had a brand new Antec supply that killed DSL signals back in the DSL days. And yes, it also wiped out my HF monitoring as well as low band and a good chunk of VHF High band.

Finding and curing EMI/RFI noise sources can be a major challenge but also fun depending on how you look at it.
One other thing to look at is ground loops if not all equipment is not powered from the same source. Sometimes a decent isolation transformer can cure that but high current ones can get expensive.
I have several months of time devoted to finding and curing sources of noise getting into my radios. Way to much to list here but in the end, it worked and was well worth the huge amount of time, effort and money I invested in it all. I'm virtually noise free from DC to Daylight now!
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Old 06-11-2016, 1:42 AM
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Quote:
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It seems that you have tried about everything while also keeping your good video card.
One thing I may have missed seeing in your posts is the video cable itself.
Have you tried a better quality video cable?
Or simply switching from DVI to VGA or the reverse just as a test to rule out the video cable as a noise source?

I've had the same issues as you and if not from the video card itself, I've found both the type and quality of the video cable to be the source of noise.
As several have also mentioned, the power supply itself but it seems you have tested that very well using different supplies.
I once had a brand new Antec supply that killed DSL signals back in the DSL days. And yes, it also wiped out my HF monitoring as well as low band and a good chunk of VHF High band.

Finding and curing EMI/RFI noise sources can be a major challenge but also fun depending on how you look at it.
One other thing to look at is ground loops if not all equipment is not powered from the same source. Sometimes a decent isolation transformer can cure that but high current ones can get expensive.
I have several months of time devoted to finding and curing sources of noise getting into my radios. Way to much to list here but in the end, it worked and was well worth the huge amount of time, effort and money I invested in it all. I'm virtually noise free from DC to Daylight now!
Hi Kruser!

What you say is very true. Originally I had a lot of problems with the railband, still do unfortunately. I have tinkered with the video card throughout this process. That aspect has been confusing because I have not seen any consistent correlation from one day to the next, but have noticed it sometimes throughout the course of an hour. It's been a while and I foolishly have not documented everything I tried as I should have; I've been working on this for two months. Just checked back in with the railband, heard some transmissions after a few minutes but very staticy. I'm going to try a more precisely measured dipole and then I will try some more suggestions for the video card/cables. I have a VGA cable somewhere around here. I believe I tried that, but I could always doublecheck. Okay, and here we go ahead, clear transmissions. It's very confusing. I just adjusted the twin lead from the dipole for more horizontal configuration. Of course I never hear anything responding to these transmissions. I use the frequencies from the local railroadradio stream, sorta works, sorta doesn't.

I like what you said about how trying to narrow down causes of rfi can be fun. You are right! It is very interesting and educational. I just wish I'd had more success. I feel like I'm getting closer though. Thanks for the ideas! Were you also trying to improve railband monitoring or something else? Also what power supplies units or equipment would you recommend based on your findings?
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