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Re: [RFI] Update on the Boston area RFI

To: Alan Robinson <robinsah@engr.orst.edu>
Subject: Re: [RFI] Update on the Boston area RFI
From: Ash Thornton <thorntonash@comcast.net>
Date: Sat, 13 Feb 2010 16:59:42 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Thank you Alan. Now that you mention it, it was the LP.

I have ordered the 440Mhz 7 element array that others have suggested  
works well for them. They have all the Radar Engineering gear so  
hopefully I can get this narrowed down with the 7 element.

Thanks again,


On Feb 13, 2010, at 3:53 PM, Alan Robinson wrote:

> A couple of thoughts............
> The fact that the noise (RFI) goes away after a storm would  
> indicate an outside source on the power line. It also means that  
> the source is not inside an arrester. So using an ultrasonic  
> locator, like the Radar Engineers Model 250, should be helpful in  
> locating the source(s) after the pole is identified.
> You didn't say what kind of yagi antenna they were using with the  
> Radar Engineers RFI locator. So I will assume that it is actually  
> the log periodic that comes with the Model 240 RFI Locator. This  
> beam is essentially a two element beam with a wide frequency  
> response. I would suggest using a multi-element yagi, such as the  
> Cushcraft A4496S, a 6 element yagi for 440 to 450 MHz. It is much  
> more directional and with higher gain. I sometimes use an 8 element  
> 685 MHz yagi. This antenna is like a "flashlight" for RFI.The Model  
> 240 does have an RF antenuator. So strong signals can be located.
> In my experience, if you get a good DF signal at 685 MHz, you found  
> the pole with the offending hardware. Then use the 250 Ultrasonic  
> to pin point the part that needs replacing.
> In one recent case I worked on the offending hardware turned out to  
> be one of the new solid state lightning arresters. Naturally I  
> couldn't get an audio signal from it. But I did have a very strong  
> DF signal at 685 MHz. Then the local utility used a Model 247-B  
> Hotstick Line Sniffer and found the part immediately. The arrester  
> was replaced and that pole has been quiet ever since. It had been  
> producing S9+ interference for more than a mile.
> Good luck with you RFI locating.
> 73,
> Alan
> ----- Original Message -----
> From: Ash Thornton
> To: RFI List
> Sent: Saturday, February 13, 2010 10:08 AM
> Subject: [RFI] Update on the Boston area RFI
> Some of you had requested I follow up on my findings here in the
> Boston area.
> And, thank you to all for the tips and suggestions.
> NStar did come out last week with their Radar Engineering VHF/UHF
> gear with a yagi for pinpointing the noise. The noise was so high
> along the power lines they could not pinpoint a specific pole or spot
> unfortunately. Not sure just what this means. So, their next step is
> to upgrade the grounds they found that were below spec.
> Interestingly, just after they were out we had a light, wet snow and
> the noise quickly all but disappeared for about 15 hours and then
> quickly rose back to previous level. This has happened each time we
> have had a storm. This last snow was so light  and the noise
> disappeared with the first few flakes it is hard to believe that
> helped, but there was a big rise in the humidity? I would assume this
> indicates an out door fault, given the correlation with snow?
> There was a very low level of noise coming from the same area, but
> did not have a chance to get back to check it with the 440 Mhz RCVR,
> but will be ready next time.
> Stay tunedand thanks,
> W1FQ
> PS
> Was thinking about calling our volunteer fire Dept to hose the poles
> down given we don't use hammers, but.......Just kidding
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