I have a repeater site at an FM tower site. For years it's been a
problematic location for us. Recently however, it's gotten quite a bit
After nearly two weeks of massive problems we finally were able to mostly
isolate our issue. It seems that the radio station's signal was overloading
my ethernet wires. I was able to pick up nearly 3 volts on the cat-5 cable,
even with nothing plugged into it!
Why it got so much worse all of the sudden I'll likely never know.
We were able to make the problem much smaller by installing ferrite beads on
the cat 5 runs. (I got them from Fair-Rite as I recall) We were also able
to make improvements by using a grounded and shielded cat 5 cable.
But just the beads themselves made a night and day difference up there.
I'm a believer now. I'll use them in all of my tower sites from here on
out. If nothing else they should help with lightning too.
The hardest thing for me was figuring out which ones to use. The size
effects the frequency I guess. There was also the one pass and wrap the
cable so that it makes multiple passes decision to make.
----- Original Message -----
From: "firstname.lastname@example.org" <email@example.com>
Sent: Sunday, February 15, 2009 10:54 PM
Subject: Re: [TowerTalk] To Choke or Not to Choke?
> I've been seeing all these articles about the Palomar, Hy-Gain, etc.
> baluns and ferrite cores are not good, like they advertise. So who is it
> that sells these special "Fair-Rite" cores?
> -----Original Message-----
>>From: Jim Brown <firstname.lastname@example.org>
>>Sent: Feb 15, 2009 8:14 PM
>>To: "email@example.com" <firstname.lastname@example.org>
>>Subject: Re: [TowerTalk] To Choke or Not to Choke?
>>On Sun, 15 Feb 2009 17:58:56 -0800 (PST), Edward Sylvester wrote:
>>>I have a LW/Inv L that I will feed thru an auto tuner at the base,
>>>with radials. Was wondering if I should bother with forming a
>>>coaxial choke (12-15 turns at 6" diameter) before it enters the
>>>shack 30 feet away.
>>I coil of coax with no ferrite is a waste of coax -- it will look
>>inductive, the rest of the line will look capacitive, and the result
>>will be lots of feedline current. You DO want a choke on the coax
>>side of the tuner, but it needs to be 7 turns through five Fair-Rite
>>#31 1.4-inch i.d. cores (commonly advertised as FT-240-31 by those
>>mark them up 4X their cost and resell them to hams). If you're
>>feeding with RG8, you will need to wind the choke before you put the
>>coax connector on -- you can fit 7 turns through those cores, but
>>only with no connector attached.
>>For a tutorial on all the technical background on this see
>>Jim Brown K9YC
>>TowerTalk mailing list
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