I'm an isp and run high speed wireless networks....
Out of my 25ish tower sites I have a couple that are a LOT of trouble.
Can't find any other cause so I'm hoping that it's just a simple harmonic or
induction on the cat5 cables.
----- Original Message -----
From: "K8RI" <K8RI-on-TowerTalk@tm.net>
To: "Marlon K. Schafer" <firstname.lastname@example.org>; <TOWERTALK@contesting.com>
Sent: Thursday, March 08, 2007 9:37 PM
Subject: Re: [TowerTalk] ferrite beads was...Re: [RFI] HIGH POWER and RFI...
> When you say Ethernet do you mean the real Ethernet coax or CAT5e?
> I've forgotten the coax impedance. Is it 50 or 75 ohms?
> I have several hundred feet of CAT5e and I think I have a 100 or so of the
> 50 ohm coax. I have about a 1000 feet of the 75 ohm.
> ----- Original Message -----
> From: "Marlon K. Schafer" <email@example.com>
> To: <firstname.lastname@example.org>
> Sent: Tuesday, March 06, 2007 11:49 PM
> Subject: [TowerTalk] ferrite beads was...Re: [RFI] HIGH POWER and RFI...
>> Speaking of ferrite beads. I need some for ethernet cable and haven't
>> able to locate a source.
>> Anyone have a good suggestion?
>> ----- Original Message -----
>> From: "Jim Lux" <email@example.com>
>> To: "Jim Brown" <firstname.lastname@example.org>; <email@example.com>
>> Sent: Tuesday, March 06, 2007 9:33 AM
>> Subject: Re: [TowerTalk] [RFI] HIGH POWER and RFI...
>>> At 07:32 AM 3/6/2007, Jim Brown wrote:
>>>>On Tue, 6 Mar 2007 09:06:45 -0500, Dan Zimmerman N3OX wrote:
>>>> >measures, inaccurately, on my MFJ-259
>>>>Ferrite chokes are essentially very low Q parallel resonant
>>>>circuits. Antenna analyzers are not very useful for measuring
>>>>ferrite chokes, for at least two reasons. First, they have a
>>>>fairly low input Z (typically 10K resistance in parallel with 12
>>>>pF. The capacitance is the major problem -- it combines with the
>>>>R, L, and C of the choke to move the choke's resonance down in
>>>>frequency to a new false resonant point, and above that false
>>>>resonance gives an impedance that is falsely quite low.
>>> Could one estimate that parasitic C by sweeping the analyzer and
>>> looking for the resonance?
>>> And, if you can assure yourself that the resonance is "far" away from
>>> the frequency of interest, one can ignore the C.
>>> Since there's really a limited number of possible mixes in use, it
>>> might be useful to come up with some sort of "diagnostic method" to
>>> identify the material using simple ham tools (like the MFJ
>>> box). Once you know the mix, and the mechanical dimensions, then you
>>> can go to the mfr charts and find the "real numbers"...
>>> At a first glance, I would think you could just try and identify the
>>> mu of the mix. Pick a low frequency to test at (so the parasitic C
>>> doesn't bite you) and measure L and work backwards from that?
>>> I'm sort of lazy and don't want to page through the FairRite catalog,
>>> and K9YC probably knows these things off the top of his head, but are
>>> all the "usual" mixes for this application sufficiently different in
>>> mu that you could use that as a sole distinguishing
>>> characteristic? Or, are there mixes with the same mu, but different
>>> loss properties?
>>> Jim, W6RMK
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