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" <ooe@odessaoffice.com>
To: <towertalk@contesting.com>
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
> been
> able to locate a source.
>
> Anyone have a good suggestion?
>
> thanks!
> marlon
>
> ----- Original Message -----
> From: "Jim Lux" <jimlux@earthlink.net>
> To: "Jim Brown" <jim@audiosystemsgroup.com>; <towertalk@contesting.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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