[RFI] Auto quieting
k8ri at rogerhalstead.com
Mon Oct 12 02:15:18 EDT 2015
Put one end of the heavy zip cord (the red and black stuff) in a vise
and the other in an electric drill motor. Pull the trigger and you have
instant twisted pair at ant twist you want. I've found it to generally
be cheaper than seperate wires if you don't purchase it at the audio stores.
I purchase CAT 5 and 6 in the 1000' boxes. I've never found one yet
that spooled out the way it should, at least to begin. It's tempting to
just pull, but that just causes a bunch of knots in the box. Any sharp
bends are likely to break those tiny, solid wires.. I typically have to
open the box and remove the first two inside layers. They are fine after
that. I cut the ends a bit long, comb them out in order, clamp them
with a pair of seizers as close to the jacket as possible (roll the
jacket back and forth and you can get right up to the jacket so the
connector will clamp on the jacket) with a length "slightly" greater
than the recommended 1/2 inch, cut them flush, push them into the
connector and clamp. Now that I have it down, I rarely get a bad one. (
I did waste a few connectors while learning). I do run them through one
of the relatively inexpensive testers though. The tester is food
insurance. I put snag proof boots over each connector. They are cheap,
and a half dozen colors is usually more than enough. You can use plain
connectors and colored tape, but the colored boots cost little if any extra.
BTW I'm not fond of the usual tiny, solid wires used in CAT-5 and 6
cables. OTOH the tiny stranded wires have not proven any better for me
and they take different connectors for the best results. NOTE: you can
not just run the wires straight through. Color for color they are pin
for pin, but there is a specific order. The 2 standard pin outs are
listed on the net!
Being able to "roll your own" can be really handy in today's ham shacks
with rigs, computers and the Internet tied together. The connectors and
boots are cheap. Call around, or stop at the work sites and ask if they
have a few pieces. There's lots of short pieces of CAT-5 and even CAT-6
for free. Be careful of purchasing the really cheap stuff on e-bay. On
much of it the jacket just falls apart after being out in the sun for
even a month or two. Many of the colors just fade to white in a short
time. Kinks are fatal for CAT-5.
On 10/10/2015 3:15 AM, Jim Brown wrote:
> On Fri,10/9/2015 10:31 PM, Roger (K8RI) wrote:
>> I fail to see where two runs of RG8 size cables in a car, large SUV,
>> or long cab pickup truck would be cost prohibitive.
> But it's wasted dollars. Most RF guys fail to realize the noise and RF
> rejection inherent in good twisted pair. For more than a century,
> telco went cross country on unshielded twisted pair running next to
> power lines. CAT5/6/7 is four high quality, 100 ohm twisted pairs,
> each with a different twist ratio to further minimize crosstalk
> between pairs.
> In a tutorial workshop I led for audio and video pros in 2005 in
> Chicago, I demonstrated a setup comparing microphones running on
> shielded twisted pair (the standard for audio) and on one pair of
> CAT5, with another pair of the CAT5 cable providing a ground for the
> microphone's shield. I excited that setup with a 5W 2M, 220MHZ, 440
> MHz talkie and and a TDMA cellphone on 900 MHz that is notorious for
> RFI. Both setups provided very good immunity, with slight RF
> sensitivity at some frequencies, and there was NO advantage to the
> shielded cable.
> By contrast, zip cord, even the "glorified" stuff sold by the
> audiophool companies, is TERRIBLE for RFI. I got more than a few
> sexual favors from sweet young things (this was a LONG time ago)
> curing RFI in downtown Chicago highrises replacing zip cord with
> twisted pair for speaker wiring.
> Tongue firmly in cheek, but not lying. :)
> 73, Jim K9YC
> RFI mailing list
> RFI at contesting.com
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