allen.edwards at oldpaloalto
Jul 3, 2008, 2:01 PM
Post #6 of 7
(397 views)
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Re: Long coax (was Re: Questions about Hauppauge...)
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Brian Wood wrote:
> On Thursday 03 July 2008 13:32:10 Alen Edwards wrote:
>
>> Peter VanDerWal wrote:
>>
>>>> Thanks. I'll probably give it a try. For right now at least the STB,
>>>> HD-PVR, and TV are all in the same general vicinity. I can probably
>>>> get away with 3 foot runs (maybe even less,
>>>>
>>> -snip-
>>> I may eventually
>>>
>>>
>>>> move the HD-PVR closer to the back-end. This would mean probably a
>>>> 25' run, but it sounds like even at that distance you are not having
>>>> any quality issues.
>>>>
>>> I used the RapidRun coax system. It's a bundled, 5 coax, cable with a
>>> single multipin connector on each end. Then you just buy appropriate
>>> wall plates (HDMI, Component + audio, Composite + S-Video, etc.)
>>> It's good quality stuff, easy to pull, and looks professional when you're
>>> finished. Plus it's reasonably priced.
>>>
>>> http://www.amazon.com/25ft-RapidRun-Video-Runner-Cable/dp/B000YTPA52/ref=
>>> sr_1_17?ie=UTF8&s=audio-video&qid=1215107352&sr=1-17
>>> http://www.amazon.com/Cables-Go-RapidRun-Component-Wallplate-White/dp/B00
>>> 0CPQ7YQ/ref=sr_1_2?ie=UTF8&s=electronics&qid=1215107462&sr=1-2
>>>
>> That is good looking cable and indeed reasonably priced.
>>
>> Just to throw another option into the mix, I use this stuff:
>> https://www.tselectronic.com/belden/9116.html
>> One thing to consider in long runs is the loss in the cable. An easy
>> way to evaluate that is that the fatter the cable, the lower the loss.
>> A bundle of these will be much fatter, and thus much less loss than any
>> multimedia cable. On the other hand, what you listed is probably good
>> enough and has some other stuff in the bundle that makes it attractive
>> for applications where it fits.
>>
>> It is hard to beat coax though. A 25 ft run of 3 coax cables would be
>> about $6. Of course, you have to buy 1000 feet to get that price. I
>> have a lot of cable left over but then again this is my second box.
>>
>> I have used it for antenna feeds, S-Video, Component, Composite, and
>> audio (preamp out with distribution amp).
>>
>
> Different types of coax are designed for different uses. For example, the
> Belden 9116 referred to above has a copper clad steel center conductor. This
> is designed for CATV applications where mechanical strength is required, as
> with aerial drops. Steel is not a great conductor, but at RF frequencies,
> where the "skin effect" is a major factor, this is not a big issue, but I
> would not use such cable for baseband video, where low frequency response is
> required.
>
> Obviously a steel center conductor has an impact on bend radius as well as
> strength.
>
> Some cable uses solid plastic dielectric, others use a foam type. Solid
> plastic has greater strength, but at the cost of higher loss at RF
> frequencies.
>
> Soft-drawn copper is a great conductor, but has low strength and can't
> tolerate a lot of flexing.
>
> Times Wire and Cable once made (and maybe still do) a special "head end" cable
> with a 60% silver/40% soft copper center conductor and a double copper braid.
> This stuff weighed about 5 times what normal CATV cable weighed but had great
> electrical properties (it was also very costly).
>
> Multiple shields are sometimes required for CATV in some environments.
> Aluminum shields are often used for CATV where low weight is a factor, as is
> low cost.
>
> Physical properties like bend radius, strength, weight, water resistance, UV
> resistance and others, as well as electrical properties like forward loss,
> maximum rated frequency, return loss, characteristic impedance and others all
> have to be considered in choosing the proper cable for a given application.
>
> Another very important factor, especially with RG-59/RG-6/RG-11 type cables
> that use crimp type connectors is that you must use the correct connector for
> the cable in use. There is no such thing as a "one size fits all" crimp
> connector, and a lot of problems happen because the wrong connector was used.
>
> There is a reason that hundreds of different types of coax cable and
> associated connectors are made, you have to choose the best one for a
> particular application. Just using what your local Radio Shack has in stock
> has led to a lot of problems :-)
>
> beww
>
>
Everything you say is correct.
I actually use 1189A cable but it is about the same (coper coated steel
core). I do use it for all these applications and it works fine. I
bought this many years ago.
Today I would probably buy this cable:
https://www.tselectronic.com/belden/7915a.html
And I would probably use these connectors:
https://www.tselectronic.com/thomandbetts/sns.html
and these adaptors
https://www.tselectronic.com/gc/video/video_adaptor.html
I stick to one connector type (type-F) because of the cost of the tool.
I use this tool:
https://www.tselectronic.com/paladin/901024.html
On the other hand, the wire I used has .04dB loss at DC and .05 loss at
10MHz for 25 feet so maybe it isn't so bad in that the DC loss is about
the same as the 10MHz loss.
The small stuff that is in those multimedia cables have .01dB of loss at
DC (25 feet) and .3dB at 10MHz. Maybe not as flat and definitely more
loss at higher frequencies.
Remember 720p BW is 37MHz.
For sure, this type of cable did a much better job with S-Video than the
typical S-Video cable you can buy. With a long run (about 30 feet) my
old projector would not sync with standard S-Video cable but did fine
with RG-6U.
It is a very important point that this type of wire is not flexible.
It is for a fixed application.
Thanks for the interesting discussion,
Allen
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