75 ohm coax

[rcbenedict1545]

Careful, 75 ohms  was picked for cable TV receiving Coax because it was lower loss then 50 ohms but it could not handle high power as 50 ohms could.  50 ohms is a power, loss compromise. 35 ohms For high power high loss,  50 ohms compromise, 75 ohms low loss low power.
Ray
W8LYJ

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[Don Wilhelm]

The voltage allowable on 75 ohm 1/2 inch hardline far exceeds the
voltage allowable for RG-213.  No problem at the limit of 1500 watts for
the ham bands.

Even RG-6 will withstand 1500 watts with no problems.

73,
Don W3FPR

On 4/1/2020 4:38 PM, Gmail wrote:
> Careful, 75 ohms  was picked for cable TV receiving Coax because it was lower loss then 50 ohms but it could not handle high power as 50 ohms could.  50 ohms is a power, loss compromise. 35 ohms For high power high loss,  50 ohms compromise, 75 ohms low loss low power.
> Ray
> W8LYJ
>
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[Jim Brown-10]

On 4/1/2020 6:37 PM, Don Wilhelm wrote:
> Even RG-6 will withstand 1500 watts with no problems.

RG6 is a VERY generic description of coax, and there are probably 100
very different cables carrying that designation. We are most familiar
with those manufactured for the CATV industry, all optimized for low
weight, low cost, low loss at VHF/UHF, and very low power. But these
cables mostly have CCS center (copper coated steel), Al foil, Al braid
shields. This causes them to be rather lossy at low RF.

There ARE a few more far more robust RG6 cables designed for
transmitting and for analog video (remember that?). I have some --
double copper braid, solid copper center. What I have is labeled
Pasternak, but I've seen a very similar RG6 in the Belden catalog.

73, Jim K9YC
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[Don Sanders]

I have used TV RG6 for over 30 years. Usually 50 feet or less and it
handled the output of my SB200 amp well. In Ecuador that was the only coax
readily available and it worked well. I recently bought a roll of 250 feet
at Walmart for $30. Checked the loss of 100 feet and was about 1.5 dB at
145 MHz. Not as good as open wire feedline but for coax very workable.
Cannot beat the price.
I also have used the  "F" connectors up to about 600 watts with no problem
and now find BNC conn at Home Depot made for RG6 Coax. There is a lot of
discussion about using RG6, usually from those who have not used it but
have heard it is not good. It is definitely better than RG174 but heavier.
I have been fortunate to have found good RG6 but I always test it before
use. It works well in an ugly balun also at HF. I usually use the 25 foot
lengths found already made with connectors on each end. I have used two
runs in parallel, center conductors of course, to feed a doublet for
multiband HF. 50 feet lengths feed my 6 and 2 meter verticals.
Dr. Don W4BWS

God Bless All
Ham Radio does not make the world go round.
Ham Radio is what makes the ride worthwhile.


On Wed, Apr 1, 2020 at 9:38 PM Don Wilhelm <[hidden email]> wrote:

> The voltage allowable on 75 ohm 1/2 inch hardline far exceeds the
> voltage allowable for RG-213.  No problem at the limit of 1500 watts for
> the ham bands.
>
> Even RG-6 will withstand 1500 watts with no problems.
>
> 73,
> Don W3FPR
>
> On 4/1/2020 4:38 PM, Gmail wrote:
> > Careful, 75 ohms  was picked for cable TV receiving Coax because it was
> lower loss then 50 ohms but it could not handle high power as 50 ohms
> could.  50 ohms is a power, loss compromise. 35 ohms For high power high
> loss,  50 ohms compromise, 75 ohms low loss low power.
> > Ray
> > W8LYJ
> >
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> Please help support this email list: http://www.qsl.net/donate.html
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>

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