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Coax differences...

Sep 12th 2020, 16:45

KC8WZF

Joined: Jun 20th 2003, 10:56
Total Topics: 0
Total Posts: 0
We all know that there are differences in the different types and brands of coax and that some types are better for the different Ham radio bands. But what about those coax cables that are not listed as a type that is commonly used for other uses but not in Ham radio. For example- RG 223U is very close to RG 58U. But will RG 223U perform the same, better or worse than RG58U? I would be interested in opinions from the ARRL family on this topic. And not just with these two, but with other coax comparisons as well.

Thanks,
Dave
KC8WZF
Sep 13th 2020, 21:11

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Double shielded cable like RG-223/U is suggested for repeater duplexer cables, as a single shield is too leaky. The transmit signal will leak through the shields and degrade the simultaneous receive signal.

http://www.repeater-builder.com/antenna/w6nbc-duplexer-book/ch9.html

For normal amateur applications there is no benefit to a double shield.

Teflon cable like RG-400 or RG-142 are great for applications where you need to run a lot of power into a small cable and can handle a bit of loss. They won't melt as easily as RG-58. The loss is about the same, however. Tiny Teflon cables like RG-316 are similarly useful for pigtails, as they won't short out from soldering like RG-174.

The largest cable I use is LDF 4-50 half inch Heliax. I have a 90 ft run going to a coax switch. It has a corrugated copper shield that is more resistant to weather damage than braided cables. They make larger sizes but I've heard they are difficult to work with. Typically 1/2 inch Heliax has the highest resale value as there is little demand for the larger sizes despite their lower loss.

RG-62/U 93 ohm coax is often used for turnstile phasing harnesses.
I've used 35 ohm RG-83/U coax for quarter wave matching sections on 6M between 25 and 50 ohms.

UT-085 and UT-141 semi-rigid coax is useful for 10GHz microwave work. RG-213 doesn't work at 10GHz, as a waveguide mode will result in signal cancellation. RG-58 is rarely used at 10GHz due to its high loss

RG-6 is perhaps the cheapest coax around as it widely used for cable TV. It has a 75 ohm impedance that can be used to make quarter wave 50 to 112.5 ohm impedance transformers. If you use a multiple of a half wave the impedance at the input will be reflected to the output. It has an aluminum shield so I suggest using the proper crimp connectors and adapters. The RF Connection does have UHF crimps for RG-6.

Zak W1VT
ARRL Senior Lab Engineer
Sep 18th 2020, 17:31

KC8WZF

Joined: Jun 20th 2003, 10:56
Total Topics: 0
Total Posts: 0
Thank you. This is a terrific response to my question. Are there any other thoughts about this topic....

Standing by...
KC8WZF
Dave

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