which coax to use??

[bluestallion]

Going to setup a base. Going to put up my yeasu 2500 and my Ranger radio with my 225 amp. Heres my question, i have 100ft of both rg8 and rg213. Which should i use for which? I do have a few repeaters around my area, but was told the loss is greater if using the rg8 with the vhf rig. Which should i use?? Please give your input. Thanks

 

[Keith_W7KEW]

It depends on the frequency you use the coax on. RG-8 is fine for HF 1-54 MHz, but once you get above that then the loss is higher. At 100 MHz RG-8 loses about 4.8dB. RG-213 has a huge loss of 7.2 dB at 400 MHz & above at 100 feet. If you are using these stations for monitoring only then RG-6 at 75 ohms is just fine since it has a loss of 5.9 dB at 1 GHz per 100 feet of coax. For transmitting on 100 MHz and above you might want to invest in LMR 600 or LMR1200.
See the ARRL Antenna book transmission Lines section 24-18.

 

[bluestallion]

I will be transmitting on both.

 

[LtDoc]

With your choices, i would use the RG-213. If the $train isn't that great, something like LMR-400 would be just dandy on VHF and UHF. Of course, the LMR-600 would be better, if you can $tand the $train...
- 'Doc

 

[Token]

Going to setup a base. Going to put up my yeasu 2500 and my Ranger radio with my 225 amp. Heres my question, i have 100ft of both rg8 and rg213. Which should i use for which? I do have a few repeaters around my area, but was told the loss is greater if using the rg8 with the vhf rig. Which should i use?? Please give your input. Thanks

Actually, you have not given enough information to really know what would be the best for your application, but I would use the newer cable for the higher frequency application. People often badly underestimate the affects of age on coax performance. If both cables are new I would use the better brand name for the higher frequency application. Example, if the RG-213 is a brand name like Belden and the RG-8 is a Chinese knock-off run the Belden at the higher freqs despite the fact that Belden lists the RG-213 as higher loss at higher freqs than some RG-8.

With that said all RG-8 is not created equal. There are many “RG-8” coaxes but the company and any additional letters/numbers are needed to know for sure what the loss curves might be _for new cable_ (as I said, old cable is unpredictable). The most glaring example would be RG-8X vs RG-8/U, they are very different cables but sometimes both are listed by users as “RG-8”. The 8/U is generally far superior but much more stiff and inflexible. Even within one manufacturer “RG-8/U” can have many, many values, for example Belden Cable list about 10 variants of “RG-8/U”, each with different losses and features. Belden 8237 is listed as “RG-8/U type” and displays 4.2 dB/100 foot at 400 MHz, while Belden 9913 is also listed as “RG-8/U type” and is 2.6 dB/100 foot at 400 MHz. Yes, Belden prints “8237” and “9913” on the cables, but they also can print “RG-8/U” on the same cable and it definitely is on the shipping labels.

By the same token Belden makes RG-213, and their designator is 8267, with 4.1 dB/100 foot at 400 MHz.

A couple people have mentioned “LMR-400” in this thread. While LMR-400 from a solid company is slightly better than the best RG-8/U type cable not all LMR-400 is the same. Cheap LMR-400 can have twice the loss (+3 dB) of a brand name like Times Microwave and be worse than any brand name RG-8/U or even, sometimes, RG-8X. Brand name LMR-400 is worth buying, if you are going for new cable, but you said you wanted to use the cable on hand.

The upshot of the whole deal is it probably does not matter what cable (of the two you listed as on-hand) you use on what radio, I am assuming the Ranger is 6 meters or down (probably 10/12 meters) and the Yaesu FT-2500 is 2 meters. Assuming your RG-8 is actually RG-8/U and not RG-8X, and that your RG-8/U and RG-213 are made by similar quality vendors, the loss delta between the two from 150 MHz down will probably be less than 1 dB in a 100 foot run. 1 dB is essentially nothing (a small portion of a single S unit), unless you are doing weak signal work, and since the FT-2500 is FM only I rather doubt that counts as weak signal.

No need to overthink it, just install the newer one on the VHF rig and be done with it.

T!

 

[Token]

It depends on the frequency you use the coax on. RG-8 is fine for HF 1-54 MHz, but once you get above that then the loss is higher. At 100 MHz RG-8 loses about 4.8dB. RG-213 has a huge loss of 7.2 dB at 400 MHz & above at 100 feet. If you are using these stations for monitoring only then RG-6 at 75 ohms is just fine since it has a loss of 5.9 dB at 1 GHz per 100 feet of coax. For transmitting on 100 MHz and above you might want to invest in LMR 600 or LMR1200.
See the ARRL Antenna book transmission Lines section 24-18.

Keith, what source did you use for these numbers? RG-8 should not be anything near 4.8 dB/100 foot at 100 MHz, even RG-8X should not be that bad, that loss is more in line with 1 GHz usage for a brand name RG-8/U with #10 AWG center conductor like Belden 7810A or TMS. Brand name RG-8/U should average more along the lines of 1.6 dB/100 foot or less at 100 MHz. Brand name RG-213 should not pull 7.2 dB/100 foot at 400 MHz, in fact it should not exhibit that kind of loss until up around 800 MHz or higher. At 400 MHz I would expect more like 3.8 – 4.3 dB/100 foot for a brand name RG-213 like Belden 8267.

Also, not sure why you are specifying LMR-600 or LMR-1200 for transmitting applications on 100 MHz and above. RG-8/U and RG-213 should be good for over 750 Watts in a 100 foot run at 150 MHz. It is going to be a very small percentage of the users out there who are in that power range. RG-8/U, RG-213, RG-214, 9913, and LMR-400 are more than enough for any but the more hard core stations on 2 meters and down at these run lengths (100 feet and less). Most users are going to notice a loss in receive signal caused by attenuation in the coax long before they run into a transmit power limitation. And the OP listed equipment that should be maybe 225 Watts (PEP) on 10 meters and 50 Watts average (FM) on 2 meters.

T!

 

[bluestallion]

I checked the coax. Its is RG8X coax. would these be fine to run my ranger and 225 amp? Thanks

 

[Keith_W7KEW]

Does the cable say who manufactured it? At 100 feet 8X has a dB loss of 7.2 to 14.0 at 1 GHz depending on the manufacturer.

 

[bluestallion]

no it doesnt say. Would using this cable for the 27mhz (CB) band be ok? The ranger i have is for 11meters, and might use the amp with it.

 

[Keith_W7KEW]

8X is great for 1-200 MHz. The losses are very high at 1 GHz

 

[bluestallion]

so itd be perfectly fine to use this coax for that approx 225 watts pep on 27mhz?? Thanks

 

[Keith_W7KEW]

Yes, 8X will handle that easily.

 

[Token]

I checked the coax. Its is RG8X coax. would these be fine to run my ranger and 225 amp? Thanks

RG-8X is significantly different from RG-8/U, which is why I said in my earlier post that some users list them both as "RG-8" but it is important to know the difference. Without a doubt, if you are not buying new coax and want to use the coax on-hand, use the RG-213 for the Yaesu and the RG-8X for the Ranger.

The 8X is not optimal for the application you have in mind, it is generally meant for shorter runs than 100 feet, but it will work for you and it will handle the power levels you have mentioned. I would not push it much harder at this kind of length though.

T!

 

[LtDoc]

There are several things you have to 'blend' to wind up with the 'best' performance. Those things include what you happen to have on hand, the length of the feed line run, and the frequency(s) of use. All of them are important to some extent. The differences can be fairly drastic, but most of the time there won't be enough differences to hear. I wouldn't waste a lot of worry on it. Some worry, naturally, but don't waste all of it, you might need to worry about something else.
- 'Doc

 

[bluestallion]

would there be much difference if i went to RG8U coax instead? Cuz i will be putting up a scanner antenna as well and could use the rg8x on it

 

[Token]

would there be much difference if i went to RG8U coax instead? Cuz i will be putting up a scanner antenna as well and could use the rg8x on it

You would be better off using the RG-8X for the Ranger and getting -8U for the scanner when you get to that point (better yet ditch the -8X and run all -8U or better). The higher freqs of the scanner would have more of a problem with the -8X than the Ranger will. Seriously, the distance is on the edge of how long I would run 8X for any application, but you should be OK. Personaly I would try it, and if you end up having issues that point to the coax then replace it, but I bet it will work for you on the Ranger.

T!