Cable types and losses

[JohnE]

been meaning to put this out there for a while,since I have had a few conversations about this w/various members.
first pics,cables from L-R w/associated N male connectors.
RG8/213 LMR400 type, 1/2Inch superflex, 1/2inch hard line also known as Heliax, 7/8inch hard line.

 

 
[ MyGMRS STAFF EDIT:  3 Photos no longer available from linked source.]
 

 

now lets talk about the losses in Db and how much power that is.
Cable type                                  loss at 100Mc                          400Mc


RG8/213                                      2.0dB/100'                              4.7dB/100'
LMR400                                       1.2                                         2.5

Hardline type                                       150Mc                              450Mc

1/2" superflex                                    1.3dB/100'                         2.3dB/100'
LMR600                                             1.0                                   1.7
1/2" Heliax                                         0.85                                  1.5
7/8" Heliax                                         0.44                                  0.8
1-1/4" Heliax                                      0.3                                    0.6

dB loss            power loss in %
0.5                        10                        100W in 90W out
1.0                        20
1.5                        30
2.0                        37
2.5                        44
3.0                        50
3.5                        56
4.0                        60

all of the above loss specs are manufacture specs, I strongly suggest that you measure your line loss w/watt meter if possible to know exactly what you are getting at the antenna.
IME most of the book specs are on the money for hard line ,RG8/213 can be a crap shoot depending on manufacturer. I've had some really bad and some pretty good.
LMR I've had a love/hate relationship w/, good cable but seems to be prone to moisture issues. wish I had pic of the 7yr old cable that pretty much self destructed.
hope this is of some help to those looking to put up a machine or control station in the future.
JE

***EDIT***

found this very useful

http://www.arrg.us/pages/Loss-Calc.htm

Edited March 12, 2022 by JohnE

[JohnE]

Don't forget. Connectors. Boy do the losses add up with those.

in the grand scheme of things it's pretty negligible  N connectors are typically 0.15 loss @10Gc, now dumb that down to 400Mc and it's irrelevant.

[axorlov]

Well, yes. This is why I said at 450MHz. The 0.6dB at 100ft is nothing in my book, and in my playbook only. Your playbook may be different. All depends on use case.

[PastorGary]

JohnE has supplied photos of common connectors for member reference (added to post 1 above)..

 

The staff is opening up this thread for questions and replies for member convenience.

[gortex2]

Thanks guys thats a great topic. At the old shop i worked at we did a similar training day for our sales folks with the same setup. They didn't understand why it took us an entire day to run hard line vs 9913. After seeing the differences in cables they also understood why the cost was so much different.

[couger100101]

OK, so this is what I'm looking at for my setup. 75' TM rg8/213 mil spec. Browning 410-490Mhz uhf fiberglass land mobile omni base antenna, and for now mxt105. Plan on upgrading the radio later. Is it safe to say I should be fine? I'll be about 35' up. 

[couger100101]

Just scored the mother load in cable. Free! Belden 9913.

[PastorGary]

Please keep in mind that Belden 9913 has fairly high losses at GMRS frequencies. My old Belden chart from the early 1990's shows a 9913 loss of approximately 3.08 dbi for roughly 100 feet.  Compare that to Hardline LDF4-50A cable at approximately 1.465 dbi loss for 100 feet.
 

[couger100101]

Please keep in mind that Belden 9913 has fairly high losses at GMRS frequencies. My old Belden chart from the early 1990's shows a 9913 loss of approximately 3.08 dbi for roughly 100 feet. Compare that to Hardline LDF4-50A cable at approximately 1.465 dbi loss for 100 feet.

 

I understand that. I can deal with a little loss for the price. Lol. I was on a text line loss calculator and played around on it with different feedlines. I should only need about 60'. If I remember right the loss was between 1.7 and 2.1 at that length. Free is hard to come buy for feedlines. Lol. As I get more into it, I'll upgrade too.

 

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[Jones]

Free is ALWAYS the right price.  ...and if your 213 is free, then you can afford to buy a slightly better antenna to make up for the loss.

[couger100101]

Yes! I love free. All good cable, they just don't have room for pre cut lengths. I already bought an antenna. Ed Fung. Dbj- uhf. Should be here Monday or Tuesday. Can't wait. From the loss calculator 9913 has a slight less loss then the 213.

 

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[Jones]

You're right couger37, (binary?) at UHF frequencies, 9913 has slightly less loss than 213.  I see you were even talking about Free 9913.  I just had 213 on my brain the other day, since I had just replaced a chunk of it at an AM broadcast station.  Free is still the right price, regardless of coax type.

 

Yes, a 12 foot RG-213 jumper will eventually burn out when you're running 500 Watts at 1.39 MHz. (Keep in mind that AM radio stations use 125% peak positive modulation, so 500 Watts is actually 2500 Watts PEP, continuous keydown, 24/7 classic rock. Cable eventually melts and arcs through. I might need to move that jumper up to half inch Heliax.

[couger100101]

You're right couger37, (binary?) at UHF frequencies, 9913 has slightly less loss than 213. I see you were even talking about Free 9913. I just had 213 on my brain the other day, since I had just replaced a chunk of it at an AM broadcast station. Free is still the right price, regardless of coax type.

 

Yes, a 12 foot RG-213 jumper will eventually burn out when you're running 500 Watts at 1.39 MHz. (Keep in mind that AM radio stations use 125% peak positive modulation, so 500 Watts is actually 2500 Watts PEP, continuous keydown, 24/7 classic rock. Cable eventually melts and arcs through. I might need to move that jumper up to half inch Heliax.

Absolutely. That's just a bit of juice running there. 1/2" or even 5/8" might be better. Just sucks when you have to pay that price. Ultimately it will be worth it in the end. I happen to get lucky and talked with a local commercial installer and dealer and they just didn't have the room to store precut feeds. I'll have a variety of lengths that should fit my needs at the moment. I will also share the wealth with family and friends that are joining me on the air.

 

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[JohnE]

2 additions

1/4" and 3/8" superflex 

1/4  losses are 2.2dB/100' @150Mc and 4.0 @450Mc

3/8  losses are 1.5dB/100' @150Mc and 2.65 @450Mc

these are great for making jumpers w/o the leakage of braided cables.

will post some new pic when I get all the cables and connectors together

[coryb27]

2 additions

1/4" and 3/8" superflex 

1/4  losses are 2.2dB/100' @150Mc and 4.0 @450Mc

3/8  losses are 1.5dB/100' @150Mc and 2.65 @450Mc

these are great for making jumpers w/o the leakage of braided cables.

will post some new pic when I get all the cables and connectors together

 

I never read to the bottom of this thread, just wanted to share my 1/2" Heliax plumbing job on this part 90 DMR repeater

 

http://mwgmrs.com/mygmrs/jumpers.jpg

[n4gix]

That's a lovely job, Corey!

[JohnE]

little overkill but I like it. nice job. 

how do you find the right angle connectors hold up to power? I have never liked using them.

[coryb27]

little overkill but I like it. nice job. 

how do you find the right angle connectors hold up to power? I have never liked using them.

 

I have not had any issues with Comscope, I can't say that for RFS, several have shorted internally.

 

That cable job was to cure some issues with a paging transmitter next to me getting into the amp, it did solve the issue. I am sure i could have used something smaller but i had a ton of 1/2 on hand.

[Kugellager]

I know this is an old thread but I found this calculator really useful for estimating cable losses in various type of coax.

 

https://www.qsl.net/co8tw/Coax_Calculator.htm

 

John

];’)

[kidphc]

Don't forget. Connectors. Boy do the losses add up with those.

[kidphc]

in the grand scheme of things it's pretty negligible  N connectors are typically 0.15 loss @10Gc, now dumb that down to 400Mc and it's irrelevant.

True. that did a calculation, with all the pl259 connectors, and lightning arrestor and it came out to a little less then a dB. Sadly, still came out almost to a 4dB loss (estimated) with a 100ft run of LMR400.

[berkinet]

...10Gc, now dumb that down to 400Mc ...

Hmmm.Somebody is dating themself 

[JohnE]

just a wee bit

[Woodcat]

I'll add my 2 cents for Corey and JohnE regarding the 90 degree coax connectors.  I am retired from the cable tv industry and I will tell you that we started using the 90's for cable management benefits but soon found out that we were experiencing far too many signal failure and signal strength loss issues to continue on with them.  We ended up doing a massive rewire to remove all existing 90 degree coax fittings in the plant. My hands experience with those issues says I will never install a 90 degree fitting in any of my radio coax connectivity.  Too many opportunities for failure and equipment loss.

Craig

[jas]

Just read this post and decided to look at my mobile setup. Found a calculator online and my first thought was: "this has to be wrong!".  So I dug some more. Found more info and they all seem to match.

 

If this is true, in essence my 15 watt MXT275 radio, coupled to the Midland magnetic roof mount (MXTA12), which comes precabled  with a 6 meter (19.7 feet) RG-58A/U coax is really only a 8.85 watt radio, not counting connector losses! That's a 45% loss.  I'm still finding that hard to believe.

 

If that is indeed true, I also find it hard to believe that here we are in the 21st century and no one has seen it fit to come up with a better cable in a number of generations....

 

I will be buying a cable splicer and pliers to shorten the cable. I wont be able to make it shorter than ~8 feet  so I'll end of with a ~12 watt radio . 

 

Live AND learn.....

 

Thanks for the post!

 

Best,

 

JAS

[axorlov]

Sounds about right. Here is the attenuation chart, that agrees with the online calculator:

https://w4rp.com/ref/coax.html

 

Better cable would be RG8X and LMR-240. I tend to use LMR-240 for permanent car installs, where you do not move radio around often and NMO mount is drilled through the roof. RG8X is more robust cable, suites better temporary installs with mag-mounts, but loss is higher. RG58U is not a good cable for UHF. And if it's in a car, you certainly don't need 20'.