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

[jas]

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'.

 

Thanks so much for the tables and info. I looked at my magnetic mount to see if I could replace the cable with 8X and it can be done but it would be quite involved and would compromise the bottom of the mount to water intrusion. 

 

So, I went looking on the net and good news!  RG8X magnetic mounts are rare, but I was able to find a Laird 8X mount in stock at Arcadian, the G8XPST. It's silver chrome but no biggie. Laird has a lot of 8X magnetic mount products including black ones but they are not in stock. Interestingly, these RG8X mounts are made by a company called Antenex Corporation, which was absorbed into Laird. here's the description:

 

"High Quality NMO cable kits and NMO magnetic mounts were the flagship product of the original Antenex Corporation, founded in Glendale Heights, IL in 1990. The company's passion and dedication to designing and manufacturing high-performance coaxial cables like G8XM for Magnetic vehicular mounting of NMO antennas continues to drive the company's success today. Owned by Laird Technologies since 2006, this dedicated group of Land Mobile Radio (LMR) professionals use quality materials and workmanship to produce a superior product."

 

On the website they have the attenuation of the RG8X  at 6.09 DB/100FT, which looks optimistic compared to the tables you sent me. Either way, this will be a lot better than what I have now. It's on the way to me plus another 1/4 wave antenna (in silver stainless). That one by Pulse - Larsen.

 

Thanks again!

 

Best,

 

JAS

[axorlov]

dxengineering.com has several magnetic mounts with RG8X. Also ebay.

[SkylinesSuck]

Soooo.....which cable should I buy from Amazon for the 25' run I need for my kid's treehouse?

[JohnE]

@25' 400 cable will be fine. you could go to FSJ 2 or 4 though but they are a little more fragile in terms of oops factor

[serrasalmus]

ok so im ready to explode here....friday im picking up some coax, my run is roughly 60 feet, i was going to get lmr 400 but the info im seeing is that 400 isnt going to be good enough for this. the cable will be sitting on the roof for most of the run and short run thru the window. i want to buy coax one time for this station and 3 months down the line i dont want to have to upgrade it.

 

so can ya help a guy out whos already lost his marbles.....

[BoxCar]

Whatever you end up getting, the outer sheath needs to be UV resistant. Not all coax coverings are.

[JohnE]

 

400 isnt going to be good enough

 

in what sense

given the weather where you are I might look into putting the cable in some PVC pipe.

As to the cable itself at, 60' 400 will be ok. the next real step up would be 1/2 inch hard line. just my thoughts

https://hosting.photobucket.com/albums/h358/erscom/off%20grid%20site/IMG_0239_zps7a34owh0.jpg

[mbrun]

ok so im ready to explode here....friday im picking up some coax, my run is roughly 60 feet, i was going to get lmr 400 but the info im seeing is that 400 isnt going to be good enough for this. the cable will be sitting on the roof for most of the run and short run thru the window. i want to buy coax one time for this station and 3 months down the line i dont want to have to upgrade it.

 

so can ya help a guy out whos already lost his marbles.....

 

What to you perceive the problem is? What are you trying to solve?

 

 

Michael

WRHS965

KE8PLM

[serrasalmus]

with all the different types of coax out there and the huba bubaloo from manufactures my head was ready to explode...however i found some lmr 400uf type from ham radio outlet its abr industries and has a uv protectant. ran down there today and picked up 75ft. 

[Lscott]

This link has some good tables for coax losses of the different types.

 

http://rfelektronik.se/manuals/Datasheets/3_8_%20LMR400%20Coaxial%20Cbl%20-%20Low%20Loss%20RG8_U%20Cable.pdf

[serrasalmus]

i ended up going with some abr industries lmr400 from ham radio outlet denver. 75ft only gives me about 10ft to 12ft of slack. on my homebrew jpole i got a swr of 1.07 with 99.86% of tx power going out with a reflect of only 0.0058%, with a power output of 4.38watts, antenna is about 35ish ft in the air i can hit the repeater thats about 30ish miles away but its a lil weak sometimes. so im really happy so far...just on that waiting bus for the kg1000g to come back in stock....unless i can find a better radio locally wich i doubt.....

[SkylinesSuck]

Can anybody speak to the losses in the different connection types as it seems pretty related? I'm looking at different antennas and I'm wondering about the differences between pl259 and N connections. Also, how to guys feel about lightening arrestors with pl259 connections?

[gortex2]

N connectors are preferred. LMR400 is fine for NON Repeater use. Do not use LMR400 on a repeater. For your base at home you are fine. Get N based surge arrestors also.

[Lscott]

Can anybody speak to the losses in the different connection types as it seems pretty related? I'm looking at different antennas and I'm wondering about the differences between pl259 and N connections. Also, how to guys feel about lightening arrestors with pl259 connections?

This seems to be a common misconception and point of confusion. Do not confuse the idea of insertion loss with return loss They are not the same and people seem to commonly interchange the two when discussing antenna systems without realizing the difference.

 

Insertion loss means exactly that, your RF energy from the transmitter is converted to heat in the coax and the various other hardware used to connect the cable(s) to your radio and the antenna. Good quality coax connectors have very low insertion losses.

 

Return loss means that power is reflected from the load back towards the source. This manifests itself has an elevated or high SWR reading.

 

The return loss is far higher on the PL-259/SO-239 type connectors on UHF and higher frequencies whereas the insertion loss maybe low. The mismatch is caused by the fact the connectors are not a "50 ohm impedance" thus causing the power reflections.

 

The most common RF connectors to use on UHF systems that have low mismatch losses are type "N", BNC, mini UHF and SMA. While the mini UHF connectors look like smaller versions of the old PL-259/SO-239 the design is such the impedance is much closer to the usual 50 ohms.

 

https://www.campbellsci.com/blog/ins-outs-rf-connectors

 

https://www.arcantenna.com/blogs/news/how-to-identify-coaxial-connectors

 

https://www.air802.com/connector-identification-chart.html

 

https://www.hamradio.me/connectors/uhf-connector-test-results.html

 

And for those looking for a bit more depth this book would be a good reference.

 

http://www.w3pga.org/Antenna%20Books/Reflections%20III.pdf

[SkylinesSuck]

Thank you for the info! If I'm reading that correctly, PL259 connectors contribute to higher SWRs and that's their downside? If I had a hypothetical setup with PL259 connectors but an already very low SWR, it would be pointless to chop them all off and upgrade to N connectors for example, right?

[Lscott]

That very well could be your case. If the SWR is acceptably low on an existing antenna system you may not want to bother. The general recommendation is for new installations one is better off going with all type “N” connectors where possible.

[SkylinesSuck]

Thanks. I'm just trying to understand the magnitude of the difference. Whenever I settle on a new antenna, I'm hoping it's got an N connector so I have an excuse to redo everything all the way to the radio in N. I appreciate the explanation!

[wrjc901]

GMRS/UHF do not skimp on COAX. 
Especially if running a long run for a tower, 
My Repeater on LMR400, about 100' though only using 50 of it atm. 
You need the highest DB gain you can get to get weak signals through
the Duplexer in the repeater. 
My Base setup (before I learned about db loss in coax.) 
Tram Dual band 1481 I think it is. just RG58 50'. 
I can't begin to hear signals the repeater can. 
Its antenna is similar, but Diamond X301 I think it was, 
picked it up from a HAM meet. 
Both have SWR 1.1 
So if someone offers you free Coax, and its not deigned 
for UHF/GMRS sell it to some CB'er and invest in the good stuff. 

I got a roll of brand new 1/2" hard line for free from a fellow 
that climbs towers for a living...... 

[dhardin53]

Back in my CB days whether degraded the less expensive coax and poorly weather protectors connection within few years. Never new it till you find you reception and transmission begins to decrease. Midwest weather are brutal on antenna  systems. 

 

[PACNWComms]

On 12/9/2021 at 10:33 AM, dhardin53 said:

Back in my CB days whether degraded the less expensive coax and poorly weather protectors connection within few years. Never new it till you find you reception and transmission begins to decrease. Midwest weather are brutal on antenna  systems. 

 

Have experienced this a lot, and also one of the reasons many contracts and maintenance programs require yearly at the minimum maintenance inspections. Rain, ambient humidity, very hot conditions, any extreme magnifies the weak points in hardware and installation. I know many people that even knowingly slack off on CB radio installs, as it is only a 5 watt radio and AM anyway.....instead of realizing that any issue in installation or quality of materials is magnified due to the low power and AM modulation. Higher power GMRS (mobile) radios allow for some leeway, and may not expose the systems limitations as much as a CB radio. Great point you made there, WX can be a huge problem.

[WRMB269]

Another way to look at Coax loss, I have always lost guys talking about dB loss and this chart also includes Watts loss and  brings the point home   PS 70cm would be your reference for GMRS performance!

EVIL COAX CHART FOR 2M & 70CM.pdf

[KAF6045]

On 4/28/2022 at 10:29 AM, WRMB269 said:

Another way to look at Coax loss, I have always lost guys talking about dB loss and this chart also includes Watts loss and  brings the point home   PS 70cm would be your reference for GMRS performance!

EVIL COAX CHART FOR 2M & 70CM.pdf 417.75 kB · 15 downloads

I would note that the chart doesn't (or I didn't see it) specify how the cable was connected to the test equipment (or was created from manufacturer specifications).

I mention this as the type of connector (and number of connectors) impose their own losses on top of the bare cable. (Which is why I just ordered custom cables: LMR-400 with PL-259 on one end and N at the other -- my window passthrough provides one N connector (each side), but the 2m/70cm diplexer combining the outputs from a TS-2000 and the MFJ 1/4 wave ground-plane I am finally getting around to installing are SO-239 sockets -- I didn't want the added loss of going through SO-239 pair at the passthrough).

The ubiquitous "UHF" (PL-259/SO-239) is, perversely, TERRIBLE at UHF frequencies, and even poor at VHF.Usable to 300MHz https://donsnotes.com/tech/connectors/BNC_N.html though it is already getting poor above 100MHz https://en.wikipedia.org/wiki/UHF_connector (apparently named before the industry standardized on "octaves": 3-30MHz HF, 30-300MHz VHF, 300-3000 UHF, etc.; back when >30MHz was "ultra high" and likely considered barely usable)

(I haven't located part-1 https://www.mwrf.com/technologies/cables-connectors/article/21846749/whats-the-difference-between-coaxial-connectors-part-2). Confusing text as the image captions show up in-line with the main text and not under the image; which means an unrelated connector mention appears sandwiched between paragraphs for a different connector.

BNC usable to 4GHz, TNC (B-bayonet, T-threaded) usable to 11GHz. No mention of losses however.

N usable to 11GHz

SMA usable to 18GHz

 

 

 

[Lscott]

If "N" connectors are too big and you need something small that can be weather proofed, good luck with BNC's, and high frequency rated have a look at the RG8 mini UHF type.

https://www.everythingrf.com/tech-resources/connectors

https://www.amphenolrf.com/connectors/mini-uhf-connectors.html

[marcspaz]

I think there may be some misconceptions about UHF connectors (and M-type) vs N-type connectors when it comes to the bottom end of UHF.  You can buy garbage UHF connectors that won't work well, 100%, but that holds true for N-type, too. 

 

N-type connectors were created in the 40's, when there were no real standards for UHF connectors, not that there is much of a standard now.  The DOD needed consistent performance, so Bell Labs created a standard to be met and created N-type connectors.

 

If you buy a quality silver/teflon UHF connector manufactured by a company like Lands Precision or Larsen (about $8 per connector, $16 per set to make a cable) you will not see any difference in insertion loss or any performance degradation when compared to a comparable price and quality N-type connector in GMRS systems.  I personally have done tests using LMR400.  I made 2 patch cables that had UHF connectors and 2 patch cables that had N connectors.  I tested them with my analyzer between 440 MHz and 500 MHz and there was exactly zero difference between 3 of the 4 cables.  One of the cables with UHF connectors had an increase in insertion loss 0.01 dB... which I am assuming had something to do with me and the way I made the patch cable or possibly the section of cable itself introduced the difference and it had nothing to do with the connectors.

 

Bottom line, we are not running enough power, moving enough data, or have high enough duty cycle that would require an N-type connector.  Our only real benefit would be for outdoor connections and utilizing the native weatherproofing instead of having to add additional weatherproofing to a UHF connection.

[Newb]

I have found the following website very helpful in determining transmission cable quality as opposed to the cost of the unit you need from the antenna to the radio.  It also lists flexability specs for the different low loss cables.   https://www.timesmicrowave.com/Products

They also list specs on connectors.