Two cable questions

[jnojr]

1. LMR400 vs. KMR400 - searching for LMR turns up a lot of "Just use KMR, it's pretty much the same!". Is it?

2. Can two runs of LMR400 (or LMR & KMR) run right next to each other without causing problems? I'm assuming that the shielding is plenty for that.

 

[AK9R]

LMR400 is made by Times Microwave Systems.

Anything else is made by somebody else. Whether or not it meets Times Microwave's design or quality control standards is anyone's guess. I would not waste my money on no-name knock-off coaxial cable.

I don't know who makes "KMR400".

 

[WA0CBW]

And yes, you can run 2 or more coax cables together.
Bill

 

[lviper]

There is a video where the guy tests the KMR400.

 

[Grounded]

1. LMR400 vs. KMR400 - searching for LMR turns up a lot of "Just use KMR, it's pretty much the same!". Is it?

2. Can two runs of LMR400 (or LMR & KMR) run right next to each other without causing problems? I'm assuming that the shielding is plenty for that.

One is authentic, while the other is an imitator aiming to deceive CB and ham operators. Coaxial cables can be run in close proximity to each other, but it is crucial to use high-quality coaxes such as Times Microwave LMR or Belden.

 

[K6GBW]

It's fun to watch people get so spun up over coax. Some have a religious fervor for this brand or that brand. At the end of the day, coax is not a complicated thing. As long as the materials and construction are good it will work fine. The numbers are only a few watts here and there. At HF frequencies 98 watts out vs 94 watts won't make a bit of difference. It's a measurable but insignificant difference. When you factor the cost of 75 feet of similar Belden or Times coax the cost difference can be significant. So for some uses I think the "lesser" brand coax is fine. I'm using Mookeerf coax on my HF radio right now. It was about 50 cents a foot for 100 feet and it works just fine. I bought it for the color! Mookeerf makes coax in white and my wife wanted my install to be low profile. Yes, I could have spent well over $100 for Belden and the radio would sound the same. Some installations it does matter though, so be smart about it. If you are using a rotor, a buried install or a mobile install then I'd opt for better stuff. For a run of the mill HF application there really no need to be too bougie about the coax.

 

[prcguy]

There is a video where the guy tests the KMR400.

What’s with this hammey testing BS? You need to stick the coax on an actual VNA (not a Tiny but an HP/Agilent) and test for precise insertion loss and VSWR with a reference load and preferably to 1GHz or more. Then test an exact duplicate of Times LMR400 for comparison. This guy uses an MFJ wattmeter?

 

[AK9R]

For a run of the mill HF application there really no need to be too bougie about the coax.

True. You've done a cost-benefit analysis. You understand what you bought and understand the impact on your antenna system.

My concern is when unsuspecting hams buy cheap no-name coax thinking it's the same as the name-brand stuff. Maybe it is. Maybe it isn't.

 

[jwt873]

I've never heard of KMR-400. I looked around and see it's made in China. [Hot Item] RF Kmr400 RF Coaxial Cable 50 Ohm Low Loss Coax Cable 100 Feet -- Sold on Alibaba too.. About .89 cents a foot.

 

[mmckenna]

I've never heard of KMR-400. I looked around and see it's made in China. [Hot Item] RF Kmr400 RF Coaxial Cable 50 Ohm Low Loss Coax Cable 100 Feet -- Sold on Alibaba too.. About .89 cents a foot.

I'd trust the CommScope CNT-400 more than the random Chinese stuff. Plus, it's cheaper:

CommScope CNT-400 - RG8/LMR®-400/9913/RG213 Coaxial Cable

50 Ohm Low Loss RG8/U Coaxial Cable

theantennafarm.com

I like the "cost/benefit analysis" comment above. That's the way to look at this. For most, this is a hobby, and budgets are a real thing. Blowing money just to get name brands and bragging rights may not be worth it for some. Especially if the difference is a few tenths of a decibel.

Most public safety radio systems are designed around a 90-95% on street portable radio coverage, so going overboard to listen to a local radio system probably isn't worth it. If the radio is decoding traffic with a low BER, it's not going to sound better with higher grade coax.

On the other hand, if it's weak signal stuff, like ham radio, chasing low band DX, etc. then maybe those few tenths of a decibel are worth the extra cost.


I ran Radio Shack RG-8 on a GMRS base station for years. It worked. I had access to a huge reel of LMR-400 and LMR-600. Didn't need better performance. Eventually had some left over 1/2" Heliax and installed that. Didn't make a bit of difference in performance since I am surrounded on 3 sides by hills and the other side is nothing but salt water until Japan.

 

[W4AXW]

I've been using DRF-400 (Davis RF) to feed HF/6m antennas for a while now and seems to be fine stuff. Made in USA. Same specs (supposedly) as LMR-400 only $0.75 less/ft. Even if it's not as quality as LMR-400, neither myself or the 120+ DX entities I've worked using it have noticed the difference. No Crapazon coax here.

7 3

 

[paulears]

For ages now we have been telling receive only users to forget expensive cable and buy 75 Ohm sat cable. Most is made in China. This Chinese 400 is expensive. My usual suppliers have it, but while the cable is cheap shipping is not!

i cannot see the antenna farm link. The UK is blocked.

 

[Grounded]

Some thought and planning go a long way when building your station. Without it, you get what you asked for. One area that needs attention and planning is managing System RF losses; the coax is only 1 part of the antenna system. You may have watt/SWR meters, antenna tuners, coax switches, jumpers, and coax connectors in the RF path. The goal is to set a maximum limit of RF losses to some number. Ideally, you want to limit system path losses to 2 to 3 dB for a simplex operation. You must add all the losses from the Transmitter output port to the antenna feed point. Coax connectors, coax, and auxiliary equipment have specified losses for your use. As a rule of thumb, you budget up to 2 dB of coax loss as it accounts for 60 to 70% of the system loss budget. The remaining is your budget for connectors, jumpers, and aux equipment.

You need to know the length and maximum operating frequency to determine what coax to use. You need to know there are RG8/213 coax and RG8/213 coax. As you can see below, there is a significant difference between the two. RG8/213 coax is a group in the .4-inch diameter coax. For example, if your highest operating frequency is 2 Meters, use the 144 MHz column to find your solution. Assume the one-way length is 100 feet. You need to use something from the RG8/213 group. Which one? Not all of them will work.

Another fact to consider: For every dB loss you allow in your antenna system, you add 1 dB of noise to your received signal.

Carry on

 

[Golay]

Myself, feedline is what I don't pinch pennies on. The best that RF Engineering has. Yeah, you can get cheaper.
Get back with me 10 years down the road when the jacket on your bargain basement coax gets brittle and strong winds start cracking it like a twig.