signal loss

[Ncfirewire]

i am running lmr-400 from my roof antenna into a Stridsberg MCA204M active multicoupler

my question is i will need four 2 ft pieces of cable to run from the multicoupler to the scanners will i lose any signal if i don't use lmr-400 for those pieces? i can do it either way but i am thinking the cable will be too stiff to work with but i will make it work if it prevents loss.

i'm not sure if a 2 ft run will make a difference or not or the fact that i have lmr-400 on the other side of the multicoupler

thanks

 

[n5ims]

i am running lmr-400 from my roof antenna into a Stridsberg MCA204M active multicoupler

my question is i will need four 2 ft pieces of cable to run from the multicoupler to the scanners will i lose any signal if i don't use lmr-400 for those pieces? i can do it either way but i am thinking the cable will be too stiff to work with but i will make it work if it prevents loss.

i'm not sure if a 2 ft run will make a difference or not or the fact that i have lmr-400 on the other side of the multicoupler

thanks

Depending on what cable you use you'll have more signal loss vs using LMR-400 (you could also have less, depending on what cable you use). The real question isn't if you'll have loss, it's will this loss be significant. The answer to the real question is unless you do a really poor job of cable selection (e.e. RG-174) or installation of the connectors or jumpers the 2 foot jumpers will not make any noticible difference. With some expensive equipment you can measure it, but just listening you won't see any difference.

 

[Ncfirewire]

you think using lmr400 as the jumpers are a bad idea? i always thought this was the best cable to use?

 

[n5ims]

you think using lmr400 as the jumpers are a bad idea? i always thought this was the best cable to use?

As stiff as it is using something smaller and more flexible is recommended. Having stiff cable attached directly to the scanner (unless something else is used to compensate) can cause strain on the scanner's connector and cause it to fail over time. It also can make the scanner difficult to place exactly where you want it.

While LMR-400 is good cable, it's not without issues. It's not recommended (by the manufacturer) for full duplex operation such as repeater use due to "passive intermod". It's also somewhat difficult to install (by non-professionals) since it's stiffer than what most folks are used to. It's also not easy to solder connectors to due to how the shield is designed (crimp type connectors do work well though, but the tools aren't cheap).

There is cable with lower loss (Andrew Heliax like LDF4-50A for example) that's similar size. While new on the reel the heliax is quite expensive, you can often find it unused as "end-of-reel" lengths for the same if not less than LMR-400. Connectors aren't cheap new, but can be found easily and are available on the surplus market at good prices.

For your 2 foot runs, you can easily use commercially prepared quality RG-58 jumpers (you may need to get 3' lengths) without issues. The cheap junk, however, may use low quality cable and connectors so check what you're getting fairly closely. Verify that if the coax is 50 ohm, you get 50 ohm BNC connectors as well (the center pin insulator on 50 ohm connectors go the full length while on 75 ohm ones it doesn't).

 

[zz0468]

I agree with n5ims here. You'll never notice the slight additional loss if you use RG58 jumpers. You're trading loss for flexibility, and in the case of 2' jumpers, the tradeoff is more than worth it.

 

[Ncfirewire]

if i were to switch my main line feed to LDF4-50A can i u use a pl 259 connector on it like the lmr-400 has on it?

 

[n5ims]

if i were to switch my main line feed to LDF4-50A can i u use a pl 259 connector on it like the lmr-400 has on it?

Yes you can (RF Industries RFU-502-H1 UHF Male for 1/2" LDF4-50A, LCF12-50J | TESSCO) but it's probably easier (at least on your wallet) to use "N" connectors since they're most common. One thing to think of is that they make "N" in both male and female versions for standard coax. Put the male on the main part of your coax and the female on a short jumper with the PL-259 (or BNC, depending on what you need) on the other end. You'll add some install flexability and save several dollars. Although the connectors may say "water proof", still do the usual moisture protection on the joint(s) that are exposed to keep things working well for the long haul.

 

[Ncfirewire]

i guess im a little confused does the 1/2 Heliax need a special type of connector different then the lmr-400 would take?

my lmr-400 has a pl-259 connector on it and i think it was no more than 10 bucks

my antenna needs a pl 259 and when i order the Stridsbergs input i can either have a bnc input or a n connector

 

[n5ims]

Yes, special connectors are required. This is mostly due to the differences in how the shield is done. In LMR-400, you have a foil layer covered by braided wires (Amazon.com: LMR 400 Cable, 75ft: Electronics). In LDF4-50A, you have "corrugated copper" which looks somewhat like that flexible conduit (CommScope / Andrew - LDF4-50A-S7 - 1.7-2.2 GHz 1/2" Foam Swept Cable). The center conductor is a bit thicker than normal, however it's close to what some LMR-400 versions use.

 

[n5ims]

Yes, special connectors are required. This is mostly due to the differences in how the shield is done. In LMR-400, you have a foil layer covered by braided wires (http://www.amazon.com/Cellphone-Mate-Inc-LMR-Cable-75ft/dp/tech-data/B003Z4MJPM). In LDF4-50A, you have "corrugated copper" which looks somewhat like that flexible conduit (CommScope / Andrew - LDF4-50A-S7 - 1.7-2.2 GHz 1/2" Foam Swept Cable). The center conductor is a bit thicker than normal, however it's close to what some LMR-400 versions use.

 

[Ncfirewire]

ok i understand now so that being said i assume when i order the multicoupler i should get the one with the n connector input instead of the bnc input to make it easier

 

[LtDoc]

For short runs which are typical for 'jumpers', the key word is 'convenience'. Using a very stiff cable means making 'compromises' in placement of the devices they are connecting. If that 'device' is very light, the larger cable can move it as it 'straighten's it's self out a little, ever had that happen?
Losses have to be fairly large before you will hear them. If the cable used for those 'jumpers' is reasonably close to that LMR-400 (the short length does make a difference) then it won't make any practical difference. (If you have to use a magnifying glass to find those small losses, then they might as well not be there, you know?)
Use what you got...
- 'Doc

 

[mpddigital]

Coaxial Cable Used for Jumpers

As long as you know what your requirements are for connectors jumpers can be made from most good coax.

We use jumpers made from LMR-400, LMR-240, Andrew 240, MILSPEC 213, RG-214, LMR-195 and last choice RG-8x and RG-58. Whatever is needed.

There really is no reason to use cheap coax cable since with short lengths the cost is all in the connectors! We charge a little over a buck a foot for LMR-400 cables, less for 240 and 195. What this means is that a 2 foot jumper costs a Max of $2.20 plus the cost of installed connectors... The difference between 400 and RG-58 jumpers made with quality connectors is $1.80!

In short cables needing flexibility use the best coax you can for your equipment considering placement, power handling and connectors needed. Most good companies offer 10-20 different connectors types available to mix and match to meet connection requirements. Making up BNC to PL-259 or Mini-UHF to N connectors jumpers is not a problem.

Considering how little difference the cost of coaxial cable makes in Jumper construction use what works best for the flexibility / loss compromise. Also remember that if you don't use quality connectors the cable you use doesn't make any difference

 

[reconrider8]

Adjustable Universal Compression Tool Rg58 Rg59 Rg6 Rg11 Coaxial Cable - Amazon.com how would this compression tool work with lmr-400 and what kinda connectors would be in use here?

 

[vannossc]

No connection with them but here's a nifty chart on coax, frequencies and losses:

Coax and Ladder Line

Scott