RG59-U Coax Loss?

[zonian149]

I have tried to find the loss statistics for RG59-U coax that I have my scanner attached to and I haven't had any luck. Does anyone have that info. I forget the brand name that I have, but I am wondering how much of an improvement in reception I would get with LMR-400 especially at 800mhz. I have a 50' length of coax. I get a very weak signal from Nashville TN which is about 35 miles away. These are trunked frequencies that I listen to on my BC796d scanner and without a stronger signal I cannot listen to them. Thanks in advance.--Gary

 

[N_Jay]

http://hamradio.arc.nasa.gov/coaxcableloss.html

Third listing when you Google 'RG-59 Loss Chart'

Google is your friend, don't fear the Google! :twisted:

 

[zonian149]

Thanks

Thanks, I did google it, but somehow I missed that websites information, looks like I am losing a fair amout of signal using the RG59-U, guess I better or me some LMR-400 or Belden 9913 soon.--Gary

 

[click23]

What knid of antenna are you using 35 miles is a good distance for picking up 800mHz. I just put up a RS discone in my attic running 50' of RS RG6QS I can pick up Chattanooga which is about 50 miles away. No luck with Knoxville as of yet.

 

[zonian149]

I have a workman 601 discone antenna $24.00 off of ebay which is also mounted in my attic. I am almost picking up 800mhz from 35 miles away. The signal is too weak to stay on a trunked frequency long enoug to follow the action. I am hoping the changing to lmr-400 will help the 800mhz reception.

 

[diskmonger]

I have a workman 601 discone antenna $24.00 off of ebay which is also mounted in my attic. I am almost picking up 800mhz from 35 miles away. The signal is too weak to stay on a trunked frequency long enoug to follow the action. I am hoping the changing to lmr-400 will help the 800mhz reception.

You should notice a HUGE difference if you are going from RG-59 to LMR-400. There is a lot of signal loss at 800Mhz if you don't use decent coax.

 

[click23]

You would see a huge difference with just plane ol' RG-6.

 

[kb2vxa]

Hi all,

RG-59U bites, go for RG-6U CATV coax and save your money from buying snake oil. Yup, the cable company uses it for good reason.

 

[Al42]

What you buy at Radio Shack, even though it's the same number, isn't the same cable.

 

[Tweekerbob]

The signal is too weak to stay on a trunked frequency long enoug to follow the action. I am hoping the changing to lmr-400 will help the 800mhz reception.

First, before you make the investment, try an experiment. Make sure you can even HEAR the system in the first place. Go into the attic (yeah it sux in the summer) and bring a portable scanner or HT. If you can decode the CC with your handheld, then there may be some benefit to switching out the coax. Another experiment you can try is to make a short jumper (6-8 feet) out of decent coax and while in the attic use it to interconnect the discone and the portable rig. Again, if you hear and can solidly decode the CC, then go ahead and try the better coax.

If you cannot solidly decode it, then the problem is not NECESSARILY the coax. You first need to get more signal into the coax before you can determine that it is indeed the coax's fault. You may have to go outside the attic and get some altitude. Or you may want to consider an antenna that actually performs well on 800 as opposed to the marginal to poor 800 performance of the typical scanner discone.

Ryan

 

[kb2vxa]

Hi again,

"What you buy at Radio Shack, even though it's the same number, isn't the same cable."

I suppose that means that Carol (RS) doesn't make CATV cable and they don't. Still they must meet the same electrical and physical specs while CATV cable is specially shielded with aluminium foil under aluminium braid. The FCC is very picky about signal egress interfering with other services, especially aircraft. Such is not needed in ordinary applications, otherwise it has the same impedance, loss characteristics and physical dimentions as ordinary RG-6U.

 

[N_Jay]

Hi again,

"What you buy at Radio Shack, even though it's the same number, isn't the same cable."

I suppose that means that Carol (RS) doesn't make CATV cable and they don't. Still they must meet the same electrical and physical specs while CATV cable is specially shielded with aluminium foil under aluminium braid. The FCC is very picky about signal egress interfering with other services, especially aircraft. Such is not needed in ordinary applications, otherwise it has the same impedance, loss characteristics and physical dimentions as ordinary RG-6U.

Some people ASSUME that if it is from RS it is of inferior quality.

And sometimes they are right.

Many here seem to be on the impression that better sheilding makes for better coax.

Loss and durability are are far more important than sheilding for scanner type use.

 

[pro92b]

Years ago Tandy did manufacture their own coax and it was inferior. Now they may purchase coax from one of the major manufacturers, but which one? And to what spec is the coax made? Too many unknowns for me - I buy Belden coax.

You're right about the shielding issue. Quad shield is touted as being almost magical but it is no better or worse than ordinary RG-6 for scanner use.

 

[Al42]

"What you buy at Radio Shack, even though it's the same number, isn't the same cable."

I suppose that means that Carol (RS) doesn't make CATV cable and they don't. Still they must meet the same electrical and physical specs while CATV cable is specially shielded with aluminium foil under aluminium braid.

The impedence and the sizes are the same. The loss isn't. The susceptibility to UV degredation isn't. (The tensile strength isn't either, although most scannists don't run 50 foot drops, so that wouldn't matter.) And foil (or quad) shielding doesn't do a thing for a scanner. That's to keep signal in the cable.

The bottom line is that there's more loss in RS cable, and it won't last as long (without introducing even more loss) as real CATV cable. (Assuming one of the larger cable companies. Mom & pop operations may buy cheap stuff - the one I worked for in the early 60s did, but CATV was brand new then.)

 

[Jimmy90]

Hi guys,
Just wanted to interject something about the RG-59 coax. Don't forget, this stuff is 75 Ohm coax. What you should be looking for is RG-58 at a minimum, which is 50 Ohm. That may be part of your problem!

 

[N_Jay]

Hi guys,
Just wanted to interject something about the RG-59 coax. Don't forget, this stuff is 75 Ohm coax. What you should be looking for is RG-58 at a minimum, which is 50 Ohm. That may be part of your problem!

The mionor impeadance mismatch is not as bad as the loss of either RG58 or RG59 at 450 and 800 MHz.

 

[kb2vxa]

Hi guys,

Let's clear up a bit of a misunderstanding here.

First, there IS a difference between RG whatever number cable and RG whatever TYPE cable, a BIG difference. Think of it as juice DRINK vs. juice, the drink can be just about any watered down juice or chemical flavored stew while juice is 100% juice. Those extra words are ways to get around the law and fool you into thinking you're bying something you're not.

Rat Shack not withstanding, use your smarts and you can't go wrong no matter where you buy. Forget about super shielded stuff unless you live in a microwave oven (;->) when UV characteristics are more important. You don't want to replace the cable every couple of years when every 10 or so will do. Yes, it all ages and goes bad in time, nothing lasts forever. Hmmm, that's why I stay away from hamfest specials that somebody took down after spending 20 years in hell.

The biggest ripoff I've seen yet is "9913 type" cable which is nothing more than RG-8U polyfoam dielectric coax. BELDEN 9913 is a horse of another color altogether and only Belden makes it, 9913 is a proprietary number. (Note it's not RG anything, it's quite unique.) Technically it's air dielectric semi rigid line, sort of a cross between coax and hard line with exceptionally low loss characteristics. If it has Belden stamped on it you're getting the real McCoy, accept no substitutes.

Consider the fact that a dipole antenna at resonance has a 75 ohm feedpoint impedance making 75 ohm coax ideal as the feedline, not 50 ohm stuff. An SWR meter will show 1.5:1 at best because it's calibrated to 50 ohms but in reality it's a perfect 1:1 match. Now if a 50 ohm antenna common on VHF/UHF is used with 75 ohm coax the same 1.5:1 ratio exists which is inconsequential considering anything under 3:1 is acceptable. Now here we're talking about transmitting and that's the ONLY place SWR is of any consequence.

When it comes to receiving, reflected loss isn't much of a factor especially when transmission line loss so greatly overshadows it. The bottom line and to put it simply is the only REAL consideration is loss in dB per 100' at the highest operating frequency. What you guys really should look into is a chart showing the common types of coax cables and choose what's best vs. what you can afford for your particular application. That will save you Googling all over the place for each cable, Google for the charts. That's right, no one alone has every type listed so you should check out as many as you find. If you want to take the extra step, compile the data into one chart of your own.

Gotcher ears on good buddy? I hope so, you look funny without them. (;->)

 

[leftystrat]

I have tried to find the loss statistics for RG59-U coax that I have my scanner attached to and I haven't had any luck.

Chuck the stuff and get better cable. I recently went over the loss and 59 is really frightening. I upgraded to LMR400, which looks a bit funny indoors, but it definitely helps. I think I got it at the same price as 213, so I went for it. I use 50' to get from the attic down 2 floors.

I use 8X for my SWL antenna. Can't hurt.