Low Loss Vs RS RG-58

[darticus]

If I get a new antenna is it worth it to get low loss cable or use the RG-58 I have from Radio Shack? I have 50 feet of RG-8X for my short wave is it better to use? Does it make a big difference? Will be running 78 feet. Ron

 

[Alliance01TX]

Coax Loss

Howdy

I would recommend you research Belden, Times Mirror and like professional companies and also have a look at this URL (Coax Cable Loss) as one-of-many examples of charts that compare & contrast cable types vs loss. Also, unless you have the tools and skills you might concider also looking at HamRadio Outlet, AES and others (including Belden, et al...) to buy your 100 ft of cable with UHF or N Type connectors.

Others will likely add comments and comments and will range from using RS Cable (which is an ok utility cable) to those of us that 'make an investment' in both the Coax and the Connectors to maximize the likely investment you make on a Radio/Scanner.

Same goes with the Antenna....make an investment is my opinion and point of view, as the lowest quality item(s) in the circuit will likely default your radio to the minimum reception unless you are real close into the transmitter....

Hope this helps....

Thx

Bill

 

[LtDoc]

What it amounts to is the length of the run and the frequency(s) of use. For short runs (less than 50 feet?) RG-58 may be acceptable. For longer runs, or higher frequencies, that RG-58 isn't exactly the best choice since it has more losses than other cable sizes. At 78 - 100 feet, that RG-58 would be 'marginal' to say the best for it.
You also would be foolish to go too far in the 'other' direction! 3inch hardline is just a bit 'much' for the typical scanner enthusiast, you know? All coaxial cables have losses. Some are just lower than others depending on the frequency of use. Checking one of those 'coax spec tables' is a very good indication of what's usable and not. Look for the lower losses kind'a cable, and then check prices. You might wanna keep your wallet from screaming too loud...
- 'Doc

 

[darticus]

Thanks guys
This cable thing is costly. I have the RS RG-58 also RG-8X cable both are new. Do I want to spend more? Maybe if its really good but it sounds like the real good stuff cost more than my radio which will be updated soon, I'm bascally on 2M and 70cm so do I need NASA wiring? Maybe my wife will say yes. Thanks Ron .

 

[n5ims]

If I get a new antenna is it worth it to get low loss cable or use the RG-58 I have from Radio Shack? I have 50 feet of RG-8X for my short wave is it better to use? Does it make a big difference? Will be running 78 feet. Ron

Based on this (Welcome to Times Microwave | Coaxial Cable - Attenuation & Power Handling Calculator) RG-58 will give you 11.3 dB of loss over your 78 feet (numbers based on a 900 MHz signal, good round # for 800 MHz band receiption) while RG-8X will give you 9.5 dB of loss (went from really bad to just pretty bad). RG-8X is designed for HF use at fairly low power and is NOT the same as RG-8 (without the X). Standard CATV coax, RG-6, would only give you 6.9 dB of loss at a lower cost (please note that RG-6 would be for scanner use and not necessarily good advice if you transmit). LMR-400 would bring things down to a quite good 3 dB of loss, but isn't that easy to work with since it's so stiff and rather costly as well.

Please note that that calculator is based on good quality coax (such as Belden, Times Microwave, etc.) not what you may find at your local Radio Shack (depending on what type or even which supplier they got it from it may be good or not so good quality cable) or often at your local CB shop where the motto is often "Cheap for me, expensive for my customers!".

Play around with the calculator to see what may work best for you at a cost you can live with (coax can go from pennies a foot to needing a large loan for the really good rigid coaxial transmission line (check out these loss numbers and drool - ch 2 is around 54 MHz and 69 is just over 800 MHz to give you a point of reference - Rigid Transmission Lines (Coax) - one sixth of a dB loss per hundred feet!!! Sure beats that 11.3 dB from RG-58, that's for sure!).

 

[wyShack]

I would say it depends on use- if you are using the antenna for strong signal work(i .e. 'local ' repeaters ect) then the RG58 will work fine( if the signals are 20db+ over s9 it dosn't mater much). If you are planning on doing any weak signal work the antenna and feedline become the 'critical' parts of your system. If you monitor aircraft or any of the satelites on a regular basis spend the extra money but there is no need to spend it if it simply forces you to 'turn up the squelch'.

 

[SCPD]

I would never use 78ft of RG-58 at 70 cm, with 35 watts out of the radio you'll get 6 watts to the antenna. The best bang for the buck would be RG-6. I know it's a 75 ohm coax but you antenna is not going to maintain a 50 ohms impedance across the entire band anyway so the slight mismatch will be more than offset by the lower loss. You can often get RG6 for free if you know a DSS installer or somebody at the local cable TV company. If not try MCM Electronics they often have surplus DSS install kits that include 100ft of quad shielded RG6 for a few bucks. I found that with RS cable the best thing to do right off is to cut off the connectors and put knew ones on, I worried with antenna for days before I finally figured out that the brand new cable from RS had a bad connector.

 

[SCPD]

Wirelessly posted (Mozilla/4.0 (compatible; MSIE 4.01; Windows CE; PPC; 240x320))

what is boils down to is you'd be better off with a $30 antenna and good coax than you would with a $200 antenna and inferior coax

 

[LtDoc]

NC4DX,
"The best bang for the buck would be RG-6"...
Sorry, but you're wrong, and for the reason you also stated, the stuff is 75 ohm impedance. That may work just fine for listening/receiving, but will always cause a mismatch if it isn't compensated for. What you may save by using RG-6 you will probably spend doing that impedance matching to transmit. It's also not the easiest stuff to work with, as in soldering to aluminum. If you're 'blessed' with oodles and gobs of it, and if you can handle making connections to it, along with that impedance matching, then by all means us it if you want to. It isn't the 'miracle cure' that it's purported to be. Or very inexpensive after doing what has to be done to make it usable.
- 'Doc

 

[SCPD]

There will be a .159 dB loss due to the mismatch at 446 MHz. Hams in Europe use 75 Ohm coax more than 50 Ohm due to the price difference. I think manufacturers sometimes even make too much of 50 Ohm vs 75 Ohm. I never use RG58 except maybe for a short jumper, but I use RG6 a lot for transmitting and have for years with no problems. An antenna over it's 2:1 bandwidth could have an impedance of anywhere between 25 and 100 Ohms closer to 50 at places and closer to 75 at others. A ground plane with horizontal radials will have an impedance closer to 75 ohms at resonance, it is brought closer to 50 by angling down the radials to a 45 degree angle. But if you want to match the 75 coax to a 50 ohm transmitter a simple transformer can be constructed from 2 pieces of coax. And yes RG6 is still lossy at 70 cm but you can often get it free and it's twice as good as RG58.

 

[LtDoc]

Pssst - A typical resonant groundplane antenna with horizontal radials has a lower than 50 ohm impedance. 'Drooping' those radials will -raise- the impedance, not lower it. A dipole comes close to 75 ohms if 'flat topped' or hung vertically, but there will still be that impedance mismatch at the 'bottom end' of the feed line instead of at the 'top end'.
As I said, there's still that impedance matching to contend with and the mechanical aspect of using an aluminum conductor. If you can handle that, and if you've got gobs of it, knock yourself out!
- 'Doc

 

[pjtnascar]

Ron- What from what I heard today on the NY repeater, I think you'll be okay with the coax you have. Is the stuff to the discone the same as what you had hooked up to the new antenna? I think if you decide to upgrade to a more powerful radio then you should consider it.

When I suggested you upgrade the coax, I meant to the discone, thinking you were losing signal to the antenna. You are losing signal, but you sounded stong enough on the repeater to be fine with what you have on the new antenna. You did say it was low loss cable so it probably okay.

BTW- I use the RG6 cable for receive on my scanners.

 

[SCPD]

LtDoc you are right about the ground plane. But unless you are planning on operating a single frequency the "mismatch" is not going to be worth worrying about. As far as the aluminum shield there are plenty of connector types that make good enough mechanical contact to not have to worry about soldering.

 

[darticus]

Thanks guys
I got the Diamond x510 and plan to use low loss coax. Have to see whats afordable. Is there a LMR 400 or something like this that might be good. I heard it might do me good at 75 feet. Thanks Ron

 

[n5ims]

Many folks have had good luck using LMR-400 so it would be a good choice for either a scanner or ham transceiver to antenna coax. It'a a bit stiff and somewhat hard to work with during the installation, but otherwise should be good.

One thing to think about is you may need an adapter or jumper at the station end (to help reduce the strain from the stiff coax on your radio's connector). If the radio connection is straight and never moves you should be good, but with a turn in the coax to reach the scanner a right angle adapter (that allows easy rotation) is a good idea. If you have many bends or move the radio alot (or it's simply a light radio) a short jumper between the LMR-400 and radio can save the radio's connector from getting damaged or causing damage inside the radio.

 

[darticus]

Someone mentioned 9913 flex. I have to look this up. Does anyone know how it compares with LMR 400? Ron

 

[SCPD]

Coax Loss Calculator will let you compare many different types of coax

 

[n5ims]

Someone mentioned 9913 flex. I have to look this up. Does anyone know how it compares with LMR 400? Ron

Minimal extra loss with the 9913 and lots easier to work with than LMR-400. Very similar diameters but the 9913's more flexable so it's easier to work with.

 

[darticus]

I ordered the LMR-400 Times Microwave Ultra Low Loss 75 feet. Should do the job. People have told me to put a short piece of flexible cable 3 to 6 feet at the end for the connection to the radio so no pressure is put on the connector at the radio due to LMR-400 cable non bend-ability. Ron