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Author Topic: Cat5 near feed line  (Read 751 times)
KB3JJG
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« on: May 11, 2003, 10:27:16 PM »

Living in an appartment I don't have many options in running my feedline. I have a cable modem that I located near the TV and ran some cat5 over to my station, the cat5 runs parallel to my rg-58 feedline for about 15 feet. I figured I'd be better off locating the modem away from my station and running the cat5. This is a better solution, I think, than running 75 ohm coax, parallel to the rg-58, to a modem near my station. Any thoughts?
Thanks in advance
joe
KB3JJG

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N0RKX
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« Reply #1 on: May 11, 2003, 10:40:43 PM »

Cat5 is unshielded cable, RG-6 is.
It would probably be better to minimize the length of the unshielded cable.
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N6AJR
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« Reply #2 on: May 11, 2003, 10:44:27 PM »

It probably doesn't make much difference.  Please get rid of the rg58 and at least go to rg 8x (about the same size but much less loss) and instead of running the wires in parallel, make one wiggle back in forth like an s to the other one.  thats why the use twisted pair for phone lines ( and cat 5 cables) because if the are not parallel they don't induce current into each other.  Try it and see what happens.  cat 5 is ok with runs up to 100 feet or so. 73  tom N6AJR
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KB3JJG
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« Reply #3 on: May 11, 2003, 11:08:14 PM »

OK, I can replace the rg-58 with some rg8x, I only have a 20' run, will it really matter???  My primary concern was the cable modem being close to my station. I recall some threads on various sites about ca modems creating noise. Thx for prompt and to the point replies gents.
Joe
KB3JJG
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W7DJM
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« Reply #4 on: May 11, 2003, 11:31:03 PM »

The thing is, there is a HUGE difference in the quality of ALL common coax's you are likely to run into, notably the "tightness" of the coax shield braid, and if the thing has a foil (in some types) and if the thing has a double braid.  (Radio shack is, or ways, notoriously band in this regard)

You could always scare up a length of "heliax" for the run near the cat 5.  Also, you CAN get shielded cat 5 cable.  I'm not familiar with the DSL and cable modem hookups, but with typical ethernet use, you are only actually useing 4 wires (2 pair) out of the 4 pair available.  It might just behoove you to reterminate the ends of your cat five so that the unused pairs are brought out at whichever end is near the modem/wall/ground point, and ground ONLY ONE END of all the unused wires.

'Course, there's always a bunch of clip on ferrites.
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K0IPG
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« Reply #5 on: May 11, 2003, 11:54:12 PM »

Don't worry about it. I'd only bother moving the cable modem if you're concerned about noise in your shack. The CAT5 won't mind any stray RF your coax "leaks".

In this case, it's probably easier for you to just plug it all in and see what happens, then fix stuff later if there's a problem. But, again, I doubt you'll have any problems.

Good luck!
Dan K0IPG
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RAD1OMAN
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« Reply #6 on: May 12, 2003, 12:49:07 AM »

kb3jjg said:
Living in an appartment I don't have many options in running my feedline. I have a cable modem that I located near the TV and ran some cat5 over to my station, the cat5 runs parallel to my rg-58 feedline for about 15 feet. I figured I'd be better off locating the modem away from my station and running the cat5. This is a better solution, I think, than running 75 ohm coax, parallel to the rg-58, to a modem near my station. Any thoughts?
Thanks in advance
joe
KB3JJG

In an apartment, you more of less need to do what you can get away with...

RG-58 is just fine, you are not running 100 feet, cat5e is just fine too, you are not running 100 meters.

You do not say is you are going to operate HF or VHF. The source of noise will most likely NOT be the cable modem, but rather your computer monitor!

If you are worried about noise or interferance, just slip a split core on the network cable at the back of the cable modem.

I run my network cable in the same cable race as my HF, VHF, and UHF runs along with my telephone cables. I use 9913 for most of my radio cables, but also use RG-6 and a run or two of RG-58. I do not get cross talk or telephone interferance on the phones, I do not get QRM from the network and I do not QRM the network. All of my cables run the lenght of the basement thru 4inch D Rings, one D per joist. I also run my 12v backup power lines tiewraped to the outside of the rings.

I run all cat5 on the voice and data lines, until I get to the cross connect panel for the voice lines and then i just use single pair cross connect, all punched down onto 66 blocks. The network is cat5 compliant throughout the network.
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AC5E
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« Reply #7 on: May 12, 2003, 07:48:10 AM »

After problems with almost all the electronic gadgets around here I went to 100% shielded coax; 9913 equvalent from either The Wireman or CableXperts; and have had no further problems. As long as the solder joint at the connectors is tight that stuff doesn't leak either way; coming or going.

One thing. You MIGHT be able to get away with using RG6 and compression fittings for a short time but the shielding is aluminum and there's no practical way to get a solid connection to the shield - and it has a ZERO power handling capability. Between those two factors it's much better to buy good coax than to try to save money with the cheap stuff.

73  Pete Allen  AC5E
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M3CMH
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« Reply #8 on: May 12, 2003, 05:14:11 PM »

I can't give much information as I haven't had the time and resources to experiment (yet)!

I've been using a Netgear F105 (5 port 10/100 switch) on my home network which is about 2 metres from my radio... you can already see where this is going! On 2m I get a lot of interference from it and on certain frequencies on 20m I can hear it. At the moment, I'm just unplugging it when I'm using the radio until I get around to rectifying the problem!

I did notice a difference when I switched between some different UTP (UNshielded, if you have problems, STP may be an option although very difficult to get hold of compared to UTP) cables I had. A manufactured cable seemed to cause a fair bit less interference than a "hand made" one - although saying this, the cable quality on the "hand made" one seems to be poorer.

Dominic
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AA8RF
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« Reply #9 on: May 12, 2003, 10:15:14 PM »

Your cat5 (cat5e or cat6 is better) is designed to work with ethernet cards and use differential signaling. The many twists and ethernet signaling circuitry likely make it pretty immune to shack RF. But it is still good to avoid running cables you do not want to interact with each other in parallel.

-Jim
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KB0NLY
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« Reply #10 on: May 13, 2003, 12:09:21 AM »

To: M3CMH

On that NetGear unit have you tried to filter or isolate the power supply for it.  I have run across more that a couple NetGear and Linksys units that were quiet themselves, but the noise was being caused by the cheap wall wart power supply.  Just a thought!

To: KB3JJG

I wouldnt worry about it until you actually experience some noise to deal with.  In my shack the cable modem, D-Link DI-704P router, and all the associated wiring is on the same desk as the main station.  The Cat 5 wiring going into and out of (4 cables out to 4 computers) the router is withing a foot of the back of the radio, and they all follow the main coax runs down the back of the operating position and through the floor to the basement.  I have yet to experience any noise or problems related to my network that were not easily solved with a few ferite beads on the cables.

I also run 100 watts on 6m SSB, 170 on 2m SSB, and 100 watts on 70cm SSB.  And although i dont operate HF a friend of mine stops by to use the radio now and then, and we have yet to see any problem with 100 watts on HF as well.  

I doubt that my station is a rare example of no problems, but i guess anything is possible.

73,

Scott, KB0NLY

AKA: The Computer Doctor

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KA0MR
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« Reply #11 on: May 15, 2003, 02:39:29 PM »

While your CAT-5 cable may have many twisted pair in them and it may be free of problems from your radio but I have a server in my shack with a switch from a router from in the house and my HF radio hears the routers song all over the place.

I am going to install CAT-5 STP (shilded) and see if i can get it out. It is a real big problem for me so I bet you will have no problem with your Internet box but you may have tons of trouble with your radio.

The Router and Switch is a Linksys not a Wal-Mart device but it still is a mess for me.
Bob
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KB0NLY
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« Reply #12 on: May 15, 2003, 03:31:04 PM »

KA0MR:

The shielded cable sure wouldnt hurt.  How close are they to the HF radio out of curiosity?  I have had to exorcise the noise demons from many a Linksys product.  Not to bash Linksys, i use there routers and other products on a regular basis because of there reliability.

I had one Linksys Cable/DSL router that was so bad that i ended up wrapping the entire router in copper mesh and grounding that.  Well it did work, despite looking not so pretty.

I got a hold of a D-Link router and put that into service when a Linksys i was running had a temporary problem with a firmware upgrade.  I was amazed at the fact that all the HF birdies where gone.  But i have also tried another D-Link model with opposite results, so its a 50/50 chance of getting a good one i guess.

73,

Scott, KB0NLY

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KA0MR
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« Reply #13 on: May 16, 2003, 07:01:23 AM »

I can move this switch anywhere in the room (10 x 20ft)
and I can get rid of it. I haven't tried core doughnuts but I am going to stck a couple on in the meantime I am going to get the STP CAT5 run.
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