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Message |
    
Nastyredz
New member
Username: Nastyredz
Post Number: 1
Registered: 9-2005
| | Posted on Wednesday, September 21, 2005 - 7:52 pm: | 
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I know i posted this before , but i cant find the thread, I have a rool of coax about 500 foot.. I need to know how i can find out the impedence of it. It is not labled , is there any way i can test it with the ohm meter? |
Tech237
Moderator
Username: Tech237
Post Number: 210
Registered: 4-2004
| | Posted on Thursday, September 22, 2005 - 8:35 am: |
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Not with an ohmmeter. You can take physical measurements anbd work it out that way. Is anything written on the coax?? |
Nastyredz
New member
Username: Nastyredz
Post Number: 2
Registered: 9-2005
| | Posted on Thursday, September 22, 2005 - 8:56 pm: |
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Nah not that i know , i didnt see anything,Ill look later on when it's light out, What it is , my neighbor worked for the cable tv company. He was throwing a whole rool of it away. it is the heavy coax cable that is used on the telephone poles. The reason im asking about it is cause ive got a whole rool of it and its ALOT!! so maybe i can use it, or maybe not. |
Tech237
Moderator
Username: Tech237
Post Number: 213
Registered: 4-2004
| | Posted on Thursday, September 22, 2005 - 9:50 pm: |
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If it is from a CATV company I'd suspect that it is 75 ohm coax. It can still be used for a CB with a little raise in SWr to about 1.5:1
I run a length for my 2m radio and it works OK. The biggest problem is fitting the connectors but give a cahnce to find it and I'll see about getting a method of doing that posted on here |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 686
Registered: 9-2004
| | Posted on Thursday, September 22, 2005 - 10:05 pm: |
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sorry, you cannot use that coax.
if your friend used it for anything related to television, it is 75 ohms and of course you need 50ohms.
DO NOT TRY IT!!! you will have an SWR of 3 or higher.
you will be able to make cable TV jumpers for all your friends however!
sorry for the bad tidings,
matt |
Nastyredz
New member
Username: Nastyredz
Post Number: 3
Registered: 9-2005
| | Posted on Thursday, September 22, 2005 - 10:35 pm: |
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Well hey its too bad, but it was just a thought. The coax is almost the size of rg 8 ! But hey if you guys need any give me a holla. your welcome to some. Im out here in ct , and im new to this board. NEWBIE LOL . anyway I figured it would be the same as the indoor cable 75ohm . oh well. Thanks anyway! |
Nobodyknows
Intermediate Member
Username: Nobodyknows
Post Number: 105
Registered: 4-2005
| | Posted on Thursday, September 22, 2005 - 10:44 pm: |
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Yeha, theres a roll of that catv coax at the thrift store i frequent. I sigh and wish it was 50 ohms and walk past it. It's been there for almost a year. Right across the isle is a $10.00 kracko 23 ch CB that has a bad mic wire. it's been there about 6 months. |
Hollowpoint445
Advanced Member
Username: Hollowpoint445
Post Number: 763
Registered: 6-2004
| | Posted on Friday, September 23, 2005 - 7:51 am: |
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If you know someone with an antenna analyzer you can connect it to a dummy load of known resistance and check it's specs. I've never used my MFJ259B to check my coax alone, but I believe there is a method included in the instructions that tell you how to do just that.
Even if it is 75 ohm coax you can use it for radio - after all cable TV is RF based. It would feed a dipole very well as a dipole's feedpoint is 72 ohms. Knowing it's actual specs would be useful to know how much power it can handle and it's velocity factor if you ever choose to use it for matching stubs etc. |
Slowhand
Member
Username: Slowhand
Post Number: 83
Registered: 7-2005
| | Posted on Friday, September 23, 2005 - 8:26 am: |
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I heard two old guys that were using 75 ohm cable
with no problems. Also with a tube amp being used I don't believe it would matter. |
Tech237
Moderator
Username: Tech237
Post Number: 214
Registered: 4-2004
| | Posted on Friday, September 23, 2005 - 9:12 am: |
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Kid-Vicious,
Sorry to tell you thsi but you are wrong. At 75 ohm coax if the antenna is properly tuned your SWR should not be more than 1.5:1.As I said earlier I have been running CATV coax on my 2m radio for the last 6 years and the SWR IS 1.5:1 (per Antenna analyser).
Connect plugs to it properly and you should have no problems. |
Bruce
Senior Member
Username: Bruce
Post Number: 3132
Registered: 9-2003
| | Posted on Friday, September 23, 2005 - 5:53 pm: |
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75 ohm will work if you match it other wise the max mismatch is 1.5 / 1 |
Nastyredz
New member
Username: Nastyredz
Post Number: 4
Registered: 9-2005
| | Posted on Saturday, September 24, 2005 - 12:01 am: |
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well once i get my station back up and running i may do some tests with it. Thanks for the info. |
Kid_vicious
Advanced Member
Username: Kid_vicious
Post Number: 689
Registered: 9-2004
| | Posted on Saturday, September 24, 2005 - 8:23 pm: |
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i stand corrected!
yet another CB myth debunked!
hows the sheilding on this TV coax?
matt |
Tech291
Moderator
Username: Tech291
Post Number: 241
Registered: 11-2004
| | Posted on Saturday, September 24, 2005 - 9:15 pm: |
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Nastyredz,
From your discription,it sounds like you have a spool of rg-11,a 75ohm catv coax.It does have its uses in radio.It can be used to make baluns and can also be used for phasing and delay lines in antenna arrays.
tech291
cef#291
kc8zpj
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Slowhand
Member
Username: Slowhand
Post Number: 85
Registered: 7-2005
| | Posted on Sunday, September 25, 2005 - 12:17 am: |
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75 ohm is good for making a co-phasing harness |
Bigbob
Senior Member
Username: Bigbob
Post Number: 2219
Registered: 12-2001
| | Posted on Sunday, September 25, 2005 - 6:33 am: |
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Yeah and you got enough for a really LONG co-phasing harness,hehe.Bigbob |
Moderator136
Moderator
Username: Moderator136
Post Number: 115
Registered: 4-2005
| | Posted on Sunday, September 25, 2005 - 10:01 am: |
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Yes i agree with Tech 291 , Looks like you have rg-11 75 ohm coax.
Yes it can be used . I run a 10 and 11 meter dipole with 75 ohm coax and also have a Heathkit balun coil Model b1 and a MFJ-944 Tuner in line, and it works good. The Heathkit balun converts 75 ohm to 50 ohm and the MFJ tuner loads to a 1.1 ratio . It dose work and i also have used tv flat twin lead also , But i have a Low pass filter inline to keep rf out of phone and tv .
If you use it without a balun you will have a mismatch and SWR will be a high and not good on the Radio.
Hope this helps!
Moderator136
CEF136
kc0svc |
Vanillagorilla
Intermediate Member
Username: Vanillagorilla
Post Number: 236
Registered: 4-2005
| | Posted on Sunday, September 25, 2005 - 10:20 am: |
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I cheesed out and used 100' 75ohm satillite tv cable for my dipole install when I restarted this hobby a year ago. I heard ,as mentioned, the dipole was 72ohm. I patched the last 10ft at the radio end with RG8. Worked great. So great in fact that I forgot about it when I switched to the antron99....still works great...SWR as low as 1:2. 1 thru 40.
Stuff is super shielded and you'd fugure It would have to be for TV/Cable usage. They NEED as little loss as possible over a long distance.
I also used a length of the standard cablevision stuff to feed the other basestation in my bedroom from the basement...SWRs are higher but acceptable for barefoot ragchew at 1:5. |
Nastyredz
New member
Username: Nastyredz
Post Number: 6
Registered: 9-2005
| | Posted on Sunday, September 25, 2005 - 7:07 pm: |
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Well i checked it out. The coax is not labled. I found out that it is indeed the coax that they run from the utility pole to your house though. It is much thicker than normal coax. I guess the only way is to just hook it up and tast it LOL |
Wally38
Junior Member
Username: Wally38
Post Number: 29
Registered: 3-2005
| | Posted on Monday, September 26, 2005 - 9:03 am: |
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I heard the 75 ohm cable coax is good for scanners also. It's what I use. Less signal loss at higher frequencies.
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Bruce
Senior Member
Username: Bruce
Post Number: 3136
Registered: 9-2003
| | Posted on Tuesday, September 27, 2005 - 5:23 am: |
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wally TRUE 75 ohm will work for many things and with only a small SWR loss. |
Nastyredz
New member
Username: Nastyredz
Post Number: 7
Registered: 9-2005
| | Posted on Tuesday, September 27, 2005 - 6:02 am: |
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so How do you test the ohms of a cable? It sounds to me like i would have to test it under some kind of load. So does the ohms of a cable change if you decide to run a thousand feet? Im guessing that the impedence would increse. Once i get a new swr meter, (mine was stolen) I will run a few tests and follow up a report. LOL |
Tech237
Moderator
Username: Tech237
Post Number: 217
Registered: 4-2004
| | Posted on Tuesday, September 27, 2005 - 10:51 am: |
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Nasty,
No. The impedence doesnt change with length of the cable, the DC resistance would change.
Impedence is a function of the wire sizes (both inner and outter conductors) and the material used to make the dielectric. Give me a chance to get home (currently sitting in a hotel room as I write this)and I'll put a better description together and post. It can be worked out using this information. |
Nastyredz
New member
Username: Nastyredz
Post Number: 8
Registered: 9-2005
| | Posted on Tuesday, September 27, 2005 - 8:32 pm: |
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so what you mean is, I would have to count the strands of wire , and the size of it . inner and outer? Oh darn. well maybe ill lop a piece of it off, cut it open , take pics and well study it lol ... |
Bruce
Senior Member
Username: Bruce
Post Number: 3139
Registered: 9-2003
| | Posted on Wednesday, September 28, 2005 - 7:23 am: |
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nasty
Just put a 75 ohm load on it and read the swr if it's low its a 75 ohm line. |
Nastyredz
Junior Member
Username: Nastyredz
Post Number: 10
Registered: 9-2005
| | Posted on Sunday, October 09, 2005 - 9:36 pm: |
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so what your saying is you would have a high swr reading with the 75 ohm coax right? |
Hollowpoint445
Advanced Member
Username: Hollowpoint445
Post Number: 805
Registered: 6-2004
| | Posted on Monday, October 10, 2005 - 12:41 am: |
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What Bruce is saying is if you test the coax with a 75 ohm load and the VSWR is 1:1 it's probably 75 ohm coax.
If you don't have a 75 ohm dummy load or 75 ohm non-inductive resistors that can handle 4 watts, you can try it with a standard 50 ohm dummy load. The VSWR should still only be about 1.5:1 instead of nearly 1:1. |
Crackshot
Junior Member
Username: Crackshot
Post Number: 22
Registered: 10-2005
| | Posted on Monday, October 10, 2005 - 11:46 am: |
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Does copper sell coax? I cannot seem to locate it on site.  |
Moderator1516
Moderator
Username: Moderator1516
Post Number: 57
Registered: 8-2005
| | Posted on Monday, October 10, 2005 - 12:26 pm: |
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go to main page and enter coax in the search box and it will take you to it
moderator1516 |
Crackshot
Junior Member
Username: Crackshot
Post Number: 23
Registered: 10-2005
| | Posted on Monday, October 10, 2005 - 1:25 pm: |
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Thanks. Found what I was looking for. |
Beeker7104
Junior Member
Username: Beeker7104
Post Number: 48
Registered: 12-2004
| | Posted on Thursday, November 24, 2005 - 9:31 pm: |
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ok....a not so technical question that looks to be technical. QUESTION......I have a 100' spool of Belden RG9/U coax, I have Amphenol PL 259's for RG8/U(Mini 8), who carries the PL 259's for the RG9/U? All I've been able to find is the connectors that will fit the 213 or the mini 8.
oh.....and.....IF copper carries them...I need 10 of them |
Moonraker
Member
Username: Moonraker
Post Number: 89
Registered: 3-2005
| | Posted on Friday, November 25, 2005 - 12:02 am: |
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Beeker, I have never heard of RG9/U coax, is it bigger or smaller than 213 or mini 8? I'm sure you know that you can buy reducers for the PL259's, but wanted to mention it just in case. If it is smaller than 213, could you drill out a mini 8 reducer to fit the coax? If it is smaller than mini 8, could you drill out a rg 58 reducer to fit? Is the rg9/u a 50 ohm cable? |
Beeker7104
Member
Username: Beeker7104
Post Number: 50
Registered: 12-2004
| | Posted on Friday, November 25, 2005 - 5:28 am: |
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It is the larger coax, Looks like the coax my dad uses on his ham tower, except it is gray in color. It is a spool of (according to the labels on the spool) Belden RG9/U is about 1/2 to 3/4" around, 95% shield the center strand is standard coax size(for the larger coax) says it is 51 Ohm coax.....this is listed on the coax itself. The pl259's I have are too small for it though(this being because I mostly use mini 8). it looks like the older style of coax....ya know....the hard to bend coax that was used in yester-year times. |
Tech291
Moderator
Username: Tech291
Post Number: 300
Registered: 11-2004
| | Posted on Friday, November 25, 2005 - 10:25 am: |
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Beeker,
belden RG9 is 10.3mm diameter,51ohm,double shielded equivelent to rg-214.
regular pl-259 used on rg-213 and rg-8 will fit.
rg-8m/rg-8x uses the same connector with a ug-176 reducer
tech291
cef#291
kc8zpj
|
Beeker7104
Member
Username: Beeker7104
Post Number: 51
Registered: 12-2004
| | Posted on Friday, November 25, 2005 - 2:53 pm: |
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ok...so why is it that I can't get it to fit inside the pl259's I have here...does the threads get in the way if the thicker shielding on this coax which is preventing me from soldering the connector to the coax? |
Tech291
Moderator
Username: Tech291
Post Number: 302
Registered: 11-2004
| | Posted on Saturday, November 26, 2005 - 10:25 am: |
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Beeker,
r.f.parts show the same connector for rg-8 and rg-9.I have never worked with rg-9 so it is hard for me to picture what your talking about,
Beeker said "...does the threads get in the way if the thicker shielding on this coax which is preventing me from soldering the connector to the coax?"
tech291
cef#291
kc8zpj
|
Beeker7104
Member
Username: Beeker7104
Post Number: 56
Registered: 12-2004
| | Posted on Monday, November 28, 2005 - 10:36 pm: |
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opps....typo....but never mind, I just had to push it harder. It will fit. |
