Author Topic: coax cable  (Read 13048 times)

Offline flycrj

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coax cable
« on: August 17, 2007, 03:25:12 PM »
Ok, I need some advise...
I am finaly getting around to buying a discone Antenna. 
http://www.radioshack.com/product/index.jsp?productId=2103160 

I just need to know which coax cable to get.  I am far from an expert on this, so I dn't know which to get, all I know is that obviously, I want a low-loss cable.  I will need between 75-100 ft of it to run from the antenna on my roof to my scanner (radioshack pro-82) in my room.
(I should also mention in case it matters...the cable will becoming down from the antenna to a T connector.  One cable will then go to my room, the other to my office...neither is more that 35 ft. from the antenna, so really it is only 35 ft. of cable from the antenna to the scanner.)
Hope that all isn't too confussing!

So hopefuly someone can help me out here, I just need to know what cable to get.

Thanks!
Connor



Offline Jason

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Re: coax cable
« Reply #1 on: August 17, 2007, 06:42:57 PM »
I'd recommend 50 Ohm RG6 or Belden 9913.  They're thicker cable, but definitely worth it for the lower loss over many feet.  RG58 quality is sometimes questionable, especially when running it in great lengths.

Offline flycrj

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Re: coax cable
« Reply #2 on: August 17, 2007, 06:56:15 PM »
ok, thanks!
Now one more detail, how do you guys have your cable run through your windows (or any way intothe house)?  I can't seem to figure thaty bit out either.

Thanks, Connor

Offline KSYR-pjr

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Re: coax cable
« Reply #3 on: August 17, 2007, 07:02:04 PM »
Now one more detail, how do you guys have your cable run through your windows (or any way intothe house)?  I can't seem to figure thaty bit out either.

Do you have air conditioner piping that runs through the wall from the outside compressor?  I run my RG-8 antenna cable through the hole in the outside wall that is plugged with a putty surrounding this pipe.

Offline flycrj

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Re: coax cable
« Reply #4 on: August 17, 2007, 07:19:29 PM »
well yes, but there is no pipe to my knowledge running upstairs.  I also thought about running it in through the attic vents, but that would require running it to the other side of the house, thus using an extra couple hundred feet of cable.  I will be mounting the antenna on a furnace exhaust pipe, but I don't think I want to drill thourgh that! 

Any other ideas?
Thanks, Connor

Offline janetva.net

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Re: coax cable
« Reply #5 on: August 19, 2007, 02:11:32 AM »
I would not waste my money on COAX unless you have money to waste  :-D

Here is what I would suggest since your coax is short with no splitters using the cheapest coax you can get your hands on or even better (FREE) try going around to apartment complexes and asking the maintenance staff if they have some extra RG59TV coax lying around they could give you

I am going to stop the ?? that some of you may have yes the RG59 is 75ohm however your scanner can not tell the difference from 50 to 75 ohm and will not suffer much loss or any at the the Air Band VHF frequencys

My feed has two 25ft sections attached together to make 50ft of RG59 75ohm coax I get signals from S-5 to 40+ over S-9 from KLAS There was NO noticeable difference between RG 9913 and RG59 at VHF Air Band frequencys ! so therefor my good 9913 went back to my Ham Radio

On the other hand your discone has negative gain over a Quarter Wave Ground Plane !!! and your using 100 or is it 50ft of coax?? that is unclear to me.........so maybe you need all the help you can get  :-D

Now this raises another ?? do you buy good coax for a discone antenna ? (buy or make) a Quarter Wave Ground Plane cut exactly to the Air Band VHF frequencys using cheap coax?

Please remember it all starts with the antenna so I think you know where I am going here  :-D

Anymore ?? please PM me I would be more then happy to help (after all its what I do)

Glenn KB6HLM
http://audio.liveatc.net:8012/klas.m3u
« Last Edit: August 19, 2007, 02:48:45 AM by janetva.net »

Offline flycrj

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Re: coax cable
« Reply #6 on: August 19, 2007, 11:29:35 PM »
There has been a slight change in plans... in order to get cable into my house, i have to run it to the front of the house, that is the closest hole.  so i will now be using as much as 100 feet of cable to each plug-in.  (It will run from accross the roof, through the attic into a crawl space, and then spilt.  One to my room, and one to my office...each equal distince from the T connector.  So it will be as much as 100 ft. from the antenna to the scanner, all though I have not measured itexactly yet.)

Yeah, I really don't know a whole lot about all of this.  I have already ordered the antenna, so i am stuck with that.  But I do ask, will the set-up work, that is with 9913 cable if i can't find other?  I am correct to assume that it would not be ideal even if it does?   

I am also a little confused at this...
"Now this raises another ?? do you buy good coax for a discone antenna ? (buy or make) a Quarter Wave Ground Plane cut exactly to the Air Band VHF frequencys using cheap coax?"

I really use all the help i can get!

sorry to be a pain!

thanks,
Connor

Offline janetva.net

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Re: coax cable
« Reply #7 on: August 20, 2007, 04:21:49 AM »
What I meant was it would have been a better choice to put up a antenna cut for the airband frequencies instead of feeding the discone with good coax since the discone is a "so called all band antenna" witch performs poorly IE: not optimized at any frequency

However if your using the discone for the other scanners in the house and don't want to put up more antennas and coax this would be a good choice for you :-)

Now with this kind of setup in mind since you are using 100ft of coax and then splitting it two ways may I suggest a good quality Active Multicoupler ?

This would help in the now huge amount of loss you will suffer no matter what kind of coax you use specialty in the UHF range !

Here is what I would recommend Active Multicoupler Model MCA202M this will give you no loss at splitting and in fact a Gain of +4 dB if you need more then 2 ports there are other models http://www.stridsberg.com/prod01.htm

The down side to this kind of set up it comes at a high price tag but it will save you from putting up more antennas and running more coax

It is my hope I did not discourage you but in fact helped you along the way to success :-)

Glenn KB6HLM
http://audio.liveatc.net:8012/klas.m3u


PS
BTW I am thinking about setting up something like that myself since I have 5 scanners running all at the same time witch requires 5 antennas !
1 discone 1 coax 1 Active Multicoupler   maybe thats not a bad idea ??  the only thing I did not like about the Multicoupler it stops at 1Ghz and 2 of my scanners can go up to 3Ghz  but I could make a nice antenna just for the 1Ghz to 3Ghz range witch is outside of the discone range anyway !

What I may end up with is a Custom tuned 5/8 wave Aircraft Band Antenna using a Muticoupler for 2 of the scanners that FEED LiveATC APP/DEP on one and TWR/DEL on the outer and then other scanners using the discone

Here is the antenna I am thinking about buying for the feeds LARSEN SUPER BASE http://wingsandwheels.com/page14.htm

O the fun goes on and on :-)
« Last Edit: August 20, 2007, 05:38:56 AM by janetva.net »

Offline dave

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Re: coax cable
« Reply #8 on: August 20, 2007, 08:02:31 AM »
You can save a substantial amount of money by using 75 ohm TV components.  You'll just need to do some conversion from "F" connectors (CATV connectors) to BNC here and there.

I have used this amplifier with good results:
<http://www.radioshack.com/product/index.jsp?productId=2103913>

If you want a more narrowband amplifier (recommended if you are near a lot of radio transmitters, TV, radio), then order a preamp from:
http://www.advancedreceiver.com

If you do use an amplifier, I recommend using this $30 filter:
http://www.universal-radio.com/catalog/filters/0880.html

The Radio Shack preamp is designed to be mounted outside (the amplifier stays inside).  Hook up the filter after the amplifier and before the power splitter.  Using the amplifier ensures that you will overcome the splitter loss, which is the critical thing.  Use a normal CATV splitter - you probably have 2 or 3 lying around like these:

http://www.oatco.com/catv_split.html

Even if you have to buy one, they're really cheap.  Just make sure you amplify before feeding the power splitter - otherwise you lose most of your signal in the power splitter.

Dave









Offline flycrj

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Re: coax cable
« Reply #9 on: August 20, 2007, 03:14:55 PM »
Ok, so what i am getting out of all this...

-It is okay to ude TV cable instead of coax regurdless of a 50 or 100 ft. run, with no big performance difference.
-Since I am running it to two connections, I shoud use an amp., filter, and splitter, in that order.  (is that still with TV cable, I assume I am to run TV cable all the way to the scanner, and use an adapter at that point?)


And if I am able to, I may be able to drill a hole in the roof to shorten the run to maybe 30 ft.  If so, does all of that still apply?  I know, I need to make up my mind! :-D 

Anyways, thanks for all the help!

Connor

Offline Lexxx

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Re: coax cable
« Reply #10 on: August 20, 2007, 05:56:21 PM »
Well, here's what I did with great results.

Built a quarter wave antenna for the air frequency I wanted. Mounted it in my attic and ran the antenna lead down the side of the house tucked in behind the rain downspout. I drilled a hole through the exterior brick wall into an office in the basement where my scanners are. (Filled the drilled hole around the cable with putty).

Here's a link to the antenna construction http://cykf.net/Liveatc/Antenna.htm

Here's a link to the system and comments about 50 and 75 ohm cable differences I found. http://cykf.net/Liveatc/Equip.htm

The Stridsberg multicoupler is very expensive and you will get equal, or perhaps even better results with the Electroline version I used. Cost me about $18.00 after delivery (Ebay).

I'd suggest you use a single feed inexpensive TV 75 ohm cable down to the multicoupler, as close to the scanners as possible.

The antenna, cable and assorted 'bits' are not very expensive. Certainly a tiny fraction of the cost of a scanner. Do it cheaply to begin with. It'll be more fun, and you can obviously get better antennas and cables after if you feel you must.

My 2 cents.

Good Luck

Lexx
www.ykf.ca

Offline janetva.net

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Re: coax cable
« Reply #11 on: August 20, 2007, 10:08:11 PM »
Well I guess I was just blowing in the wind there :-(

Anyway I am not sure if I would agree with Daves radioshack TV amplifier can you imagine all the intermod the two radios would suffer? and its very noisy amp

I see why Dave suggested the filter however you would not need one with a good multicoupler :-)

This is why I suggested a good Active Multicoupler to solve two problems IE: insertion loss/intermod

 "port-to-port isolation of the coupler. Isolation will reduce the possibility of RF interaction between receivers caused by local oscillators"

However if your two radio scanners are only scanning the same VHF band this may not be a problem at all

Maybe this is what Dave was thinking here?

Please correct me if I was wrong but I thought that you was going to use the other scanner for Scanning other bands?

If the two are only for the Air Band VHF  then go the cheap route (mine was almost free) I am using TV coax with a home made antenna total cost $3.00 lol


Glenn KB6HLM
« Last Edit: August 20, 2007, 10:33:35 PM by janetva.net »

Offline flycrj

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Re: coax cable
« Reply #12 on: August 20, 2007, 10:20:41 PM »
I should have made myself a little more clear, sorry.  The 2 connections are for the same scanner, it is just so that I can plug it in at either spot.

Offline janetva.net

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Re: coax cable
« Reply #13 on: August 20, 2007, 10:45:34 PM »
HA HAAAA  :-D

Now I am on the same page sorry for the misunderstanding  :roll:

Ok now that would not be a problem at all  since your radio is not connected to another radio !

Now the only thing I would suggest then would be to terminate the end your not using and then your radio will not suffer any loss from your splitter or from it becoming a antenna itself !

Well I feel much better now  :-D and I am very happy if I helped in anyway

Again sorry for the misunderstanding

Glenn KB6HLM


PS
you don't need the Multicoupler with that kind of setup save your money and just use a cheap splitter insertion loss will be very low since you only have on radio hooked up to it !
« Last Edit: August 20, 2007, 11:07:06 PM by janetva.net »