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Keithinatlanta
| | Posted on Saturday, November 01, 2003 - 5:44 pm: | 
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Forummaster, please post this else where if needed. However, if you do, please leave question here as well and ask everyone to answer at other posting site, if possible Thanks.
Hey guys, unconfuse me here. We all read about radios and antennas. Let's talk COAX. Give me a guide to go by. I see Rg 8 RGu 8, etc etc etc. How do you choose what coax for what application? I want to get my CB base station set up. Nothing fancy, just a new Super Scanner with a Lafayette 40 channel AM/SSB base. Which coax do you use? Does the height of your antenna determine which one to use? What I would like to see is a CHART to go by. Maybe there is a web site already for ready reference. So take off here guys and let's see what you come up with. I would find it hard to believe that I am the only one who needs this education. And then again, you never know! Thanks in advance!
Keith in Atlanta |
de
| | Posted on Saturday, November 01, 2003 - 7:42 pm: |
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Ok first lets start off with a good chart of the common coax types. One good chart is in the ARRL Handbook in the Transmission Line Section. Any of the printing in the recent years will do.
Looking at the charts you will see numbers, numbers numbers. But here are the good rule of thumb(s). Note the size/diameter of the coax. The bigger the coax the more power it will take. Also note the ohm charistic of the coax. All legal CB radios operate on 50 ohm coax. All modern ham radios operate on the same 50 ohm coax. BUT if you use a device called a Transmatch or Tuner you can convert 600 ohm or higher ohm coax into a friendly 50 ohm value thus making your radio happy.
Now coax does not have to be coax. You can use ladder line or even old fashioned 300 ohm tv twin lead as coax if you use the transmatch referenced above.
It should be of interest to know that the old timers of the ham world made their own transmission line using just wire and spacers. AND amazingly it is incredibly efficient, BUT it is of high ohm value so they had to use a tuner to bring transmission line down to a happy value for their transmitter.
Lastly you will note on the chart the loss numbers for a set of radio frequencies. Loss is wasted energy that never makes it to the antenna. These numbers are usually in db's Now DBs go something like this. For each three DBs you double or in the case of coax loss reduce the power by half. So if a type of coax has a db loss of 3 DBs then half (reverse of double) of the incomming signal never makes it to your radio. And likewise if you transmit half of your signal power never hits the antenna.
I hope I have not confused you. If you have any questions on Coax aka Transmission Lines you can find complete details in the ARRL Handbook or the ARRL Antenna Book. |
Ca346
| | Posted on Saturday, November 01, 2003 - 7:42 pm: |
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I ended up buying 213 coax because it is very low loss coax. But the search went on forever. I bought it for the low loss factor, NOT by price. I am hoping I will not have to replace anything for awhile. I have two lines of 213 coax that are 110 ft each to a polarized antenna. I have 100 ft of plain old RG58 to a vertical multi-band antenna. I am waiting for the IMAX 2000 from COPPER to use the 50 ft of RG58mini-x left over from something. Come to think of it, I may be replacing the mini-x.
This should be an interesting thread! |
Ca346
| | Posted on Saturday, November 01, 2003 - 9:22 pm: |
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Realized I had a senior moment in my previous post. The cable I ended up buying was RG8/U. It had the lowest loss of the coax I looked at. 1.7db/100ft. |
Kattracker
| | Posted on Saturday, November 01, 2003 - 9:54 pm: |
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Keith,
To put it simply,... RG-213 would be very good for your set-up.
Kattracker |
Keithinatlanta
| | Posted on Saturday, November 01, 2003 - 10:04 pm: |
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Ca345, I hope you are right about " This should be an interesting thread". I want it to be just that. Sometimes we get on here to discuss and just argue. I hope I can learn from this one, as I hope others can learn from it as well. de, thank you for your comments to. I am looking forward to more info from everyone. It will be interesting to see if someone says "yea I tried that, and I had to change to ...". Anyway, let's hope it brings some more great info like you two just provided. For others who might post, just remember, I am running a plain old 40 channel cb with a NEW Antenna Specialists Super Scanner. No modified radios, no export radios, etc. Just plain old jane, if you will. Thanks!! Wait till you see my next question regarding this topic, once we have finished this one.
Keith in Atlanta |
Moderator558
| | Posted on Sunday, November 02, 2003 - 2:05 am: |
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Here is a comparison calculater maybe it will help
http://www.timesmicrowave.com/cgi-bin/calculate.pl |
Bigbob
| | Posted on Sunday, November 02, 2003 - 7:20 am: |
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Hey,consider this,the more % shield the less loss and better tvi control with standing waves,at high power coax heats up,conductors expand lengthwise,the jacket and shield try to prevent this,foam dielectric is soft and mushy and I've seen cut-aways where the center conductor has melted the foam and contacted the shield on key-downs,it can happen with solid dielectric but takes longer unless the dielectric is teflon much higher heat resistance,jacket may burn off before center conductor migrates in cases of to much power being applied,now the jacket teflon is best it is stiff,abrasion resistant,and can with stand a grass fire,type cl-2 or ncv is second it is stiff slightly less abrasion resistant than teflon and can last 30 years, there is no plastisiser in it to make it flexible,cheap pvc unmarked jacket is soft and flexible and usually shiny,it may last 10 years before cracks are visible and is not as strong and abrasion resistant as ncv or type cl-2,I use RG8 solid-dielectric type cl-2 jacket and mini-8 foam-dielectric type cl-2 jacket.At ten years the line was taken down,tested and judged o.k. 4 watts in 3 3/4 watts out,watt meter on each end terminated by a 50 ohm dummy load,this line is 135 feet long.When it comes to transmission line don't spare the pennies,unless you want to take it down every ten years and test it's efficiency.My father-in-law thought he made a great deal bought a radio a star-duster and 300 feet of coax used, we spent two weekends setting every thing up,and we had fun dxing,well ten years and another pres.washington and a super scanner,he wasn't getting the reports he thought he should be,so down came the coax,it is OLD,4 watts in 1/2 watt out, "perfect"match ,he was dumbfounded couldn't afford to buy new,so cut coax in half,happy day bad spot in half we didn't use,a crack allowed water in and ruined it,this section was buried.Bigbob |
Buck
| | Posted on Sunday, November 02, 2003 - 8:26 am: |
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My runs are relatively short (40') but I use RG-213 for everything. 11 meter, 6 meter, and 2 meter. The 213 has been great for my application
Buck |
Tech808
| | Posted on Sunday, November 02, 2003 - 9:25 am: |
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We use RG-213 for everything including all jumpers inside of shack.
Never had a problem.
58/U Type = 500 watt Maximum
MINI 8/U Type = 1000 watt Maximum
8/U Type = 2000 Watt Maximum
213 Type = 5000 Watt Maximum
Lon
Tech808
& 1st Sargant |
Znut
| | Posted on Sunday, November 02, 2003 - 10:45 am: |
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Considering all factors such as loss, power handling, durability and cost the best choice for any band up to 30mhz is without a doubt RG 213.
If you are going over 250 feet or so then you may consider lower loss options. |
Kirk
| | Posted on Sunday, November 02, 2003 - 9:23 pm: |
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Put me down for RG-213, but use RG8x for inside jumpers. |
mikefromms
| | Posted on Monday, November 03, 2003 - 6:44 pm: |
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Where did you find a new Super Scanner?
mikefromms |
Keithinatlanta
| | Posted on Monday, November 03, 2003 - 9:32 pm: |
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Hi Mike. I found it on the web about 1 1/2 years ago. I also found a PDL II Quad right before that. Unfortunately, they are both still unopened in their original boxes, waiting for me to put them up. With my business travels, it is hard to get things done around here. I have seriously considered selling the PDL II, and just going with the super scanner. Know what I mean?
Keith in Atlanta |
Pig040
| | Posted on Tuesday, November 04, 2003 - 9:55 am: |
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Superscanner is more convenient, PDLII is a true beam, much better antenna, even though the superscanner is a popular curiosity. Keep em both! But if you only put one up, make it the PDLII, you wont regret it! |
mikefromms
| | Posted on Tuesday, November 04, 2003 - 6:45 pm: |
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I've had both and loved them both. I have my best memories with the super scanner when it was high in a tree and was powered by a Cobra 2000gtl and an extra 150 watts! Man, I was jellin' then.
mikefromms |
Keithinatlanta
| | Posted on Wednesday, November 05, 2003 - 10:15 am: |
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Hey Mike and Pig. YOu may not believe this, but I have just found a place that still has the Moonraker 4 Beams for sale! They sent me an e mail confirming that they still have some and how much they cost.
Keith in Atlanta |
Keithinatlanta
| | Posted on Thursday, November 06, 2003 - 4:49 pm: |
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Now some of you say one way for jumpers, and others say another way. So which way is best, or does this qualify for either way is a ok? Thanks.
Keith in Atlanta |
808xyl
| | Posted on Thursday, November 06, 2003 - 5:47 pm: |
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Very Simple, use which ever one fit's a person's need's best to use for jumper's.
RG-8 type rated at 2000 watts
RG-213 type rated at 5000 watts and is a little more expensive.
If you are not going to have high power then either will work.
As 808 can get carried away at times we use RG-213 for everything.
Make's me feel safer!
1st Sargant
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Keithinatlanta
| | Posted on Thursday, November 06, 2003 - 6:24 pm: |
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Ok 1st Sargant. Now let's fine tune this for my set up. As stated in my first post, I will use a Super Scanner with a Lafayette am/ssb 40 channel radio. NO power, just plain jane here. Based on that, is rg8 good enough, what about the mini rg8 or rgu8, or whatever? Now folks, come back to me with what I need for my set up. I understand the need for 213, but since I will not be running ANY power, is it still necessary? Again thanks to everyone for input.
Keith in Atlanta |
Sandbagger106
| | Posted on Thursday, November 06, 2003 - 6:45 pm: |
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Being a "budget minded ham" I use RG 8/U for runs less than 100 feet and at freqs, from 7 megs up to say 30 megs. I also use RG 8/U at 150 megs for runs up to 50 feet or so. 7 megs and below I use real inexpensive RG 58/U, low loss at that freq range up to 100 feet. Uhf is where you best be shelling out the big bucks for quality cable. I also use ladder line for some applications. The bottom line here is what freq and how long the run will be. sb106 |
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