| Author |
Message |
    
Thegriz
New member
Username: Thegriz
Post Number: 1
Registered: 3-2005
| | Posted on Monday, March 21, 2005 - 6:21 pm: | 
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What are the signal dB loss curves for both RG8X Mini Coax and RG8U Coax in the 26 to 28 Mhz ranges? I would think there would be some web posting where you would see the dB loss on say the Y-axis versus distance on the X-axis...or something similar.
Thanks for any help anyone can provide here,
Griz |
Marconi
Intermediate Member
Username: Marconi
Post Number: 408
Registered: 11-2001
| | Posted on Monday, March 21, 2005 - 8:42 pm: |
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You could check the loss facts between the two and use your imagination a little or you could put 4 watts into each with a dummy load and meter at the other end and just see what you get. This won't give you that X/Y axis business you are looking for, but it will suggest that there is a considerable difference starting at about 50' and longer.
I check my lines this way and I see the difference and it is good enough for me. |
Dx431
Advanced Member
Username: Dx431
Post Number: 992
Registered: 2-2002
| | Posted on Tuesday, March 22, 2005 - 1:33 am: |
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Try this site.....http://www.timesmicrowave.com/cgi-bin/calculate.pl |
Thegriz
New member
Username: Thegriz
Post Number: 4
Registered: 3-2005
| | Posted on Tuesday, March 22, 2005 - 2:49 pm: |
|
Marconi...good suggestion. Should provide some valuable insight for already established setups.
However, still looking though for something along the line of my previous message as a reference for planning. Otherwise I need to do duplicate setups for the coax's considered. This just wouldn't be practical or cost effective.
Thanks. |
Bruce
Senior Member
Username: Bruce
Post Number: 2378
Registered: 9-2003
| | Posted on Tuesday, March 22, 2005 - 3:26 pm: |
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WHAT?????? X? Y? sounds like beams with E and H planes
I aggree with marconi he is right best way is when you know how much you need put 4 watts in and measure what you get out .....
Example on the 440 mhz band ( 3/4 meters ) RG8X with 4 watts in will give you about .2 watts out at 100 foot .....( 13 db loss ) not a good choice ... however at cb you should get about 2 watts or 3 db loss ....... RG8 will give a slightly less loss..... both will work just fine and the LESS coax you use the less loss.
If you get 2 db or less ( about 3 watts out ) dont even worry about it. |
Marconi
Intermediate Member
Username: Marconi
Post Number: 410
Registered: 11-2001
| | Posted on Wednesday, March 23, 2005 - 9:55 am: |
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You're right about planning, but that only gives you what the spec of a line call for and not the real results. That is why I check the real line every time before I go up. All lines are not the same, even among the same brand you can sometimes see a difference.
Dx431 gives you a good site to look at for your planning ideas. Physical differences can also be important in some installations. |
Tech237
Moderator
Username: Tech237
Post Number: 143
Registered: 4-2004
| | Posted on Saturday, March 26, 2005 - 12:03 pm: |
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Take a look at any year of THe ARRL Handbook they all have a chart showing the loss of different coax over 100ft at several different frequencies.. |
Mikefromms
Advanced Member
Username: Mikefromms
Post Number: 533
Registered: 6-2003
| | Posted on Friday, April 01, 2005 - 10:35 am: |
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I say use the best coax you can afford. Often the coax is overlooked in the antenna system. I've even seen guys use 15o foot of rg-58 and then wonder why they can't hear what I hear. Use the best you can afford. Save up and get it. The longer the run of coax the better the coax grade should be. For example, I run LMR-400 for a 150 ft run. Wow!
mikefromms |
