BiQuad Antenna Maximum Coax Length?

wyoung71 · #1 (**permalink**) 03-30-2008, 03:18 PM

Hello All,
I was wondering if someone could answer a question as it pertains to coax length with a home made BiQuad antenna. I designed a BiQuad antenna for my production plant and the antenna works well. The issue I'm having is I need to roof mount the antenna and run coax to the antenna. How much would be considered the maxium length of coax cable I could use before I notice signal lose/degredation? I have exsisting coax from and old Sprint braodband connection that is no longer in use. All the examples on the net I can find use a short length of coax before they tie into the pigtail. Am I way off base here thinking this is possible?

Thanks,
Bill

WiFiNewbie · #2 (**permalink**) 03-30-2008, 07:48 PM

The maxium length of coax cable for Low Loss cable 400 is 20-25M.

wyoung71 · #3 (**permalink**) 03-31-2008, 03:46 PM

Thanks WiFi.

Mark Oney · #4 (**permalink**) 03-31-2008, 06:11 PM

LMR400 cable loses 6.8 db per 100 feet, or 22.2 db per 100 meters.

A 100 foot run of LMR400 negates the benefits of a 7 db gain antenna.

LMR600: 4.4 db /100 feet, 14.5 db / 100 meters

Plan Alpha is to mount the AP or wireless bridge on the mast, and use a long run of CAT5 to a router in the building. You can use up to 185 feet of CAT5.

rids · #5 (**permalink**) 04-03-2008, 11:30 AM

Hi Guys, We're building a biquad antenna feed because it offers very good performance and is pretty forgiving when it comes to assembly errors.Biquad antennas can be built from common materials, which is nice We did have to buy some specialized parts before getting started though. This summer the longest link ever was established over 125 miles using old 12 foot and 10 foot satellite dishes.

wyoung71 · #6 (**permalink**) 04-05-2008, 03:39 PM

Hey thanks guys. I know it's funny becasue I work for a concrete company I have all these parts lying around in the IT office and I get curiosity seekers asking "We geetin any porn on that thing?". Suffice it to say these people are as dumb as "Rocks" LOL. Ok well enough of that. I guess my next question is two-fold.

1. How do I find the focal point of the parabolic dish?

and

2. Any ideas on making my access point on the bridge weatherproof? I've seen tupperware and such but I was thinking more along the lines of a lock box of some sort. The problem is that I'm in Phoenix, Az. and the summer temps are hot. Just last year had about 110 day over 100 degrees farenheit. I think I need a cooling system of some sort?

Thanks

Bill