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cushcraft r8 antenna problems

Jul 9th 2012, 03:15

Bmagill

Joined: Jul 6th 2012, 16:13
Total Topics: 0
Total Posts: 0
I just assembled and put up my new cushcraftR8 antenna. Being very meticulous to assemblyI am currently unable to tune ANY of the 8 bands at all. Im getting greater than 10:1 swr and cannot tune in at all. Ive rechecked all connections and grounds. Does any one have any ideas?
Jul 10th 2012, 13:42

K0BG

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
The R8 is a loaded half wave antenna. As a result, it is very susceptible to stray capacitance from surrounding objects, and it needs to be mounted free and clear as possible. I don't recall the exact wording, but the manual does state that the antenna must be mounted above ground level, and away from trees, fences, and other structures.

Jul 10th 2012, 17:01

Bmagill

Joined: Jul 6th 2012, 16:13
Total Topics: 0
Total Posts: 0
The antenna is mounted up on the roof of my single story using the recomnmended chimney mount and a 5' mast so its a minimum of 35' from earth ground.
Jul 10th 2012, 19:35

WA0CBW

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Have you checked the coax for a short or open?

Bill
Jul 11th 2012, 12:47

K0BG

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I agree with Bill on the coax.

If you're measuring the SWR in the shack, and the antenna has reactance (mistuned), then the reading in the shack could be almost anything. If you know the exact length of the coax feed line, that length can be factored out, and give you the SWR at the antenna.

One thing you want to recheck is the way the black box is mounted, and connected. The instructions are a bit vague, but the pictorial is self explanatory.

Jul 12th 2012, 09:03

Bmagill

Joined: Jul 6th 2012, 16:13
Total Topics: 0
Total Posts: 0
Hi guys, Thanks for the input. A fellow hammer came over yesterday with an antenna analyzer and did confirm the problem is the Matching Network box, antennas dead throughout all bands. Now Im at the mercy of Cushcraft to get me a new one sent. Thks again.
Jul 12th 2012, 12:35

K0BG

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
No mercy needed. MFJ's warranty is solid! Again. Make sure you have the box attached correctly. It is very easy to get it wrong.

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