AVS Forum banner
Status
Not open for further replies.
1 - 6 of 6 Posts

·
Registered
Joined
·
695 Posts
Discussion Starter · #1 ·
I'm heading back up onto the 30' ladder to install a rotor this weekend. I've got a CM 9521A rotor and a CM 7775 pre-amp. Mounting the thing isn't really an issue (pretty straightforward), but my question is how/where to mount the rotor vs. the preamp. The preamp should be mounted as close to the antenna as possible, but obviously the rotor is gonna go up there first, right? If I mount the preamp just below the rotor on the main mast (on the opposite side as the front of the rotor), am I going to get any interference or other problems? Any recommendations or suggestions would be appreciated.


Also, can anyone recommend a good tool to tighten those damn nuts on the CM 7775 preamp? I can't get my 6" crescent in there, and the bolts are too long for a socket!
 

·
Registered
Joined
·
3,681 Posts
I am just another hack, not a professional so take this for what it is worth.


Here's what I did. Attach the antenna to the small section of mast on the ground. Attach the pre-amp as close to the antenna as reasonably possible. If you have a yagi a few inches (maybe 6") or so below the antenna. Wire it together with the 300 ohm stuff. Make sure it it ri=ght while on the ground. Then carry the assembly to the roof, and mount it to the rotor. Attach the coax, and make sure the connections are weather proofed. Leave a loop of coax so that the antenna spins freely.


SM
 

·
Registered
Joined
·
1,273 Posts
Quote:
Originally posted by Randy Boecker:

Also, can anyone recommend a good tool to tighten those damn nuts on the CM 7775 preamp? I can't get my 6" crescent in there, and the bolts are too long for a socket!
Do yourself a favor -- before you climb the ladder, stop by a hardware store and buy a 7/16", deep socket. All the rotor and preamp nuts are this size. It makes things alot easier.


No need to get too carried away with the "as close as possible" stuff for the preamp. The attenuation through 10 ft. of RG-6 is negligible. Go ahead and mount it below the rotor (with a generous loop so it doesn't get wrapped around the mast when the rotor moves). By trying to mount the preamp too close to the antenna, I'd worry about the preamp housing de-tuning the antenna.


------------------

You have a right to install OTA and dish antennas on property under your control.


See http://www.fcc.gov/csb/facts/otard.html
 

·
Registered
Joined
·
3,681 Posts
My amp was 300 ohm in, 75 ohm out. I wanted to keep as little 300 ohm twin lead as possible, and wanted it away from the rotor. Secondly, my antenna was a 8 array bowtie, so I could mount the amp behind the reflector.

Aside from that, I don't think an amp 6" from a antenna will "detune" it, but I would have emphisized the "reasonable" and not the "as close as possible" in my suggestion.


Like I said, I'm a hack, not an installer.



SM
 

·
Registered
Joined
·
1,273 Posts
Randy's preamp is 75 ohm input; my comments were addressed specifically to his situation.


------------------

You have a right to install OTA and dish antennas on property under your control.


See http://www.fcc.gov/csb/facts/otard.html
 
1 - 6 of 6 Posts
Status
Not open for further replies.
Top