HD7698P VHF signals dropout intermittently

[punkinheadedboy]

New HD7698P antenna install. Initial scan got both VHF channels and some UHF. Added a Channel Master preamp and rounded out the UHF channels that are available at zip 52068.
Its mounted on a Rohn tower approx. 19 feet off the ground. New cables and connectors.
Getting all the major network channels, PBS, ION, Fox, CBS, NBC, ABC.

Now I'm one month into the install, getting ready to drop the dish and go OTA only.

My 2 VHF channels (7and 9) start acting up. First it is low signal part of the day, then strong signal later. Sometimes they are strong for a few days...

Now the 2 VHF channels are gone. No signals.
UHF channels are just fine.

Took the preamp out of the loop, and still no VHF signals.

Any ideas?

Thanks

[punkinheadedboy]

checked the vhf channels this morning.

They're back, and strong.

What could be going on here?

[southwoods]

I am having the exact same problem. Have you come up with a solution yet?