I suspect that all Jointennas are 20 years old, and that ChannelMaster has been selling off its, "New, old stock" since the 1990s.
It is less important now with digital signals than with analog ones. What bothers me more is that the Winegard UT-2700 UHF notch traps are in unshielded cases, because unshielded components are more efficient as UHF antennas than as VHF antennas. That, and the fact that Winegard more than doubled their price half a dozen years ago. Nevertheless, I always make sure I put the unshielded, cheap traps at the "top" of any filtering chain I make. I had about twenty, tuned cylinder trap pairs made up by CE Filters before they went out of business to pass 7-9 and 11-13, but in downtown DC environments, too much 9 makes it through the channel 11 highpass filter, and so I put a channel 9 Jointenna ahead of it to knock down channel 9 another 20dB. If I put the Jointenna after the shielded cylinder, the ingress would be a problem.
Similarly, with the old Tru Spec UHF BPFs, I always install them "upside down", using the connector labeled as the output as my input, because the shielding is better on the end of the filter that is labeled input.
That's what I was going to recommend once we got to the point where we had determined that out-of-band signals were contributing to his problem, but beyond that, I am skeptical about intermodulation being his problem, I've never had combined 7 and 9 damage the 11 such that it made the difference between reception and no reception. I think he more likely has multipath aggravated by an obstructed transmission path. Unfortunately, with digital signals, we can't see the ghost images like we could with analog, so even after we have remedied a problem, we often don't know for sure how much each element of our remedy contributed to our success.
Edited by AntAltMike - 12/14/13 at 9:42am