Convert old VHF/UHF deep fringe antenna into VHF high?

[joseph10]

All,
Hello. I am new to the forum. I have been having problem with the high band VHF channels since the digital switch (channels 8, 11, 13).

I have an antenna in the attic and it is one of the old school "deep fringe" antennas - starts with about 6 dipoles starting with a 5' span, working down to a 3' span - then a bunch of UHF dipoles at the end.

The channels that were left on UHF or re-assigned to UHF are near 100% signal strength with just a 1' piece of coax running into my channel master 7777 preamp. So, it doesn't seem like I need much of a UHF antenna for near-perfect reception. So, I think just having a single high band VHF antenna should work for the 8,11,13 and all the UHF.

Since this old antenna was designed to be a full band VHF/UHF antenna, the dipoles on the long end are targeted to the lower channels (2-6).

I found a dipole calculator on another site. What would happen if I shorten all 6 dipoles to match the 3 channels I need. In other words, cut them down to have 2 dipole pairs for each channel:

Channel 8 -> center at 184Mghz @ dipole half length at 1.27' (total span is 2x of that)
Channel 11 -> center at 200Mghz @ dipole half length at 1.17' (total span is 2x of that)
Channel 13 -> center at 212Mghz @ dipole half length at 1.105' (total span is 2x of that)

Would that help this antenna perform more like a high VHF (7-13) antenna? Or would it just completely mess up the impedance of it and ruin it? From the reading I have been doing, the boom length doesn't affect the impedance, correct?

The only other choice I have is to buy one of the high VHF antennas, but I thought this idea might be worth a shot first.

Any help or inputs would be greatly appreciated.

Thanks,
Joseph

[tigerbangs]

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