Post Transition VHF Antennas

[Mike500]

From viewing Solid Signal | Digital Converter Boxes, DIRECTV® Systems, HDTV Antennas, DISH Network, satellite equipment and home entertainment supplies & accessories and other manufacturer's sites, I only see a very few of these......I guess the shelves are still full of antennas that still work with vhf low channels 2-6.

Since almost no station transmits in vhf low (except for a few low power analog stations), post transition antennas need not be wider than 35 inches.

I found this Winegard as a fine example;

Winegard HD 7694P High Definition VHF/UHF HDHD769 Series Antenna (HD7694P) | HD7694P [Winegard]

I have a Winegard HD7210P that has been up on the roof for over 10 years and has provided superb performance bot before and after the transition.

I have only one VHF channel at 7 (actual rf). So, I'm going up on the roof to cut the 110 wide reflector to 35 inches and the main elements to 33 inches.

That means that the active elements will be ab exact 1/2 wave length for channel 7.

I'll report the improvement, if any. If not, the antenna will be more compact and less prone to wind and snow damage.

 

[Tower Guy]

Since almost no station transmits in vhf low (except for a few low power analog stations), post transition antennas need not be wider than 35 inches.

There are about 40 low band VHF allocations in the US. Just yesterday the FCC allocated channel 5 to Fond du Lac, WI.

Misinformation such as in your post causes too many people to buy the wrong antenna and wonder why they don't get all their channels.

I predict that you will screw up the impedance of your antenna when you trim the low band elements. It might still work anyway, and it might not.

 

[Mike500]

Actually, I've done it. Using the Zenith DTT900 converter box, I'm getting a 7-8 mark increase on the signalmeter on the converter on Channel 7.1 (actual rf 7 vhf). Since I receive no other channel, it's like an exact cut channel 7 rf antenna.

I used the director/reflector length formula recommended in the ARRL Handbook yagi antenna formula.

The original single reflector was a lot wider than it needed to be, as it was designed to accomodate VHF low channels. Electronically, on rf channel 7, anything above 35 inches is not visible to the signal and does nothing. If can hurt, if there may be a large reflecting object in front of the antenna and out of phase with the driven elements and the reflector.

Since the lingitudinal spacing has not been changed, the reflector and the directors performed the same as before, electronically.

So, I wouldn't recommend just randomly cutting the elements.