Hi Fox TV,
Sorry, didn't see your reply earlier... I do my testing with an Apex 502 converter box that provides signal strength and signal quality readings. An example graph of my testing with attenuators is attached. Note signal strength has a strong linear relationship with margin to dropout indicating that the Apex is measuring signal strength rather than some other measure. Also note, signal quality was 100% until the margin decreases down to 5
dB or less. A good picture was observed until margin to dropout fell to 2
dB or below. However, recordings on my HTPC have many video/audio errors when signal quality is less than 100%. For that reason, I need to achieve a margin to dropout of least 10
dB for all my channels.
I did try a 4-bay with shorter spacing between bays and shorter elements (supposed tuned higher than my original DIY). Margin to dropout was only 1 to 2
dB higher with the new antenna, not enough to solve the problem.
Adjusting antenna aim to favor ch 47 has merit. I have attached a graph that shows the effect of aiming off axis on margin to dropout. Aiming directly at ch 47 tower saves 4
dB for that station but whacks ABC, PBS, and CBS by 14
dB. That's too large of a whack, given that my distribution losses equal 20
dB and I need to maintain at least a 10
dB margin for each channel.
IMO, a pre-amp or distribution amp is the better choice.
Best,
Rick
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