You only have two VHF stations, channels 7 & 9, from DC. The rest, regardless of displayed channel number, are UHF stations. The additional high-VHF antenna would be needed only for these two stations as the DB4e (nor the DB8e) would be expected to receive the VHF channels reliably, if at all.
Quote:
|
I purchased a Channel Plus 2532 2-way combiner to combine VHF and UHF
|
This is the incorrect device for this task, it is only a simple splitter/combiner. The correct device is called a UVSJ.
Quote:
|
will the Antennacraft Yagi HD Antenna Y5-7-13 get me a decent signal or would the 10 foot model be necessary?
|
The larger antenna would improve signal strength and noise margin by several dB. Whether that would make an appreciable enough difference in your attic to make it worthwhile is impossible to predict.
Quote:
|
Would the DB8e offer significantly improve signal strength over the DB4e if I leave both antennas pointed at D.C.?
|
I'd usually expect a 2 to 2.5 dB improvement in received signals strength and noise margin improvement. Whether that would make an appreciable enough difference in your attic to make it worthwhile is impossible to predict.
Your TVFool plot suggests that an attic installation will be inadequate at this location. You may wish to reconsider your choice if you find the attic location's reception lacking.