Another Kingshootr Thought Experiment Query

[kingshootr]

Background: This is the eventual shop/metal building I'll have my radios in (just listening at first to 135-175MHz for the GP 3-E (80%) and CB/GMRS/FRS for the SkyScan (20%). The GP 3-E is new to me, it'll be the first time I'm using it. It covers 95% of the frequencies my soon-to-be little town (Show Low, AZ) uses. The SkyScan is what I'm using now in the Phoenix area for general scanner listening with a couple SDR dongles. For the walkie talkie stuff I'll have separate radios for them.

1] Will the sloped roof, approx. 2ft below the SkyScan, offer any kind of usable ground plane effect to the antenna? On the current rooftop mount, I welded 4 radials to the base plate that the antenna sticks to. On the new building, if I were to shine a light down from the antenna to the sloped roof - the light would bounce out to the left where all the signals will be. The terrain to the right of the building is rising mountain (nothing to be heard from that direction.) Would that sloped steel roof offer any usable function to picking up signals from the valley on the left?

Or stop overthinking it and add radials to the SkyScan pedestal...

And I asked before but I'm not sure I correctly understood the answer - in this configuration - how much separation is suggested between the two antennas (distance and/or height offset?)

 

[mmckenna]

1] Will the sloped roof, approx. 2ft below the SkyScan, offer any kind of usable ground plane effect to the antenna? On the current rooftop mount, I welded 4 radials to the base plate that the antenna sticks to. On the new building, if I were to shine a light down from the antenna to the sloped roof - the light would bounce out to the left where all the signals will be. The terrain to the right of the building is rising mountain (nothing to be heard from that direction.) Would that sloped steel roof offer any usable function to picking up signals from the valley on the left?

That far under the antenna, it's not going to play a role. The welded on radials will act as the ground plane.

And I asked before but I'm not sure I correctly understood the answer - in this configuration - how much separation is suggested between the two antennas (distance and/or height offset?)

I might be wrong on this, I know I've got it wrong before, but I think you want two wavelengths to make sure nothing is made directional. 2 wavelengths at your lowest frequency ~151MHz = 13 feet if you can do it. Less will probably work fine. I am open to corrections, though. I think your GP-3E on top is a good plan. The SkyScan probably won't be your main VHF antenna, so you can put it closer since your lowest operating frequency will be UHF, then 48" might be a good sweet spot.