Since the HF loop-on-ground antenna is working well for me in the noise department, I thought I'd dip my toes into the pool of insanity with much smaller folded-dipole versions for VHF Low / 6M and Airband.
I haven't built them *yet*, but toyed around with EZnec enough to see that they might be viable for skywave reception, and possibly a solution to noise problems when no other measure is successful.
Very simple really up at these freqs. Folded twin-lead (or windowed ladder line etc). 4:1 (300/75 ohm) balun transformer. RG6 back to the shack. Maybe toss in some more ferrite common-mode choking to keep the pattern clean and guard against any noise ingress too, especially since you may not be using isolated transformers.
A 9:1 isolated transformer seems ideal, but I don't have any of those in my junkbox so maybe a cheapie 4:1 will have to do.
VHF LOW (3:1 swr or better) 40 - 55 mhz -- 8 feet long.
6M specific - (2:1 or better) 54mhz -- 7 feet long
Airband specific - (2:1 or better) 120 mhz - 3 feet long
CONS:
Right off the bat you are looking at least -12 to -15 dBi loss. That's db over Isotropic at the lower angles. Hot scanner front ends might do ok.
Useless overhead pattern. Well, maybe not for airband.
Directionality - not much - just a big hemisphere. I guess just put it down in whatever way you find convenient.
Line Loss: at these frequencies, wide banded-ness is not the goal. Line loss can rear it's ugly head, so resonance, such as is, (lower than normal) seems important. You also have a very heavy ground-loss reactance to deal with obviously.
For me, this will be more of a science experiment, because I don't really know what to look for on lowband, and I'm pretty satisfied with my airband reception with "normal" antennas.
I'm just thinking of it as a last ditch attempt to get a less noisy environment for those who are at wit's end and are willing to go to the ends of the earth (pun intended) to monitor without bleeding ears.
I'll need someone to join me in the padded cell later, so if you beat me to it, let me know.
I haven't built them *yet*, but toyed around with EZnec enough to see that they might be viable for skywave reception, and possibly a solution to noise problems when no other measure is successful.
Very simple really up at these freqs. Folded twin-lead (or windowed ladder line etc). 4:1 (300/75 ohm) balun transformer. RG6 back to the shack. Maybe toss in some more ferrite common-mode choking to keep the pattern clean and guard against any noise ingress too, especially since you may not be using isolated transformers.
A 9:1 isolated transformer seems ideal, but I don't have any of those in my junkbox so maybe a cheapie 4:1 will have to do.
VHF LOW (3:1 swr or better) 40 - 55 mhz -- 8 feet long.
6M specific - (2:1 or better) 54mhz -- 7 feet long
Airband specific - (2:1 or better) 120 mhz - 3 feet long
CONS:
Right off the bat you are looking at least -12 to -15 dBi loss. That's db over Isotropic at the lower angles. Hot scanner front ends might do ok.
Useless overhead pattern. Well, maybe not for airband.
Directionality - not much - just a big hemisphere. I guess just put it down in whatever way you find convenient.
Line Loss: at these frequencies, wide banded-ness is not the goal. Line loss can rear it's ugly head, so resonance, such as is, (lower than normal) seems important. You also have a very heavy ground-loss reactance to deal with obviously.
For me, this will be more of a science experiment, because I don't really know what to look for on lowband, and I'm pretty satisfied with my airband reception with "normal" antennas.
I'm just thinking of it as a last ditch attempt to get a less noisy environment for those who are at wit's end and are willing to go to the ends of the earth (pun intended) to monitor without bleeding ears.
I'll need someone to join me in the padded cell later, so if you beat me to it, let me know.
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