I've had a lot of fun with the DOG (dipole on ground) and also the LOG (loop on ground) rx-only antennas. Inspired by KK5JY project
https://kk5jy.net/rx-dipole-array/
The normal DOG for 160-20m is simple dipole 36 feet of insulated wire( 18 feet each side) attached to an isolated 9:1 transformer, and choked at the feedpoint so as not to make your transmission line part of the antenna, destroying the pattern. Despite the coax being on ground, (that is the run back to the shack in this case) my own EzNec testing with a wire attached at near ground level simulating a common-mode problem, made me put one inline. We are dealing with a lossy antenna, and the last thing you want to do is make the directional pattern squirrely.
The reason I use a 9:1 transformer is to broad-band it somewhat. We know that when bringing an antenna down low, the impedance goes lower. But at some point very close to the ground, the impedance rises again - mostly from reactive ground-loss components. So while a low swr isn't the goal here, lossy matching broadbands it a little better than a straight connection. At least for me.
Great for side-yards or other areas without a lot of overall space for a loop. But feeding it in the center can sometimes be a problem when trying to bring the coax back to the shack in very restricted areas.
Enter the *end fed* version.
Simply in order of attachment:
18 feet of insulated wire attached to a 9:1 transformer.
18 foot coax jumper
CMC, or common mode choke
Coax run back to the shack of whatever length you need.
The 160-20m dipole itself consists of one side being the 18 feet of insulated wire. The other side of the dipole is utilizing the common-mode part of the 18 foot jumper braid (outside braid surface). This is now CHOKED off to finish the dipole. And of course the normal run of coax back to the shack.
I used a PAR / LNR Precision "end fed swl" antenna transformer for this. And for the choke a "MyAntennas" CMC choke for rx-only, which works well, and covers well into the BCB.
For the test, I used some common 18 foot coax jumper for one side of the dipole, but if you like it, you may want to go with the type that can stand weathering.
Use your own components if you like, but since we are playing tricks with the common mode being part of one side of the dipole, do not skimp on your RF common-mode-choke. If you cheap-out here, you will make the run back to the shack part of the antenna, and will have some pretty useless directional patterns along with coupled noise. The MyAntenna CMC choke seems to do a really good job for me.
Like the LOG, anything on ground is lossy. We know that up front. BUT we are playing the signal-to-noise game now. See KK5JY antenna project for a better way to explain it than I can.
https://kk5jy.net/rx-dipole-array/
The normal DOG for 160-20m is simple dipole 36 feet of insulated wire( 18 feet each side) attached to an isolated 9:1 transformer, and choked at the feedpoint so as not to make your transmission line part of the antenna, destroying the pattern. Despite the coax being on ground, (that is the run back to the shack in this case) my own EzNec testing with a wire attached at near ground level simulating a common-mode problem, made me put one inline. We are dealing with a lossy antenna, and the last thing you want to do is make the directional pattern squirrely.
The reason I use a 9:1 transformer is to broad-band it somewhat. We know that when bringing an antenna down low, the impedance goes lower. But at some point very close to the ground, the impedance rises again - mostly from reactive ground-loss components. So while a low swr isn't the goal here, lossy matching broadbands it a little better than a straight connection. At least for me.
Great for side-yards or other areas without a lot of overall space for a loop. But feeding it in the center can sometimes be a problem when trying to bring the coax back to the shack in very restricted areas.
Enter the *end fed* version.
Simply in order of attachment:
18 feet of insulated wire attached to a 9:1 transformer.
18 foot coax jumper
CMC, or common mode choke
Coax run back to the shack of whatever length you need.
The 160-20m dipole itself consists of one side being the 18 feet of insulated wire. The other side of the dipole is utilizing the common-mode part of the 18 foot jumper braid (outside braid surface). This is now CHOKED off to finish the dipole. And of course the normal run of coax back to the shack.
I used a PAR / LNR Precision "end fed swl" antenna transformer for this. And for the choke a "MyAntennas" CMC choke for rx-only, which works well, and covers well into the BCB.
For the test, I used some common 18 foot coax jumper for one side of the dipole, but if you like it, you may want to go with the type that can stand weathering.
Use your own components if you like, but since we are playing tricks with the common mode being part of one side of the dipole, do not skimp on your RF common-mode-choke. If you cheap-out here, you will make the run back to the shack part of the antenna, and will have some pretty useless directional patterns along with coupled noise. The MyAntenna CMC choke seems to do a really good job for me.
Like the LOG, anything on ground is lossy. We know that up front. BUT we are playing the signal-to-noise game now. See KK5JY antenna project for a better way to explain it than I can.
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