J-Pole I made
- Thread starter TheSnake
- Start date
- Status
Ubbe
Member
Are there anyway for you to do a comparison to a dipole or even a 60cm 1/4 wave with some groundplane in that same location as the j-pole? Just to see how much difference there are and if it's worth all that work.
J-pole's are narrow banded, great for amateur use but not so much for covering a whole frequency band. Would be interesting to know how it performes even compared to a 60cm telescope on a portable receiver while sitting on the roof and monitoring some fixed stations.
/Ubbe
Ubbe
Member
The radio amateur K9ERG have some great advice:
Another approach to the problem is the "J-Pole" antenna. In this design, the antenna is elevated at least 1/4 wavelength above ground, thus eliminating the ground losses and "normalizing" the radiation pattern. The Impedance matching between the low impedance feed line and the high impedance of the end of the dipole is accomplished with an open wire stub matching network. A shorting bar is placed at one end of a 1/4 wavelength of open wire line, the dipole is then connected to the open end, and the feed line is connected at the point where the impedance of the feed line matches the impedance of the stub. If Co-axial cable feed line is to be used, a BalUn MUST be used. Attempts to feed this antenna directly with co-ax have met with disastrous results. The 0 Ohms reference point is at the center of the short, NOT somewhere up the side of the "J".
Antenna Theory
/Ubbe
Another approach to the problem is the "J-Pole" antenna. In this design, the antenna is elevated at least 1/4 wavelength above ground, thus eliminating the ground losses and "normalizing" the radiation pattern. The Impedance matching between the low impedance feed line and the high impedance of the end of the dipole is accomplished with an open wire stub matching network. A shorting bar is placed at one end of a 1/4 wavelength of open wire line, the dipole is then connected to the open end, and the feed line is connected at the point where the impedance of the feed line matches the impedance of the stub. If Co-axial cable feed line is to be used, a BalUn MUST be used. Attempts to feed this antenna directly with co-ax have met with disastrous results. The 0 Ohms reference point is at the center of the short, NOT somewhere up the side of the "J".
Antenna Theory
/Ubbe
majoco
Stirrer
I made a folded J-pole waay back in the 1980's when I first got my ham ticket. It's been through 5 house moves and never missed a beat apart from a bit of the usual inspection/maintenance. I can hear a repeater that's 120km away and I can work one that's about 50km away and I'm on flat land near a river. I don't have a balun, just a choke in the base.
Attachments
Ubbe
Member
- Status
Similar threads
