Ham Radio Help Desk

Many makers of J-poles for 2 meters claim they can also be used at 70 cm.

It may not be intuitive at first, but the answer, at least from an antenna pattern standpoint, seems to offer some hope.

It is difficult to calculate the feed-point impedance of a J-Pole perfectly since it is a tapped system. However, the calculations I ran for 430 MHz suggest it is somewhat close to a good match.

Here is the same J-Pole from Cebik’s collection with 146 and 430 MHz…

2 meter j-pole at 146 and 430 MHz.

The currents on the long vertical section act a bit like a long wire pointing straight up as shown in this comparison plot…

2m J-Pole Plot at 146 and 430 MHz

The pattern for 430 MHz, shown in green, is wild and certainly suggests this is not the ideal antenna for the job. However, if you look closely at the low elevation detail…

Close up of 2m J-Pole at 146 and 430 MHz.

…you will see a reasonable lobe of power at a low angle.

This simulation was done with the antenna at 300 AGL by the way.

So can you use a 2 meter J-Pole at 430 MHz and expect reasonable results. EZNEC suggests a cautious yes. However, be real sure about your SWR before you try this. It might not be what you expect.

Tags: 2m, 70cm, j-pole