Jpole antenna using a TV balun, avoid feedline radiation

[Ed in Tx]

How much power you reckon one could transmit through that type of a balun?

[wa2ise]

Originally Posted by Ed in Tx

How much power you reckon one could transmit through that type of a balun?

I've gotten about 10 watts thru one. But that's likely about as much as I could expect. These twinlead Jpoles are usually used with handhelds in hotel rooms when traveling.

For more power, you could get a bigger ferrite toroid (one good for VHF work), some ethernet cat5 twisted pair (balanced 100 ohm), and make your own 4:1 balun.

[dewdude]

The main issue I have is that a F-connector is a 75-ohm connector where as a BNC is either 50 or 75...but you're still going to a 50 ohm transmission line. There would be an impedance mismatch in the F to BNC adapter...or should be.

[Ed in Tx]

Not that big a deal. 50 Ohm/75 Ohm mismatch is 1.5:1 VSWR and about .18 dB loss.

[Findm-Keepm]

I was taught in Channel Master's CATV/MATV school that most 75/300 ohm baluns are actually 72/300 ohm - that they were designed to match the natural impedance of some antenna, I've forgotten which one - dipole?. The older CM 8281 baluns (75 - 300/300) for coax/F to VHF/UHF 300 were listed in the catalog as 72 ohms initially, but Winegard, Finco and Blonder-Tongue all used 75, so the assimilated.

So I guess any mismatch is even lower if they are indeed 72 ohm....