scwis

We might have a dog in our schematic collection. Visitor Rick writes “Your 5/8 wave antenna schematic is probably incorrect…”

We might have a dog in our schematic collection. Visitor Rick writes “Your 5/8 wave antenna schematic is probably incorrect…”

The drawing calls for 12 gauge wire on a .25″ form. 12 is huge! I don’t think you could get 6 turns on a .25″ form. I can’t even get 16 through a prototype board. Looking at the picture I’m guessing its 21 instead? I’m building a coil with 18 (the largest that fits through a proto board) and will let you know what happens on my antenna analyzer.

UPDATE: Looking at it again, I’m beginning to think that it may have been a poor scan and should be an 8 instead of a 2 or rather 18 gauge. I used an adjustable 6 meter fiberglass antenna for the vertical and set it to 80 inches for resonance on 87.9 MHz. If that’s the correct length, I’m going to switch it to a stainless steel CB whip cut to size. I will paint the whip dark gray and use it for a stealth antenna as I’m not supposed to have outside antennas. I doubt if anyone will notice something that slim or complain.

UPDATE:I finished the cap/coil assembly and will mount it in PVC today. I have an MFJ antenna analyzer for verifying the design. I give up! I tried everything and couldn’t get it to tune. I noticed that the text talks about a series circuit but the picture shows a parallel circuit so I even tried rewiring it in series. In the search for more information I found out that the 5/8 wave may not be a very good antenna for FM BCB. LB Cebik says that (at HF anyway), a 1/4 ground plane will have the same angle of radiation, as long as they are both mounted high enough. I’m not sure this will hold true at FM BCB, but if I can’t get a 5/8 to match with an antenna analyzer, there is not much hope for the average hobbyist.

I’ve also read forums where many people were not thrilled with the results of a 5/8 wave. Being as the 1/4 ground plane is much easier to match, I’m giving up on the 5/8 and will build a 1/4 wave.