The PVC pipe on hand here was 1-5/8" in diameter, so I dropped a turn (or a little less -- just over 11 turns for each of the two wires), figuring if it didn't work, I'd start over. It's also only got one color of wire, as I have a nice big spool of sky-blue insulated #14, purchased awhile back for antenna experiments. I scribbled on the ends of one winding with a black marker. You don't even really have to do that, since the bifilar windings are flat: the wire that starts on top, ends on top. Here's the completed balun:
And a close-up of the connections at the coax end:
The top end is just 6-32 nuts and bolts (mostly brass) and solder lugs.Here it is all wrapped up in self-amalgamating tape:
It didn't change the tuning, so I guess it must be okay stuff at 7 mc/s.Refinements: use fatter brass hardware for the antenna connections. Use polystyrene drain tubing, sold as "styrene" for the coil form: it has better properties than PVC at HF. Mount the coax connection facing down! And you could do like the pros and encapsulate the whole thing in PVC pipe. (I have one somewhere around here, a slightly more sophisticated trifilar job, coated with epoxy. It had held up well, last time I saw it. --If I could only remember where!)
Have you tried that Windom on any other bands besides 40M yet? I'm starting to think about getting back on HF and that is just about the right size for my space. If it tunes up without too much drama on 30M I'm sold.
ReplyDelete30m with an "original ham bands" antenna is always tricky -- I have not tried it yet. As time permits, I'll fire up the Scout and see. It'll be well off resonance.
ReplyDelete30m dipoles are small enough that in the past (when I had a G5RV, which is not happy on 30), I have just strung up a dedicated antenna for that band. You could do a similar offset-feed Windom if needed to fit the space.
Thanks. I've been doing a bit of EZNEC modeling and it looks like a single wire to do 40 and 30 will have to be too long. Maybe I'll try a fan dipole first.
ReplyDeleteYou might be interested in this article on how ham radio operators are helping the fire fighting efforts out west
ReplyDeletehttp://www.denverpost.com/news/ci_20852619/colorados-amateur-radio-operators-fill-wildfire-coverage-gaps?IADID=Search-www.denverpost.com-www.denverpost.com
Sorry about anonymous posting, but I don't fit any other category
CMcDermott
CMcD, thanks for the link -- and consider "Name/URL," which does not *require* that you enter a URL or your real name. Not that I mind anonymous posting: it's what you say that counts!
ReplyDelete