Monday, June 8, 2020

6 Meter Dipole Antenna Project

After reading  SiG's post on Radio Propagation, and seeing his comments about the big 6 Meter opening he was enjoying, I made some comments about rarely operating 6 Meters, but enjoying the times I did.

In mentioning that I only have one radio that will transmit on 6 Meters, and that radio will be going on eBay soon, he replied that I should make a 6 Meter Dipole, hoist it up, and give my hand a try at the upcoming ARRL June VHF Contest that's scheduled for this coming weekend.

Hmmmmm....do I have enough "stuff" to build a decent antenna?

Wire? Check! Plenty of 12 gauge Davis RF "Flex Weave" on hand.....

Center insulator? Check! I have a Hy-Gain center insulator new-in-box.....

End insulators? Check! Would you like plastic or ceramic?

Support rope? Oh, yeah, got several hundred feet. Would you like new, or slightly used?

So I cracked the books, came up with some dimensions, and proceeded to cut wire, and belay the insulators to the ends of it.

Took me an hour to round up all the bits and pieces, and about another hour to lay out the wire, measure it to length and cut it, install the end insulators, crimp/solder some ring lugs on the free ends, and bolt it all together.

Here it is stretched out on the garage floor. It's about 9' end-to-end.



Oh, and since it's a Dipole ("Balanced") antenna being fed with Coaxial Cable ("Unbalanced"), we'll need a "Choke Balun" (more accurately a "Line Isolator") to keep RF current OFF the outside (The Shield) of the coax.

A simple VHF coaxial choke consists of 4 turns of cable, "solenoid wound", in a ~3" diameter. I wound mine using 48" of RG-8X cable and a cardboard Morton Salt container as a form. I put some cables ties on it to keep it from unwinding. This took another couple of hours to round up the parts, find something to use as a 3" coil form, cut the cable and put connectors on it, wind it, and secure it with cable ties.

Here's my feed line choke. Identical in function to the one I made for my 20 Meter (14MHz) vertical, but scaled down for 6 Meter (50MHz) operation.



And all put together and waiting to be installed. I taped the coax connection to the center insulator, both for some weather proofing, and to prevent the connector from loosening up when the antenna sways in the wind.



I was planning on hoisting it up today and connecting my antenna analyzer to it, BUT....it's windy as all get-out, drizzling on-and-off, and just not a nice day to do it. I'll get it hoisted up and swept on Tuesday.  That gives me tonight to get the radio and power supply set up and ready to connect to the antenna once I've got it in the air.

This is the first 6 Meter dipole I've ever built, and I'm sure I'll be in for a few surprises once it's up in the air and I connect the analyzer to it.

I'll be running my Old Faithful Yaesu FT-847 transceiver "Satellite Radio" as it's the only rig I have with 6 Meters. I'll easily be able to get this dipole mounted "In The Clear" more than a half-wavelength above ground, so it should work about as well as a dipole can work. And with 100 Watts of RF power out of the radio, and maybe 35' of low-loss feedline, I should be able to work most of what I can hear. If there's a good opening I should be able to make a lot of voice contacts, my preferred mode. If voice mode is too noisy/weak for me, I can switch over to one of the digital modes like FT8, and make lots of contacts.

More pix when it's in the air.

8 comments:

  1. I'm looking forward to the AAR(s). :)

    ReplyDelete
    Replies
    1. There's a local guy who's huge on the 6 Meter band, and it'd be nice to talk to him. If the band isn't "open" all I'll be able to talk to are "local" guys, out to 75~100 miles, depending on what they have for antennas.

      If the band *is* "open", meaning it's supporting propagation, I can probably make contacts out to maybe 1000~1200 miles.

      Should be interesting, as I haven't been active on 6 Meters in about 18~20 years!

      Delete
  2. Mea Culpa...

    I first got on 6m back in the early '00s - '03, I think - but toward the end of cycle 23, which was quite a bit stronger than the last one. I had put up a Tennadyne log periodic HF antenna to replace the tribander I had been using. I had an Icom HF+6 radio and decided to see if its autotuner would tune it on the 3rd harmonic of something and it did. Within my first two days, I had worked Argentina and Chile on transequatorial prop. Some backyard measurements showed it didn't really point where it was aimed, but it was serviceable until I got a small 6m antenna. Another log periodic because it also gives me 2m.

    I'd highly recommend you use FT8, if you don't already. The only drawback is that it's not the mode for brief openings. It's conceivable that you could work brief (< 1 minute) openings with CW while you need a minute or more for FT8.

    ReplyDelete
  3. I never operated 6 back when I was in Illinois because.....TVI!

    The only time I operated 6 in Kommiefornia was with the FT-847 and a full-size 5/8 wave Antenna Specialists commercial antenna a friend "loaned" me. I had one big opening, and that was the one I told you about.

    My Flex 5000 covered 6, and I had an Arrow Antenna 1/4 wave vertical up about 25', but I never heard anything except a few beacons. I didn't listen much, either, because the band always seemed dead. I've done a lot of digital stuff on HF, FT8, WSPR, WSJT, PSK31, etc, etc, and I have a SignalLink with the correct cable for the 847, so after I get the antenna hoisted up I'll swap the FT-1000D cable that's on the SignalLink now for my FT-847 cable, and other than setting levels, I'll be good-to-go.

    I have FLDigi and WSJTX on this PC, along with SSTV, so I'm covered there. WSJTX can do some modes specifically designed for weak-signal 6 Meter ops.

    Time to go hoist the antenna and get On The Air!

    ReplyDelete
    Replies
    1. I never operated 6 until analog TV went away. Our local NBC outlet was channel 2 and we’re fringe signals - or less.

      It was open today, mostly to the islands - Trinidad, PR, Anguilla and that area. There were stations in Puerto Rico stronger than locals. Hawaii was open to 7-land. Didn’t see any to CO, but haven’t looked in over an hour.

      Delete
    2. It's up, but I haven't swept it or taken pix. Had to some for some chow.

      New post to follow shortly.....

      Delete
  4. LOL, lots of 'spare parts' laying around, huh??? :-) Looking forward to the AAR too!

    ReplyDelete
    Replies
    1. Hey, "Be Prepared"! This falls into the "Expedient Antenna" category, and I'm pretty good at that.

      None of the parts are expensive, but I buy good quality stuff, so I've probably got $50 in in it.

      If I built it from scrap wire, and used cut-up soda bottles for insulators, it would be free except for the coax.

      Delete

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