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Archive for the ‘Antennas’ Category

The Wonders of a Resonant Antenna!

Posted by id2722732.zcviw.xyz on January 20, 2007

Jim and Dennis     Dennis Burton, N5DRB, and me.

Dennis, N5DRB, and I finished vertical number two today, in the cold and rain… But this time it didn’t go quite as smoothly!

First of all – I couldn’t find anything… Between a quick tidy up of the shack before receiving visitors, moving all of my tools and parts out of the truck so it could be repaired, and an amazing series of memory lapses on my part, I couldn’t put my hands on anything we needed. If it weren’t for Mendy’s help in finding all the stuff, we may never have finished it.

Then there was the weather to contend with. It sprinkled on and off all morning, but about the time we decided to put it up outside, it really started to come down steadily, and the temperature started to drop. Towards the end, our fingers were starting to freeze.

Despite all this, we finally got it all up and started tuning. Poor old Dennis went up and down the ladder a few times, mainly because my “cheap and nasty” whip design (6ft aluminum rod inside a 6ft aluminum tube – I was going for better efficiency…) made it much harder to adjust the top section, cause the adjustment is too high off the ground. So he had to unscrew and remove it each time.

Tunning  Isabelle is helping me tune the antenna…

Finally we got it set up for 20m, spread some make some make shift radials and plugged it into the K2 (now moved to the guest room to reach the back yard…) Following the excellent results of antenna one at Dennis’ house. We had high hopes, but alas we couldn’t get the K2 to tune it! Best we could get was about 4:1. I re-attached the analyzer to check and it was spot on resonant at 14.050Mhz, and had a 50 ohm resistance.

By then it was time for Dennis to head home, and I was very disappointed, but kept on feeling we were missing something – was it a bad coax joint, not enough radials? Anyway, I went and dried off a little, grabbed a chair and the K2 manual and sat down to see what was going on. Sure enough, I finally noticed that in all the rush, I had switched the K2 to antenna 2! So we were trying to tune an open circuit the whole time… I guess I didn’t have my Wheaties today.

On pressing the antenna 1 switch, the speaker just about jumped out of the case as signals came pouring in like I’d never heard before on my short wire over the roof. Oh the wonders of a resonant antenna! Sure enough, on hitting the tune button, it immediately set to 1:1 and stayed that way over most of the 20m band without the tuner even switching once.

I listened around on the CW sub band and signals were coming in really well, so I wondered how it would go on SSB. I’d never had much luck with that and the microphone hadn’t been plugged in for months, but sure enough signals were booming in – mainly from the west coast. Fortunately, the North American SSB QSO party was in full swing and there were people calling from everywhere – Nice!

I was getting out great and worked about a dozen stations from California to Alabama, all with only 10Watts. And the noise floor had dropped drastically compared with the long wire. You should have seen the smile on my face!

Later on that night, I braved the sleet to run outside and set the loading coil tap for 40m and it tuned up really well again. The load resistance wasn’t quite 50 ohms, but maybe with the whip fully extended it will be better, and I may try a base shunt capacitor later as well.  The QSO party was still running, and though the signals were a little weaker, I was still able to work California, South Dakota and Texas on SSB with 10 Watts. Tried tuning 80m, but even with the full loading coil I could only get down to around to about 4.5MHz. Tomorrow, I’ll extend the top whip to its full length and try again.

Next I’ll try it with only the 4’6” base section and see how it goes. Stay tuned…

Posted in amateur radio, Antennas, ham radio, Home Brew | Leave a Comment »

Home Brew Loading Coil for AD5X Vertical

Posted by id2722732.zcviw.xyz on January 14, 2007

Dennis and CoilCompleted Coil

This weekend, Dennis (N5DRB) and I made a loading coil for the second of our AD5X portable vertical antennas. The coil is also based on the design of Phil Salas, and you can see his article for making it at http://ad5x.com/images/Articles/CoilRevB.pdf .

We used a piece of 3 inch PVC pipe as the core, however we screwed 6 inch lengths of edge stip onto the pipe to hold them a little more securely while we wound.

 Edge Strip fixed to coreimg_4844.JPG

We unwound about 6 feet of wire at a time and stretched it as straight as possible before winding it onto the form, trying to keep the tension even. This was definitely a two man job. Once the coil was wound, we masked the former with tape and filled the edge strip with 5 minute epoxy and let it set up overnight.

Stretching the WireMasking for the Epoxy

Next day, Dennis removed the coil from the form, which took a little effort cause we wound it on pretty tightly. He tapped gently on each of the four spacers to slide it off. He then fabricated the coil supports as described in the article using the 3/8″ fibreglass rod.

The final step is to solder the coil onto the brass rods and it’s ready to go…

Unmounted CoilReady to Solder

Posted in Antennas, ham radio, Home Brew | 4 Comments »

AD5X Portable Vertical Antenna

Posted by id2722732.zcviw.xyz on January 7, 2007

Vertical Antenna

Saturday, January 6th, Dennis (N5DRB) and I complete the first of our AD5X portable vertical antennas. Using an MFJ antenna analyser, we were able to tune the antenna all the way from 80m to 10m, with low SWR and close to 50 ohms on all major bands (after careful adjustment of both top whip length and coil tapping below 20m.)

After that we couldn’ wait to get the K1 hooked up and start operating. We chose 20m initially, and as soon as we powered up, the band came to life. Our first contact was with a HI station in the Dominican Republic (about 2000 miles) and later we had a brief exchange with an 8R station in Guyana (3000 miles). Also worked a station in Virginia at 3 watts using a PAC12 vertical. Needless to say, we were both pretty pleased and there were plenty of smiles…

Here’s another picture of the center loading coil, looking up. You can also see the 4 guy ropes clearly.

Loading Coil

This version has two x three foot sections of 1/2″ tube making up the lower vertical section, the full lengh MFJ coil with the fibreglass rod, and the MFJ 10′ whip as the top section. Dennis added some brass screws to secure the brass couplings, and crafted a nice four point guy ring which fits neatly over the top of the coil section.

While the extra length has enabled the antenna to tune down to 80m, it also made it a little tricky to assemble and tune, as the top of the coil section is at about seven feet! A step ladder was required! So we may have to rethink the extra length for it to be truly portable…

Can’t wait to get mine finished and running!

You can get more information on the original construction here:

http://ad5x.com/images/Articles/VerticalRevH.pdf

And Phil Salas has lots of other interesting articles and presentations on his web site http://ad5x.com/

Posted in Antennas, Home Brew | 12 Comments »