Radio W4KAZ

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Field Day Antennas 2008

This year will probably be a Vee beam for 40m, fed with ladder line and a tuner. Interesting factoid: Vee beams that are odd multiples of 1/4 wave seem to have impedances similar to loops, and can be fed with the standard quarter wave matching section, although that will limit their utility to a single band.

80m will probably be a dipole, 20m is uncertain. The Vee may be pressed into 20m service, and will be used if there are decent 15m or 10m openings.

Throw down a comment if you have a favorite.

Amended 6/4/08: Ok, maybe a loop on 20m. Probably diamond shaped and fed at the bottom.

Hexbeam Broadbanded

I was really hopped up when I ran across the web site of G3TXQ. I was particularly hopped up by his documentation on his hexbeam experimentation, particularly the modified geometry broadband version.

I played around with my own experimental hexbeam for 17m/15m/10m, back in 2000-2001, right after I had re-licensed. There’s no magic to the antenna, but it does give one the performance of a 2 element yagi in a much smaller physical space. The hex design is right at the top of my “really interesting stuff” list. Its one of the things I corresponded with W4RNL over. ‘RNL was not a great fan of the design, but agreed that it did have its place. I’m not sure of the reason for my own illogical interest – just one of those things.

But back to G3TXQ. He has taken the step of modifying the geometry of the reflector. He indicates that this change will improve the f/b ratio and also gives a broad match that is closer to 50 ohms. The classic Hexbeam design has an impedence in the 20 to 25 ohm range. The G3TXQ version has a flat SWR across the 20m through 15m bands, and most of 10m. Way Cool. Even better, the modeling shows the best SWR and best f/b ratio seem to happen at approximately the same frequency.

I’m thinking about a 15m monoband version now. I guess its also time to go back and surf the hexbeam yahoo group again.

More N1LN Antennas Flying

N1LN is still chipping away at flying all of his antennas. Two more went up on Saturday for the 20 meter stack. This has been a fun project to watch go together, as I’ve not been involved with anything of this magnitude before. It is probably not so much fun for Bruce yet-he and Laurie are doing 99 percent of the work themselves. He still has a great deal of work outstanding, but it is really coming together for them very well, and they have planned for it for a long time.

I you want to see the photos, continue to the full page.

Continue reading More N1LN Antennas Flying

New Ears – Addendum

Wow, the relocated, refitted, and repaired 40m and 80m antennas really sound a lot better than before.

The 80m folded dipole is also now almost perfect from an SWR standpoint. It is under 2:1 from 3550kc thru 3850kc, and the rig’s autotuner can easily match it across the rest of the band. The low SWR sweet spot is about 150kc wide, and centered on 3700kc. This antenna was constructed per cookbook dimensions from the ARRL Antenna book’s chapter on ‘portable’ antennas.

I’ve also worked out a switching arrangement for 20m and 160m, which both require an antenna tuner. 20m is a ladder line fed dipole, and the 160m antenna is a 160 foot long inverted-L with about 70 feet vertical. I have the inv-L routed through my jumbo homebrew tuner to an MN-2000, and the 20m direct to the MN-2000 through a balun.

I expect to add a 20m vertical soon, for a just-in-case backup/alternative. I also expect to find a way to incorporate a homebrew antenna switch to reduce the number of feed lines snaking through the yard into the basement.

But Biological Antenna Supports are still holding on to their leaves, so I have many hours of maintenance ahead.

New Ears

I had a few minutes to spent playing around with the new antennas, just listening around. The guys calling CQ for the Pennsylvania QP were booming in here on 40m during the afternoon. The 40m dipole really seems to be hearing well.

On 80m, the new antenna was showing a very high noise level across the band, and it sounded similar to the AGC pumping from a strong nearby station.

“Hmmmmm…” thinks w4kaz, eyes vacant and scratching head idly.

Turns out my 80m antenna is now flat broadside to the WPTF 50KW antennas that are about one mile to my NNE. I have an 80m bandpass filter I built a couple of years back. Plugging that into the line cleared up the WPTF problem, dropping the broadcast QRM from S7 to S0. Its still there, but its very low level now. Not many signals on in the afternoon, so I need to carve out some time to spend in the shack playing around some.

Lesson: 50 KW at less than one mile distance is undesirable. (Yeah Homer, I know….doe-OH!)

Biological Antenna Support Structures

I spent much of the day tugging on lines and shooting new lines up into the trees. We had a really blustery day back in the late spring that knocked a lot of the weaker branches out of the trees. As luck would have it, one of those smacked the 80 meter folded dipole, snapping the light cord I was using to hold it up.

That was a bit of a problem. The line I had placed for 80 meters was probably 80 feet up, although the antenna was only up at about 50 feet. With the leaves already back on the trees, I couldn’t shoot a line back to the same spot, which would have been my first reaction to the problem. Instead, it forced me to think a little harder. (Queue soundtrack of rusty hinges squealing….) How best to make lemonade from the lemons?

Continue reading Biological Antenna Support Structures

N4A Antenna Support Hardware

I added more N4A photos to the N4A website. The last few frames at the bottom of the N4A photos page show some close ups of the gear we used on the beach for the Iota expedition.

I was a bit surprised at just how well the 21 inch stakes worked as guy anchors. They really held firm. These stakes were cut from 42 inch”deck balusters” I got from the local big box for about 75 cents each. They are just pressure treated 2×2 material. I cut each baluster in half, so two vampire killers are obtained per baluster. I expected to need to back these up with additional stakes, but they held the 36 foot mast with just dipoles very well. It took only one stake to hold each guy. The second surprise was how easily they came out when pulled straight up rather than at the 120 degree guy angle. Continue reading N4A Antenna Support Hardware

IOTA

Planning to operate IOTA with N4YDU at the end of the month.

Cleaned up and tested the SWR on a couple of vertical antennas today. One is a hy-gain ATV18 I got on loan from NT4D. This antenna has seen one too many field days. The so-239 on the base is broken, but I can use a short coax jumper to feed it. The 10 metertrap seemed intermittent at first, but is working for now.

The other is a 20 meter quarter wave that I made from parts of a broken CB 5/8 wave. The base was sound, but I needed to do a bit of surgery on the upper elements. I also replaced the bolts with hose clamps, and some of the rusted hardware with stainless parts. This is a project that had been laying around, but a trip to the beach moved it up the list.

FCP Photos

A few photos of the FCP(folded counterpoise) at the W4KAZ QTH.

W4KAZ post about the FCP.

Picture of W4KAZ junction box

Picture of W4KAZ junction box

Picture of FCP transformer in its mount at W4KAZ

Picture of FCP transformer in its mount at W4KAZ

Picture of center junction of W4KAZ FCP

Picture of center junction of W4KAZ FCP

Picture of center junction of W4KAZ FCP

Picture of center junction of W4KAZ FCP

Poor quality scan of W4KAZ FCP drawing, missing juntion detail on three conductor side

Poor quality scan of W4KAZ FCP drawing, missing juntion detail on three conductor side

Picture of PVC spreader

Picture of PVC spreader. Nails inserted through holes demonstrate intentional mis-alignment

Picture of PVC spreader on FCP

Picture of PVC spreader on FCP

Picture of cable tie used as spreader on FCP

Picture of cable tie used as spreader on FCP

Picture of PVC spreader on FCP

Picture of PVC spreader on FCP

Picture of 2-wire leg of FCP as hung at W4KAZ

Picture of 2-wire leg of FCP as hung at W4KAZ