Ham Radio Tower

[GaryM]

Pat,

Here we go! The Glen Martin tower is an aluminum construction, 70' in height. It has two levels of Kevlar guys and comes with earth augers for attaching the guys. The tower incoporates their Voyager system where the rotor and antennas can travel up and down one face of the tower on a set of tracks. The tower is triangular with an 18" face. No need to climb the tower. When you need to work on antennas, or going on vacation for a couple of weeks. just lower the tram to ground level and greatly reduce the wind load. OK, you need to droop the guys toward the tower if your antenna boom is more than a few feet long, but it's not hard to do.

It may not work as well as I anticipate, but should be a lot safer to work on. You can get more information here: http://www.glenmartin.com/catalog/page3.html

[Mike_Dumond]

Looks like a nice system, but drooping the guys to lower the antenna would make me nervous a bit. I think I'd have to see one in person before I was comfortable with it. With that said, I'm jealous [img]/forums/images/icons/grin.gif[/img]

73's WA1ZPD

[GaryM]

That's a point to consider. But, there are two levels of guys, and only two of the three guys at a level need to be drooped at a time. And they can be retensioned as soon as the boom has cleared them. So I figure most cases, they're loose for about 10 minutes or less. And I'm hoping to have the non-drooping guy facing the prevailing wind. I really like the idea of being able to work on antennas almost at ground level. A friend, K9SD, has two 120' guyed towers that have to be climbed for service.

A 70' non-guyed tower that's rated for the same load is almost double the cost. So if it doesn't work out I'll try something else.

[Pat]

Gary, How about an update on the tower situation? Around here one good reason to lower the tower is high wind. Since our weather is so very difficullt to predict (with any reasonable degree of reliability) you'd be needing to lower the tower during a fair wind event. As the direction isn't always stable it might make slacking the guys a nervous activity.

Still, more height for less bucks is attractive. How do crankups with guyed or unguyed upper sections compare? Tilt over towers might be great for verticals and VHF/UHF but a decent sized beam makes for using a really tall ladder to get to the "works" without smacking anything into the ground.

Hope springs eternal from the human breast... so I still hope to find an affordable oil derrick so I can have a stairway to the top and a couple observation platforms on the way up. I figure I could climb to the top, mark all the pieces and dissassemble it on the way down, haul it and reassemble from the ground up. I have a oxy-acetylene rig mounted to an old backpack frame for ease of dissassembly.

Pat

[GaryM]

Hi Pat.

I had a contractor install the 4x4x4 concrete foundation and base mount. And instead of trying to screw in the earth auger anchors for the guy wires he drilled a 2' dia. hole and set the anchors in concrete. I don't think they're going anywhere soon!

I started to join some tower sections last night while waiting for the satillite TV guy to show up, and fond that I had received the wrong length braces that jump the tower section joints. Called Glen Martin Engineering today and havn't heard back yet.

I did order and receive my 6M beam. It's a M2 6m5x model. 5 elements on an 18' boom. Our club has the same one and it works well.

For HF I'm considering a Force12 XR-5 or C3. The XR5 covers 10-12-15-17-20 meters with no tuner and elements for all 5 bands. The C3 covers the same bands with no elements for 12 and 17. Uses a tuner for those two. Performance is close, but I think I'd prefer the XR5.

Still need to pick out a 2M beam.

The GM 1870A is rated for 18 sq. ft. at 80 MPH. A lot of manufacturers rate their towers at 50 MPH. We know how realistic that is! I'll probably end up with about 14-15 sq. ft. of load, so should have some extra margin.

The guyed tower gives you more load for less money. The Voyager eliminates climbing so yeah it's a little trouble slacking the guys and cranking the tram down. But it's a lot less trouble than a fall off a 70' tower.

As you said, a crank down tower, or a crank down and tilt over, still require some climbing or a tall ladder.

[Pat]

Gary, It sounds like you'll be setup pretty well. I'm envious. You have chosen well, Grasshopper! All this tower and beam talk reminds me of the tower and beam on top of Point Loma in San Diego, CA. It was left over from what was previously NELC (Naval Electronics Laboratory Center). It survived several mergers and renames and is now a part of the SPAWAR SAN DIEGO complex (Space and Naval Warfare Research... or whatever) ANYWAY..

The beam is a HUGE HF log periodic. I don't know the actual tower height, just tall and very heavy duty. It has something like 13 elements or so. Its "keel" was a triangular tower looking assy run horizontal. I'm sure they biased it in manufacture so it was straight when horizontal and loaded. Its swing radius is like a baseball diamond. The lab's ham club had sometimes access to it. It got out just fine. Ahh, our tax dollars at work. I drove by it thousands of times and always dreamed of having something like it, impractical but oh well, we can dream.

If I don't find a used derrick that can have regular stairs, I'll settle for something I don't have to climb real high. I have climbed lots of towers, some way over 100 ft many times. It is not my favorite thing. Tilt overs with "real" beams require way tall ladders that are more dangerous than climbing the tower. At least with a crank up you can get within something like a section and a half of the ground which isn't so bad. Your solution, like most, is the combination of tradeoffs and compromises that you picked as suitable for you. I really like your solution but tend to prefer a crackup at this location (baring a derrick) because I can lower the tower for high wind situations. If maint were the only issue for me, you have found a near ideal solution. I have this, perhaps unrealistic, concern for high winds, living as we do only a few miles from ground zero of tornado alley.

If I can find an economical source of utility poles (I have a source of a $50/hr util pole setting truck with auger) I might experiment with rhombics and other layouts of skywire.

Uhhhh, those holes drilled into concrete in place of augers... what concrete?

Pat

[GaryM]

The holes were drilled in earth and filled with concrete!

Rombics are nice if you have the space and lots of supports.

One of the Boeing clubs in Washington State had an antenna as you describe. A log periodic is good if you need to cover all the band with a somewhat efficient antenna. But a three or four element Yagi is better on the band it's designed for.

[Pat]

Gary, Right, efficiency at resonance is tough to beat. My ARRL Ant Handbook is truly ancient and probably doesn't even cover many modern designs. It sure doesn't have anything for the recent WARC bands.

I don't have a "shack" set up right now except for the cab of my 1Ton Dodge with VHF, UHF, CB, and FRS. My Drake 7 line equipment is fossilizing in boxes waiting to see the light of day and feel the power. Luckily my "7" will transmit from the AM broadcast band (down to about a meg) up to 30 meg so whatever bands are approved in that range, I'm covered. It isn't state of the art and wasn't the best when it was new but it works pretty well and has provided a lot of fun.

Some of the best action I had on personal equipment was with an Atlas 350 and then the Drake, both loaded through an antenna tuner into the insulated backstay of my sailboat.

Fiberglass boat, so no shielding for the shack SO... with the Atlas 350 cranked up on certain freqs you could draw sparks between the mike and your lips.

One phase of my varied past had me as a field service engineer in marine electronics where we used lots of random wire with tuners as well as trapped verticals, loaded horizontal helical dipoles, and so forth.

A friend, coworker, and fellow ham (N6AAM, Ancient Atrophied Man ) bought up a supply of surplus Collins trailing wire antenna tuners (used in aircraft). Pretty old technology, TUBES. Silver plated metal bands wrapped up on aluminum drums to reduce inductance or on ceramic one to increase inductance, servo driven vacuum caps, and so forth. Quality stuff, just OLD technology.

We cleaned them up, repaired them through canabalization of their stricken bretheren and designed and built solid state 12vdc inverter power supplies to run them. B+ was 250 volts and there were a couple other voltages that I don't recall. Housed the power supplys in "spare" tuner cases freed up through the canabalization for parts program.

You gave the tuner a low power sample at your operating freq and it tuned up a random long wire to way better than 1.5:1 VSWR, often 1.1-1.2 or so depending on longwire installation, proximity of metal, wires, etc. If you shifted freq a tad to avoid someones splatter or whatever it would track you automagically.

I got involved for the fun of it and to help out a buddy. He sold and installed several of them for long range fishing boats.

One of my favorite long wire antennas was hand tossed over a tree limb and tuned with a QRPP tuner. It was for a CW only battery operated Heathkit Tribander. I used to also take it on buisness trips in a small suitcase packed along with a small variable loaded vertical suitable for hotel room windows and balconies. Amazing what you can do with a couple watts and luck.

Pat

[GaryM]

The tuner you describe sounds similar to the SGC-231 antenna coupler that I have. You feed it with coax and a 12V supply. It will tune a random wire from 160 meters to 6 meters. The wire is connected directly to the unit. There's also a ground connection. But, it can feed a long wire, can feed two wires as a dipole, can feed a loop too. In the manual, available on their website at www.sgcworld.com, they illiustrate it's use in a sailboat just as you describe. The coupler can also feed a vertical whip for mobile use.

The Boeing club in St. Louis, I'm the President which means I have to help with all the projects, just got their 70 CM repeater back on the air after about a three year absence. The old repeaters power supply failed, and since it was a borrowed unit we replaced it with an Icom unit. But we found that running two repeaters on one antenna and a diplexer didn't work too well with the Icom. Although it worked fine with the old unit. So we finally got our act together and put uo two antennas. Brand new Celwave, old Phelps-Dodge co., commercial quality antennas. They weigh about 30 pounds each and are mounted on 2.375 dia aluminum masts. Coverage seems pretty good to about 30 miles on the West. We've not had a chance to check other direstions yet. So far we are happy with the results of our efforts.

[Pat]

Gary, Many of the automatic tuners have several discrete capacitors that are switched by relay to find the best match and some have tapped inductors switched similarly. This is done automatically based on a phase detector that determines if the load's reactance is capacitive or inductive (recall ELI the ICE Man?) The Collins aircraft trailing wire tuners we used had variable vacuum caps and variable inductors which gave infinite, i.e. analog variability as opposed to discrete steps with relay connected caps. OF course this had way more mechanical components than just relays. They had servo motors and gear trains to position the variable components. Did a great job but more maint required than with a "modern" unit.

We installed some SGC equipment in marine service, including antenna tuners. I used manual tuner on my sailboat. Last tuner I used there was the matching unit for the Drake TR-7, completely manual in operation. I made a chart for all the bands and setup after a band change only took a couple seconds. Of course, if $ were not an issue, I'd have gone automatic. We did ham on one of the Collins at my buds house with both a Drake TR-7 and his S-line. He was a Collins S-line kinda guy. He ran a Collins S-line tranceiver mobile from his VW bug. Bugs were great, enough passenger legroom/kneeroom to underdash mount the S-line and clear the legs of a 6'2" 230lb shotgun rider (me).

Pat