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| | Posted on Tuesday, November 06, 2001 - 12:42 am: | 
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The Skylab T233 Omni-Directional 10-11 Meter Base Station Antenna
A non-technical review
I recently have had the pleasure of reviewing the Skylab T233 antenna for Copper Electronics Inc. (copperelectronics.com). This all aluminum, omni-directional, antenna, manufactured by CTE, and Italian company, is the new version reminiscent of the old Antenna Specialist Starduster M400. As a matter of fact, it is exactly the same as the Starduster.
Upon receiving the antenna from Copper Electronics, I carefully unwrapped it and layed out all the parts, and started to look over my new antenna.
This antenna is a little more complicated to assemble than the tried and true Solarcon A-99. Once you figure out where all the elements and radials go it's simple. Unfortunately the instructions supplied with this antenna are marginal at best, and somewhat vague. The pictures are abbreviated, but you can figure them out. If you already know what the antenna is supposed to look like assembled then putting this thing together is very easy.
When you first unwrap the Skylab it will look like someone sent you a tent! There is a lot of aluminum in the box, and a bag of parts and hardware but don’t get discouraged, the best way to tackle this task it to lay all the parts out on the floor, sit down, relax, and enjoy putting it together. That's part of the fun involved in this hobby!
When you get your Skylab antenna you will find that it is not much more than a 102" whip with a ground plane kit. Okay it's more than just a eight and a half foot piece of stainless steel, even though this antenna has no loading coil. After all, we all know the 1/4 wave 102" whip is the most efficient antenna out there! This is an antenna design that has been around for many years, and some of our elder radio operators I have spoken with hold the old Starduster in very high regard.
TECHNICAL SPECIFICATIONS
Overall the Skylab T233 is just over 18 1/2 feet from the top of the vertical radial to the bottom tip of the ground plane radials. Electrically this is a 1/4 wave antenna. It is constructed of anticorodal aluminum, which, in lay terms means it will not rust or corrode. The impedance is 52 ohms, and the manufacturer claims this antenna is capable of 7 dB gain. The manufacturer also claims this antenna will withstand 75 MPH winds, and handle 800 watts. This wattage rating may be a little low for some users, and I personally can’t see why the Skylab wouldn't be able to handle far more than that. After all with decent coax a 102" whip will handle whatever you put through it.
The ground plane radials are fastened to the mounting mast, this prevents whistling in the wind and also keep those long radials from blowing around and loosening up. This is a good thing for those of us who want to put up an antenna and forget about it for many years!
ALL of the antenna's radials are made out if aluminum like I mentioned previously, and they are fluted. They are not smooth like other aluminum antenna radials I have seen, and this is done for strength, and durability, and keeps the radials from being bent as easily. Unfortunately, the hardware holding the antenna together is of marginal quality. I would recommend using machine screws and nuts to assemble the antenna instead of the provided sheet metal screws. An oversight by the manufacturer, and probably used to keep costs down.
There are also anti-static radials, a little over 4 inches long, which are mounted in the center of the vertical radial. This helps dissipate static charges built up in the antenna, and may prevent your antenna from being struck by lightning.
I will say this about the way you have to mount this thing. It is a little unorthodox. Most omni-directional antennas are clamped right to the side of the mast and up they go. With the Skylab, the antenna sits on top of the mast and is held on by two set-screws. Since the SO-239 connector will be hidden inside the pipe, you have to run the coax up through the mast and then connect it to the antenna before mounting the antenna to the mast. A little weird perhaps. But look at it this way. Your PL-259 connector and the end of your coax is protected from the elements of nature by being inside the mast. The connectors are always the weakest link of your feed line, so keeping them out of the weather is actually a plus! Don't worry about the fact there is only 2 set screws holding your antenna on the mast, because the clamps that hold the ground plane radials to the mast provide a lot of support as well, and this antenna is very lightweight. On the flip side of this, mounting the antenna in such a fashion became difficult while all the ground plane radials are in place. I definitely favor the traditional way to mount antenna, by clamping it right to the side of your mast. The SO-239 connector in the base of the antenna will not allow you to screw a PL-259 into it! It’s too tight, and you can only manage to get the coax connector into the antenna about a quarter of an inch. This is a problem, that upon conferring with other people, I found they had as well. So I tried to sand down the center conductor of the PL-259 with a little sandpaper to get it to fit. No dice. I eventually had to drill the center of the SO-239 out. This is not something I bargained for, nor something I would look forward to in assembly this apparatus.
SWR and BANDWIDTH
If you plan on using this antenna for 10 and 11 meters you should be fine. The top most radial can be adjusted for higher frequencies by sliding it down in the lower element. Unfortunately, I found that this antenna performs poorly (as far as SWR goes) in the lower realms of the 26 MHz band. I found an SWR of 1.2:1 on the 40 channel CB band, but seems to increase more sharply outside of that band without adjustment. The A-99 seems to be a bit more broad banded, especially below channel 1. The reason for this, I believe, is that the Skylab lacks any decent adjustment to operate in a lower frequency range due to the fact that you can only slide the top most radial up so far before you run out of room. For straight CB use, this antenna will perform well regarding SWR's, but lower frequency out of band operation, it performs poorly. The A-99 offers rings on the base of the vertical element which can be turned to adjust band operation. The only way to adjust this antenna, is like I said previously, to move the top most portion of the vertical element up and down within the bottom portion. Which means you have to take the antenna down to adjust it. Not cool.
This antenna will have no problems covering the 10 and 11 meter bands and can be shortened for higher frequencies for commercial or public safety use. Adjusting the length is easy, just loosen the set-screw holding the top portion of the vertical radial in place and move it up or down. This is fine, if you get it right on the first try. Or else you have to take the antenna down to make the adjustments, which could be a pain in the butt. This is a 10 - 11 meter band antenna so there isn't much room for adjusting for considerably lower frequencies. However the manufacture claims efficient operation down into the 26 MHz realm. Leave the top radial off completely and trim a little off the bottom radial, and it just so happens that this antenna is almost perfectly sized as a 5/8 wave, 2 meter antenna! This antenna also makes a very good scanner antenna for the HF and VHF bands!
Below I have included two charts. One showing the bandwidth and SWR at various frequencies for Solarcon's A-99 and the other showing the same information regarding the Skylab T-233. You will notice that the A-99 is far more broadbanded and covers an impressive 2.07 Mhz at an SWR of 2.0:1 or lower. The Skylab only holds an SWR of 2.0:1 inside of 1.34 Mhz spectrum. This antenna will serve just fine on the straight 40 channel CB band plan and beyond. You will notice a difference as the where the center of the band falls for each antenna. The A-99 is centered right around CB channel 30. Although the factory documentation states the antenna comes tuned for channel 20. The Skylab, I tuned myself, to around channel 20.
 
| Solarcon A-99 Bandwidth | 2.0:1 or less 26.145
2.0:1 or less 28.215 | 2.07 | 1.9:1 or less 26.205
1.9:1 or less 28.165 | 1.96 | 1.8:1 or less 26.245
1.8:1 or less 28.115 | 1.87 | 1.7:1 or less 26.265
1.7:1 or less 28.055 | 1.79 | 1.6:1 or less 26.495
1.6:1 or less 28.005 | 1.51 | 1.5:1 or less 26.615
1.5:1 or less 27.965 | 1.35 | 1.4:1 or less 26.695
1.4:1 or less 27.895 | 1.20 | 1.3:1 or less 26.775
1.3:1 or less 27.825 | 1.05 | 1.2:1 or less 26.855
1.2:1 or less 27.725 | .087 | 1.1:1 or less 26.995
1.1:1 or less 27.605 | 0.61 |
| | 2.07 MHz bandwidth @ 2.0:1 or less | | 1.35 MHz bandwidth @ 1.5:1 or less |
| Skylab T-233 Bandwidth | 2.0:1 or less 26.505
2.0:1 or less 27.845 | 1.34 | 1.9:1 or less 26.525
1.9:1 or less 27.815 | 1.29 | 1.8:1 or less 26.595
1.8:1 or less 27.785 | 1.19 | 1.7:1 or less 26.685
1.7:1 or less 27.755 | 1.07 | 1.6:1 or less 26.705
1.6:1 or less 27.715 | 1.01 | 1.5:1 or less 26.765
1.5:1 or less 27.685 | .92 | 1.4:1 or less 26.845
1.4:1 or less 27.535 | .69 | 1.3:1 or less 26.995
1.3:1 or less 27.455 | .46 | 1.2:1 or less 27.215
1.2:1 or less 27.255 | .04 | | 1.1:1 or less | N/A |
| | 1.34 MHz bandwidth @ 2.0:1 or less | | .92 MHz bandwidth @ 1.5:1 or less |
PERFORMANCE
I was using the same radio and microphone and the same length of coax for both tests, so I tried to remove as much of the variables I could to keep this a fair comparison. I also kept both antennas at the same height as well. Both antennas were grounded by the same type of cable and grounded to the same area on the mast as well as the same ground rod.
Locally, I didn't see much of a difference. Signal reports using the Skylab vs. the A-99 were very similar, and almost unnoticeable. The Skylab does boast a much cleaner receive than the A-99. By this I mean, RF interference around the antenna seemed to be minimized. This is very good for receiving weaker, fringe signals, that normally would be covered by noise and static.
Most of the local stations I worked told me I didn’t sound as loud using the Skylab, as I was using my A-99. Although signal strength on their S-meters was similar, those stations reported that I didn't seem to have the same punch as I did when operating on the A-99.
Although adjacent channel bleedover on the receive end is the same as the A-99 (due to the sensitivity and rejection of the receiver used), there seemed to be less splatter and bleedover coming from the Skylab vs. the A-99. Once again, I remind the reader that local users didn't see the same "punch" with this antenna as the A-99.
DX is another story! Although trying to get accurate signal reports in the typical "fade in, and fade out" of the FX signal were almost impossible, Some folks recognized the difference and made it clear to me that the Skylab was a far better DX performer than the A-99. The cleaner receive made it easier to pull weaker skip signals out of the mess and pile up that is frequent on the skip channels. I believe the ground plane elements, which lower the Skylab's angle of radiation, seemed to direct more of my system's power towards it's target rather than into the ground, where they are wasted. These elements may have also attributed to the better, and more quiet receive I mentioned before.
FINAL THOUGHTS
I will give credit where credit is due. This antenna works great for DX use and has a beautiful, clean receive, but for average local AM ragchewing it's no better than Solarcon's A-99.
Assembly is the biggest draw back on using this antenna. The instructions are poorly written, and the hardware provided is of marginal quality. You HAVE to use a 1 3/8" mast to put this antenna up. The reason for this, is the base of the antenna and the ring that connects the arms for the ground plane radials will only fit on or over a mast 1 3/8". The SO-239 connector will not allow you to screw a PL-259 into it. It has to be drilled out! Not good!
If you like experimenting with new antennas and like to tinker around with equipment, go for it! It's really not a bad antenna, it's inexpensive and price wise compares to the A-99. It works well, and properly assembled should provide a lot of enjoyment.
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