i just purchased this atas-25 used, but in practically unused condition. i thought the first thing i should do is to test it under the actual working conditions i plan to use it in. and yes, i realize it's designed for outdoor use, but i needed an indoor antenna, so please keep that in mind when reading this review.
first off, the vertical part of the antenna is made from gun cleaning rods. if it ever breaks, i anticipate being able to ride over to wal-mart and visiting the sporting goods department for replacement whip pieces. the one included appears to be aluminum. you can buy replacements (from your local gun shop) made of brass or stainless steel if you don't like aluminum.
i found it would not tune on 40m. hold on- let me explain. the ceiling in my home is standard 7 feet 8 inches. using the tripod i had and three whips, i could not extend the coil fully. i suspect i probably could have reached 40m if i could have extended it some more. if you plan on using this antenna indoors, you may have the same problem.
a chart follows that tells what swr i was able to get when tuning the unit using an mfj swr analyzer to check it.
absolute lowest frequency with three whips: 9.275mhz 1.5:1
absolute lowest frequency with two whips (fully extended): 7.685mhz 1.7:1
3 whip sections all the way retracted no match anywhere.
2 whip sections all the way retracted no match anywhere
1 whip section all the way retracted 1.2:1 at 65.000
could not extend fully with three whips because of hitting my ceiling.
2 whip sections fully extended 1.7:1 at 7.685
2 whips no good match on 20m. 2:1 at 14.350mhz
18.150 2 whips 1.3:1
21.400 2 whips 1.2:1
10.125 1 whip 1.2:1
18.140 1 whip 1.2:1
21.350 1 whip 1.2:1
24.900 1 whip 2:1
27.185 (cb) 1 whip 1.2:1
28.400 1 whip 1.3:1
50.125 1 whip no match
50.125 no whip, no radials 1.6:1
146.520 no whip with radials 2.3:1
146.520 no whip no radials 1.1:1
could not test 440, my meter doesn't go there.
i have not had an opportunity to try this antenna outdoors in the wide open spaces. i'm certain the wiring in my home, the metal ductwork, my refrigerator, and other metallic objects cause difficulties in obtaining good matches. the length of the whip on 10m causes me concern that there is not enough radiating surface to make good contacts. the efficiency has to be somewhere along the lines of a radio shack gutter mount cb whip. i'd be suprised if i were able to make any contacts on 10m. in fact, on any band below 10m where only one whip was used for a decent match, i suspect the efficiency is so low as to be a total waste of time trying to make contacts. you could probably do as well on a wet noodle. i think a telescopic whip would have been a better choice, because having to work within the constraints of fixed-length whips (one whip, two whips, or all three, with no other alternatives) seems to limit the flexibility of the unit. i will probably manufacture my own adapter to allow the top of the antenna to accept a standard 3/8-24 thread telescopic 9 foot whip from mfj. this will allow the least amount of loading coil to be used for maximum efficiency. as far as removing all the whips and radials and using only the loading coil as a radiator for 6m, 2m, and 440, the efficiency probably only marginally better than a rubber duck.
one variable aspect of this antenna is the tripod. the one i have is metal throughout, so the tripod legs become part of the ground system of the antenna. some tripods have plastic mounts, and this would insulate the antenna from the tripod legs. there is nothing in yaesu's instruction sheet to indicate which type of tripod is preferred for proper tuning of the antenna.
there is some ambiguous language in the tuning chart. what is the difference between "no connection", "do not connect", and "not used"? in english these all mean basically the same thing! are they referring to the tuning rods or the radial wires? the rest of the instructions are well written.
as far as the overall design, simplicity of operation, durability, and aesthetics aspects, i think yaesu has a winner! personally i would have preferred that they package two of these units together and included 9 foot telescoping whips and some type of center insulator to allow you to make a rotatable dipole of sorts, and priced the set around $250.00. but if you do that, the adjustable coil would have to go somewhere else besides the center, and weight and angle-of-moment with resultant force against the center insulator would become an issue.
hopefully i'll get to try this antenna out in an outdoor environment real soon, and i fully expect it to tune better under those conditions. since my primary purpose is to use it as an indoor travel antenna, that was the condition i tested it under.
73, -kr4wm
