[Antennas] ATAS-25

Tue Dec 27 01:24:14 EST 2005

All,
The Antenna in Question is the ATAS-25 its listed as this:
The *Yaesu ATAS-25* is just the ticket for / Field Operations/. It 
covers these amateur bands: 7, 14, 21, 28, 50, 144 and 430 MHz. The 
bands are covered by manual changing the supplied elements and hand 
adjusting <http://www.universal-radio.com/catalog/hamhf/4044adj.jpg> the 
coils. See the chart below. HF and 6 meter power capacity is: 100 watts 
SSB/CW 50% duty cycle and 50 watts AM/FM. Power capacity for 144/430 MHZ 
is 50 watts in all modes. Maximum height is 7.2 feet (2.2m) 2.05 lbs. 
(930g). An Allen wrench and three radial wires are supplied (20, 9.8 and 
6.6 foot). It comes in a small box only 24 x 4 x 2 inches. More info @ 
http://www.yaesu.com/downloadFile.cfm?FileID=965&FileCatID=158&FileName=ATAS-25_OpManual.pdf&FileContentType=application%2Fpdf 
<http://www.yaesu.com/downloadFile.cfm?FileID=965&FileCatID=158&FileName=ATAS-25_OpManual.pdf&FileContentType=application%2Fpdf>
*I got an e-mail back from Val, who wrote:*
The ATAS-25 is not what I would call a simultaneous-resonant antenna on 
all HF bands. In other words, this antenna is really intended for 
temporary portable use and must be retuned each time you change bands. 
As such, it is not the best antenna for SWLing purposes.
This antenna is tricky to use but I would above all, suggest that you 
read the manual. The manual only has you place all the radiating 
elements (3) on the antenna when you are either on 40M, 15M, and 
perhaps on the CW portion of the 20M band. As you go up in frequency, 
you drop off upper radiating element sections per the manual 
instructions, leaving on the bottom coil assembly. Until you tune the 
bottom coil assembly, the radio/antenna combo will be 
dead............noise wise.
In order to tune this antenna, put out all the HF radials as this will 
serve to further reduce the SWR and thus enhance the antenna 
performance. Now, for sake of conversation, lets limit the tuning to 
one band....40M. Simply place three of the radiating elements onto the 
top of bottom coil assembly. Now, ensuring the coax from the antenna is 
hooked up to the radio, turn the radio onto the appropriate band and 
turn up the volume. Now, within earshot of the radio, raise/lower the 
bottom coil assembly until you hear the band noise peak on the radio. 
(If you don't hear a peak in the band noise, remove one of the radiating 
elements and repeat.) At this point, you are what I would say 
rough-tuned which should prove adequate for SWLing purposes. 
Now, if you were licensed to do so, you could go back to the radio and 
"squirt" a little 7 MHz RF into the antenna and check the SWR. If the 
SWR was still a little high, you would need to go back to the antenna 
and slightly twist the coil assembly CW or CCW, each time going back 
to the radio to check the SWR.
Yes, you will get a workout as it takes several trips back and forth 
between the radio and the antenna. Here is the big gotcha': The tuning 
of the antenna will be affected by your body so be patient.
Need to change bands?............The whole process starts over again!
Is there any easier way to tune this beast? Yes, through the use of one 
of the popular antenna analyzers manufactured by companies like Autek 
and MFJ.
Murray, the great thing about this antenna is that tuning it will give 
you plenty of exercise to shed those extra pounds from those extra 
pieces of pie you consumed over the holidays!
_/*MY TAKE*/_/* */_/* :-\
*/_
This sounds easy. So for 6 meters I am guessing that I should put out 
no radials on the ground and no radials in the vertical section of the 
antenna coil. Then move it up and down with the vol. up and the squelch 
open and when the band noise gets real hi that should be the point I 
stop walk around to the radio and give it a try? 
PLEASE LET ME KNOW WHAT YOU THINK. I NEED THE HELP.
73'S
KB3LZV