[Yaesu] First Look at the LDG AT-897 autotuner for the FT-897

2003年4月03日 13:18:33 -0600

For the past week, I have been testing a pre-production unit of the new LDG 
Electronics AT-897 autotuner. My observations are presented in the 
following paragraphs.
First, the AT-897 is designed to bolt onto the FT-897 not unlike the 
FC-30. The feet on the side of the FT-897 can be removed and installed on 
the AT-897. The metal-encased AT-897 weights about 1.5 pounds (0.7 kg) and 
has dimensions of approximately 1.5" W by 3.25" H by 10-5/8" D.
When you tune, you can hear the relays latching and unlatching as the match 
is being determined. Otherwise, it is a very quiet unit since it has NO 
fan and is effectively in deep hibernation (drawing essentially no 
current). This is due to the latching relays and the innovative electronics 
design by LDG.
During the testing, I operated the FT-897 on both an internal battery and 
an external power supply and found no different in the operational 
performance of the AT-897. Power for the AT-897 is taken from the FT-897's 
CAT/Linear jack so no additional power source is necessary. Since the 
AT-897 is connected to the FT-897's CAT/Linear jack (via a supplied jumper 
cable), a feedthrough CAT/Linear jack is provided on the rear panel of the 
AT-897. Utilization of the AT-897 does not block your use of the 
CAT/Linear jack.
The FT-897 has several "oddities" that makes conventional tuning difficult 
in some cases. One example is that the high-SWR foldback (very fast) 
doesn't just reduce the RF output, but turns it off for a short time 
(several hundred milliseconds). This results in a bit longer tuning time 
for the AT-897 and the relays sounding like they are stuttering a bit.
I tested the FT-897/AT-897 combination with a small number of 
antennas. During these tests, I typically used the W4RT Electronics 
One-Touch Tune (OTT-897) module to allow tuning to occur when I simply 
pressed the AT-897's tune button. When I put the FT-897 in a carrier mode, 
the AT-897 behaved the same manner as when the OTT-897 was used. The 
OTT-897 just makes tuning a lot easier (and the OTT-897 is also powered by 
the FT-897). The antennas I used for the testing included a short whip, a 
long wire, a 5-band Hex-Beam, and a GAP Titan (and a dummy load too).
The AT-897 has a single push button and LED on its front panel. The push 
button serves two functions. If you depress and release it quickly, the 
tuner is placed in a bypass configuration. If you press and hold it for at 
least 1/2 second, the tuning starts. (You should release the button when 
the tuning starts.) The red LED illuminates to indicate that the AT-897 is 
tuning. You can monitor the SWR using the FT-897's SWR meter (indicator) 
or an external SWR meter if you desire. I did both. Also, I used the 
MFJ-259B to check the SWR of the antennas. FWIW, the FT-897 SWR meter is 
about as useful as the one in the FT-817!
The LDG Electronics AT-897 Autotuner specifications include the following: 
tunes 6 to 800 ohm loads, 10:1 SWR; tunes in 0.6 to 8 seconds, typically 4 
seconds for large impedance changes and only a second or so for small 
changes in impedance such as when QSYing in the same band; operates over 
1.8 to 54 MHz; requires as little as 100 mW RF to tune and can handle over 
100 W.
In operation, the AT-897 performed flawlessly and always found a good match 
on all bands from 160-6 m. An interesting experiment was to attempt to 
match the Hex-Beam outside of its normal bands. This is a 2-element wire 
beam covering the five bands from 20-10 m. The AT-897 easily found an 
excellent match on all five bands including the upper end of 10 m where the 
SWR is over 4:1. I used the AT-897 to attempt to match to the Hex-Beam on 
6 m, 30 m, 40 m, and 80 m. On each of these bands, the AT-897 found a good 
match with the residual SWR being from 1:1 to 1.3:1. According to the 
MFJ-259B, the SWR ranged from 2.5:1 to over 7:1. I attempted 160 m, but 
the SWR was > 25 according to the MFJ-259B. Consequently, an acceptable 
match could not be found --- outside of the AT-897's tuning range.
The GAP Titan is an interesting test on 80 m. My Titan is tuned for 3950 
kHz, but I like to operate CW at times down near 3500 kHz. I had found in 
the past that the LDG RT-11 or the AT-11MP (my Z-11 as well) all found a 
good match at this frequency. The Titan's SWR at 3500 kHz is about 6:1 or 
so. The AT-897 found a good match just like the other LDG tuners.
I stuck a 6' long whip into the antenna input jack on the AT-897 and 
attached a counterpoise with an artificial ground included (MFJ-931). The 
AT-897 (@ 20 W) had no problem finding a good match from 40-6 m. On 17 m, 
I had to shorten the whip about 6" to obtain a match.
The long wire was non-resonant. The AT-897 had no problem finding a good 
match (1.0:1 to 1.4:1) from 160-6 m. As with the whip, I used a tuned 
counterpoise with the MFJ-931 included. Although I have the external balun, 
I never used it in my tests.
As I mentioned above, I tried tuning at both 100 W and 20 W. The inclusion 
of the OTT-897 in the system certainly helped in performing all of the 
tests. I also used my FT-817 at both 5 W and 0.5 W to check the low-power 
tuning performance. The AT-897 worked fine from 0.5 to 100 W input. This 
reminds me of a question I am often asked, "Will the AT-897 work with other 
radios?" The simple answer is of course. Just provide it with power and a 
carrier, and it will tune. This is how I used it with the FT-817.
Although the AT-897 tuning time is specified from 600 ms to 8 seconds, I 
observed 2-4 seconds in general with one case being about 5 seconds. The 
AT-897 tuning algorithm has two basic modes, viz., the normal tuning mode 
and the fine or quick tuning mode. The tuner actually selects the proper 
mode. If the sensed SWR is > about 1.7:1, the normal tuning mode is first 
used to search the "matching space" using an efficient method developed by 
LDG. Once an initial match is found, it switches to the fine tune mode 
automatically to complete the matching process. If the initial SWR sensed 
is less than about 1.7:1, then the fine tuning algorithm is used 
first. For example, when I had tuned on some band and then QSY maybe 50 
kHz, I would touch the tune button and the retune would almost always take 
< one second. I also noted that when I first tuned an antenna that had a 
very high SWR, the residual SWR might be 1.4:1. A second touch and the 
AT-897 often (not always) would improve the match just a bit more to 
perhaps 1.2:1 or less. Frankly, that's only dropping the "loss" due to 
mismatch from just under 3% to 0.8% or a difference of less than 1/10 dB. 
Having this dual mode tuning is very nice from an operational point of view 
I found. I note that the current versions of the Z-11, RT-11, and AT-11MP 
have this feature as well.
Many thousands of hams, including me, are using LDG autotuners 
presently. My bottom line is that I have found this new LDG AT-897 tuner 
to demonstrate the same first-class autotuner performance LDG user expect 
and to integrate nicely with the FT-897. LDG and W4RT collaborated to 
develop this autotuner system that really works with the FT-897.
I expect W4RT Electronics to start shipping the AT-897 and OTT-897 (these 
are available now) about April 25 based upon current information.
73,
Barry - W4WB
W4RT Electronics
www.w4rt.com