Last update: 16.April.1999
AT-11 Automatic Antenna Tuner and IC-706 to AT-11 interface


AT-11 Automatic Antenna Tuner

The AT-11 is a full or semi automatic antenna tuner. It tunes from 30 MHz to as low as 1.8 MHz, taking no more than six seconds, acomplishing the tuning algorithm regularly within the first two seconds. It was develloped by WD8OYG and the first version was publish on QST as Dwayne L. Kincaid, An Automatic Antenna Tuner: The AT-11, QST, pp. 35-39, January 1996.

               Specifications:

                                    Size: 6.5 x 8.5 x 2.5 (Board 6.0 x 8.0 x 1.0)
                                    Configuration: Switched "L" Network
                                    Inductor range: 20 uH
                                    Capacitor range: 2700 pf
                                    Tuning time: 0.1 to 6 seconds, 3.0 average
                                    Current consumption: 15 to 500 ma, 250 average
                                    Voltage requirements: 11 to 14 volts
                                    Microprocessor controlled
                                    1.8 to 30.0 MHz coverage
                                    Tunes 6 to 800 ohm loads
                                    Power range: 5 to 100 watts (150 @50% duty cycle)
                                    For Dipoles, Verticals, Vees, Beams or and Coax Fed Antenna
                                    Kit Builds in 6 to 8 hours (average)

I find it a wonderful antenna tuner, being the right companion for my Icom IC-706 MK II G, specially when I want to go mobile! And it is as good as and quite cheaper than the comercial models available... So wonderful that I decided to develop an interface to connect it to my IC-706, allowing the IC-706 tuner features and front panel button to work. You should be asking by now why would I want that if the AT-11 interfaces virtually with every rig without anything special... Well, does tuning at the press of front panel TUNE button, automatically switching from the current working mode to CW and lowering the output power to 10 Watt, and returning to the previous mode and power when tune is complete sound good enough for you? That is what my IC-706 to AT-11 interface does!! And you do not need to power the AT-11 externally as it takes power from the IC-706 (do not worry, the IC-706 can provide up to 4 A). And, of course, there is a design and kit available for the IC-706 to AT-11 interface!!

Let's get back to the AT-11. The first step is deciding to build the kit! Than you have either to buy a kit, that you can have for $180 USD from LDG Electronics (plus duane costs for European hams!), to buy only the 68HC11 processor from LDG Electronics and get all other parts around (and building it on perfboard) or to do as I did... I just bought the Printed Circuit Board, the 68HC11 processor and the 34064 chip from LDG Electronics (USA), the T106-2 toroidal cores from Amidon Corp. (USA), the relays Omron G5LE-12V from Farnell (UK) and all the other parts on the local stores. Do you want to see my beautiful AT-11?!

The kit bought as so from LDG Electronics or buying parts around is very easy and fun to build. You just have to follow the well written Assembly Manual and it should work as soon as you fire it on! Just take some care if you are substituting parts. I1UW wrote his personal experience in Rinaldo Briatta I1UW, Accordatori per HF - 2ª parte: Accordatori automatico, RadioKit Elettronica, pp. 35-39, Oct 98; according to him capacity between relay contacts and coil may prevent the tuner to tune higher bands. Relay switch speed is also very important; this may slow down the tuning algorithm or even force the AT-11 not to find the correct match, specially with the newer processor version running at 8.0 MHz.

If you plan on replacing relays, either for a cheaper unit or a commonly available model (for you), direct case replacements for the Omron G5L-12V or Omron G5LE-12V are Matsushita JS1-12V, NAIS JS1-12V (these are the same as Matsushita) and Zettler AZ941-1CT-12D. Table 1 shows a comparison between these three types regarding to switch speed and capacity between contacts and coil. I wrote WD8OYG and he advises the one from Matsushita may be slow.  I1UW used a relay from Weidmuller RF011012 (with good results) not case compatible with the ones from Omron (he assembled his unit on perfboard); he measured capacity between contacts and coil to be as low as 1 pF for those relays; if you are trying other relays, please check capacity between contacts and coil and discard units with high capacity values.
 
 

Relays
Close Time
Release Time
Contacts-Coil Capacity
Omron G5L-12V
10 ms max
5 ms
pF
Omron G5LE-12V
10 ms max
5 ms
pF
Matsushita JS1-12V
Approx 10 ms
Approx 10 ms
pF
NAIS JS1-12V
Approx 10 ms
Approx 10 ms
pF
Zettler AZ941-12V
Typical 6 ms
Typical 2 ms
pF
Zettler AZ942-12V
Typical 10 ms
Typical 5 ms
pF
Table 1

You may also save a little bit on inductors! I1UW also replaced the original T106-2 inductors for six air core and two T94 toroidal inductors. Tables 2 and 3 show original inductors and capacitors, and the ones used by I1UW. In Europe, T106-2 and T94-2 toroids are stocked by Barendh, in The Netherlands.
 
 

 
WD8OYG
WD8OYG
I1UW
I1UW
Inductor
uH
Winding information
uH
Winding information
L1
0.11 1 bottom turn - AWG18 on T106-2 0.06 1 turn - wire 1.5mm over 10 mm
L2
0.22 2 bottom turn - AWG18 on T106-2 0.11 1 turn - wire 1.5mm over 23 mm
L3
0.39 4 turn - AWG18 on T106-2 0.22 2 turns - wire 1.5 mm over23 mm
L4
0.59 6 turn - AWG18 on T106-2 0.40 3 turns - wire 1.5 mm over23 mm
L5
1.25 9 turn - AWG18 on T106-2 0.70 5 turns - wire 1.5 mm over23 mm
L6
2.50 13 turn - AWG18 on T106-2 1.20 8 turns - wire 1.5 mm over23 mm
L7
5.00 18 turn - AWG18 on T106-2 2.50 18 turns - 3 wire 0.22 mmover T94-2
L8
10.0 26 turn - AWG18 on T106-2 5.00 24 turns - 3 wire 0.22 mmover T94-2
Table 2

Let's now take a look at the capacitors equivalence table... It seems that I1UW followed the original article as published on QST. Assuming so, the values presented by WD8OYG are updated and should be followed.
 
 

WD8OYG
I1UW
Capacitor
pF
Cap. info
Capacitor
pF
Cap. info
C54 10 10 C54 5 10 + 10 - series
C55 + C56 20 10 + 10 -parallel C56 10 10
C57 40 39 C57 20 10 + 10 - parallel
C58 80 82 C59 40 39
C59 150 150 C60 80 82
C60 330 330 C61 160 150 + 10 - parallel
C61 680 680 C64 320 220 + 100 - parallel
C62 + C63 1280 680 + 680 - parallel C65 640 560 + 82 - parallel
Table 3

If you have trouble finding the wire, remember that Amidon Corp. (USA), Bytemark (USA) and Farnell (UK) stock it. If you live in Portugal there is a company called ELAB LDA selling small amounts of wire, or simple ask someone that works wiring transformers. Here you may get a wire table or a AWG-to-mm wire conversion table.

By the way, I guess it is worth getting a 4:1 ballun for the AT-11. Just buy BA-1 from LDG Electronics , a AB200 kit or an extra T130-1 when you buy the other toroids from Amidon Corp., Bytemark (USA) or Barendh and wind it up. Take a look at the BA-1 Assembly Manual.
 
 

IC-706 to AT-11 interface

What is it and  how it works?

The IC-706 to AT-11 interface is a small device that allows you to better connect you IC-706 to the AT-11 antenna tuner. It allows you to turn on and off the AT-11 (on automatic mode) pressing just once the IC-706 front panel TUNE button. Pressing the IC-706 front panel TUNE button for two seconds will switch the IC-706 from the current working mode to CW, lowering the output power to 10 Watt and outputting a 10 Watt carrier, and returning to the previous mode and power when tune is complete.

Where does it connect?

The IC-706 to AT-11 interface connects the IC-706 Tuner Control Socket to a Mini-Din Connector mounted on the AT-11 back panel.

... And what about power?

If you are connecting the AT-11 to an Icom IC-706 rig (IC-706/IC-706 MK II/IC-706 MK II G) through an IC-706 to AT-11 interface you do not need a power cable; the AT-11 is supplied by the IC-706. If you are not connecting it to an IC-706 or are not connecting through the IC-706 to AT-11 interface, just use the regular AT-11 power cable.

How does the design look like?

Well, it is just a PIC16F84 processor and a few parts... just press here to get a GIF! By the way, here it is a GIF for an assembled unit and cable.

What about parts/kit availability?

A complete kit or parts (such as pre-programmed PIC, PCB, relays,...) are available from me. Sorry, I cannot take electronic cash - only bank notes, bank transfers and checks (must add charges). Table 4 shows cost for complete kit and parts as well as shipping costs for most common destinations.

Table 4



Bibliography
 

Rinaldo Briatta I1UW, Accordatori per HF - 2ª parte: Accordatori automatico, RadioKit Elettronica, pp. 35-39, Oct 98

Dwayne L. Kincaid, An Automatic Antenna Tuner: The AT-11, QST, pp. 35-39, January 1996

AT-11 Automatic Antenna Tuner Assembly Manual V2.4a, LDG Electronics

AT-11 Automatic Antenna Tuner Assembly Manual V2.4b, LDG Electronics

BA-1 Balun Assembly Manual, LDG Electronics

IC-706 MK II G Instruction Manual, Icom Inc.

Matsushita JS1, relay datasheet

NAIS JS-RELAYS, relay datasheet

Omron G5L(E), relay datasheet

PIC16C84, Microchip processor datasheet

Zettler AZ941, relay datasheet

Zettler AZ942, relay datasheet



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