User review of the ICOM AH-4 auto tuner.
By Matt Erickson KK5DR Oct. 2004. These little auto whip/wire tuners have been on the market for a few years, but I have recently acquired a new one for use with my IC-746Pro in a field type operation. Above is a picture of the tuning unit, shown with the plastic cover installed. The
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entire body of the cover is plastic, with chrome plated metal mounting plates screwed to the back half on top and bottom. The unit is fully weather tight, with seals on every seam.
Above is a picture of the internal parts of the tuner unit. Notice the rubber gasket that seals the two halves of the cover. There are also seals on all the cable entry ports as well as the ground lug, and the output insulator. In the center of the photo, can be seen, the input coax cable connector. Next to the coax input port is the ground line attached to the external ground lug. On the right hand side of the picture is a short red wire which is the RF output line to the antenna insulator. The AH-4 uses relay switched LC networks for matching of the output antenna. There are 1,040,000 possible LC combinations that are selected by the CPU in 2.5 seconds or less. The unit is designed to operate from 3.5 to 54MHz, with a wire/whip of 23ft. long or more. For operations on 7-54MHz only, and shorter radiating wire/whip can be used. If the unit is to be used in a mobile installation,
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the ground should be a heavy strap bonded to the frame of the vehicle, and the tuning unit should be mounted as close to the whip as possible, preferably with a feed length of 12" or less to the whip. The CPU is shielded in the silver box in the upper left of the photo above. At the upper center is a gray terminal strip where the control cable is to be connected. While the unit is powered up, there are 45 memories that are automatically saved after a tune cycle on a given frequency, after that, the unit uses the memorized settings to retune each time the transmitter is keyed, in under 1 second. When the unit is powered down, the memories are lost. The AH-4 is rated at 125 watts input maximum. It is recommended that either a heavy ground strap be used in a mobile installation, or on portable/field operation should use a set of at least three counterpoise wires of equal length to the radiator antenna. I plan a set of four wires about 30' long each for counterpoise, and a 30' wire for antenna. The control cable is only 16' long, I wish it was twice that long, to get the unit farther away from the radio, and the operator. I made a special RF input cable with the addition of a toroid cores that will choke off any RF current returning to the radio on the outside of the coax or the control cables. One small potential problem I could see, would be the formation of water condensation inside the tightly sealed unit when operating outdoors in all types of weather. A simple fix is to place a small packet of silica gel inside the unit before it is sealed up. This packet will absorb any trapped water vapor inside. Changing or recharging the silica gel pack about once every few years would be a good idea. I have found that silica gel can be "recharged" by placing it in a gas type kitchen oven with only the pilot light on. Leave the pack there for about 5-7 days, and the gel should be recharged by then. Field test My first test of the AH-4 was using a single 12ga. insulated stranded wire for the antenna 30' long, pulled up into a tree just off my porch. The counterpoise system
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uses the same wire, but there are four of them at 30' long each. The exciter must be placed in CW mode to tune the AH-4, it tunes at a reduced output automatically. I used my IC-746Pro as the exciter for the AH-4. The antenna port #1 must be used since when the unit is connected to the exciter, the internal ATU is automatically bypassed and "EXT" is displayed on the front panel display. It only works through ant port #1 for HF/50MHz. I started on 17mtrs, but due to the poor conditions these days my calls went unanswered, same on 15mtrs. In this time of low sunspots and weak propagation on the higher frequency bands, some times the more effective bands are below 20mtrs. I went to 40mtrs where I found strong daytime activity, and my signal was reported to be good, very readable. No RF feed-back was detected, thanks in part to my toroid chokes and good ground plane created by the counterpoise system. Tuning was quick, under 1 second, and the memories worked fine. I was able to hop from band to band once the tune points were memorized on each band. The longest tune time I noted was about 2.5 seconds. It is too bad that the RAM is "volatile" meaning that when the unit is powered down all memorized tune points are lost. Perhaps someday an updated AH-4 design will have "nonvolatile" RAM memory. I consider the field test to be successful, even with the poor conditions. It proves that this system can be used very easily when backpacking, camping, or on Field Day. Its quick and easy, and fairly effective.
Field Day 2006: We used the AH-4 on FD with an IC-7000. The radiating wire was 90 feet of 12ga insulated stranded copper. The ground radials were the same wire but cut to 30 feet, with four runs laid out in a fan pattern in the opposed direction from the radiator wire. The radiator was about 15-20 feet above ground running horizontal. The system worked very well, tuned very quickly and seemed to radiate very
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well. The bands used were 80-10mtrs. There were no problems with the tuner or radio during the entire event. Conclusion The AH-4 is a nice little package, excellent for mobile whip tuning, and backpacking, as well as QRP remote antenna operations. I don't really like the short control cable, it should be at least 25' long so when operating a ground mounted vertical, the radio can be located somewhat out of the main radiation field, but with the 16' cable, the operator is nearly on top of it. I added 25 feet of four conductor unshielded cable to the control cable with the connector installed on the radio end of it. I added about 40 feet of coax to feed the tuner. Now the unit can be placed a good distance from the operating position, or high in a tree. I plan to use my AH-4 when I'm out camping, and on Field Day, for quick and easy to install 80-6 meter antennas. The unit tunes quickly and nearly flat, typically 1.2 or less. Tiny, quick, and easy to install and use. To learn how tuners/couplers work click here. 73 de Matt Copyright 2006 M.A. Erickson, KK5DR. All rights reserved.

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K9EQ AH-4 Universal Interface Users Manual
K9EQ AH-4 Universal Interface www.hamoperator.com

Rev. 5

Page 1

Table of Contents

Forward....... 3 Warning........ 3 Description and Introduction....... 3 Board History....... 3 Why use the AH-4?....... 4 Basic Interface...... 4 Full Interface....... 5 Construction....... 5 Basic Version....... 6 Optional components...... 7 Construction Notes....... 8 Component Identification...... 9 Verification....... 9 Initial Basic Version Checkout...... 9 Initial Full Version Checkout...... 10 Final Basic Version Checkout...... 10 Final Full Version Checkout..... 11 Circuit Description....... 11 Installation....... 12 Operation....... 14 Basic Interface...... 14 Tuning....... 14 Setup...... 15 Power output control using AM mode..... 15 Full Interface...... 15

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Troubleshooting....... 16 Schematics....... 18 Parts List....... 21 AH-4 Radio Interface Theory of Operation..... 23

Forward

An updated version of the manual may be available. Check with www.hamoperator.com for updates as well as additional information and feedback from other users. This product may require modifications from the stock design to work with your radio. Information on interfacing with different radios will be published when available.

Warning

It is possible to damage your equipment by using the interface described in this document. Use of this document, the AH-4 Universal Interface, or any information from www.hamoperator.com is done at your own risk. Do not use this information unless you are willing to assume all responsibility. The kit employs components that can be damaged by electrostatic discharge.
Description and Introduction
Hello, and thank you for your interest in the K9EQ AH-4 Universal Interface. The interface is designed to allow you to use the Icom AH-4 remote automatic antenna tuner with virtually any HF rig. I started this project after I purchased an Icom 706 and AH-4. I was very impressed with how well the tuner worked. It was almost effortless to build wire antennas, throw them in the trees, and work plenty of DX. The first contact with my first antenna (a loop I built in the garage) was with Belgium! I looked at other antenna tuners on the market and concluded that the AH-4 was the one I wanted to use. It is well designed, rugged, and priced very competitively. From my point of view, it had only a few disadvantages. The documentation that comes with the tuner is not very good and I couldnt use it with my other radios. While I really like the 706, Id like to be able to use the tuner with my Yaesu FT-990. I addressed the first disadvantage by publishing information about the AH-4 at my web site, www.hamoperator.com. The second disadvantage is addressed by the K9EQ AH-4 Universal Interface.

Board History

The first version of the interface was the basic version. It would tune the AH-4 when the TUNE button was pressed, but the user had to set the rig to a carrier mode and adjust the output to 5-15 watts. I presented the board to a good friend of mine, K0ZE, for review. His comment, You could get twice as much stuff on the board. Well, being a ham radio operator and being cheap er. I mean frugal I couldnt let board space go to waste! Hence, some improvements were made. The first improvement was to have the board generate a 1 KHz tone. If you were in SSB, this would eliminate the need to change modes. You could also adjust the tone level to control the power output (assuming speech processing is off). The second addition was to provide an ALC output to the radio. This 0 to 4 volt signal would cause the transmitter power to roll back to 5-15 watts when the tuner was engaged. (More on this later).

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Getting a negative voltage from a positive supply was a bit tricky. Once again K0ZE came to the rescue. Why not use one of those RS-232 chips that generate their own negative and positive voltages? So a MAX 232 was placed on the board. Its very sad to see an RS-232 chip with only one port in use! Thats when I added a computer interface to allow logging and rig control programs to communicate with the rig. Well, if you have RS-232 and you can key the transmitter, you almost have everything you need to interface the computers sound card to the radio. I would, after all, like to run PSK31. A few resistors and capacitors later, I was running PSK31. Proud of my new board, once again I showed it to K0ZE for his approval. His comment, You could get twice as much stuff on the board. While K0ZE figures out what features should be added, I now have a full interface that lets me use the AH-4 with virtually any radio, simplifies the tuning process, provides computer control of the radio, and lets me run PSK31.

Why use the AH-4?

The K9EQ AH-4 Basic Universal Interface allows the use of the Icom AH-4 and similar antenna tuners with most HF rigs. The AH-4 is intended to be used with certain late-model Icom radios, such as the IC-706 and IC-746. The AH-4 communicates with the radios using two control lines. Since the radio and the AH-4 can communicate, the AH-4 offers the following advantages over conventional wide range automatic antenna tuners: o o Tuning is accomplished using about 10 watts of power from the radio. The power from the radio is split between a dummy load and the antenna thus the radio sees a maximum SWR of 1.1:1 while tuning this prevents damage to the rigs finals. A maximum of 350 mW is radiated during tuning minimizing QRM. Other hams will appreciate your use of the AH-4. Tuning is never done under full load. This can prevent premature failure since the contacts of the tuning relays never switch while high voltages are applied. There are over 20 relays in the AH-4! There is positive indication that tuning has been accomplished. The tuner can be disengaged at any time permits receiving on other frequencies. The best bang for the buck. The AH-4 is less expensive than similar tuners on the market.
Unfortunately, those without the appropriate late model Icom HF rigs have not been able to take advantage of the AH-4. That is, until now. The K9EQ Universal AH-4 Interface allows the AH-4 to be used with virtually any HF rig. Once installed, the tuning operation is simple. There are two versions of the interface: a basic and a full version. The basic version allows the AH-4 to interface with almost every HF rig. The full version adds an RS-232 and a computer sound card interface.

Basic Interface

Some people may not actually want all of the K0ZE-inspired features. For these folks I have broken the board down into the original basic interface and a full interface. The following tuning process is used with the basic interface: 1. Set the rig to the desired HF frequency.

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If you are not in SSB or have not connected the audio interface, change the mode to one that emits a carrier (AM, FM, or CW) and adjust the power output to about 10 watts (watts will work). (If you are in SSB, you will need to turn off speech processing.) Push the TUNE button. The AH-4 will automatically tune. A status light indicates that the AH-4 is tuning and the final tune status. Reset the rigs mode/power (if it was changed) and begin operating. Note that any many cases it is only necessary to retune when changing bands.

To be compatible with the K9EQ Universal AH-4 Interface, the HF rig should have: o o o A convenient means of adjusting output power. Availability of a mode that emits a carrier (AM, FM, or CW) A keying line that operates at a maximum of +20 volts and 100 ma. (The interface will pull this line to ground when it needs to key the transmitter.) The radio generates a 1 KHz tone when tuning. This allows the use of SSB modes. If the speech processor is turned off, it may not be necessary to adjust power output when tuning. (Note that this feature may or may not work reliably depending upon how stable the rigs output is for a given audio level.)

Full Interface

The full interface adds the following features to the basic interface: o The interface generates an adjustable negative ALC voltage. This reduces the transmitters output when tuning. (Note that this feature could require frequent adjustment since the radios characteristics may change with temperature and voltage.) An RS-232 interface that allows computer-based rig control and logging programs to interface with the radio. The interface can be used with Icom and Yaesu radios. (Kenwood should work also but has not been tested.) The RS-232 interface will key the radio when DTR is asserted. This allows a computer sound-card based program, like Digipan, to key the radio. A computer sound card radio interface has been implemented. This allows SSTV, RTTY, CW, PSK31, and other sound card-based software to work with the radio.
For more information, please visit www.hamoperator.com. I am always interested in hearing your comments about this manual, the interface, the AH-4, or any subject you care to discuss. 73s, Chris, K9EQ

Construction

The K9EQ AH-4 Universal Interface may be built using prototype construction techniques or by using the printed circuit board. These assembly instructions assume that you are using the printed circuit board Rev. 2. Construction options: The board may be built with the one of the following three options: K9EQ AH-4 Universal Interface www.hamoperator.com Rev. 5 Page 5
TUNE and UNTUNE buttons on the PCB TUNE and UNTUNE buttons on the PCB and also mounted externally External TUNE and UNTUNE buttons
The following options are also available o o LEDs on PCB LEDs mounted remotely
External buttons and LEDs allows more flexibility in mounting, while onboard components make it simpler to build and get working.

Basic Version

The basic version requires the following parts: C1, C2, C3, C4, C5, C6, C7, C8, C17, C18 D1, D2, D3, D4, D5, D6 J1, J2, J3 L1, L2, L3 Q1, Q2, Q3 R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R13, R14, R15 U1, U1S, U2 X1 PB1, PB2

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Fig. 1 Assembled Basic Board

Optional components

The following components are not required and may be substituted as follows (with the corresponding change in protection, RF immunity or feature). Required substitute action and change is indicated. F1 short, provides short circuit protection. D6 short, provides reverse voltage protection. L1-L3 short, provides RFI protection D4, R6 open, provides power on indication.

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Figure 2 PCB Component Layout Pin 1 Pin 1
Construction Notes Electrostatic warning: U1 and U3 may be damaged by electrostatic discharge. Ground your body using the appropriate equipment prior to handling these components or the board once these components are installed.
View the board com ponent side up with lettering upright. Refer to Figure 2 for parts placement. Use the photograph on the cover of this manual for additional parts placement assistance. It is recommended that you use a DVM to verify the component values of the resistors. A magnifying glass may be useful for reading other component part numbers and values. When looking at the front (flat side) of the 78L05 with the pins down, the pins from left to right are: Output, Ground, Input. When looking at the front (flat side) of 2N3904 or 2N3906 with the pins down, the pins from left to right are: Emitter, Base, Collector. K9EQ AH-4 Universal Interface www.hamoperator.com Rev. 5 Page 8
The narrow side of Q1-Q3 and U2 represent the flat side of the device. All components mount on the top side of the board. U5 and R24 are not used. These are on the board to allow for future software development with non-volatile memory. The short pin on the LEDs is the cathode and is attached to pin 1 (square pad). J1, J2, and J4 can use right angle connectors. This may simplify connection depending upon how the board is mounted. See the parts list. The connector kit includes right angle connectors. The basic version requires a jumper from pin 9 to 16 of U3. This is done to prevent the rig from keying up as the input to the microprocessor floats.

Component Identification

Component 100 ohm resistor 220 ohm resistor 1 k resistor 4.7 k resistor 100 k resistor 22 pf capacitor.001 uF capacitor.1 uF capacitor 10 uH inductor Identification or Marking brown-black-brown red-red-brown brown-black-red yellow-violet-red brown-black-yellow 104 Green body brown-black-black

This completes testing of the interface board. Connect it to the power supply, rig, and AH-4. Perform the following in-circuit tests. 1. Turn on the power supply. Adjust the rig for no power output (i.e., RF and mic gain turned down, SSB mode). Press the TUNE button. Verify that the rig switches to transmit for about one second and then returns to receive. The status LED should be flashing. If this test fails, verify that grounding the TX-OUT line causes the rig to transmit. Make darn sure you didnt connect the TX-OUT line to something that either has voltages much higher than 13.8 or something that can source a lot of current like the power supply. Place the rig in AM, FM, or CW mode. Key the rig and adjust the power until it is about at 10 watts. Unkey the rig. Press the tune button. Verify that the rig keys on for several seconds then unkeys. Verify that the status light is on. Check the SWR. It should be less than 1.5:1. If this test fails, check wiring between the AH-4 and the interface. Turn the RF power up to 120 watts (or whatever the radio will do, whichever is less). Transmit. Verify that the status light remains on and the SWR is less than 1.5:1. If not, verify that RF is not getting into the control lines. Reduce the RF output of the rig to less than 10 watts. Change to a frequency where it is known that the antenna has a high SWR. Press the UNTUNE key and verify that the status light goes off. Key the rig and verify that the SWR is higher.

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Final Full Version Checkout
1. Connect the interface to the radio. Perform the following tests for those features that you intend to use (or are connected). (See Installation section for connection details.) Connect the rig to a dummy load and set it to SSB. Turn the speech compressor off and adjust the mic gain to a normal position. Monitor the RF output. Press tune. Verify that RF output is generated. Adjust R14 to vary the output. Key the mic. Verify that there is no output. Use Digipan on the computer to key the radio (select DTR for keying the radio). Verify that Digipan can key the radio. If not, verify that the RS-232 cable is wired correctly. Transmit with Digipan. Verify that RF output is generated. Adjusting R16 should vary the RF output. Adjust audio levels on the computer, if necessary. Connect the rig to an antenna. Verify that Digipan shows signals on the waterfall display. Adjust audio levels on the computer, if necessary. Hey, it works! Go get some of that DX!

Circuit Description

Refer to the K9EQ AH-4 Universal Interface schematics. L1/C1, L2/C2, and L3/C3 are used to filter RF that may be present on the control lines. When the microprocessor, U1, asserts START, Q1 conducts with base current limited by R1. This causes the AH-4 control line START -OUT to be pulled to ground through D1. D1 provides protection against a reverse polarity connection. Similarly, when the microprocessor, U1, asserts Tx, Q2 and associated components cause the HF rig connected to L2 to key. This design assumes that the HF rig is solid state and uses an approximately 13.8 V control line shorted to ground to key the transmitter. If this is not the case for your radio, additional interface circuitry may be required. When the KEY-IN signal from the AH-4 is asserted (brought to ground), Q3 conducts with base current limited by R3. When Q3 conducts, the KEY line to the microprocessor, U1, goes high. D3 is an optional component that provides reverse polarity protection for Q3. R4 forces Q3 to a known state when the AH-4 is not connected. The power supply for the HF rig and AH-4 is connected to +13.8 In and ground. This voltage is regulated down to +5 by U2 for use by the microprocessor U1. C4 and C5 provide stabilization for the regulator. R6 and LED D4 provide an indication that power is applied. X1, C6, and C7 form the clock circuit for the microprocessor, U1. The frequency is not critical but should be near 2.4576 MHz. The microprocessor uses software timing loops. Running the controller at higher or lower clock speeds may cause timing errors with the interface to the AH-4. R8/PB1 are used to start the tune operation. Normally U1-RB6 is pulled high by R8. When the push button is pressed, the input is forced to ground. The microprocessor detects this state change and begins the tune sequence. Similarly R7/PB2 cause the microprocessor to untune the AH-4. The tuning status is indicated by LED D5. The LED current is limited by R9. The value of this resistor may be increased to reduce power consumption.

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Computer audio connections should be made to line out and microphone in. Typical Connections basic AH-4 operation (no PSK31) Interface J1-1 J1-2 J1-3 J1-4 J2-1 J2-2 J2-3 Key line ALC Input Audio input (mic level) Rig AH-4 Pin 1 Pin 2 Pin 3 Pin 4 Power Supply Comment KEY-OUT START -IN 13.8 V to AH-4 GND to AH-4 Grounded to key rig Connect only if using ALC option Audio output to rig. Connect only if using audio tone to generate RF output for tuning. Connect to rig for main ground 13.8 Power in

J2-4 J2-5

For PSK31 operation with a computer, add the following connections Interface J4-1 Rig Computer GND Comment Audio GND to computer w/series resistor to minimize ground loop currents. Audio out to computer Audio in from computer Audio in from rig (use phone patch out or other source). No connection
J4-2 J4-3 J4-4 Phone patch out

Line in Line out

For computer interfaces, add the following connections Interface Rig Computer Comment

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Interface J4-6

Rig Serial Data Out

Computer
Comment Short with J4-7 for rigs that have a common in/out data line (Icom). Short with J4-6 for rigs that have a common in/out data line (Icom).

Serial Data In

J5-2 J5-3 J5-4 J5-5
Serial data in Serial data out DTR GND
Data sent to computer Data received from computer
Operation Basic Interface

Tuning

1. Turn the power supply and the HF rig on. The power LED on the AH-4 interface should light. The status light should be off. 2. If you have connected the audio interface and are operating SSB, turn off speech processing (if on) and skip to step 5. 3. If you are operating SSB, switch to a mode that generates a carrier such as CW, AM, or FM. 4. Adjust the power output to approximately 10 watts. 5. Press the TUNE button on the interface. The status LED will begin to flash and the rig will key on the air. Within a few seconds the rig should unkey and the status light should remain on. This indicates that the AH-4 is in line and tuned to the rigs frequency. 6. Readjust the rigs mode and power and being operation. Note that if the AH-4 does not tune because you are running SSB and are using the audio interface, you can adjust the mic gain setting to trim the power output. Also check to make sure that speech processing is off. If it is on, it will tend to max out the RF output. (That is, after all, why we want to run speech processing.) The AH-4 can be removed from the antenna circuit by pressing the UNTUNE key. This should be done when changing bands otherwise the receivers sensitivity will be reduced. The status indicator has the following meanings: o o o o Off AH-4 not tuned and is out of circuit (bypass mode) On The AH-4 is tuned Flashing (slow) The AH-4 is tuning Flashing (fast) An error has occurred and the AH-4 is not tuned. This can occur when the AH-4 is not connected.

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If you intend to operate SSB and want to automatically generate the correct amount of RF output for tuning, you will need to adjust the audio output level. If you are operating CW, AM, or FM or have not connected the audio interface, no adjustment is necessary. 1. Connect the rig to the AH-4 and antenna. 2. Adjust the microphone gain on the rig to where you normally run it. 3. Turn speech processing off. 4. Set the rig to SSB. 5. Switch to 10 meters. 6. Monitor the RF output of the rig. You can do this with the RF output meter in the rig or an external meter. If you dont have an RF power meter, you can still adjust the interface by trial and error. 7. Turn R14 on the interface board fully counter-clockwise. 8. Press the TUNE button. If the tuner does not tune because the power is below 5 watts, turn R14 clockwise a small amount. Repeat until the AH-4 tunes. 9. If the AH-4 does not tune because the power is above 15 watts, turn R14 counter-clockwise a small amount. Repeat until the AH-4 tunes. 10. Repeat steps 8 and 9 for the other bands on which you intend to operate. Note that once you have completed calibration, you can make small adjustments to the mic gain setting to change the power output during tuning.
Power output control using AM mode
Many radios on the market allow you to adjust the AM carrier output level. This can be used as a convenient way to adjust the power output during tuning. Simply set the carrier output to about 10 watts. Set the rigs mode to AM prior to tuning and hit the TUNE button. Return the rig to your desired mode when tuning is complete and you are ready to operate. This is a good method to use if you dont plan to use AM. If you do use this method either turn R14 fully counter clockwise or omit resistor R15 since audio output is not necessary.
Full Interface Power output control
The power output during tune may be automatically controlled via one or a combination of several techniques. Use either the AM technique or the SSB/audio output technique discussed under the basic interface (above). Disconnect the ALC feature if you dont plan to use it. The ALC feature generates an ALC voltage during tuning. The voltage can be adjusted in the setup mode by turning the power on while the TUNE button is pressed. In this mode the rig will transmit and the ALC voltage will be generated when TUNE is pressed. Set the rig to a carrier mode, or use the tone feature with SSB. Press TUNE and adjust R12 until an output of 5 to 15 watts is obtained on all bands you plan to use with the AH-4. Note that the ALC set point may change due to temperature, band, voltage, and other K9EQ AH-4 Universal Interface www.hamoperator.com Rev. 5 Page 15

operating conditions. If you plan to use this mode, I recommend mounting an adjustment pot on the interface enclosure panel (not included).

Computer Interface

If the interface is used with Icom equipment, JP1 must be installed or, preferably, jumper J4-6 and 7 together when making the cable. Do not use this jumper with Yaesu. The interface should operate with Kenwood radios as well, but this has not been tested. TRXManager is a good rig control program. The demo version of this program will allow you to test the interface of virtually any radio. The interface also provides for keying of the radio via the computer using the DTR pin.

Computer Audio Interface

This interface uses resistors and capacitors to couple the computer and the radio. Some PSK31 interfaces use transformers and optical isolators to reduce audio hum. I have not had a problem with audio hum on any of my equipment using this interface. R23 was provided to allow additional ground isolation between the computer and the interface/rig. Normally this resistor can be shorted. If you have problems with hum and suspect a ground loop, try using resistor values of 10-100 ohms. Follow the instructions with the sound card program for adjusting the audio input and output levels on the computer. When using a sound card interface, turn speech processing off. With the mic gain set to a normal position, adjust R16 for the correct RF output level for the mode you are using. Visit www.hamoperator.com for links to software that can be used to test the interface.

Troubleshooting

Visit www.hamoperator.com for late breaking news and to post comments and questions regarding the interface. Symptom: Funny things happen when transmitting. The AH-4 untunes or other unexpected events occur. Solution: RF is getting into the control lines. Use appropriate RFI techniques to filter all connections to the interface. Symptom: The AH-4 tunes on some frequencies but not others. Solution: The antenna system is not appropriate for the frequency where there is a problem. Try making changes to the antenna. See www.hamoperator.com for antenna suggestions. Symptom: The AH-4 does not tune on any frequency. Solution: Either the antenna is not connected or there is an error in the wiring between the rig, the interface, and the AH-4. Symptom: The AH-4 attempts to tune but stops right away and remains untuned. Solution: The rig must put out 5 to 15 watts of RF or tuning will not proceed. Verify that the rig is putting out the appropriate amount of power when tuning is started. Symptom: The status LED flashes on and off when I first apply power to the interface. Solution: This is normal. It indicates that the microprocessor is running. Symptom: Is there some way I can force the START-OUT and TX-OUT lines on and off for testing? Id also like to be able to tell the status of the KEY-IN line.

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Solution: Yes there is. Use the debug mode. Press and hold the TUNE button and then apply power to the interface. When the TUNE button is pressed, the START-OUT line will be asserted. When the UNTUNE button is pressed, the TX-OUT line will be asserted. The status LED will turn on when the KEY-IN line is asserted. To resume normal operation, remove and restore power. Symptom: My rig always keys up when I run a particular software package. Solution: The software package is probably asserting DTR. Either press the UNTUNE button when turning the board on (this prevents DTR from keying the transmitter), or power up the board after starting your computer program. If you have the basic version, place a jumper between pins 9 and 16 of U3. Sympton: My PSK31 program will not key the rig. Solution: Power the board off and on again (see above for DTR disable). Configure the software to assert DTR to key the transmitter. Symptom: When I key the radio the RF output shoots up even when Im not tuning. This is particularly bad when I turn up the mic gain. Solution: Audio may be getting into the radio via a ground loop between the interface, power supply, and radio. Take the interface ground directly from the radio. Symptom: The audio output is hard to adjust. I have the pots turned down almost all the way. Solution: See above. Also, it may be necessary to increase the values R13, R15, and/or R17 to reduce the audio gain to the rig. Symptom: There is not enough audio output to drive the computer. Solution: Decrease the value of R18 and/or increase the value of R19. The board is designed to use mic level inputs. Some rigs wire all audio inputs in parallel. Another low impedance audio source may be loading down the boards output.

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Schematics
+5 J3-1 100k KEY-IN J1-1 10uH C3.001 uF 4.7k Q3 R4 4.7k KEY L3 R3 D3 2N3906 RIG AUD-OUT J2-3 0.1uF 4.7K 1K C18 R17* R16* R15 R5 TX-AUD 4.7K COMP-AUD-IN J4-3

START-OUT J1-2

L1 D1 10uH Q1 R1 START C1.001uF 2N3904 4.7k RIG AUD-IN J4-4 4.7K R19* 0.1uF R18* C19* COMP-AUD-OUT J4-2
220 TX-OUT J2-1 10uH D2 J4-1 COMP-GND J2-4 C2 J1-4 J4-5 J4-J3-2 78L05 UC5 10uF J1-3 +13.8 OUT 2 CuF K9EQ AH-4 Universal Interface Rev. 2b Sheet 1 of 2 Copyright 2001-2002 K9EQ and HamOperator.com Green R6 D4 R23.001uF 2N3904 +5 J3-5 4.7k Q2 R2 TX L2

F1 J2-5 +13.8V IN 1A

R10 100

Page 18

X1 U1 R13 R14 C17 TX-AUD START 1uF 1K TX KEY 4.7K PIC16C18 RARAT0CLK O S C MCLR O S C VSS VDD 13 RB0 RBRB1 RBRB2 RBRB3 RB4 RA2 RA3 C7 22pF

2.4576 MHz

C6 22pF
UNTUNE J3-3 +5 TUNE C8 R9 220.001 R8 R7 4.7k +4.7k DJ3-4 24Cxx** A0 A1 A2 Vdd WR SCL 4.7k R25**

+5 J3-8

STATUS

Vss SDA U5

C9* 1uF C11* 1uF 16 MAX1uF* CData from rig J4-6 Data to rig J4-7 R24* C15* 1K.001uF RS-232 Jump pins 9-16 when JP1-2 JP1-1 U3 not installed TTL C1+ C1C2+ C2T1in T2in R1out T1out T2out R1in RS232 COMP-GND V6 C10* 1uF U3* V+ 2 D7* R21*

C13*.001uF

-5V R12* R11* J5* 9 5K 0K TX-ALC J2-2

R2out R2in GND 15

K9EQ AH-4 Universal Interface Rev. 2b Sheet 2 of 2 Copyright 2001-2002 K9EQ and HamOperator.com

Jumper for Icom

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UNTUNE

J3-4 D1 J3-5 Green J3-2

D2 Red

K9EQ AH-4 Universal Interface Rev. 2b Interface ControlsConnection Copyright 2001-2002 K9EQ and HamOperator.com

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Parts List
Designation C1, C2, C3, C8, C13, C15 C4, C5 C6, C7 C9-C12, C17 C18, C19 C14, C16 D1, D2, D3, D6, D7 D4 D5 D8 F1 J5 L1, L2, L3 PB1, PB2 Qty 1 4/6 2/2 2/2 1/5 1/2 0/0 4/5 1/1 1/1 0/1 1/1 0/1 3/3 2/2 Description Capacitor, Disk Ceramic 0.001 f Capacitor, Aluminum Electrolytic 10 f, 25V Capacitor, Disk Ceramic, 22 pf Capacitor, Aluminum Electrolytic 1 f, 25V Capacitor, Disk Ceramic. 0.1 f Not used 1N4007 (may use 1N4001) LED, Green LED, Red Diode, Zener, 1N5231 5.1 Volt Fuse, resetable, 1A Connector, 9 pin sub-D female PC mount Inductor, 10 H Push Button, Momentary Source Jameco 15190 Digikey P4049A-ND Jameco 94211 Digikey P5148-ND Jameco 15405 Digikey P4016A-ND
PCB Q1, Q2 Q3 R1 R4, R7, R8, R13, R15, R17, R18 R5 R6, R9, R19, R21 R10 R11, R20 R12 R24 R14, R16 R23 R22, R25
1/1 2/2 1/1 8/10 1/1 2/2 1/1 0/2 0/1 0/1 1/2 0/1 0/0
Printed Circuit Board Transistor, NPN 2N3904 (General purpose) Transistor, PNP 2N3906 (General purpose) Resistor, watt, 4.7 k Resistor, watt,100 k Resistor, watt, 220 Resistor, watt, 100 Jumper Potentiometer, 5 k Resistor, watt, 1 k Potentiometer, 1 k Resistor, watt 10 Not used
Jameco 177674 Digikey 1N4007DITR-ND Jameco 34606 Digikey P564-ND Jameco 34622 Digikey P566-ND Digikey 1N5231BDICT -ND Digikey RUE110-ND Digikey A2100-ND Digikey M7825-ND Jameco 162886 Digikey P8006S User supplied - external K9EQ PCB01-001 Jameco 178597 Digikey 2N3904-ND Jameco 178618 Digikey 2N3906-ND Jameco 31026 Digikey 4.7KQBK-ND Jameco 29997 Digikey 100KQBK-ND Jameco 30470 Digikey 220QBK-ND Jameco 29946 Digikey 100QBK-ND Jameco 43078 Digikey 36G53-ND Jameco 29663 Digikey 1KQBK-ND Jameco 42964 Digikey 36G13-ND Jameco 29882 Digikey 10QBK-ND

Quantities are for the basic/complete kit.

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Designation U1 U1S U2 U3 U3S U4-U5 X1
Qty 1 1/1 1/1 1/1 0/1 0/1 0/0 1/1
Description Integrated Circuit, Microprocessor, 16C54C-04/P custom programmed IC socket, 18 pin, for above IC, Voltage Regulator, +5 volt, 78L05 Integrated Circuit, RS-232 level converter, Maxim MAX232CPE IC socket, 16 pin, for above Not used Crystal, Quartz 2.4576 MHz Connectors only included with the connector kit Mating connector for AH-4 (Molex 03-09-1041) Pins for above (Molex 02-09-1104) Connector, 4-pin, Molex KK (optional)
Source K9EQ IC01-001 Jameco 112230 Jameco 51182 Digikey NJM78L05A-ND Jameco 24811 Digikey MAX232CPE-ND Jameco 112221 Jameco 101274 Digikey X069-ND Digikey WM1308-ND Digikey WM1101-ND Digikey WM4202-ND (st) or Digikey WM4302-ND (rt ang) Digikey WM2002-ND Digikey WM4203-ND (st) or Digikey WM4303-ND (rt ang) Digikey WM2003-ND Digikey WM4206-ND (st) or Digikey WM4306-ND (rt ang) Digikey WM2006-ND Digikey WM2200-ND

P4 Pins for above J1

1/1 4/4 1/1
P1 Mating connector to J1 J2

1/1 1/1

Connector, 4 pin Connector, 5 pin, Molex KK (optional)
P2 Mating connector to J2 J3, J4

1/1 1/2

Connector, 5 pin Connector, 8 pin, Molex KK (optional) (J3 must be straight) Connector, 8 pin, For P1, P2, P3, P4
P3, P4 Mating connector to J3, J4 Pins for P1-P3

1/2 17/25

Note: Jameco is generally less expensive than Digikey. Jameco: www.jameco.com Digikey: www.digikey.com A complete kit of parts is available from K9EQ. Visit www.hamoperator.com for details. Please report any errors in this manual to K9EQ.

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AH-4 Radio Interface Theory of Operation
The AH-4 interfaces to the radio with a two-wire connection. A START signal is issued by the radio to start the tuning operation. A KEY signal from the tuner indicates when: the tuning has started; the tuning has failed; or the tuning has been completed. The tuning operations works as follows: 1. 2. 3. 4. 5. 6. 7. 8. 9. A tuning operation is requested by the radio the radio asserts the START line. The AH-4 microprocessor is reset and begins running its program after approximately 300 ms. When the AH-4 is ready, it asserts the KEY line (AH-4 routes the RF through the power divider, measurement circuitry and tuning network). The KEY signal causes the radio to transmit a carrier at about 10 watts of output power. The AH-4 verifies that the power is between 5 and 15 watts. If not, the AH-4 aborts the tuning operation. If the power is between 5 and 15 watts, the AH-4 begins the tuning operation. Approximately 250 ms after the AH-4 starts tuning, the radio removes the START signal. When tuning has been achieved, the AH-4 remo ves the KEY signal and switches the RF to pass only through the tuning network. The microprocessor is then halted. The radio stops transmitting when the KEY signal is removed. If the AH-4 was unable to achieve tuning, it removes the KEY signal for 20 ms, asserts it again, waits 200 ms, then finally removes the KEY signal. This causes the radio to indicate a not tuned condition. If the band is changed on the radio, the tuner is reset. This causes the tuning network to be removed from the circuit.

The AH-4 uses 12 volt inverted logic and an open collector transistor to ground to perform signaling. The radio provides 13.8 volts to the tuner. It also provides a START line that is pulled up to 13.8 volts inside the radio. The radio pulls the START line to gro und to assert the signal (start the tuning operation). Similarly, the AH-4 pulls the KEY line to 5 volts through a 22 kohm resistor/diode combination. The radio also pulls this line to 13.8 volts through a resistor. The AH-4 pulls this line to ground to assert the signal (indicate tuning status to the radio.)

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