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Inside the Icom AH-4 Tuner

This paper describes the Icom AH-4 wide range antenna tuner. It attempts to compensate for a rather

sparse instruction manual by providing information on how to interface the AH-4 with any HF radio. In

addition, it also provides recommendations regarding antennas for fixed locations. An overview and

description is presented as well. Those who are interested in antenna tuners (the AH-4 in particular)

and those who just plain like to look into the guts of hardware and see how things work will want to

read on.

Chris, K9EQ

Table of Contents

Table of Contents

AH-4 Operation

K9EQ

Page of

Содержание AH-4

Страница 1: ...garding antennas for fixed locations An overview and description is presented as well Those who are interested in antenna tuners the AH 4 in particular and those who just plain like to look into the g...

Страница 2: ...following reasons During tune the radio always sees a low SWR typically 1 1 1 or less This is because the RF is switched to a 10 1 power divider during the tune operation Only approximately 350 milli...

Страница 3: ...2 AH 4 Design FIGURE 1 BLOCK DIAGRAM OF THE AH 4 AH 4 Operation K9EQ Page of 3 8...

Страница 4: ...flat top via ladder line In both these cases the AH 4 works extremely well This is a photograph of my AH 4 It is feeding a 30 meter flat top The antenna is about 20 meters high and is fed with 450 oh...

Страница 5: ...FIGURE 3 A VIEW OF THE INSIDE OF THE AH 4 AH 4 Operation K9EQ Page of 5 8...

Страница 6: ...fies that the power is between 5 and 15 watts If not the AH 4 aborts the tuning operation 5 If the power is between 5 and 15 watts the AH 4 begins the tuning operation 6 Approximately 250 ms after the...

Страница 7: ...FIGURE 5 FAILED TUNING RESPONSE The command to reset the tuner causes it to pass thru tuning network out of circuit FIGURE 6 TUNER RESET AH 4 Operation K9EQ Page of 7 8...

Страница 8: ...s the START line to ground to assert the signal start the tuning operation Similarly the AH 4 pulls the KEY line to 5 volts through a 22 K ohm resistor diode combination The radio also pulls this line...