Icom AH-4 страница 4 Скачать руководство пользователя

Страница: 4 / 8

3. Inside the AH-4

I use the AH-4 primarily to feed balanced antennas. I’ve modeled a number of antennas using EZNEC

and I never seem to have good luck when the antennas are unbalanced. An example of an unbalanced

antenna is a long wire connected to the RF out port and the ground connected to, well, ground. I

much prefer feeding either a loop, with the AH-4 right at the feed point, or a 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 ohm ladder line.

Note that the RF output is on top and the RF ground is on the bottom. I’m not sure why they did this. It

makes one believe that the tuner cannot work with a balanced feed. Nothing could be further from the

truth. It works great. Note that the metal mounting brackets are not grounded.

FIGURE 2: AH-4 IN OPERATION CONNECTED TO BALANCED ANTENNA

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...