Reducing harmoncs on a NATO 2000

[HeliJimbo]

Good evening all,

I just thought I'd share a little filter I've added to my NATO 2000 to reduce the harmoncs.

I was given the rig as a scrap chassis so have done quite a lot of work to get this thing going but it has been a great little project.

Having looked at the harmonics, i thought I'd try and reduce them a little as I thought they were still a little too high.

0086BFE5-3407-4B22-A7D9-DEC391D9D334_1_201_a.jpeg

So I built this little filter today and fitted it inside the radio and as you can see from the results, the harmonics have dropped drastically.

C196DB73-4DD8-4641-9D9B-4AD24D0A88AD_1_201_a.jpeg

I'm super happy with the result!

E966286C-676E-4629-9CBA-D6AB796DCBD6_1_201_a.jpeg

[cb4ever104]

Looks nice. Any reduction in output power with it fitted ?

[Buick Mackane]

Great work

[HeliJimbo]

Looks nice. Any reduction in output power with it fitted ?

Hi,

Natuarlly there is some loss.

The calculator I used estimated about -0.3 db of which is quite close.

Hope that helps?

[Auldgeek]

Excellent! Well done

[HeliJimbo]

Here's all the values if anyone is interested.

The outside capacitors were 100 pF
The inside one was 220 pF
The inductors were 360 nH

For the coils I just used a nanoVNA and a trim tool I had to wrap the wire and I kept wrapping until I got the inductance above.

Initially I used a calculator from M0UKD and got these values.

Diameter 8mm
Length 15mm
Number of turns = 10

[Auldgeek]

Looks nice. Any reduction in output power with it fitted ?

Hi,

Natuarlly there is some loss.

The calculator I used estimated about -0.3 db of which is quite close.

Hope that helps?

Do you reckon your Nato without the filter, was typical of that board, or did you attempt to remove the harmonics by normal tune-up as per service manual? Just curious.

[Otter]

The manual quotes harmonics will be lower than about -53dBc. The radio looks like it was about -45dBc before mods.

[HeliJimbo]

I did the full tune-up as per the service manual and compared to another NATO I had and the harmonics were exactly at the same level.

For the sake of a little work I thoight why not put one in, even if it's just because I can.

:-)

[Auldgeek]

For the sake of a little work I thoight why not put one in, even if it's just because I can.