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ADX-S No RF power above 18 MHz

 

Hello group,

I've assembled the ADX-S kit from crkits.com. The construction manual is well written and gives excellent advice during the process. Everything worked the first time.

RF output from my ADX-S between 7 MHz and 18 MHz is fine (2-3 W), but there is no output from 21 MHz and above.

I've tried the following to rectify the power problem:?
  • Matched 3 x BS170 from at batch of 12. Matching parameter Vgs. No change.
  • Swapped the 3 x BS170 with 3 x 2N7000 (they were matched from a batch of 10). No change
  • Bypass C22 and remove D6 and R12. No change
What to do now?

73 from OZ1BXM Lars Petersen
 

Do you have a method of checking the filters?? Like a nanovna?? You'd have to build a fixture for that but there is almost adequate information out there to do that properly.? The BS-170s are pretty terrible at the higher frequencirs but you should get some power out of them.

Fred W0FMS
 

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Also, check if there is any power out between 74ACT244 and BS170. The 21 and 28MHz should give about 1 watt.

Thanks,

Adam

On 2024/3/16 4:51, Fred Spinner wrote:

Do you have a method of checking the filters?? Like a nanovna?? You'd have to build a fixture for that but there is almost adequate information out there to do that properly.? The BS-170s are pretty terrible at the higher frequencirs but you should get some power out of them.

Fred W0FMS

 
Edited

Hello again,

Problem solved!

I had swapped L1 and L3 on some of the LPF modules, and that does not work. Guess I've had a dull moment!

Now my ADX-S delivers the following output:
40m: 3.1 W
30m: 3.0 W
20m: 3.1 W
17m: 2.1 W
15m: 2.0 W
12m: 2.0 W
10m: 1.9 W

Next step is to connect an antenna and make some QSOs!

Thanks,

OZ1BXM Lars Petersen
 

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Congratulations! I am interested to know what caused the mistake. Wrong manual?

Thanks,
Adam

在 2024年4月8日，19:53，oz1bxm_lars_petersen <oz1bxm@...> 写道：

?

[Edited Message Follows]

Hello again,

Problem solved!

I had swapped L1 and L3 on some of the LPF modules, and that does not work. Guess I've had a dull moment!

Now my ADX-S delivers the following output:
40m: 3.1 W
30m: 3.0 W
20m: 3.1 W
17m: 2.1 W
15m: 2.0 W
12m: 2.0 W
10m: 1.9 W

Next step is to connect an antenna and make some QSOs!

Thanks,

OZ1BXM Lars Petersen

 

Hello Adam,

The manual is correct - it was entirely my mistake. I forgot to read the text on the LPF PCB.

73 OZ1BXM Lars??

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