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Junior,

When doing a two-tone and single tone test I do not see these
harmonics.

Carrier suppression is not what I would like but no harmonics.

tim ab0wr

On Sat, 24 Mar 2018 09:50:30 -0700
Júnior PY2ADA via Groups.Io <aaj280174@...> wrote:

Testing with the micro bitx in the spectrum analyzer, I found that
the harmonics reduction is very low. Has anyone else done this
measurement to compare? The photos are 3 per band (fundamental,
second harmonic and third harmonic). 73 de Júnior
PY2ADA

Ashhar,

I had 60db of external padding between the transmitter and the SA plus
30db padding in the SA itself.

That should have been about 10 microwatts (10watt/1,000,000) of actual
power feeding into the SA.

Now I have to admit I haven't verified my pads for a long time but I
don't think they are far enough off to make a huge difference since I
was just looking for relative relationships.

And I didn't see any harmonics that weren't at least 50db down from the
fundamental.

I have adjusted my drive level and bias to get as clean of a signal as
possible. That's about 10 watts out on 3290kc. I haven't checked the
other bands yet.

I may diddle with the bias and drive some more to see if I can get more
power while staying clean but I'm pretty happy with it as it stands.

tim ab0wr



On Sat, 24 Mar 2018 18:32:02 +0000
"Ashhar Farhan" <farhanbox@...> wrote:

i hope you guys are using sufficient attenuation ahead of the spectrum
analyzer. typically, if you change the attenuation, the harmonica and
the fundamental should fall exactly the same dbs.
- f

On Sat, 24 Mar 2018, 23:55 Tim Gorman, <tgorman2@...> wrote:

Junior,

When doing a two-tone and single tone test I do not see these
harmonics.

Carrier suppression is not what I would like but no harmonics.

tim ab0wr

On Sat, 24 Mar 2018 09:50:30 -0700
Júnior PY2ADA via Groups.Io <aaj280174@...>
wrote:

Testing with the micro bitx in the spectrum analyzer, I found that
the harmonics reduction is very low. Has anyone else done this
measurement to compare? The photos are 3 per band (fundamental,
second harmonic and third harmonic). 73 de Júnior
PY2ADA

I haven't heard any further discussion on this.
Are we in compliance with FCC at 22-28 db down on the second harmonic?
Andy

Yes, FCC requires -43dBc for these frequencies. My preliminary measurements (back in December) revealed that, although close, my unit didn't meet those specifications. Close, but not quite. Therefore I use an outboard filter until I can find time for an easy solution. Admittedly, I have not revisited the problem yet and have made several changes in my case and so should do that shortly. Screen shots are attached. Worst case was 30m with just less than -36 dBc.
I don't like to bring up a problem without having a solution prepared but there it is. Sorry. 73, Don

Mine too runs at about -40db for the 3rd harmonic of 3920khz. Good but
not quite good enough. On a two-tone test My carrier suppression is
only about 20db and the 3rd harmonic on a two-tone test is not the best
either at about 34db.

For a 10 watt peanut whistle I'm not worrying a great deal. Using an
outboard filter is an option.

tim ab0wr

On Mon, 09 Apr 2018 07:17:19 -0700
"Don, ND6T via Groups.Io" <nd6t_6@...> wrote:

Yes, FCC requires -43dBc for these frequencies. My preliminary
measurements (back in December) revealed that, although close, my
unit didn't meet those specifications. Close, but not quite.
Therefore I use an outboard filter until I can find time for an easy
solution. Admittedly, I have not revisited the problem yet and have
made several changes in my case and so should do that shortly. Screen
shots are attached. Worst case was 30m with just less than -36 dBc. I
don't like to bring up a problem without having a solution prepared
but there it is. Sorry. 73, Don