¿ªÔÆÌåÓý

  1. BITX20
  2. Topics

The issue I spoke about on the V4 with 20m and CW FCC tests

Laurence Oberman
 

I had mentioned this issue I have on the V4 that looks like RF
coupling or leakage when testing CW on 20m for FCC compliance.

I don't see it with SSB but if you transmit for long enough spurs will show up .
See the document I shared.

I only just got my Axicoms to replace the relays.

Strangely enough not seen on 15m, 17m or the higher frequency bands,
also not seen lower than 14Mhz.

Other than that the V4 has been fine, now replacing with V5 and my son
gets the V4.

Question is who else has see this.

ubitxv4-20m-spurs.pdf
ubitxv4-20m-spurs.pdf

 

I do not have pictures, however I have seen just the reverse:? When first keyed, the spurs appear, then fade as the transmitter remains on.? This is with or without an audio signal.? Suggesting that something is changing as the circuits warm up?? Thing is, I have seen this every time, even after letting the rig on for a period of time.? I at first attributed to an issue with the SDRPlay SA, and that may still be the case,? After reading your post, not so sure.

FWIW
73
Evan
AC9TU
 

Both cases come from the same source, heating in the amplifier usually the pre-driver
and driver stages but it can include the finals.

Its not thermal stable and parts do heat up and their bias shifts.

Allison
Laurence Oberman
 

Thanks a lot Allison
Just wondering why the same heating issue is not there on other bands.
Regards
Laurence

On Sun, Mar 10, 2019, 2:59 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
Both cases come from the same source, heating in the amplifier usually the pre-driver
and driver stages but it can include the finals.

Its not thermal stable and parts do heat up and their bias shifts.

Allison

 

It is but not as visible.?

If the output filters are less than correct it gets worse.? ?Also if you pushing
power the LPFs will show heating effects remember 10W max even then
your pushing it.??

CW mode is a square wave driive so the harmonic content like previously
discussed is about 20db greater than for SSB not push to clipping

Allison
 

Laurence

I also grasp your observation that its mostly on one band. On 20m try touching L5 and other toroids to see if they are in the act. Then try another band. We should never assume we are experiencing the same thing as someone else reported, yes I have been guilty here in the past.

Curt
Laurence Oberman
 

Thanks Folks, Curt, I have time tomorrow to take the cover off and
debug some more.
Will report Back.

I tried to reproduce when I first saw it on 20 by repeating the test
on 80, 40, 17 and 15 and did not see it.
However to be honest did not spend a lot of time on the other bands as
I operate 40 and 20 based on my current Antenna setup. For sure its
not there on 40m.
The G5RV needs repair and I have no appetite to go out in the New
England winter and fight with it. :)

Regards
Laurence

On Sun, Mar 10, 2019 at 4:24 PM Curt via Groups.Io
<wb8yyy@...> wrote:

Laurence

I also grasp your observation that its mostly on one band. On 20m try touching L5 and other toroids to see if they are in the act. Then try another band. We should never assume we are experiencing the same thing as someone else reported, yes I have been guilty here in the past.

Curt
 

Laurence, how much power do you get on CW on the affected band and on 40m? Which SA are you using? Can you add another 20db attenuator to see if there is any changes?


Il 10/mar/2019 23:41, "Laurence Oberman" <oberman.l@...> ha scritto:
Thanks Folks, Curt, I have time tomorrow to take the cover off and
debug some more.
Will report Back.

I tried to reproduce when I first saw it on 20 by repeating the test
on 80, 40, 17 and 15 and did not see it.
However to be honest did not spend a lot of time on the other bands as
I operate 40 and 20 based on my current Antenna setup. For sure its
not there on 40m.
The G5RV needs repair and I have no appetite to go out in the New
England winter and fight with it. :)

Regards
Laurence

On Sun, Mar 10, 2019 at 4:24 PM Curt via Groups.Io
<wb8yyy=[email protected]> wrote:
>
> Laurence
>
> I also grasp your observation that its mostly on one band. On 20m try touching L5 and other toroids to see if they are in the act. Then try another band. We should never assume we are experiencing the same thing as someone else reported, yes I have been guilty here in the past.
>
> Curt
>



 

Nata Net
See you on Natanet
Will work you as last call.
Dave k0mbt

1 - 9 of 9