160M Harmonic Measurements - First Results

[K1JJ]

Hola!

I kinda forgot about checking 160M AM signals for harmonics, since no one requested a test so far.

Anyway, tonight at about 10:30PM, I tuned into the ssb guys on 3772 and heard a loud AM carrier and audio QRMing them. I tuned down to 1885 just as someone signed out. Missed him, whoever it was. It could have been something on 3772 fundamental too. Not sure at this point.

But, I hung around and checked out the four guys still on frequency.  Here's what I found just listening on 1885 and 3770 for the second harmonic:

Joe, N3IBX was S9+20 on 1885 and clean on 3770. [below the noise floor]

Duane KK4AM was S9 +10 and clean on 3770.

XXXXXX  [I contacted him privately already] was S9 +25  and S9 on 3770.  Not real "bad" but still causing a hetrodyne on the 3772 group.  This is just a relative test only, with "db down" not meaningful.

K1VIV, Joe was S9 +10 and clean on 3770.

Bear in mind that the conditions were not real hot tonight, so things need to be rechecked, but everyone but XXXXXX was below the noise floor on 3770. There is also some digital noise on 3769 that is masking things too.

So, over the next week I will give a listen to more stations. The best bet would be to listen into the Gray Hair Net and check out many stations in one session. Next Tuesday, maybe.

XXXXXX was not loud enough on 3772 to be the main problem that the guys were complaining about in the past, however.

If anyone else has the time, please listen to AM stations you may hear on 160M and  post results here. Maybe we can get things cleaned up if we all work together.

73,
T

[WA1GFZ]

Tom Great idea on checking. I made a simulation program for a double pi filter if anybody needs another 30 to 35 dB of attenuation. A number of cap values will work.
Center cap double the input and output. 2000 pf I/Q and 4000 pf center gives about 35 db. Copper tubing coils would make a nice los loss filter.  fc

[Vortex Joe - N3IBX]

Tom Vu,
           Very interesting findings and I appreciate you posting the information. I think I know who station "X" was and thank you for not posting his call. He's always produces a clean signal to my knowledge, and perhaps his transmitter just meeds some minor tweaking. I think he was the one running a single 4-400A in the final stage of his transmitter.

I was on a modified DX-100B at 110W output. Duane, KK4AM was on a ricebox-leenyar combo at probably the same output, and Joe, N1VIV was on a Viking II with a similar output. Joe is in SE Ct. Duane, in central Va., and yours truly in SE Pa.

I'll fire up the T-368,HT4-H,Gates BC-1T, ART-13,Viking I,Viking II, etc etc etc etc periodically to see if I'm causing any undue harmonics. I'd be interested to find out. I usually run low power (100W) unless the "afflack" crowd comes in and quirms us or chasing AM-DX on the band.

BTW, I wasn't aware a problem existed on 3770KC.

Very Best Regards,
                         Joe Cro N3IBX                       

[K1JJ]

BTW, I wasn't aware a problem existed on 3770KC.

Very Best Regards,
                         Joe Cro N3IBX                       

Hi Joe,

Here's the link for the 160M harmonics post last week under "announcements"..  Guess you missed it.

http://amfone.net/Amforum/index.php?topic=6776.0

Glad others will be joining in to check out the balance of signals on 160M.  I've never been a KC cop and hate even mentioning others' signals with problems... but somebody's gotta do it... 

Frank, your low pass harmonic filter is a great idea. Simple and effective. I once had a similar one that worked on 75M for harmonics above. Worked very well. I could feel a little warmth in the coils, which is normal for a sharp roll off.  This should be a last resort thing, since many can be fixed with standard circuitry that is working correctly.

73,  and please keep posting results of the passed signals here - and  label "XX" for the ones that fail - contact them yourselves. Offer them help with another test and refer them to this link and the one above for info.

T

[Pete, WA2CWA]

Great work Tom. I think you should apply for "Official Observer" status.

Send these cards but it needs a Tom Vu background



And Wear the "Official" Shirt

[k3zrf]

I know where you got that tee shirt pic, Pete. Would you believe that is a neighbor of mine!