Harmonics problem how to find

Tore Andersson

This question is not a problem with flex equipment but I'm using flex radio and looking for aid from the community. Please remove post in case this does not belong here.

I have a problem running SO2R. This has nothing to do with the flex it does its job but something in my house or my neighbors house causes the harmonics to be distorted. Most likely we are talking about some switched power supply. 
What I have done is to try to find it in my house and switched of all power running the 6600 on battery without connection to ground. As a result the problem improves a lot even though it still does not look ideal. Attached is a picture of receiving on 14.040 with my TH11 and transmitting on 3.510 with a dipol antenna when main power is switched of (electrical cabinet outside house)

When I turn on the fuses inside the house the distortion gets worse - for every fuse. There are two fuses that stands out and that is the fuse with the longest electrical wires (light outside and to the furthest room top flor of my house).

In general when trying to find the problem inside my house with a hand held device receiving on 14.040, every time I come close to an electrical wire the disturbance intensifies. If I for example stand in the middle of the garage where there are no electrical wires close the signal strength is very low but if I then walk close the a power outlet it goes up to S9 on my handheld.
With that said my believes is that my electrical wires in the house works as a transmission antenna. This is also strengthen by the fact that if I turn my beam with its backside against my house the problem is way smaller then with the beam turned towards the house.

Below is a picture what the disturbance looks like when beam is pointing to the house and all electrical fuses are turned on.


I would like for suggestions on how to find this problem a good strategy to follow e t c. I understand it can be all sorts of things like a rusty bolt on my tower - and believe me I have tried to trace those kind of things but the hand held is silent like a mouse close to my tower.

73's de Tore SM0NCS / SC0N

Stan VA7NF

You have a problem - The "noise" is picked-up or created in your electrical wiring.  Nothing new here, just stating the obvious.

There is a trick that MAY help - Snap-on Ferrite beads will suppress (insert a high impedance) in the flow of signal on these wires.

Place these ferrites on an open section of wire and sniff (few turns of wire on a coax lead) both sides of the beads - you MAY find a different level on one side - pointing the direction of the noise.  Slow process but it may work for you.  Depending on your wiring this may work at your fuse/breaker panel to isolate the culprit; you already have success on turning off breakers.  Good luck is important.
p.s. I still like DF loops while walking around your property or neighbourhood; these require pre-amps if the signal is weak.  You did indicate your beam gave the largest signal aimed towards your house; pity.

Tore Andersson

Many thanks for your post.
Interesting idea I will try that - might point me in the direction inside or outside my own house maybe.
The problem with the beam direction is that I do not have lot of neighbours and they all lie in the same direction more or less from the tower as my own house does.

Tore Andersson

Stan I have tried your ideas and I cant see any big differens. It might be that my equipment is not sensitive enough but impossible to notice any difference on either side.

Although I noticed something today the harmonics signal on 14.040 when transmitting on 3.510 is sometimes a pure tone when walking around my area. When coming closer to my house it is never pure. BUT if I listen directly close to any of my guy wires from my tower the signal is pure. Care to try to explain ?

Best Regards 
SM0NCS

Stan VA7NF

Hello Tore,
I'm thinking you have two problems, 1) the harmonics and 2) mixing with noise

Assumptions: Ant 1 is your 20M beam.  80M is on an antenna
Your panadapter view is around 100K (2.7K Rx bandwith is 1/2 a division)
You are transmitting a 100W CW carrier at 3.510

What I see on your image: A strong signal with modulation (visible on the low side) repeating every 1Khz and more random on the high side.

Question 1: When you key up does the entire 40M display drop down?  i.e. is your modulation >100Khz wide or around 15Khz wide with the rest of the display background?

Also observed:  There is also interference across the band repeating roughly every 500Hz.
Q2: Does that interference disappear when key-up?

Test the following to isolate/eliminate a transmitter bias problem:
Connect 80M to a dummy load and monitor:
a) The fundamental (screen capture - this time showing the side and bottom scales)
b) The harmonics (14.040 zoomed way in  +/- 5Khz and +/- 1Khz) to show the modulation sidebands.  The 6600 should show even 60Hz sidebands.
c) Drop the 80M power by 10 and see if the 20M signal drops by other than 10db
d) Repeat c) again ( 1W)

Test two:
Connect 80M to an antenna and monitor on 14.040
a) Capture a screen shot
b) Drop power by 10 (e.g. 100W - 10W)
c) Capture a screen shot.  See if the signal strength also drops by 10db

Test 1 will validate the transmitter.  If not clean - Open a ticket

Test 2 will check for a nearby diode detection.  The noise and 4th harmonic may drop off at different power levels.

Happy Hunting

  

Tim - W4TME

Depending on the power of the transmitted signal, this could be something rectifying in the antenna system or in the AC wiring generating real signals. 

Tore Andersson

Thanks a lot again for your aid guys. Stan I will study your reply this weekend and follow it through. Great that you are trying to help - this problem is very annoying even looking for a new house as a possibility since I really can't live with this.

Tore Andersson

Tim,The power does not seem to be an issue. The power test that Stan wants me to make (and I will do it exactly as he describes) I have already done and the main carrier on the harmonics 14.040 follows more or less the theoretical power reduction I did Drop from 100 to 50 reduced about 3 db then down to 25 dropped from 100 close to 6 db and finally I tested 1 W and that was around 20db down compared to 100 W.

The interference on the side does not follow this logic though.

The problem is still there when transmitting 1W even though with smaller amplitude.


This pictures shows transmission on 1W - notice the two products beside the transmission. They are approx on 14.017 and 14.063.

I'm also certain this is not a flex problem I've had the exact same problem with other radios for example (K3s + TS590) independent on receiver/transmitting station.

I do belive this is rectifying in my AC wiring system - everything points in that direction. However I currently have no clue how to find it.

Yesterday I measured the strength of the signal close to my neighbor's main electrical cabinet and all but my cabinet and my closest neighbor shows low signal. The closest neighbor and my cabinet has S9+ signal on 14.040 very raw signal.

I can hear the signal on the other neighbors as well but there is no difference close to their electrical cabinet and couple of meters from them.

This has lead me to think the problem is either in my house or my closest neighbor.

I'll try to do some more investigation Saturday and post here.