Noise Spikes on 40 meters

Thomas NE7X

I am having a noise spike issue only on 40 meters with my new 6400M. When I first tune it on from a cold start, the receiver is good, no noise spikes. I can be in listen mode for several hours and the noise spikes do not appear. However as soon as I transmit, the noise spikes appear and do not go away. A reboot does not eliminate the noise spikes, Only when the 6400M is power off for several hours and then powered on are the noise spikes gone. Then when I transmit they immediately reappear. I tried different power supplies, (Astron 35 amp and MJF25 amp) and even a deep cycle 12V 100 amp battery. Same issue. Also when I disconnect my antenna from the 6400M , the noise spikes disappear, then reappear when the antenna is reconnected. It appears the noise is coming into the receiver via the antenna. It seams like there is some front end oscillation occurring right after transmitting. I opened support ticket number 22739.

Robert Lonn

A few things I have done in the RF world over the years... First a very good grounding of all radio equipment.. Second is any DC cable going into a radio has a RF Choke in line right were the DC power enters the radio.. When you pull off the antenna, have you tried to Short Out the PL-259?? Also have you tried shorting out the SO-239 on the radio after this happened.. Not to say something is not right in the front end of the radio,,, but Stray RF in a ham shack has caused a lot of crazy things with radios... On the Icom IC-7610 forum, a user was getting a increase in his received noise floor, and the more TX power he used, the more noise would be generated in RX.. Turned out to be a in line RF Choke that was in a way Charging Up... Found that one of the PL-259 connector leaving the choke was not real tight.. After tightening up the connections, his issue went away... Another chapter in the continuing episode of Black Magic RF world...

Robert

Thomas NE7X

I was running ver 2.1.33 so I tried ver 2.1.32. Same issue. I disconnected ALL cables from the 6400M, leaving only the DC power cable and antenna. Same issue. Opened a second slice, same issue in the 2nd slice. Tried adjusting the AGC, AGC-T, TNF, FDX, NB, WNB, NR, and ANF. No difference. The problem is ONLY on 40 meters, all the other bands are good.

Wayne

I had a problem with 40m the noise baseline was riding on a low level sine wave nothing I did would help. Only affected 40m It was a wall wart powering my computer near the rig. i took away the computer and wall wart and used a differemt computer and 40m is ok again.

KC7ES

Perhaps the RF is causing something else to start generating noise. Example, my garage door opens/closes when I’m QRO on 40m. After I unkey, the motor creates hash on 40 until it stops moving.( I’ve tried some chokes on the opener circuits but need something to gobble up the RF on the controller. ). “It’s a mystery!”

Thomas NE7X

I put the 6400M on a deep cycle battery, the noise spikes were there. I then turned off the main 200 amp house breaker, the noise was still there. I thought maybe it might be coming from the neighbors house, however when I let the 6400M set for a few hours, then power it on, the noise is not there. Then as soon as I transmit, the noise spikes return. I have a really good shack ground, 20-10ft copper clad steel ground rods tied together with 00 wire cadwelded. I did add some torrid chokes to both the DC and antenna coax, same issue.

Wayne

From the picture they are happening evety 3.5khz or 5khz maybe its the chip that runs the display affected only by the 40m freqs maybe someone left out a metal shield.

Thomas NE7X

Here is an example, noise spikes are 4 KHz apart

7.143.800  <->  7.147.800  <-> 7.151.800  <->  7.155.800  <->  7.159.800  <->  7.163.800   <->  7.167.800  <->  7.171.800 <->  7.175.800    etc etc etc....

Could this be a clue ?
 

KC7ES

Perhaps a variable speed motor signature? My heat pump blower greats havoc every 18khz. But you stated you turned off your main breaker ; could the RF be turning on a neighbor’s variable speed pool pump? Does this happen at all power levels?

Wayne

My rf used to turn on the touch base lamp in the bedroom till my xyl unplugged it. Maybe its turning on the neighbors wireless led light generating the noise until he discovers it several hours later cussing and turning it off. Then you startup your radio and the noise is gone till you transmit again turning it back on.

Wayne

You may have to take your radio to a friends or ham club and try it there to verify its ok and caused by your environment. Does it do it in a dummy load also and at all power levels?

Jim-KB1ZNV

I have 10kHz spaced spikes on 80M on my 6600M, but I also had then on my 7300 when the antennas are connected, none when no antennas connected. Still haven't found the source - maybe from a neighbor radiating thru the antennas. Still sleuthing. Any suggestions?

ctate243

Although this looks like in shack RFI, the way it presents itself is odd. Opening the support ticket was a good choice

Thomas NE7X

I performed the following test two times today, with the same results

6400M powered off for two hours. Powered on the 6400M on 40 meters from a cold start. NO noise spikes. Tuned around and listened for approx. 2 hours, no noise spikes. Keyed the transmitter and called CQ. After I un-keyed, the noise spikes were present. No matter what I did, reboot, power off, anything, the noise spikes are still there. Powered off for approx. 2 hours, power on, the noise spikes are not present. Keyed the transmitter, unkeyed and the noise spikes are present.

This is really weird !!!!   Noise spikes are evenly spaced 4 KHz apart.

Sergey KN7K

If noise introduced after every time you transmit, it seems like not external RFI, but internal. I would call for support. Sergey, KN7K

Thomas NE7X

I have confirmed the following over ten+ times, its repeatable

1) 6400M power off for several hours.
2) Power on the 6400M and place receive on 40 meters
3) No noise spikes are seen on the display
4) Switch bands (20, 30, 15) then back to 40 meters, no noise spikes are observed 
5) Listen to QSOs and nets for hours on 40 meters, no noise spikes observed
6) Transmit on 40 meters, noise spikes now observed only on 40 meters.
7) Reboot, or whatever, noise spikes still observed only on 40 meters
8) Power off 6400M for few hours, power back on, noise spikes are not observed

I was talking with a few local hams this weekend about my issue. One suggested the following

The noise spikes are being generated by some consumer device (TV, switching power supply, internet, light dimmer, etc etc etc). I placed my 6400M on a deep cycle battery, pulled my QTH 200 amp house breaker to off, noise spikes still observed. This tells me its not coming from a consumer device in my QTH, must be a neighbor. When I disconnect the antenna from the 6400M, the noise spikes are not observed. So the noise spikes are coming into the 6400M via the antenna.

My friend suggested when the 6400M is power on from a cold boot, the wide band noise blanker detects the noise spikes.and blocked then out into memory as noise. So they are not observed. As soon as I transmit, the wide band noise blanker memory registers are cleared, and now the noise spikes are observed.

Could this be what is happening? If so, how do I get the wide band noise blanker to clear these noise spikes after I transmit?

Varistor

Perhaps a bad capacitor in the bandpass filter chain? When you TX you charge it and then it takes a few hours to discharge.

Neal - K3NC

Tom, I am correct that these spikes do not appear when you do this test into a dummy load?

Thomas NE7X

Yes, the spikes do not appear when connected to a dummy load. This is the same as when I disconnect the antenna from the 6400M, the noise spikes are gone.

The noise spikes appear to be coming into the 6400M via the antenna. However when I first power on the 6400M from a cold boot, the noise spike are not there, Then when I transmit, the noise spikes appear. I can repeat this scenario over and over and over. 

It appears the WBN is removing the noise spikes when I first power on the 6400M, However after I transmit, the WBN is no longer removing them.

Gerald-K5SDR

Thomas,

If the noise spikes are not present on a dummy load but are present on an antenna, you can be certain that they are generated outside the radio.  Depending on the time of day and which neighbors are home, I see almost those same signatures from time to time.  It may be in your hours or a neighbor's house.  I can almost assure you it is not the radio itself.

Gerald

Mark K1LSB

Thomas,

1)  How much power are you running?  Do the noise spikes occur even when transmitting using only one watt and no amplifier?

2)  Do the noise spikes persist even if you physically disconnect the feedline coax from the Flex antenna port?  If they do, they probably aren't coming from outside the radio.

Mark

George KF2T

Remember the "good old days" when we just had to worry about RFI FROM our radios?

Thomas NE7X

Recommendation

On my ICOM IC-7700 there is an AUTO NOTCH to eliminate a consent carrier within the receive passband. With the Flex-6400M, there is a TNF notch which is a MANUAL NOTCH to eliminate a consent carrier within the receive passband. It would be really nice if Flex would implement an AUTO TNF notch filter I think this would resolve my issue 100%.

 

73s  ‹(•¿•)›   Thomas NE7X…