Your QRN Noise S meter Reading

Submitted by wa2mqk on Thu, 12/29/2016 - 13:54
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My Kenwood TS-440S receiver has an S-7 S meter noise floor reading across the HF bands. Could we do a survey of club members to record their local S meter noise levels? Local AC power line AM noise sources limit our natural HF receiver noise sensitivity levels. Is an FM modulation our only recourse?

AE3D - Thu, 12/29/2016 - 23:02

My noise floor is not nearly so high. I have the Kenwood TS-570D. At the moment if I turn on the 40m pre-amp I can get the noise up to S-5. Without, its considerably lower, and of course on 30-10 meters it is much lower too.

N3ADF - Fri, 12/30/2016 - 07:28

sorry to hear you have high QRN problems. Mine seem to come and go mostly on 20m.

I just helped K3BEQ build and install a 60m slopper dipole. For three days he was working 60m well. Then the QRN went to S9+20 across the band. I drove over with my HF rig in my truck, listening as I drove around his neighborhood. Very high QRN but found where it was super high. A power pole just block from his QTH that had a pole pig transformer. We noted the power pole number and called his ham friend that contracts for Pepco noise problems. He will be out soon to isolate down to the bad connection and put in a repair work order.

I suggest that you turn off/unplug as much as you can inside the house. Wall warts are notorious for generating QRN. Also florescent lights and space heaters. If then you still haven't found it, I'll drive my truck around your neighborhood and see if we can spot it. Make a list of signal levels on each band including broadcast AM and FM. This will help so I only have to hunt on one band.

wa2mqk - Sat, 12/31/2016 - 10:44

Jim: I'm following up on all your tips to identify my S-7 noise level. I have previously turned the main house AC power breaker off and run the transceiver on battery power with inconclusive results. However a portable AM radio still detected high AM noise around the large service entrance power cables leading in from the power meter (West side of house).
Next, I am going to run the transceiver off a good spare car battery I have while sitting in my truck (engine off) 60 feet from the East side of my house and hooked directly to my 20 meter dipole antenna hung 30 feet off the ground (overhead) to have a comparison reading if you end up driving your truck around my neighborhood. I'll let you and the club know the results in about 2 weeks or so. Thanks for the response, Bob Weber WA2MQK

wa2mqk - Sat, 12/31/2016 - 11:15

Keith: You and Jim (N3ADF) have given me good info to plan my next QRN noise test parked in my truck next to my house. Your S-meter readings sound at least five S units lower than mine (no RF pre-amps or attenuators switched in). So if one S unit equals 6 dB, my QRN is 5x6=30db (1,000 times the power) of your QRN! That wipes out a lot of signals in my receiver. I plan a basic signal sensitivity check of my receiver, but with the antenna connector terminated in a 50 ohm dummy load, my S meter reads essentially zero S units across the HF bands (as opposed to the S-7 reading with a 20 meter dipole antenna). Thanks for the response and I will keep you informed of further neighborhood testing. Bob Weber, WA2MQK

WA3SKN - Mon, 01/02/2017 - 15:56

You have a local noise source. And will want to find it and fix it. You want a directional antenna, for 40 meters build a ferrite rod or shielded loop antenna. DF the noise source by triangulation... it can be a challenge. There can be more than one source and you find the loudest first, then the next loudest, etc. Hopefully it will all locate in your property and you will not need to get the neighbors involved.
Good luck with the project!

-Mike
WA3SKN