Can someone help me with my sanity

I have just spent a couple of weeks working on noise floor level across HF and did a great job !

I finished off a GM3SEK mains filter on Saturday and tested it before casing it up with S0 of noise on 20m.

I cased it up and put the shack back together and now have S3 !!

Have the recent conditions increased things ?

Have I missed something or caught a dial , I have checked RF Gain.

MY FT847 meter is not falling below S3 on 20m , I have bacon frying on 40m but still only s3 of noise (no antenna for these bands or below)

Bands as below

160 - s1
80 - 0
40 - s3
30 - s1
20 - s3
17 - s2
15 - s0
12 - s0
10 - s0

Band has been poor these couple of days with elevated noise floor.

The noise floor levels you're experiencing now is every amateurs wet dream.

Ha , thanks for the reply.

I was very pleased with my noise floor at our new QTH.

Pretty simple setup , Qtr wave verticals with chokes at either end of the coax run and a mains filter with GM3SEK design.

I will see if things settle down. just listening VK2SD on 20.

Would compare the VK2 signal with you but I'm taking part in a USA net thing on 24.970

What freq is he on?

He was 14,215 Qrt now I think

10m activity group on 28.570 if you want to see if you hear anything from the states.
Website is HFqso.com, handy resource for checking propagation

Thanks for the link. I will have a look and make a note of it.

Check out the website, they start off on 17m and work upwards before finishing on 10m, we're just wrapping up on 10m now

S3... Lucky you.

I have S4 with a shop nextdoor but one thats got enough lighting to make Blackpool look dim.
40 & 80 its S9+ bacon frying.

Still waiting for Ofcom's final decision.

Personally two sticks of dynamite should suffice.

Interesting to hear what other people have.

I am still determined track down the S3

It is a very subtle noise , could almost be mistaken for just the band but i think it is something causing it.

Almost like ssssshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhssssssssss , looks like it is over 14, 21 and 24 mhz.

Thanks for the replies.

What was your noise floor levels before putting the mains filter in line?
What's your rig receiver and are those readings with pre-amps off.
Signal to Noise floor ratio is more important than a 0 noise level, as it stands I don't think I ever seen reading on a vertical antennas so low, you' ll need to do comparisons with other stations to see how easy they are copying a same station and what report they're giving as the current S3 noise won't be a burden if on similar equipment they can't copy what you hear. For instance I choose to operate the higher bands with pre-amps on which elevates my noise floor but it also makes my receiver more sensitive to weaker signals.

What was your noise floor levels before putting the mains filter in line?
The mains filter has made small changes , the choking of the coax more so.

What's your rig receiver and are those readings with pre-amps off.
Pre-Amps - off

Signal to Noise floor ratio is more important than a 0 noise level, as it stands I don't think I ever seen reading on a vertical antennas so low, you' ll need to do comparisons with other stations to see how easy they are copying a same station and what report they're giving as the current S3 noise won't be a burden if on similar equipment they can't copy what you hear. For instance I choose to operate the higher bands with pre-amps on which elevates my noise floor but it also makes my receiver more sensitive to weaker signals.

Yes , i am just setting things back up after some inactivity. Need to get some operating under way to see how things are etc.

Like you I've very recently got back onto the HF bands after a 10yr period of inactivity.

I resumed as a SWL'er about this time last year experimenting with various active whips and cheap loops. I'm in a typical suburban location, plagued with PLT devices outside the amateur HF allocations, the usual switched mode PSU stuff, some Solar Inverters, and VDSL2 leakage from the overhead telephone lines.

I finally settled on a MFJ-1886TR receiving loop to do all my radio snooping with. This is mounted on a small rotator so I can null out point sources of interference. It also works very well at peaking wanted signals, especially on lower frequencies.l

At the beginning of this year I decided it was time to get back into recklessly squirting RF all over the place. My antenna situation is a 30ft Random Wire for 40m to 10m for transmitting. This is arranged as a sloper with the feed point about 6ft agl and the distant end at about 30ft. I have a line isolator in the feedline about 20ft from the feed point. For receiving I'm using the MFJ-1886TR broadband loop. This is mounted four feet above ground and on a lightweight Yaesu Rotator.

Below are my receive figures as measured on my Icom IC-705



MFJ 1886TR Loop 40m-6m RW


160m S0 S0

80m S0 S5 (Increasing to S9 above 3755KHz)

60m S2 S9 (SMPS interference)

40m S0 S5

30m S1 to S2 S5

20m S0 S3

17m S0 S3

15m S0 S5

12m S0 S1 S0

10m S1 S5


These measurements were done at 13:45 with a bandwidth of 3KHz/SSB.


One of the reasons, as there were a few, why I shut up shop 10yrs ago was due in part to the amount of interference. Back then when I contacted the RSGB EMC people for advice it was suggested I try IRLP/Echolink and/or D-Star for out of country contacts. Last year I contacted them again and this time I was advised to canvas my neighbourhood to find the sources of interference. I knew what the sources of interference were/are, I was a signal's and protocol analyst with GCHQ before my health deteriorated, I was just after some assistance as OFCOM were not interested. The words Chocolate and Fireguard spring to mind, with the phrase "As much use as" tagged as a preamble.

It sometimes feels like an exercise in futility when chasing that illusive zero noise-floor level. In my case I had to go against my principles and shell out on a relatively expensive receive antenna instead of building my own, which I can no longer do due to health type stuff.



Edit. Apologies, I had created the table with proper spaces but these seem to be ignored by the website.

Thanks for the reply and interesting information.

I note you have quoted to S readings for each band, is that a comparison ?

Yes. The first value is the small receiving loop and the second value is the 30ft random wire. I did format the results into a table, and when I edit the post everything is correctly spaced. But once posted all the spaces are ignored and it ends up looking like a confusing mess.