QRM Question

Hi Everyone,

I very excitedly set up the SS9900 and erected the sliver rod on a mounting pole roughly 2meters from the ground, connected everything up and switched on the radio and was met with an S7 of noise on all the bands including uk 40 and also on all modes. 

Has anyone else experienced this? Will moving the antenna up higher like on the side of the building help? Someone did reply to my call for a radio check on uk 19 but even though the signal was an S8 the audio was unreadable because of the noise. 

Thanks

Chris

26CT4373

It's a sign of the times.
Solar panels phone chargers led lighting and last i can think of Christmas lights.
Plenty of info on here somewhere if you do a search.
Bit busy roasting meat's at the moment to look and point you in the right direction sory.

The further you're away from switch mode power sources the better, and most Christmas Lights use these, so unless you can get some distance from your house and those of your neighbours, you'll prolly not see the noise floor lower until after the 12th day of Christmas.

If you build an NVIS Wire Antenna and put it somewhere between 1/8th and 1/20th of a wavelength AGL you'll lower the noise floor the lower you get, and can improve the signal by laying a wire on the ground below it as a reflector.

40m, 60m, 80m, 160m, usually work NVIS during any 24 hour period, just keep an eye on the critical frequency (FoF2).

Hi Alan, Wayne,

Thank you for replying really appreciate it. I am beginning to wonder if the noise is actually coming from the BT overhead cable outside the boundary of the house.

Kindred wrote:

Hi Alan, Wayne,

Thank you for replying really appreciate it. I am beginning to wonder if the noise is actually coming from the BT overhead cable outside the boundary of the house.

had a Ham friend with local noise, turned out to be a lamp post after some RDF, and the company wouldn't come out and sort their interference.

So I feel your pain mate.

Broadband power line adapters can be the cause of serious interference (that's the ones you plug into your mains sockets to send data around your house). If anyone within 500 yards has them in their house you will likely get problems from them.

One way to check if these are the source is to check frequencies above 28mhz as these devices are normally filtered to stop interference to the ham bands but not the CB bands.

what's the noise like on the hf 360?
regards
mark

I have the 360 along with a cobweb and eflw.
The 360 does work and with the plus kit it is not bad with qrm but the other 2 are better.
Location could help as mine is fixed to the house and not that far from the ground.
Some say they work well low but at the bottom of the garden well away from all qrm sources but being disabled my aerials get put in the easiest place if you with me.

Markone wrote:

what's the noise like on the hf 360?
regards
mark

Hi Mark,

The noise on the 360 is an S6-S7 on most of the bands

so more location then equipment ?just a thought does any neighbours have plasma tv, i had one and it blanked out all bands or you could wait a week until the dreaded fairy lights have gone. Does the nb take out the s6 on the 991a? .just trying to help if I can
take care
mark

LED lights can cause qrm.
Strang thing i found when trying to lower my qrm was to replace the 240v led lighting in my shack with 12v led lights and running of the same psu.
Doesn't make sense but it's true in my case.

The strange thing is in April all the noise disappeared on the HF bands but returned one day in September.

Kindred wrote:

The strange thing is in April all the noise disappeared on the HF bands but returned one day in September.

Sounds like someone's central heating came on, possibly controlled by HIVE or something like it.

I thought about heating but not sure on it.
Wouldn't hive work just when turning on and then at off time.
Strange one that.

There's ways to reduce interference, one might be to charge a leisure battery and operate your HF radio directly from that, to remove any possible AC generated RFI.

Distance is the next thing, the further from any possible sources of RFI your antenna and receiver, the better.

Then use high angle radiation from an antenna at least 1/8th wavelength or less AGL, but no good for anything above 10MHz as only low angle radiation will likely work for multiple hops/skips.

Other than that, if you can look at the actual spectrum interference, you might be able to get filters in-line with your receiver/transceiver, to isolate the interference.

Such things as ferrite rings with coils of the coax feeder wound through them are a basic help is removing parasitical signals causing local qrm.

Other than that you need a frequency analyser, and do some RDF for the RFI source, and try and isolate it, or get a utility company to replace equipment causing interference.

It's not an easy process, but start with what you can easily remove by where you have the antenna erected.

Wireless wrote:

Kindred wrote:

The strange thing is in April all the noise disappeared on the HF bands but returned one day in September.

Sounds like someone's central heating came on, possibly controlled by HIVE or something like it.

I had thought it may be a heating system also. If it disappears suddenly I will speak to my neighbours see if they have switched anything off. I have made a loop to go out looking to see if I can track down the interference using the 817 but its not been great weather wise.

Maybe it has something to do with the 45db adjustable Gain Control.     So perhaps back off the gain a bit then ?

Wireless wrote:

Kindred wrote:

The strange thing is in April all the noise disappeared on the HF bands but returned one day in September.

Sounds like someone's central heating came on, possibly controlled by HIVE or something like it.

Hive works at 2405Mhz - 2480Mhz.

Hi Guys, Just to update you on the qrm. I still get an s9 on the SS9900 but I have found the noise source on the HF 360 on the 991a. I erected a dipole in a inverted V in the garden and the noise on the 20m and 40m bands disappeared(the dipole is a trapped dipole for 20/40m). It was roughly 2meters of the ground I raised it up another meter and the noise was an S9+10 on both bands. I also discovered when I transmitted I caused the signal loss on the cctv system that got me thinking so switched off the DVR and the noise went. Put the HF 360 back on the radio and the noise level has dropped to an S2 on 20m and S4 on 40m and is virtually zero on the other bands I can actually hear stations now.

Thanks 

Chris