Background hiss on the band

[k4kyv]

Last night I noticed an unusually high background hiss on 75.  Not static crashes, not electrical rf hash, just a high background white-noise effect, uniformly  spread across the band, running about S-8.  Most AM carriers quieted it down, but it was extremely piercing and annoying whenever the AM station would drop the carrier or I tuned away from the frequency.  The sync detector seemed to make it worse, but it was still bad with the envelope detector.  It was just as bad as the background hiss you hear with 2m CB FM when the squelch is turned off. I found myself reaching for the gain control when the other station was about to stand by, just to save pain in my ears.

Has anyone else noticed this?  I assume it is atmospheric, but could it be some kind of spread spectrum trash?  I am considering building up a squelch circuit, like what is used for FM, for use in such occasions.  I have noticed the high background hiss before, but it is not there every night.

[Pete, WA2CWA]

I tend to hear more high background hiss during the extremely cold and low humidity winter nights on the low bands. I was monitoring 75 last night and didn't find it particularity unusual. But, I'm also one who can sit for hours monitoring background noise on 6 meters waiting for scatter signals to pop out of the noise.

[W9GT]

I have noticed the high background noise as well.  Sometimes it is hard to distinguish from "normal" noise which is made up of many components including computers, consumer junk electronics, power line noise, etc.  However, this noise just stays at a high level.  Could be solar noise or atmospheric noise or ?  I also was battling high noise on VHF this past weekend, however, it seemed more sporadic and perhaps local in nature.  6 M seems
to be the point in the spectrum where noise peaks anyway.

I have seen various opinions and dissertations regarding an overall increase in the ambient noise floor level in the past 20-30 years.  I don't know if anyone has really assembled meaningful data or if there is any concrete evidence to support that claim, but it sure seems that way.

73,  Jack, W9GT

[kb3qay]

I have'nt been listening the past few days, but an active group of sunspots is currently generating some near C class solar flares according to Spaceweather.com - Jim - KB3QAY

[W5COA]

Howdy Don,

Yes, I noticed a higher level of background noise on 80m a couple of weeks ago. I was at my "quiet" rural location in East Texas, where I am able to discern such things, as opposed to my city qth, where the locally generated noise obscures everything.

Unfortunately, I am not out in the country on a daily basis, so cannot make a quantitative or continuing assessment. I will start checking more carefully, now that I know someone else is hearing the same condition.

I am also going to try to locate the source of a "tick", which occurs at about one tick per second. It sounds like an electric fence charger, but fades in and out like it comes from far away. It is not overpowering, but is annoying.

73,

Jim W5COA

[KD6VXI]

I've got that same impulse type noise here, off and on, across all the bands from 18 mhz and below.

Gets frustrating, amplitude changes during the hours (propagation related maybe), but the actual signal itself seems to be pretty consistent...  Doesn't change pitch or anything else much.

West coast here..

--Shane
KD6VXI

[flintstone mop]

I have been hearing not so much the high hiss sound but the ticking on 75M. Static discharge from the extreme cold WX??
I thought snow falling on to the wire antenna can make ticking sounds too.

[KM1H]

Maybe related to approaching snow storms?

[KD6VXI]

I don't think that's the problem here.  I know what the 'precipitation" static sounds like in my rxers, and this is NOT the same.

This is almost like a low duty cycle pulser....  You could count the ticks / minute, at least on this end of the us.  I just took a listen from 160-10, and did NOT hear it anywhere.  Grabbed an Italian qso while I was at it on 17, too

It's an interesting sound, to be sure. 

--Shane
KD6VXI

[k4kyv]

If you are using a link coupled tuner, try clip-leading a 2.5 mHy rf choke to ground on each side of the line.  I have had problems with that ticking from static build-up on the antenna that eventually discharges, then  re-charges, etc, sort of like a relaxation oscillator.  With parallel tuning, it is a simple matter of permanently placing an rf choke from the mid-point of the coil to ground to bleed off the discharge.  With series tuning, a choke is required for each one of the feeders, since no continuity to ground is built into the tuner.  In any case, the choke should be installed at a low rf potential point.  Otherwise, the inductance of the choke will affect tuning, much like the plate choke does in a final that uses pi-network output, and the characteristics of the choke become critical.  Place the choke at a low potential point, and about any old choke will do, as long as it has sufficient inductance.

Even with a pi-network directly feeding coax line, use an ohmmeter to see if you have DC continuity to ground at the output terminal of the transmitter.  Some rigs have a series blocking cap at the output, or else just leave the pi-network coil floating.  A well designed pi-net will have a choke to ground to bleed the discharge, but it may have opened up.  If no continuity is measured, try strapping a choke across the output terminal to ground and see if the clicking goes away.

Since the problem occurs during receive, the problem may not lie with the transmitter, or the tuner if the tuner is used only with the transmitter, but the discharge can still trigger arc-over during transmit.  But in any case, make sure the antenna feedline shows continuity to ground on receive as well as transmit.

As indicated by the fading effect, it could be a distant electric fence that is actually radiating to the ionosphere, and reaching you via sky wave.

That is one of the major concerns in the unlikely event that BPL should ever become widespread; with thousands of systems simultaneously in use continent-wide or world wide, all that distant radiation combined might trash up the entire hf spectrum by raising the general noise floor everywhere.

[W2VW]

NB has mis-adjusted his PLL.

[KD6VXI]

Don,

I've got a discharge inductor on the antenna.  Have to, with the amount of static buildup I get up here.

You DID bring something up, though.  I have an 'electronic' meter...  One that isn't read, but a guy drives by with something connected to a laptop and it transmits my meter reading to his computer directly.  Supposedly it's two-way, they can shut the meter off remotely.

I wonder if this isn't my problem...

--Shane

[K5UJ]

While trying to find out about another problem (my lousy DTV reception) I came across this article which mentioned "sky noise."  The author was addressing VHF frequencies but his findings about what he terms sky noise are probably applicable at HF.  Scroll down a bit to "A Missing Parameter in DTV Planning."

http://tvtechnology.com/article/85628

(for those who are interested in the entire DTV reception over the air article the sceond part is here: 
http://www.tvtechnology.com/article/90160 )

rob

[W9GT]

I listened last night and took special notice of the S-8 background hiss on 75 Meters.  It certainly didn't hurt overall propagation, however.  I was able to work Gary, K4XK in Florence, AL with his Retro 75 AM rig running 2 Watts....Oh by the way, I was also using my Retro 75 also running 2W.  That was my 5th Retro to Retro QSO.

73,  Jack, W9GT

[sndtubes]

Could it be that we just don't usually hear the background hiss because it's usually covered up with lightning crashes, etc.

[flintstone mop]

Could it be that we just don't usually hear the background hiss because it's usually covered up with lightning crashes, etc.

At this time of the year lightning crashes are almost non-existent. A lot of folks who work these frequencies daily can hear the smallest changes and the hiss would be an additional sound along with the usual atmospherics. This time of the year we usually see an S2-3 of noise. And operators living in urban areas may hear more noise from the neighborhood. Summertime can bring on S-9 to 20 over crashes.

Fred

[sndtubes]

Could it be that we just don't usually hear the background hiss because it's usually covered up with lightning crashes, etc.

At this time of the year lightning crashes are almost non-existent. A lot of folks who work these frequencies daily can hear the smallest changes and the hiss would be an additional sound along with the usual atmospherics. This time of the year we usually see an S2-3 of noise. And operators living in urban areas may hear more noise from the neighborhood. Summertime can bring on S-9 to 20 over crashes.

Fred

Well, that actually was my point, Fred.  Since there is almost continuous atmospheric noise from thunderstorms on 80/160 during the summer, we wouldn't really notice the background hiss because the lightning crashes cover it up.  Having said that, it really doesn't explain the nights that 80 and 160 are almost noiseless.  So, I guess my theory is really not valid anyway.

[k4kyv]

Sometimes that background hiss is uniformly S8-9 across the spectrum here with no static crashes, obvious local electronic smog, QRM, etc.  Other times under the same condx, the S-meter doesn't budge off the peg. I am wondering if it could be some kind of spread spectrum or digital hash, or if it is strictly atmospheric/cosmic.

[WQ9E]

Don,

I have noticed this on 75 also and I am in a quiet rural location.  A lot of times I use my Pierson KP-81 to monitor a frequency on 75 because it does have squelch and I noticed several nights where the squelch had to be set much higher than normal to quiet the set.  I remember a few days last year with the same conditions.

This morning 75 was back to S-3 background noise.

Somewhere east of me I have something that charges up with static from the wind.  At first I thought it was line noise but it only occurs when it is extremely dry and very windy.  In moderate wind or gusts it creates a burst of noise with an almost musical tone that will last about 3 seconds total from peak through decay down to nothing.  With higher winds each discharge event lasts a little longer and with sustained winds it is almost constant.  It has to be very cold (well below freezing), dry and windy for this to occur and it isn't nice weather for noise hunting.  I built a small receive loop with a preamp at the loop and I can null this to almost nothing so it is more of a curiosity than a real problem but I would like to find and cure it.  I have run the midwest classic net on 3885 several times using this loop and fortunately no stations are directly in either of the sharp null directions.

When I first had this problem I bought one of the MFJ noise canceling boxes  but I found for my use the small loop is more effective.  It was fun playing with the MFJ and it does a great job on an interfering station but requires a lot of adjusting.  While learning how to use it I was able to drop WWV from S-9 down to S-2 by adjusting the phasing between the main and "noise" antenna.

[w1vtp]

I've noted something of the same sort here particularly today. I think we all know line noise when we here it. This is not like that at all. My noise on the good days do not fall as low at yours Don.

I sure woiuld like to know how to get rid of it.