Question of propagation on 40M

god's toy

Hi guys,

So the last few weeks I'm tuning into the IRTS news on 40M and two things are making me question my set up.


1. Getting a whining noise that moves up and down the frequency around 7.123Mhz and I have to play with preamp, filters and PBT settings to get around but only for it to come back around a little later on. it moves up and down the bands... funny it hangs around the places I like to RX on!


2. When the noise is gone the irish operators are all very low but the UK ones are fine. I'm thinking local conditions are not wonderful this last while?.


This has been the norm for me for over month or so and I'm wondering if it's just my rig, something local to Wicklow or just conditions around Ireland.



Thanks.

65535

Hi,
The optimum ham frequency for all Ireland use is the 3.5 MHz band, anything higher is for further distance (UK etc)
Although I don't know if the news is on 80M ?

As for the interference you could try and see if other operators are getting that as well and that it is not just a local problem, try listening on the web at

http://websdr.ewi.utwente.nl:8901/

Tune to the same frequency and see if the interference is there, it could be local or global

god's toy

Thanks for the info.
Before the bands went to hell with noise on me, the 40m news was about the only time I would hear Irish operators. Would hear at least 20 EI's from all over Ireland no problem but never outside of that... Im often wondering if Irish HF users only broadcast once per week!¡! ..

I think they have news on 80m aswell but I've never been able to hear it ( unsure if its just too much noise or just my antena as its really only good down to 40m (half G5RV,)

I'll have a look at those links and hope that gets me closer to an answer.

Thanks!

thelordgod

The daytime conditions on 40m for the past few Sundays has been terrible - its not your setup. Noise levels have been high in general for the past few months. Usually I can call in on 40m but a few times recently I have heard nothing only noise. The news is on 80 at 12:00 but it will be difficult for you to receive it on the 1/2 size G5RV. 40m is a very volatile band - usually its fine for local chat but it can change in an instant to favour dx traffic.

And yes some ops only crawl out of the woodwork on a Sunday morning...

martinsvi

you can't hear 80m on 1/2 size g5rv, I have one myself, it's pretty bad even for 40m. I built an inverted L out of wire and a pole, I attach additional lengths of wire for different bands, it works way better than G5RV

as for the noise - 80m isn't really a band you can rely on during summer. Last few weeks have had unstable weather conditions, lot's of thunderstorms over in UK and France, there's lot's of static in the air thus the noise.. but your original problem sounds like interference so I would investigate it by turning just about everything off except for the radio and see if it's anything local that's causing it

god's toy

martinsvi wrote: »

you can't hear 80m on 1/2 size g5rv, I have one myself, it's pretty bad even for 40m. I built an inverted L out of wire and a pole, I attach additional lengths of wire for different bands, it works way better than G5RV

as for the noise - 80m isn't really a band you can rely on during summer. Last few weeks have had unstable weather conditions, lot's of thunderstorms over in UK and France, there's lot's of static in the air thus the noise.. but your original problem sounds like interference so I would investigate it by turning just about everything off except for the radio and see if it's anything local that's causing it

Thanks!
The strong UK stations come in 'OK' on 80 with my half G5 but that about it as nothing local is heard, but as you say it's not cut for it and I knew that when putting it up but it's all I could do at the time.

The noise is an odd one as it moves up and down the band on many frequencies so if I'm hearing someone on say 7.123 it will start on 7.120 them move up slowly to around 7.125 and back down again and start over. for the record I also hear one on 11M at 27.555 ....
Yep going to have shut everything down and hook up the solar backup and see if it's something in the house, only thing is nothing changed here when it first started to show up two months ago.


Thanks for your help!

martinsvi

god's toy wrote: »

Thanks!
The strong UK stations come in 'OK' on 80 with my half G5 but that about it as nothing local is heard

I have a suspicion that some of them drive with 500w or more, not something you would see in Ireland. When you do pick them up on a tuned antenna, their bandwidth and splatter is all over the place..

god's toy wrote: »

The noise is an odd one as it moves up and down the band on many frequencies so if I'm hearing someone on say 7.123 it will start on 7.120 them move up slowly to around 7.125 and back down again and start over. for the record I also hear one on 11M at 27.555 ....

is that not over the horizon radar by any chance? https://www.youtube.com/watch?v=UfpRvxox-po

god's toy

FYI it sounds like this but is just a few Khz wide and moved up and down the band plus is repeated around the whole HF spectrum.

Some days very strong others weak like skip and is there even if the bands are closed.

martinsvi

well if it's there when the bands are closed, it must be quite local. Try switching circuit breakers (or fuses or whatever you have) in your home one by one and see if they're coming from your home. It can be anything, I can hear and odd splatter when my neighbor starts his car for example

65535

Can you try the rig in the car - is it a 12V model ?
I would try running it from a 12V battery with all mains electricity temporarily turned off if that is possible.
If you are looking at a local interference problem it could be anything from the power supply to a light bulb.
I even had a mains extension lead cause interference once time.

god's toy

It's kinda odd that this noise started the first day of the summer thunderstorms and I put it down to atmospheric conditions but never went away.

Yep your idea sounds like a plan alight! Will be doing just that as soon as I get back from work tonight.

Thanks!

martinsvi

in that case is your rig grounded? Perhaps a static buildup somewhere, you would nearly want to wire your rig to a cold water pipe for a moment to see if it would discharge, if there's anything there.. I have never seen static building up on a rig like that so not sure if what I'm suggesting is something out of sci-fi books, but what you said about how it started definitely hints in this direction. Perhaps there's some capacitance between your antenna and tuner (of you have any) that wouldn't let the static disappear

watty

Or static discharge has damaged the RF front end.

It's always a good plan to disconnect unused aerials (and possibly even earth them) and disconnect power cables any period of Thunderstorms or prolonged absence.

I've no idea how good the change over aerial earthing switches are.

god's toy

Ok have an update!

Good news, I have found it!
On shutting down the power to the house and using the backup solar cells/battery for a day it was gone completely so its housebound then, and so I started connecting household items to the inverter, one by one powering them on to see if I could find the offender.

I starting with things closest to the rig itself and then only after a short time I found what it was, the power supply of the radio itself!

HOWEVER (and heres where it gets odd) the interference moves up and down the bands depending on how bright the background lights are set on the radio? wait wha???, Meaning I can turn them up or down and they affect how strong it is on that one frequency. Odd or what?

Have more investigations to do on this and going to look at all my earth points and as watty said make sure the antenna is earthed BUT at least I have something to work with now!

65535

Well done, glad you found it.

watty

Get a different PSU.

Many SMPSUs shift frequency as well as duty cycle with load.

god's toy

Thanks watty and everyone for your help.


Going to make this my project to eliminate this noise before giving up and buying a new psu.

Feel a bit like a fool for not knowing/finding it out first before coming here but to be honest my skills are more IT than ESB!

But that's why I love o'le Boards.ie!

65535

Just one thing - capacitors store a lot of energy - ensure they are discharged if you are touching anything on the circuit.

If it is just the lights you could disconnect them ?

god's toy

65535 wrote: »

Just one thing - capacitors store a lot of energy - ensure they are discharged if you are touching anything on the circuit.

If it is just the lights you could disconnect them ?

Its funny, its the lights built into the radio, but yep turning them brighter or dimmer shifts the noise away from the frequency I'm on so its workable for now.

65535

What kind of radio is it

god's toy

Icom R75