new LED street lighting...
recently I decided to hook up the trusty Tecsun 660 Shortwave radio to the outside 21 meter long wire urban wire antenna for some SWL
in metropolitan Adelaide. as this was a working system in 2017
but got only noise & Interference from 1MHz up to 18MHz thinking it was a loss of the impedance transformer grounding by a earth wire failure.
I did re-test the external antenna and its indoor impedance transformer circuit, transformer grounding and the coax . however no fault found in the antenna
so I decided to build a passive 0.5 to 30MHz tapped coil antenna tuner box with attenuator for receiving shortwave in the hope that this may help?
however I decided post to the forum. before wasting any more time and money on SWL
I have not used the shortwave radio for a year or two and new LED street lighting may have something to do with it?
see image here is the outside 21 meter long wire urban wire antenna setup I use. its a copy of the Technical and historical site SWL antenna design.
this was ok back in 2015 when I did first got the Tecsun 660 and needed a good SWL antenna.
I will also note that a 891KHz AM signal is so strong it will drive the multimeter continuity test piezo buzzer as a speaker
I get ABC Adelaide radio station 891 kHz AM on my multimeter piezo buzzer. even though the station is on the other side of the city .
Do you have (V)DSL services in the area. Depending on underground or overhead connections they tend to generate a lot of "noise" up to 17 or 35 Mhz
And powerline network adapters, they generate a ton of RF crap.
Coincidentally I did the same, dug out my HF receiver a couple of days ago in order to sell it, I have S7+ of noise across most of the HF bands from Powerline. DSL, PCs printers, lighting and whatever else. OK, that was with a random wire out the back of the rig but still not good
I'm running an Inverted L but in a suprisingly quiet environment; I prefer it for sending, while I use Whips or active loops for receiving.
Certainly the noise level increased over the years, so no surprise that it can be shocking to listen on the frequencies after longer abstinence.
but many problems with antennas are home made; most common of course will be, that not only the antenna receives but the feedline too due to common mode currents. Many believe it's a TX only problem, but it's a rather nasty issue on the RX side too.
Also drowned feedline, corroded connectors and all the sort of things can cause rx problems.
after such a long idle time, it's absolutely needed to verify the antenna system first; afterward you can start searching for external qrm sources.
also if you have a strong local station, you have to count with any kind of intermodulation, if the receivers frontend is not really well designed. under such conditions you're going to see design flaws very easily and in very nasty manner.
And powerline network adapters, they generate a ton of RF crap.
and then some more; switching power supplies used inside home, plasma TV sets, solar panels... and more, all those generate a dense "cloud" of interference, then add the interference coming from neighbourhood and the one coming from public stuff like street lights, AC power transformers and so on, and it's easy to understand the kind of "RF polluted" environment we live in; I must say that from that point of view I'm lucky, I live in a very small town, uphills, and my usual noise level is around -120 to -130 dB so I can't complain about that, but I've friends "suffering" the RFI issueQuoteCoincidentally I did the same, dug out my HF receiver a couple of days ago in order to sell it, I have S7+ of noise across most of the HF bands from Powerline. DSL, PCs printers, lighting and whatever else. OK, that was with a random wire out the back of the rig but still not good
You're not alone, a randomwire (or an "inverted L" as the one used by the OP) aren't exactly the quietest antennas, sure, many years ago, when the RFI was much lower, they were ok, but nowadays if one isn't living in a pretty quiet (from RF standpoint) place, a randomwire won't exactly be the best choice. I'm NOT saying it won't work, mind me, an endfed wire antenna is the simplest to setup, is almost stealth and offers decent performances in TX, but when it comes to reception, in my humble opinion, it would be a better idea considering a loop antenna, it's simple too, but it offers better S/N ratio and, if it's a vertical loop, the NULLs it offers will be useful to attenuate some strong noise source
Can you tell us what happens when you flip the switch on the side that says DX, Local and Normal, with the internal antenna and then with your external antenna? Try to do it on something thats somewhat audible but noisy.
and maybe walk around the house with the internal antenna and see what it does in different rooms?
this should be quick to do
Ive spent at least $100 on ferrite bead RFI suppressrs, and i feel its made for enormous improvements over no ferrites.
found the source of the noise! it was the lab computer. so no internet when SWLing
the shortwave bands have returned to normal, computers are noisy
ferrite bead RFI suppressrs do work and they are free with most used electronics. old TV's & PC's have them.
Anyhow, happy to hear you found the noise source, now it would be a good idea finding a way to tame it so that you'll be able to use your computer even while SWLing
yes true its a Lenovo desktop pc with a custom VGA DVR unit on the video it is a one year project that finally works .Quote
So, if you disconnect the PSU, does the noise disappear ?Quotebrings me finally this conundrum, software defined radio on shortwave defined on what hardware?
non of my 3 SDR USB units worked with window's anyway. microsoft and China don't really get along'
If you're using RTL dongles, you'll need to start by installing the proper drivers, see here for infos, at any rate, SDR units aren't "plug and play", to work they need their proper drivers and, in some cases, the proper "ExtIO" library to interface with the receiver program.
sadly the noise has returned, radiating from the AC mains. centered around 6MHz from neighbors.
making any long wire antenna over the house useless. so taking to the backyard with the Tecsun 660 in hand
on SSB 40 meters a 200W uk? amateur radio station was reporting that a VK station had heavy QRM
so we SWL-ers are not the only one's with this.
I may need to relocate any long wire antenna away from anything. going portable to the local park and throwing a wire up a tree for better DX
-as excuse to get out of the house.
sadly the noise has returned, radiating from the AC mains. centered around 6MHz from neighbors.
making any long wire antenna over the house useless. so taking to the backyard with the Tecsun 660 in hand
on SSB 40 meters a 200W uk? amateur radio station was reporting that a VK station had heavy QRM
so we SWL-ers are not the only one's with this.
I may need to relocate any long wire antenna away from anything. going portable to the local park and throwing a wire up a tree for better DX
-as excuse to get out of the house.
QuoteCan you tell us what happens when you flip the switch on the side that says DX, Local and Normal, with the internal antenna and then with your external antenna? Try to do it on something thats somewhat audible but noisy.
and maybe walk around the house with the internal antenna and see what it does in different rooms?
this should be quick to do
found the source of the noise! it was the lab computer. so no internet when SWLing
the shortwave bands have returned to normal, computers are noisyQuoteIve spent at least $100 on ferrite bead RFI suppressrs, and i feel its made for enormous improvements over no ferrites.ferrite bead RFI suppressrs do work and they are free with most used electronics. old TV's & PC's have them.