These days, the use of various USB-based power cables and supplies is pretty much universal.
You might think that using battery-powered USB supplies doesn't produce RFI that harms amateur radio reception. Sadly, that isn't always true.
The most common problem is that where a small transformer steps down 12VDC to USB's standard of 5VDC.
In field tests with my mobile setup, I've found that connecting a USB cable to the outlet of such a transformer - even when the other end is not connected to a load, produces very considerable levels of RFI - on my TS480's lazy 'S' meter, it reaches about S7. WSPR reception is not an option with that kind of interference!
Yesterday, I had forgotten to bring my lithium power bank with me, which I normally use to power my Raspberry Pi, because it doesn't lead to any RFI at all. Having come a fairly long way, I looked around to see what I had in the car that would let me use the car's USB outlet without RFI.
It turns out I had two good quality TDK split ferrites around the sound card interface. That was probably redundant, so I used it to put three rounds of the USB power cable around the core, immediately where the cable left the transformer outlet.
Immediately, the RFI dropped dramatically, with the S-meter now not registering, though there was a small amount of weak residual hiss. Using the second, smaller ferrite at the computer end, the RFI was eliminated altogether, provided one eliminated any stray capacitive paths by careful positioning of the Raspberry Pi itself.
On a later outing, I found the solution to the residual RFI was to wrap the USB connector from the Raspberry Pi to the soundcard interface around a large ferrite (see below for details). Now I had absolutely no RFI at all.
With these measures, and with the results obtained on WSPR as reported in a previous post, I was able to turn a day spoiled by RFI into a successful mobile outing.
The specific ferrites I used were a large TDK ferrite, type ZCAT 3035-1330 (13mm inner diameter), originally supplied with my TS480SAT for interface RFI suppression, and the smaller one, a TDK ZCAT 2032-0930, 9mm inner diameter. Both are widely available online, albeit at about £5 or more each, but be careful to choose a reputable supplier, to avoid cores made of river mud, rather than the proper mixes!
Showing posts with label rfi. Show all posts
Showing posts with label rfi. Show all posts
Friday, 6 September 2019
Wednesday, 22 May 2019
New internet connection - no copper!
For many years, my QTH, being very rural and yet not exactly far from civilisation, has suffered from terrible internet connectivity.
In the years 2008-2010, we had nothing but dial-up speeds, mostly due to the distance from the exchange (about 2km or more).
We then acquired a microwave internet link paid for by the Welsh Government. In fairness, the Government did what they could to solve a country-wide problem. But they and the taxpayer simply ended up being ripped off: grants to installers were a maximum of £1000 for equipment, and so, as was entirely predictable, most charged the Welsh Government £999.99!
This really didn't work very well at all, although when it did work, speeds were reasonable (about 8Mbps). The service was up and down, and often off altogether. Worse, the connection from router to the rooftop antenna generated terrible RFI, which I recorded at the time. The company, having now made its directors a lot of money, was sold off and service standards dropped off a cliff.
We got rid of that system about 2015.
We then bought a mobile wi-fi box from 'EE'. This worked very well until near the end of the contract, when we suddenly found unusual transactions that we hadn't agreed to. They tried to take a large amount of money from us, but we complained and eventually recovered all of it.
That was the end of 'EE' mobile broadband.
We then tried Vodafone. This worked very well until last month, when the transceiver failed. During those years of mobile data boxes, the infrastructure locally has improved dramatically. We now have super-high speed fixed broadband fibre passing in front of our house, and so I decided to connect to this, to end our internet woes.
There was a lot of misunderstanding about the role of copper wires. When you buy a package of phone and broadband, the network operator insists on copper cable for the phone. That's OK, so long as no data is transmitted along it, potentially - and as widely reported across the UK - creating RFI. The main problem is imbalanced line conditions with VDSL2, which causes very wideband RFI, leading to some very sad stories of operators who have operated successfully in urban areas for decades now being wiped out.
The first engineer told me that, despite a fibre connection being fixed to my house last week, all my services would be along copper wire. "No way!" said I. "You can take your services and stick them where the sun don't shine!"
Then, later the same day, and entirely unexpectedly, a fibre engineer arrived. Being female, she was much more helpful! She installed everything via fibre, with the only wires being power (12V, easily converted to linear PSUs if needed), and a very short WAN cable.
In total, the system, including the two SMPSUs, generates no detectable RFI on any amateur band.
So, if you are in the UK and thinking of a broadband package from BT, it is often now available all the way to your indoor connection via fibre alone - no copper wires at all! Just make sure to bring the engineer in for a cup of coffee as soon as they arrive, and tell them about your radios and ask exactly how the services arrive at your home. If you don't like what you hear, put a hold on the installation.
It's also an idea, if you want to be treated like a new build home that will tend to get fibre-for-everything, that any existing copper wire you may have could have 'come down in a storm', if you catch my drift...
In the years 2008-2010, we had nothing but dial-up speeds, mostly due to the distance from the exchange (about 2km or more).
We then acquired a microwave internet link paid for by the Welsh Government. In fairness, the Government did what they could to solve a country-wide problem. But they and the taxpayer simply ended up being ripped off: grants to installers were a maximum of £1000 for equipment, and so, as was entirely predictable, most charged the Welsh Government £999.99!
 |
| Free equipment from the Welsh Government - but it was not very good. |
This really didn't work very well at all, although when it did work, speeds were reasonable (about 8Mbps). The service was up and down, and often off altogether. Worse, the connection from router to the rooftop antenna generated terrible RFI, which I recorded at the time. The company, having now made its directors a lot of money, was sold off and service standards dropped off a cliff.
We got rid of that system about 2015.
We then bought a mobile wi-fi box from 'EE'. This worked very well until near the end of the contract, when we suddenly found unusual transactions that we hadn't agreed to. They tried to take a large amount of money from us, but we complained and eventually recovered all of it.
 |
| Good, until we were landed with some mysterious service charges we never used! |
That was the end of 'EE' mobile broadband.
We then tried Vodafone. This worked very well until last month, when the transceiver failed. During those years of mobile data boxes, the infrastructure locally has improved dramatically. We now have super-high speed fixed broadband fibre passing in front of our house, and so I decided to connect to this, to end our internet woes.
There was a lot of misunderstanding about the role of copper wires. When you buy a package of phone and broadband, the network operator insists on copper cable for the phone. That's OK, so long as no data is transmitted along it, potentially - and as widely reported across the UK - creating RFI. The main problem is imbalanced line conditions with VDSL2, which causes very wideband RFI, leading to some very sad stories of operators who have operated successfully in urban areas for decades now being wiped out.
The first engineer told me that, despite a fibre connection being fixed to my house last week, all my services would be along copper wire. "No way!" said I. "You can take your services and stick them where the sun don't shine!"
Then, later the same day, and entirely unexpectedly, a fibre engineer arrived. Being female, she was much more helpful! She installed everything via fibre, with the only wires being power (12V, easily converted to linear PSUs if needed), and a very short WAN cable.
In total, the system, including the two SMPSUs, generates no detectable RFI on any amateur band.
 |
| At last, broadband connected by fibre - with no RFI! |
So, if you are in the UK and thinking of a broadband package from BT, it is often now available all the way to your indoor connection via fibre alone - no copper wires at all! Just make sure to bring the engineer in for a cup of coffee as soon as they arrive, and tell them about your radios and ask exactly how the services arrive at your home. If you don't like what you hear, put a hold on the installation.
It's also an idea, if you want to be treated like a new build home that will tend to get fibre-for-everything, that any existing copper wire you may have could have 'come down in a storm', if you catch my drift...
Wednesday, 7 November 2018
LED Security Light - no RFI!
In the past, so-called security lights were incandescent units with bulbs that typically blew up after a few months. Due to the cost of the whole lamp being close to the cost of the bulb, most people would not bother replacing the light, leaving it to rust on the side of the house.
But now, we have LED lights! These offer about the same light of a 250W incandescent unit in a package that is small, lightweight and typically only uses 10W.
Of course, as someone involved with astronomy, I would very much encourage you to fit a PIR-operated unit, and ensure it is pointed downwards, where it won't uselessly light up the sky, disturb neighbours, and cause glare that diminishes, not aids visibility.
For us hams, LED lights are yet another potential source of RFI, often from unfiltered mains connections that allow the switch mode PSUs in these lights to inject interference directly into our wiring.
I bought a new LED unit earlier this week, for a demonstration of light pollution at the Snowdonia National Park headquarters. It cost me just £8. Even better, it produces no discernible RFI on any of the ham bands. All the others I've tested have been so incredibly RFI-noisy that I put them in the bin immediately.
If you want one of these in the UK, you can find them here. Elsewhere, you can probably find the same thing from the product reference number on the box pictured above, as they are mass-market things likely sold under a plethora different names.
But now, we have LED lights! These offer about the same light of a 250W incandescent unit in a package that is small, lightweight and typically only uses 10W.
Of course, as someone involved with astronomy, I would very much encourage you to fit a PIR-operated unit, and ensure it is pointed downwards, where it won't uselessly light up the sky, disturb neighbours, and cause glare that diminishes, not aids visibility.
For us hams, LED lights are yet another potential source of RFI, often from unfiltered mains connections that allow the switch mode PSUs in these lights to inject interference directly into our wiring.
 |
| No detectable RFI! |
I bought a new LED unit earlier this week, for a demonstration of light pollution at the Snowdonia National Park headquarters. It cost me just £8. Even better, it produces no discernible RFI on any of the ham bands. All the others I've tested have been so incredibly RFI-noisy that I put them in the bin immediately.
If you want one of these in the UK, you can find them here. Elsewhere, you can probably find the same thing from the product reference number on the box pictured above, as they are mass-market things likely sold under a plethora different names.
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