Ofcom latest missive
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John Fell
If you are having a slow moment ,have a read of the latest Ofcom release of Mobile phone mast radiation levels - to 4 decimal places .....
Spoiler alert - they all passed with some headroom . 73 John G0API |
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4 DPs of percent, ie resolution of -60dB Some were as high as 40dB down on ICNRP levels Andy On Fri, 28 Oct 2022 at 12:24, John Fell <john.g0api@...> wrote:
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alwyn.seeds1
Dear All,
I had a lengthy, rather heated, exchange with a technical representative of a major professional broadcast aerial manufacturer who was insisting on quoting aerial return losses to the nearest 0.01 dB. Even when I sent him the spec. of the VNA he was using, he continued to insist that, because the display on the VNA gave the return loss to two decimal places of a dB, that was an accurate result. To make matters worse, he was measuring the return loss at the station end of a 200m long feeder, albeit a low loss feeder. My suggestion that he needed to send an underling with the cal-kit up to the aerial, to arrive at a return loss for the aerial itself was not warmly received. Regards, Alwyn G8DOH _____________________________________________________ Alwyn Seeds, Director SynOptika Ltd., 114 Beaufort Street, London, SW3 6BU, England. SynOptika Ltd., Registered in England and Wales: No. 04606737 Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom. _____________________________________________________ |
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After doing about 20 years rigging. I came to the conclusion, many of those making key decisions. Had as yet not reached the level of incompetence. They justly deserved. Reg G8VHI -------- Original message -------- From: "alwyn.seeds1" <a.seeds@...> Date: 28/10/2022 12:49 (GMT+00:00) To: "UK Microwaves groups.io" <UKMicrowaves@groups.io> Subject: Re: [UKMicrowaves] Ofcom latest missive I had a lengthy, rather heated, exchange with a technical representative of a major professional broadcast aerial manufacturer who was insisting on quoting aerial return losses to the nearest 0.01 dB. Even when I sent him the spec. of the VNA he was using, he continued to insist that, because the display on the VNA gave the return loss to two decimal places of a dB, that was an accurate result. To make matters worse, he was measuring the return loss at the station end of a 200m long feeder, albeit a low loss feeder. My suggestion that he needed to send an underling with the cal-kit up to the aerial, to arrive at a return loss for the aerial itself was not warmly received. Regards, Alwyn G8DOH _____________________________________________________ Alwyn Seeds, Director SynOptika Ltd., 114 Beaufort Street, London, SW3 6BU, England. SynOptika Ltd., Registered in England and Wales: No. 04606737 Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom. _____________________________________________________ |
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That Ofcom response is expressed as percentages of the ICNRP value, not dB - presumably so the great British unwashed can comprehend it. In which case four decimal places of a linear value makes perfect sense. In a percentage, means down to -60dB (ICNRP) can be described. And anyway, 0.0001% of max allowed looks good It's all PR Andy
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Robin Szemeti - G1YFG
The more interesting question is, as (from my brief sample of reports) no site came close to the exposure limit .... by a factor of 1000 .. at what point should Ofcom simply respond "look, everything we have ever measured has been safe by a factor of at least 1000. We have no intention of measuring anything again until something changes by at least a factor of 10, or maybe 100, we'll take 10 sample readings across the country, now kindly stop bothering us". On Fri, 28 Oct 2022 at 13:06, Andy G4JNT <andy.g4jnt@...> wrote:
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Robin Szemeti - G1YFG |
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Paul G8AQA
Dear All,
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I recall making loss measurements to 0.001dB. This was simple loss and not return loss. We had to go to extraordinary lengths to achieve this. We even had to design our own connectors. All of this was done in laboratory conditions with temperature control. For technical representative I assume you meant salesman. I am pleased you did not call him an engineer as it would have brought the profession into disrepute. Regards Paul G8AQA On 28/10/2022 12:49, alwyn.seeds1
wrote:
Dear All, |
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KENT BRITAIN
"Why be Approximately Correct when you can be Precisely Wrong! (To the nearest .001 dB!)
On Friday, October 28, 2022 at 08:29:04 AM CDT, Paul G8AQA via groups.io <paulnick@...> wrote:
Dear All, I recall making loss measurements to 0.001dB. This was simple loss and not return loss. We had to go to extraordinary lengths to achieve this. We even had to design our own connectors. All of this was done in laboratory conditions with temperature control. For technical representative I assume you meant salesman. I am pleased you did not call him an engineer as it would have brought the profession into disrepute. Regards Paul G8AQA On 28/10/2022 12:49, alwyn.seeds1
wrote:
Dear All,
I had a lengthy, rather heated, exchange with a
technical representative of a major professional broadcast
aerial manufacturer who was insisting on quoting aerial return
losses to the nearest 0.01 dB.
Even when I sent him the spec. of the VNA he was
using, he continued to insist that, because the display on the
VNA gave the return loss to two decimal places of a dB, that was
an accurate result.
To make matters worse, he was measuring the return
loss at the station end of a 200m long feeder, albeit a low loss
feeder. My suggestion that he needed to send an underling with
the cal-kit up to the aerial, to arrive at a return loss for the
aerial itself was not warmly received.
Regards,
Alwyn G8DOH
_____________________________________________________
Alwyn
Seeds, Director
SynOptika Ltd., 114 Beaufort Street, London, SW3 6BU, England. SynOptika Ltd., Registered in England and Wales: No. 04606737 Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom. _____________________________________________________
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Julian, G3YGF
Typically, in London, they are around 0.2% - that is about -27dBm.
Seems a bit high though...
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It all depends on how they chose the sites and whether the different frequency bands were actually measured at the same instant... The results are probably good to +/- a few dB... But measurements to 1/1,000,000 are rather meaningless - note the disclaimer with it: Disclaimer:
The results detailed in this report apply only to the tests made
at the reported time, using the test equipment detailed. They do
not indicate that on another date an identical set of results
would be achieved, due to changes in local environmental
conditions or other factors which may or may not have an effect on
the measurement results obtained at that future time.
The presentation of statistics is an art form... Julian On 28/10/2022 14:09, Robin Szemeti -
G1YFG via groups.io wrote:
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Wilko
No amount of expert knowledge will ever convince the tin foil hats. Not in the UK, not in NL, essentially nowhere on the planet.
Now.. who mentioned *Dark* Ages? As long as they can watch silly cat videos or tweet nonsense they are 59 happy😵 bah.. Wilko PA1WBU
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Alan
John Thanks for the link to the Ofcom Survey. I had a look at one area, Stevenage Herts, close to Ofcom's Baldock Base. They surveyed five places without saying exactly where they were. They used a 3 axis E-field antenna and a receiver from Narda. There is a very unusual issue with above 2.5GHz field strength
measurements, that the base stations can use beam forming to steer
a narrow beam at a user and that different usage patterns will
cause different intensity beams to be radiated in different
directions at different times so measuring the exposure at one
point is not so simple. This is overcome by a method described Here where you demand a high data rate signal from the base so it
sends you a strong and narrow beam which nicely defines the max
possible exposure unless some one else puts a similar demand on
the base station. I have never seen much written about the methods used in 5G but there has been much reporting of how 5G can cause Covid and that some idiots have tried to burn base stations but often hit UHF Tetra bases or old tech cell sites instead. There are a few clues in the Narda info about 5G which is in the link. The 2.5 GHz and above bands are used in small cells in high
population density areas, the UHF bands are used in rural
locations where the range is much longer. An interesting detail is
that a sheet of coated glass can produce a 30 dB loss at 20 GHz.
So 5G might experience very high losses inside modern offices and
apartments that have been built for low heat loss and low Solar
Gain with metal coated glass and foam & foil insulation. I have used Pilkington E-Glass ( which has a metal layer on one
side) for screening at LF & MF in the distant past. It might
be possible to find other uses for such glass. Etching the
metallisation could produce frequency selective surfaces and a
microwave equivalent of Polaroid sheet. It might be possible to
plate it up if fewer ohms/square were needed. I had a look at the Narda propaganda about their antennas, could not find anything about how they make a three axis E-field antenna. They do make a higher frequency antenna ( 24.25-29.5GHz) with an internal down converter so that the cable has up to 6GHz signals. So returning to the opening topic of the Stevenage Field survey, where you look makes a big difference, the area is rural and high/medium density residential, the frequency bands give a clue where the survey was made but just where you survey has a major impact on the results, leaving out the survey locations seems odd as does having so few locations. Locally ( Welwyn Garden City Herts) there has been a substantial
number of resident's objecting to 5G masts but there have also
been many out of area objectors who seem to be trying to slow/stop
5G deployment for their own reasons. I have spoken to many local
residents about their concerns, there are two main objections-
"eyesore" and " health risks" but the Government has tried hard to
push through deployment giving objectors very short appeal times.
The people that have objected have very little understanding of
the "Tech" and the real risks, they are frightened by the unknown
invisible radiation. I do feel that the deployment could have been
handled very much better and that the fear could have been greatly
reduced with better information from the Government and the
Telecoms Operators. 73, Alan G8LCO
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John Fell
Thanks for the link Alan.
24GHz is stopped quite well through tinted double glazing , where 10GHz and below is not . The on the fly beam forming is technically interesting and the stated possibility of increasing the active elements from 32 upto 1024 , if fully combined as a spot beam , would be very interesting .I have no idea , but would think the maximum call capacity must be a tad limited on these 5G systems trying to accommodate all the marginal field strength mobiles ? The German way sounds to be based on common sense - if the maximum PA output /cable run length -system combining losses /antenna gains/range length are all factored , it should be possible to pre-determine the anticipated field strengths at any point within the normal coverage and just measure for compliance ? ( allowing for the beacon and traffic mode level changes) . I could see Drones involved and all sorts of toys to keep the lads in work for ages - what happened to the tethered or circulating Airship based lookdown distribution systems ........ah Johny foreigner's drones ...pop. 73 John G0API On Fri, 28 Oct 2022 at 15:41, Alan <g8lco1@...> wrote:
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Jules - M0UGA
John,
Off topic to a degree but if you have an interest in phased arrays & beamforming do watch the following video on YouTube. https://www.youtube.com/watch?v=B_icccUpxV0&list=PLOJ53vjDKIf8dmi6DN5ylqi2iZnbu2lpP&index=101&ab_channel=JonKraft It certainly gives you a feel for the toys that available are out there if the bank balance can accomodate. The essence is though that the technology is trickling down.. It arrived in commodity WiFi routers some years back on a far simpler and smaller scale than the cellular networks are really just beginning to employ but to me at least it is all fascinating. Cellular networks (LEO satellite internet constellations too) and the equipment manufacturers behind them employ some state of the art technolgies that perhaps I could talk about for hours. The average Joe doesn't care how it works, just that it does, but on a deeper level the way that cellular radios and associated tech has evolved is complex, built layer upon layer and truly a modern wonder. It is a rabbit hole that has kept me occupied for many, many hours both professionally in years gone by and as a hobbiest ;-) 73 |
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Perhaps you do a write up giving an overview of technologies as they've grown - RadCom or radcom plus would love it. Andy On Sat, 29 Oct 2022 at 14:56, Jules - M0UGA <m0uga.uk@...> wrote: John, |
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John Fell
Jules , Andy just beat me to it . I am sure a technology overview article in Radcom would be very welcome . Thanks for u-tube link 73 John G0API On Sat, 29 Oct 2022 at 15:12, Andy G4JNT <andy.g4jnt@...> wrote:
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Cheers Andy LoL
Maybe & I'm not saying no, but it would be a book not a magazine article. From a hobbiest point of view I guess we are always looking to see how some technologies might be employed to benefit us pratically in some way.. Other than perhaps working LEO sats (and I think someone already has an ongoing project going on there..) using beamsteering and spreading knowledge generally, such an article might at least generate some interest in "How It Works" ;-) What some handsets are now capable of is a case in point. For example, the latest top of the line devices with compatible Qualcomm baseband silicon are now capable of aggregating 6 carriers (6CA and sometimes referred to as "layers") across multiple bands at the same time to gain bandwidth as that bandwidth is always in contention with other handsets on the network. How many bands are there now? Well lots, and that is only going to increase with Ofcom consulting this year on 24/40Ghz MMwave cellular in the UK. Currently it's my understanding that EE are using the most with 5 layers available at some recently upgraded sites but where I am in Herts I'm only seeing 4CA, so I'm feeling hard done by ;-) Just don't get me started on the SDR cabinet & masthead radios being rolled out across the networks which are capable almost beyond belief and going back to where this started those SDRs are in turn connected to the stunnningly capable 'Massive MIMO' panels doing their thing. Truly "future tech" that is actually only in it's infancy from a utilisation point of view at this time. Many people's interest in cellular ends with have I got an internet connection to log on to KST?.. It's just a phone!! Well it's really not. Like I said hours ;-) 73 Jules |
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John Fell
Interesting u-tube thingy Julian. My youngest Grandson would recognise the library of RF parts from Minecraft ..... That kit must have cost the developers a lotta money but a rapid prototype system that is anchored in real world performance . It is becoming a grid based World we live in . 73 John G0API On Sat, 29 Oct 2022 at 14:56, Jules - M0UGA <m0uga.uk@...> wrote: John, |
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John Fell
Well I for one am interested in explanations from within the Industry Julian. I guess a few others on here also work still . My standby battery banks are fully charged and the inverter can power the TV and portable LED lights , so I will be OK - for about 5 Hrs .... 73 John G0API On Sat, 29 Oct 2022 at 15:57, Jules - M0UGA <m0uga.uk@...> wrote: Cheers Andy LoL |
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Jules - M0UGA
I'll start work on it. Publication date TBC ;-
I'm sure you'll be OK this evening so don't have the batteries on standy. As an aside the fella behind the YouTube vid on another video gives you a nice insight into further expansion and experiments that can be done with recent revisions to the ADALM Pluto. As noted in the video link posted (if folks don't watch it), want to get your Pluto on 10Ghz? It can be done... |
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