The real electromagnetic emissions danger

I live 1.2km away from Sutro Tower in San Francisco. At my wife’s request I was trying to calculate the safe radius at which emissions from the transmitters at Sutro Tower are of the same power as a cell phone held a meter away, with back-of-the-envelope calculations using the inverse square law and Wikipedia’s table of radio powers.

I was shocked to find out the total power from the transmitters is about 8 megawatts, not in the kilowatt range I was expecting, and once reached 29MW. For comparison, the power of France’s first-generation PWR nuclear reactors is 900MW, and a typical cellular tower is 100W to 500W. If I use 2W as the reference, this yields a “safe” radius of 2km, which excludes many desirable San Francisco neighborhoods like Twin Peaks, Forest Hill or Noe Valley.

I looked up the most recent Environmental Impact Report following the DTV transition, and it mentions a FCC maximum allowed flux level of 0.2mW/cm2, and the measured levels in the Midtown Terrace neighborhood immediately adjacent to Sutro Tower reach 4% of this max level.

On further investigation, this is not one of those situations where US standards are significantly more lax than those in Europe, as France or the UK have the same level, derived from an international NGO called the ICNIRP. Interestingly, according to the WHO the maximum allowed emissions in such environmental paragons as Russia and China are one hundredth as high as those in the US or Europe and are just as science-based as those from ICNIRP (remember, for all its faults, the Soviet Union ranked very highly in maths and physics education & research, and in health care).

The ICNIRP/FCC standard is equivalent to a 25W isotropic emitter within a 1 meter radius, or 12x 2G GSM cell phones. Anyone who has experienced the squeal of unshielded and unpowered speakers next to an actively transmitting GSM phone will be skeptical about their claims that this is a safe level. Their methodology is based solely on the thermal effects of non-ionizing radiation, as if this were a mere microwave oven shielding exercise, and assumes that cells are otherwise unaffected by electromagnetism or cumulative exposure. This seems unwarrantedly optimistic.

People worry about cancer risks associated with radio frequency emissions from cell phone towers and cell phones themselves, but the real risk comes from overlooked obsolete technologies like TV and FM radio.

What to do? Getting a site survey from a Professional Engineer using calibrated equipment costs $1,500, which is something you would only do as part of a final inspection while buying a house. Most RF power meters sold on places like Amazon, usually in the $300 range, are pieces of junk with suggested applications like detecting paranormal activity and ghosts. Most likely solid engineering and metrology are optional given their application domain. Professional T&M gear like an Agilent V3500A or a Wandel & Goltermann/Narda EMR-300 cost $2,000 and $6,000 respectively, so the DIY route is also expensive.

Update (2014-03-08):

My father worked on some projects in the Soviet Union in the Seventies. He told me their workplace safety standards were much more stringent than the ones in the West. Workers were not allowed to lift weights above 25kg, for instance.

Posted in San Francisco, Soapbox | 1 Comment

Fixing Mac software update NSURLErrorDomain error -1012

Software Update for system components on my home Mac Pro has not worked in a while, and I have had to resort to manually downloading and applying updates. The updates just wouldn’t appear in the Mac App Store app where they normally should.

After upgrading to Mavericks, I finally figured out why. Instead of silently ignoring the updates, Mavericks displays a not-so-helpful error message “NSURLErrorDomain Error -1012”. On inspecting network traffic from the App Store app, I noticed it connects using TLS 1.2 to, then aborts. It then hit me – in 2011, after Comodo was hacked, apparently by elements affiliated with the Iranian government, I revoked the trust setting on their root certificates. The certificate for is signed by Comodo, and thus Software Update could no longer establish a secure connection to Apple and that’s why it was failing.

This is not the only time a Certificate Authority was hacked. Dutch CA Diginotar, which included the Dutch government among its clients, suffered a breach, apparently also involving Iran. Microsoft, Mozilla, Google and Apple promptly revoked Diginotar’s root CA certificates, which quickly led to the company going out of business. I guess Comodo is larger (the EFF calls them “too big to fail”) and better politically connected (it helps when you have people like Phillip Hallam-Baker on the payroll), and managed to elude the same punishment it richly deserved.

Apple should really step up its game and ditch a security provider which demonstrated incompetence at its alleged core competency, and I filed Radar bug report 15328323 to urge them to do so. In the meantime, the way to fix the error message is to temporarily reinstate trust in the Comodo root CA.

Update (2015-10-29)

At some point in the last 2 years they switched from Comodo to Symantex (probably 2014-04-13 when the current certificate was issued). Unfortunately, Symantec has its own problems.

Posted in Mac | 1 Comment

Afsheen’s mindset list

Beloit College is famous for its Mindset List, which explains to teachers the radically different world view students have, because their assumptions and experience are different. One example from this year’s list: “GM means food that is Genetically Modified”.
I tried to imagine what the list looks like when my daughter starts University.
Some are no-brainers, as they have already occurred:

  • A phone call has always involved both video and sound
  • A computing device is always touch-enabled

For some others, I may have to go out on a limb:

  • Cars have always been self-driving

Update (2015-08-25):

  • House roofs have always been tiled with solar panels
Posted in Soapbox | Comments Off on Afsheen’s mindset list

Vancouver vacation tips

  • Swan Laundry will pick up your laundry at your hotel, wash and fold it, and return it the same day for a $50 flat fee.
  • Wind Mobile has an unlimited 3G hotspot plan for $35 per month (they will throttle you if you exceed 10GB in a month), a better deal than any US carrier offers. They sold me a refurbished Huawei hotspot for $45 (why should the NSA have all the fun listening in?)
  • Urban Fare is an excellent place for breakfast and fancy groceries, specially the Shangri-La location.
  • The Blue Water Cafe is my favorite restaurant in town.
Posted in Uncategorized | Comments Off on Vancouver vacation tips

The wild parrots of Forest Hill

I got an unexpected but quite welcome treat this morning for my birthday. A mini-flock of 6-8 red-masked parakeets, better known as the wild parrots of Telegraph Hill, descended on a hawthorn tree in my back yard and proceeded to gorge themselves on its berries for nearly an hour.

Posted in San Francisco | Comments Off on The wild parrots of Forest Hill

Street sweeping reminders in iCal

Parking signSan Francisco sweeps streets twice a month in residential neighborhoods, and you will be fined if your car is parked on a street being swept. On my street, the schedule is the first and third Monday of each month, between 9am and 11am. I was trying to create reminders to myself in my calendar. Unfortunately, iCal does not have the ability to specify a recurring event with that definition.

No matter, Python to the rescue, the script below generates a year’s worth of reminders 12 hours before the event, in iCal vCalendar format. It does not correct for holidays, you will have to remove those yourself.

"""Idora street sweeping calendar - 1st and 3rd Mondays of the month 9am-11am"""
import datetime
Monday = 0
one_day = datetime.timedelta(1)
today =
year = today.year
month = today.month
def output(day):
  print """
SUMMARY:Idora street sweeping
""" % {
    'end': day.strftime('%Y%m%dT110000'),
    'start': day.strftime('%Y%m%dT090000')
for i in range(12):
  day =, month, 1)
  while day.weekday() != Monday:
    day += one_day
  output(day + 14 * one_day)
  month += 1
  if month > 12:
    month = 1
    year += 1
Posted in Mac, Python, San Francisco | Comments Off on Street sweeping reminders in iCal

How the iPad Mini killed my iPhone

The single greatest feature of the iPad is the fact it cannot receive phone calls. Despite being a telecoms engineer by training, I despise phones, and it seems the millennial generation shares my disdain, as it favors less intrusive means of communication like texting.

The iPad is an essential device for me. I am on a 2-year upgrade cycle (at best) for phones, a 5-year cycle for my desktop Mac Pro, and have stopped using laptops altogether, but I will get every single iteration of the iPad. Now, even though my jacket has a pocket sized large enough to hold my full-sized iPad, the weight and bulk means I seldom did so, and kept it in my bag, which I rarely take out with me when going out for lunch. When I saw the iPad Mini and how lightweight it was, I bought one and started carrying it with me all the time.

The Mini is not a replacement for my Retina iPad, as my worsening eyesight makes it a strain for sustained reading, which is why I kept my grandfathered unlimited AT&T data plan on the full-sized iPad and got a limited Verizon plan on the Mini.

No, the device that was displaced is actually my iPhone. The iPad Mini weighs barely twice as much, is thinner, fits in my jacket pocket but has a screen 4 times the size while remaining single-hand-holdable, and is actually usable as a web browsing device or eBook reader, unlike the iPhone’s cramped screen. I don’t believe in the 5-inch phablet form factor, which combines the cramped screen of a phone with the the bulk of a tablet, i.e. the worst of both worlds. I find I never use the iPhone as anything else than a dumb phone any more. I consume less than 60 minutes of voice per month, and if my wife and my startup’s co-founder would let me, I would ditch mobile phones altogether.

Alas I am unable to cut the wireless phone tether, but there is no point in my spending $100 a month on an unlimited data plan for my Verizon iPhone 4, so now that my contract ended, I ported my number over to my old unlocked AT&T iPhone 3GS with a prepaid plan from Airvoice (a MVNO that has the cheapest rates I could find online). At $0.10 a minute without any exorbitant cellco taxes or spurious surcharges, I can expect to spend $6 a month, or 94% savings. That more than covers the $20 a month I pay extra for the iPad Mini’s data plan. The only reason I still use an iPhone instead of switching to a dumbphone is the automatic address book synchronization with my Mac and iOS devices.

Posted in IT, Soapbox | 2 Comments

The ultimate irrelevance of image quality

Months ago I showed my father how to take screen shots on his iPad and iMac, and he routinely takes them while using FaceTime video conferencing with my 1 year-old daughter. Due to poor bandwidth at home (we live in San Francisco and are subject to the tender mercies of AT&T’s not-even-third-world-grade DSL), the image quality can be described as blurry VGA at best. Yet he is happy with the results, and even made a photo book featuring many of these screenshots, showing the wide range of fleeting expressions she displays. When printed at passport photo size, the fuzziness is surprisingly passable. He has also gotten my technophobe mother in the game.

I spend a lot of time obsessing over the finer points of camera and lens technology, and how to wring the best technical quality out of my photos, but my parents show how content trumps presentation.

Posted in Photo | Comments Off on The ultimate irrelevance of image quality

Sony RX1 first impressions

Despite my hatred of all things Sony, I purchased two of their cameras in the last few months: a RX100 for my wife, and a RX1 for myself. the bragging rights of a full-frame sensor with a Zeiss 35mm f/2 prime were too much to resist.

  • This thing is built like a tank. It feels very dense.
  • The mode, AF and exposure compensation knobs, while not locking, have tight detents and are impossible to knock off their settings by accident.
  • The big lens means limited handholds, and the lack of a textured grip means it is quite slippery. I dropped mine on a concrete floor, entailing expensive repairs (it was still functional, but the focus ring was no longer spinning smoothly). A wrist or neck strap is a must-have with the RX1.
  • It is not compact by any means, comparable to the Sigma DP2 Merrill in bulk. Due to the lens protrusion, it is less pocketable than my Fuji X100.
  • The lens, while excellent in terms of sharpness and vignetting, has very severe barrel distortion. Lightroom can correct for that, but you lose resolution in the process.
  • Unfortunately it is merely a Sonnar, not a Planar or better yet a Biogon. I don’t remember the 35mm f/2.8 Sonnar in the Contax T3 having this much distortion, though.
  • Autofocus is only so-so.
  • Image quality at high ISO values is outstanding, as you would expect from a full-frame sensor from the leading manufacturer today.
Posted in Photo | 4 Comments


This is a popup the iOS6 App Store shows me when I try searching for a Google Maps app.


Posted in Mac | 1 Comment