Sunday, November 17, 2019

On the air with new antenna!

You can see our new 86 ft inverted-V-non-resonant dipole on top the "Whitfield" building at Evergreen Woods, our new QTH.  Fed by 400 ohm ladderline to our 2nd floor apartment at the right, it was a long slog to get installed.  Lots of help from friendly facilities staff, however.  A 4:1 balun connects our ladderline to either the Flex-6500 directly or through a Heathkit SA-2060A Antenna Tuner.

First test shows it's a good 40 M antenna, easily matched with the built-in ATU of the Flex-6500.  Other bands can be a challenge, but the SA-2060A will tune this system over 160 - 6 M -- at least if you're willing to crank those knobs!

My first on-air test was on 80 M with the SA-2060A.  This is a difficult match, because the 86 ft dipole is close to a quarter-wave at 3.6 MHz.  Does it work?  I set it up with WSPR at 5 W transmit power to see what came back.  Partial results of the first few minutes:

Timestamp Call MHz SNR Reporter RGrid km az
2019-11-18 02:36 AA6E 3.570022 -24 HB9TMC JN46lj 6279 55
2019-11-18 02:38 AA6E 3.570021 -24 PA0O JO33hg 5815 48
2019-11-18 02:36 AA6E 3.570022 -24 TF1VHF HP84wl 4091 34
2019-11-18 02:34 AA6E 3.570025 -27 KA7OEI-1 DN31uo 3263 284
2019-11-18 02:34 AA6E 3.570023 -18 VE6JY DO33or 3250 309
2019-11-18 02:38 AA6E 3.570022 -27 KX3DX DM79 2723 276
2019-11-18 02:34 AA6E 3.570022 -25 N6GN/K DN70ll 2697 279
2019-11-18 02:34 AA6E 3.570022 -26 N5SNT EL09wq 2618 249
2019-11-18 02:38 AA6E 3.570018 -25 KI5WA EM11jk 2435 251

So I think we pass.  Best DX is HB9TMC in Switzerland, 2279 km = 3901 miles, with a Kp index of zero suggesting OK propagation..

I had been worried about interference from our building HVAC and other systems. It's there, but so far it's no show-stopper.  My first tests, inside the apartment, were a total disaster, but being 20-25 feet above the roof gets rid of most of it.

Thursday, August 15, 2019

Casing the Environment

We have completed our move to Evergreen Woods, at least to the point of unpacking many of our boxes of "stuff".  Time to check out the Electromagnetic Environment. 

It's not all good or all bad. The fact is that we're inside a fairly large complex of 249 apartments and commons buildings.  We are in a rural/suburban setting, but the buildings have complex systems for HVAC, data networks, and power distribution.  So we expect a somewhat challenging RFI situation for HF.  You see one example above.  All the peaks (separation ~106 kHz) seem to come from one source that probably gets here via the AC power line.

I am using a Flex 6500 SDR as an RFI receiver with an EMCO 6502 active loop antenna.  The antenna sits at my new second-floor operating position, not far from some metal objects that probably affect the measurements.  The proposed antenna site is on the roof above the third floor, which is probably (hopefully) a somewhat better location!

Zooming in to get some finer detail, we see three of these peaks in the 40 M band:

A working hypothesis is that these may come from the building elevator system, with the glitches occurring during elevator motion.

This 106 kHz frequency comb is not quite fatal for ham radio, because in most cases you can choose an operating frequency away from the RFI.

There seem to be several sorts of RFI that become visible at various operating frequencies and various times of day.  Some of them are quite broad (no narrow spectral peaks), and some are impulsive, like ignition interference or PLC-type digital signaling.  The Flex 6500 has several noise blanking options that are at least partially effective.

The antenna is probably going to be placed above the flat roof shown below:

A diagonal run of about 100 ft looks possible, using 20 ft masts.

Stay tuned for further developments!

Wednesday, July 03, 2019

Migrating from Branford to North Branford CT

AA6E moving on, see my web site:  The big shack picture is fading into history.

We are thinking about quality instead of quantity here, as far as the ham activity goes.

Saturday, June 15, 2019

Beginning of the End for FB

I killed off Google+ last year and started a little tradition.  Today, I've killed off Facebook.  At least, I'm deleting my personal account at FB.

Why would I do that?  Glad you asked!

  • Facebook has a near monopoly position in social media.  Benefiting from the "network effect" ("value" increases as the square of the number of users increases), FB has triumphed over all its competitors in the medium-long-form sharing segment.
  • Monopolies are generally bad.  Anti-trust law evolves much more slowly than technology.
  • Facebook governance is effectively in the hands of one individual, who shows little appreciation for the public interest or the social impact of his company.
  • As a "free" service, users are persuaded to share way too much data with the service, often thinking it's just a matter of keeping up with friends or touting our lifestyles to the world.
  • Facebook makes lots of money by packaging and reselling our data to commercial or political interests.
  • For many users, Facebook is addictive.
  • The Facebook model especially encourages evil forces (read Russia or US ultrapartisans) to influence our political system, spreading rumors and all kinds of divisive false information.
  • Facebook has very little "quality control".  There are weak attempts to suppress pornography,  political abuse, and illegal conduct, but these are not very effective.  For FB, quality control means reduced profits.
  • Apart from the shady business model, Facebook has a serious "signal to noise" problem.  Over time, your friends (and friends of friends) can easily overwhelm your news feed with irrelevant and distracting (to you) material.  As a reader, you have little control over what you see in your news feed.
  • The selection algorithms are obscure to users.  They are meant to keep you engaged and clicking, but not to be useful.  It can be really hard to return to a particular item you remember seeing a few hours ago.
None of these points are particularly original, I know.  But you did ask!

I'm still here on Blogger (another "free" service).  It's part of Google, and Google is another collector and reseller of my data, I know.  Especially when I use Android, Drive, or Maps, or many other services.  I use Twitter, too.  Twitter is short form (mostly), and I seem to be better able to filter what I read.  And there's Amazon, and there's even Reddit, and more.

Saturday, April 06, 2019

Antennas, cheap

We are going to be taking down the ham antennas, because we're moving to a retirement community.  This happens.

On the positive side, our new community is interested in supporting amateur radio (to some extent?), and we may have a chance to develop a new "farm".  See my article on ham radio in retirement communities.

Sunday, August 12, 2018

Some AREDN progress

We have been working on bringing up an AREDN mesh network at ARRL HQ and here at AA6E.  AREDN, the Amateur Radio Emergency Data Network, has developed from the HSMM project (High Speed Multimedia, see web sites here and here.)  AREDN supports a "mesh network" running under FCC Part 97 (Amateur Radio) rules on allocated frequencies some of which are close to standard "WiFi" (2.4 and 5 GHz).

Ubiquity Nanostation Loco M5 AREDN node
What is mesh networking?  Simplified, it is a way to interconnect more or less randomly located network nodes that may come and go, such as in response to emergency requirements.  Each node may originate data or may relay data to adjacent nodes. Networking software automatically routes packets by the best paths through the mesh, from source to destination.  Certain mesh nodes may have gateways to other networks, such as the commercial Internet.  Certain nodes may have special servers (web, email, file, etc.) that are made available to the network.  In general, AREDN mesh networks are set up to be independent of commercial communications services as much as practical.

At AA6E and ARRL, we have implemented a test network to learn about AREDN technology and to try out configurations that might support a variety of routine and emergency communications needs.  The first setup uses up to 4 Ubiquiti NanoStation Loco M5 devices with custom AREDN software.  These form a small-scale mesh, currently all within the ARRL Laboratory.

A test bed setup at AA6E uses two of these nodes to demonstrate network capabilities.  Below is a block diagram of the tested network.
The AREDN network is at the right.  One Loco M5 device supports a laptop computer (where I am writing this article).  Through the radio link at 5.9 GHz, the two Locos support a bit stream of up to about 30 Mb/s using a 10 MHz RF channel.  As seen by the laptop, the Loco provides an IP address through its own DHCP server.  Traffic is routed to the second Loco, which in turn supports two VLANs (partitions of a single Ethernet connection).  One is a generic "LAN" connection that will support Ethernet devices like the Raspberry Pi which is acting as a small webserver for our test.  The Pi will also support SSH, VNC, and many other services as needed.

The second switch port supports another VLAN for "WAN" connections, e.g., to the Internet.  Through the Internet router it obtains an address on the household LAN.

L to R: Raspberry Pi 3; Netgear GS105E VLAN-aware switch; Toshiba Laptop

This setup demonstrates many of the functions we would need in an operational network.  We still need to set up facilities for node to node bridging that we would need to build up a larger network, supporting multiple operating bands, etc.

There is nothing "new" here.  It's all been done elsewhere, but we are climbing our learning curve.

Saturday, April 28, 2018

Gone Streaming. Sorry, Comcast.

So sorry to hear that the cable TV industry is suffering because of the growing defection to streaming media services.  See this recent Fierce Cable article. We seem to be entering a meltdown, where increasing cable prices encourage more of us to "cut the cable" and go to streaming solutions.  That means that cable companies have to increase their rates, which leads to more defections.

You don't want to be the last one to switch over in a game like this.

We aren't the first by any means, but our sky-high bill finally got to be too much when the last of our introductory discounts disappeared.

Technically, the Comcast service in our area is very good.  Internet performance has inched up over 250 Mb/s.  Unfortunately, the monthly charge is running around $1 per Mb/s.

So we had an abundance of bandwidth and a similar abundance of channels -- most of which we never used.  The Internet bandwidth is sweet when I want to download a new Linux DVD every 6 months, but how much is that really worth?

TL;DR. We have just dropped cable video and phone service and cut back our Internet speed to 60 Mb/s -- quite enough for our small household.  These changes cut our Comcast payment by 70%!

The new system is built on a Netgear CM600 modem, an Asus RT-N66U WiFi router, an Ooma Telo VOIP box, and a Roku streaming device. (Our nice Sony HDTV predates "smart TV".*) In addition, we're watching more over-the-air TV, mainly to get the PBS Newshour live.  (PBS hasn't figured out how to live stream, it appears.) In this location, we need an amplified antenna that mostly works for us indoors, but it will need to be installed outdoors for solid performance.

The thorny issue now is how to make sense of the many streaming services.  People worry about what will be happening without "net neutrality".  The Internet is likely to fragment into walled gardens.  As others have pointed out, this already is happening in the streaming market.  Do I want Amazon Prime, Netflix, Hulu, CBS Now, etc.?  There are several providers for live streaming TV channels, too. Each of these has some interesting content.  Even if I didn't mind paying for all of them, the data management gets to be overwhelming.  There is no simple navigation or program guide I know of that crosses those boundaries.

Brave new world?  Chaos?  All of that. Glad to help the cable industry find its destiny.

* Smart TV: I worry that the "smarts" get obsolete well before the "TV" does.  Integrating them should help simplify the user experience, but the quick obsolescence is a worry.

Monday, April 09, 2018

Frequency Measurement Test

The old way: BC-221 meter
April 6, 2018 was my second attempt at the ARRL Frequency Measurement Test in which amateurs are invited to measure the exact frequency of a test signal transmitted from a central site. The first time, years ago, I came out OK with a manual procedure using my old TenTec Orion radio, carefully calibrated against the US NIST Time and Frequency Station WWV. Measurement accuracy depended on an imprecise estimate of the WWV calibration compounded by an imprecise measurement of the W1AW test signal.

This time, we've upped the ante, using the FlexRadio Systems 6500 transceiver (an SDR radio) with its GPS Disciplined Oscillator as a master frequency reference.  The reference is said to be accurate to some parts in 1012, though we have no way to verify that number at this time.  If the receiver is tuned to a known frequency just below the test signal in upper sideband mode, so that the received signal shows up as an "audio" tone.  (In this SDR receiver, there is no "audio", since everything is digital.  That bypasses various audio measurement problems that might otherwise have cropped up.)  The fldigi software package is used in its "spectral analysis" mode to accurately measure the offset, combined with the known local oscillator tuning, to yield a good measurement of the unknown RF frequency.  The software outputs an Excel CSV file that records time and best-fit frequency each second.

Here in Branford, CT the antenna for 20 M is a 3-element SteppIR at 40 ft pointed west. For 40 M and 80 M the antennas were dipoles oriented NW-SE, more or less.

This exercise involved transmissions on the 20, 40, and 80 Meter amateur bands from K5CM in eastern Oklahoma.


The actual numbers as transmitted are reported on the FMT results page for 2018.

Band  F Measured (Hz)  F Actual (Hz)   Error (Hz)
20M  14,121,963.42 +/- .08*  14,121,963.34   +0.08
40M   7,064,257.09 +/- .20*   7,064,257.06   +0.03
80M   3,598,169.5**   3,598,169.73   -0.23

* Error bar quoted is 1/2 the total peak-to-peak frequency excursion in the 2 minute test transmission.
** 80M results were compromised by a data handling problem.  Precision is reduced, and an error bar could not be estimated.

WWV reported geomagnetic conditions Kp=2 and Ap=9 during the test.

The graphs at the right show the (almost) raw data measured on the 20 and 40 M bands.  The 20 M signal strength was quite good, touching S9+10 dB, and the measurements appear largely free of statistical noise. The major feature is an sine-like variation that presumably reflects true changes in the signal data path.  I believe that the "glitch" at the left is an artifact of an initial mis-adjustment of the radio.  It was left out of the average calculation. (Ignore the "even samples" tag.)

The 40 M signal was about S8, i.e. up to 16 dB weaker than on 20 M.  This probably produced much of the short-period noise on the graph. However, we might also expect the ionosphere to produce more variability on the lower frequency.

For 20 and 40, we calculate a simple average frequency, after eliminating the initial points on 20 M.  Note that we might have done better of we could weight the samples according to instantaneous signal strength.  There are two sharp dips in the 40 M data that may well have arisen from deep signal fades.  If they were eliminated, we would have a slightly higher frequency estimate, which would have increased our final error value.

Because of the problems with the 80 M data, there is no meaningful graph to plot for that band.


The final error (Measured - Actual) is under 0.1 Hz for the two fully analyzed bands, while the 80 M error is -0.23 Hz based on fewer data points.  These are surprisingly good, leaving relatively little room for improvement given the "noisiness" of ionospheric propagation conditions.  Presumably, we might get a somewhat better measurement if we had a longer test run, perhaps 5 or 10 minutes or more, or if we got lucky and had a period of super-stability in the ionosphere.