Happenings

We all like to hear what other hams are up to, and we'd love for you to share some of the fun projects you've been involved in.  That's what the weekly round table discussion is for, but if you've got something noteworthy you'd like to share here too -- especially if you have pictures -- just email me the information.

Also, news of upcoming events is posted to this page.

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Cheap GHz VNAs!

posted Dec 25, 2020, 2:23 PM by Charles Boling

Sorry I didn't post this in time for you to gift yourself one today. Merry Christmas!

One of the pieces of test equipment that many hams would love to have but don't want to spend the money on -- besides an FM deviation meter (Serious? $200 for uncalibrated hunk o' junk from the 70's? Why doesn't one of my cheap Chinese HTs come with one built into it? It shouldn't be that hard, and it would be useful!), perhaps a topic for another time -- is a good Vector Network Analyzer (VNA).

What's that you say, you don't even know what that is, much less that you'd been asking for one? Well, let's take a closer look. What's a network analyzer? The word "network" may conjure images of Ethernet cables & switches, but in this case it refers to LRC networks -- electrical circuits exhibiting inductance, resistance, and capacitance. The tool is often called an "antenna analyzer", because the most popular use for hams is analyzing antenna systems.

What can you do with it?  LOTS of things, but let's start with a big one: a glorified SWR meter. An SWR meter will indicate a degree of impedance mismatch by showing the amount of power that is reflected back to your transmitter. Anything higher than that coveted 1:1 shows that some power isn't being transferred to the antenna and out into the ether where you want it to go. (A 1:1 doesn't guarantee that the power's going where you want it too -- merely that it's not coming back to you -- but that's enough said about that.)  The classic way to adjust an antenna for the band you want to operate on is to use a meter to check SWR at least at the bottom, middle, & top of the band.  Measure it at multiple points and you can connect the dots to produce a more informative graph.  Wouldn't it be convenient if you could be lazy and just press a button, and watch an SWR graph over any range of frequencies appear? Neato! You could instantly see what an antenna was good for and what it wasn't (as well as if you had a broken coax)

In addition to SWR (which is derived by measuring forward & reflected power) the analyzer can compare timing/phase to compute complex impedances, showing resistive, capacitive, and inductive components so you can understand what's going on "behind the scenes" with the circuit represented by the antenna and easily compensate to create a more appropriate match. A dual-port analyzer isn't limited to measuring reflected signals, but can be attached to the "input" and "output" of an electronic circuit to make similar measurements.  Or, how about the equivalent of a TDR (time domain reflectometer -- something that sends an electrical pulse down a wire and then checks the amplitude/time of the returned signal) that compares behavior at different wavelengths to tell you where that damaged section of coaxial cable is? When you have hardware that can generate a precise signal and just as precisely measure what come back, then the rest is all mathematics, i.e. software, so if you can modify the software, you can add features and make it smarter at will.  Open-source it, so that people who are smarter than you in some areas can contribute, and the possibilities grow.

Traditional VNAs were/are the tools of the well-equipped laboratory, and very expensive -- tens of thousands of dollars.  Within the past couple of decades, I've started to see "antenna analyzers" marketed to hams at more affordable prices.  One class of these are simple self-contained handheld devices that are crude and not that big of a step up from an SWR meter.  Another entry into the market was W6BIG's AIM4170 and similar devices, one of which I bought 13 years ago for $500. It has no display, but must be attached via RS-232 to a computer running MS Windows, where its accompanying software works its magic.  It was a fantastic device when it was introduced, but only went up to 180 MHz. Over the years I've wanted to upgrade to a UHF-capable unit, but the prices around $1k are a deterrent. Besides, having to lug a laptop around with it (and keeping a copy of Windows just for that, when all I normally run is Linux) is a pain.

A NanoVNA showing a Smith chart

I was delighted when KF7ZIM sent me a link to a product known as NanoVNA. It combines the basic RF hardware w/ a low-cost mobile computing board powered by a Li-Ion battery and a full color LCD touchscreen, running Linux and an open-source program to implement the VNA functionality and UI.  It's a lot better than the cruder analyzers from MFJ, etc. -- closer to the power of my AIM but w/ the portability that I want, and best of all, it goes over 1GHz, at last granting me access to 70cm & beyond. All this starting at $50!? Wow!

Since the original NanoVNA was produced, there have been hardware and software revisions, and different companies making them using hardware of varying quality. Versions are now available that can use the 9th harmonic of the 300 MHz clock to make useful measurements up to 2.7 GHz.  Alexander & I bought one towards the low end of the market for $54 shipped.  It was a low-risk way to evaluate the platform, and it was exactly what he needed for his employer, who runs a fleet of trucks w/ CB radios.  There was a bit of a learning curve for us (the kid who wrote the software is Japanese, and there's still a lack of detailed high-quality English documentation) but we got it all set up so that all one has to do is turn it on and press the scan button to get an SWR graph of the CB band (and just a little on either side for context). Any dummy can use it to get an instant picture of the health of the antenna system on a truck.

Most pre-made devices come as kits that include the calibration loads and everything else you need to make it work.  We found that if you care about absolute accuracy you really do want to calibrate it over a narrow range of frequencies that you're graphing, but this is helped by its ability to store profiles with calibration parameters to go with the display settings. When used properly, its measurements compared favorably to my more expensive instrument.

Having a device like this is not only convenient, but educational, encouraging experimentation and helping you learn more about antennas. You may be surprised (sometimes pleasantly!) how some of your antennas behave on frequencies that they weren't necessarily designed for, and something like this can definitely aid in quickly validating (or re-validating) an antenna system and assuring you that it's functioning as intended. If you've never played with one before, or if you're looking to upgrade without spending a lot of money, now's a great time!

'Sup's that go "Boom"

posted Dec 6, 2020, 7:28 PM by Charles Boling   [ updated Dec 25, 2020, 12:34 PM ]

We like the 'sup's -
The 'sup's that go "Boom".
We're Alex & Chucky
And We like the boom.

(with a nod to the '80s' hit, "Cars That Go Boom" by L'Trimm)











KD7TJR's power supply didn't fare as well. It had previously blown a fuse and damaged a resistor. As it turns out, one of a pair of power transistors failed. Alexander removed the resistor and, after some time examining the schematic, determined that it was likely that doing so would remove the voltage applied to the base and likely reduce the load that the transistor was sinking. I was trying to get "real" work done and not paying too much attention myself, but we decided to power it up briefly and measure the current draw.

Looks like it was the wrong approach; apparently the base was biased from somewhere else and removing the resistor (which would've happened by itself had we powered it up a 2nd time with it still in there, judging from the damage done by the previous run) opened the emitter-collector gate wide, and the resulting current rush violently melted the collector pin.

The good news is that, as you can see, I did catch some good pictures of its final act (which blew a couple more components as well) in spite of the fact that the stupid camera was set for 120fps, but for some reason it merely duplicated each frame 4x, making it effectively 30fps.

If you look carefully at the first picture (click the pictures to see full-size copies), you can see a single streak coming from the collector. It progresses from there. My mini tripod disappeared, so I was holding the camera in my hand, and my involuntary jerk is obvious.  It was a loud crack and a bright flash!

It was interesting watching & listening to the video slowed down 32x (1fps); in the frame before the first one shown, you can hear the initial small "boom" that of that first spark, then you can hear multiple explosions as the fireball builds; it sounds like a barrage of cannon fire. Neato! Sad, though; we decided that it's not worth the effort of buying & replacing multiple parts when we don't even know for sure that the transistor was the root cause, so we're laying the whole thing to rest.

Power Supply Repairs

posted Nov 4, 2020, 11:37 PM by Charles Boling   [ updated Nov 4, 2020, 11:38 PM ]

Something over a decade ago, Ray bought VHF radios for all of the units in the stake and put them in the church buildings with antennas & other things needed to set up a field-expedient radio station. All of the power supplies are the same model, Samlex SEC-1223. In 2014, one of the supplies started making noise, and I determined that the cause was a set of failed capacitors. As I wrote at the time:
for several years around the turn of the century several Taiwanese
manufacturers used some bad formulas for the electrolyte in their caps
that rotted them, and millions were put on the market with severely
shortened life -- in some cases as little as a few months.  It was a
huge deal, w/ computer manufacturers like Dell taking a lot of heat and
losing a ton of money having to replace failed motherboards (I know one
guy who had a board w/ over 30 failed caps on it), and "re-capping"
high-end boards became a lively business.  That pretty much all blew
over after the 1st decade, but I suspect that these caps were part of
that group.
More testing:
Power supply open w/ arrow indicating problem caps

I tested the supply, and the output is still pretty good -- 13.8V drops
to 12.7V under 70W load w/ <1V ripple -- so I don't think any other
components are damaged yet.

I put it on a scope and confirmed that without a load there's a lot of
pseudo-random noise on it; with a slight load it stabilizes to a 2-tone
waveform w/ the primary frequency around 50kHz (I didn't bother to
measure it carefully -- just going from memory of approximate size on
screen and dial settings) and the 2nd an octave up and almost as strong
(any higher harmonics weren't obvious) with ~20% jitter.  Putting a
~60-70W load on it (my radio transmitting on high) made it go bananas,
with a large variance in amplitude and frequency, peaking at over 1V.  I
listened on another radio while transmitting and verified that no lower
frequency components were making it through unfiltered by my rig (an
IC-208H).

These 3 caps just sit across the outputs to stabilize it and work w/ the
chokes to get rid of the last of the ripples, so they don't directly
affect most of the circuit and unless they short instead of open they
shouldn't do catastrophic damage unless the inductors don't choke enough
and allow higher-voltage spikes somewhere that take out something more
important.  Judging from what I saw on the scope, that probably won't
happen, but it's possible that it would throw something upstream off
just enough to destabilize the PWM chip or something so it shouldn't be
used until they're replaced.

I found someone else who had the same problem
and learned from his mistake to measure the physical size of my caps
instead of believing the 16x25mm specs.  Sure enough, with the change in
board layout (ours is 3 in a straight line, but all the official pics
show one offset w/ inductors in the corner where it might otherwise be)
they tightened the spacing, and the 16mm won't fit!

Equivalent caps are about $1 each:

It was a good education for Alexander as I led him through the process of testing and fixing it.

Apparently, that radio was used more than the others.  Fast forward 6 years to last Sunday...
It was pretty funny today. Remember during the exercise when the Castle
Alexander &amp; Steven working on the PS

Rock radio wasn't working right?  Bp Morkert brought it to me at the
stake ctr today so I could inspect & test it, trading parts (e.g.
microphone) w/ another radio if needed. I pulled the stake radio out to
use as a receiver, turned on its power supply, and poof! Smoke began
pouring out. "Not worries -- I have another one!" I pulled out the
Longview 3rd radio, turned it on, and a few seconds later *it* began
producing smoke!  All 3 supplies were emitting a complex sound that,
well, sounded like a classic failing switching supply.

CR's supply isn't smoking yet, but it's putting out bad power. The radio
can transmit @ 5W w/o noticeable artifacts on the received audio, but as
the power draw goes up it gets worse. Needless to say, Bro. Morkert
didn't return with a radio...

I'm going to open them up and inspect them, and assuming that it's what
I think it is, I'll order enough caps to do all the radios in the stake.
 Once these are back in operation, I'll start pulling the remaining
working radios and replace the caps *before* the supplies fail....
My middle boys are going to get a lot of soldering
practice, and Alexander's going to be doing a lot of teaching.

I ordered 30 more capacitors, and Alexander & Steven fixed those 3 radios this evening. That's a total of 4 down and 6 to go! A good education for Steven; I think I'll have William help with the next few that come in.

Thurs Jul 30 Simplex Exercise

posted Jun 28, 2020, 12:23 PM by Charles Boling   [ updated Jul 30, 2020, 6:32 PM ]

OTVARC Mascot

The Oregon Tualatin Valley Amateur Radio Club has invited us to participate in their 5th Thursday Simplex Contest (previously the Fifth Wednesday Simplex Contest) starting July 30th @ 7PM (don't be late!) on 147.54 MHz FM.

This opportunity to participate with OTVARC will replace this quarter's regional ERC simplex exercise, and I encourage everyone who's free that evening to join us! Each station should keep a log of who they hear (there's a log sheet on the page linked to above), and submit it afterwards so we can see who can talk to whom. Paul Gerke, KF7SKD from Vanc. West Stake, has volunteered to sift through the reports; please email your results to both otvarc@gmail.com and kf7skd@qsl.net. When Paul's finished with his analysis, we'll see that all participants get a copy.

ERC Goals

  • Exercise your skills (esp. listening)
  • Test your equipment (emergency power, anyone?)
  • Map all the propagation paths -- who can hear whom

Operating Hints

  • Open your squelch so that you can hear weaker stations
  • Make sure you're in simplex mode (no TX shift)
  • Listen so you can get a feel for the protocol, but don't be afraid to transmit!
  • Get on early, if possible, so you don't miss anything

Logging

  • In the notes, please include a 2-digit "RS" signal report for each station heard
    • 1st digit = Readability
      • 1 = Detected but 100% unreadable
      • 2 = Occasional words understood
      • 3 = Readable w/ considerable difficulty
      • 4 = Easy copy
      • 5 = Perfect (full quieting)
    • 2nd digit - Strength
      • 1-9 (use your S-meter if possible)
      • 1 = Barely detectable
      • 9 - Extremely strong
      • If you submit a reading outside 1-9 (e.g. "0" or "S9+60") we'll probably clamp it to the 1-9 range when we aggregate the statistics.

Update:
I added an alternate log sheet, in OpenDocument Spreadsheet and PDF formats. You may find the spreadsheet a lot more convenient to use.
When done, you could export it to PDF and attach both formats so Paul and OTVARC can choose which they want to work with depending on what they're doing (printing/viewing vs. extracting data)

Simplex Nets canceled

posted May 24, 2020, 10:27 AM by Charles Boling

The Thursday & Sunday simplex nets, a/k/a "The Charles, Lloyd & Kevin net", has been canceled for lack of participation. It was a fun experiment, and I did enjoy getting to talk to my two net buddies more than once a week!

Simplex Nets

posted Mar 28, 2020, 1:35 PM by Charles Boling

To allow more opportunities for us to connect on the air -- and to stretch our simplex muscles -- we're going to add two VHF simplex nets during the week:
  • Sundays 9:30-9:45 AM
  • Thursdays 5:45-6:00 PM
Both nets will be held on 146.46 MHz. I will transmit a 100 Hz tone, but will keep my squelch open.

These will be semi-formal nets; I will announce them, and will act as net control as needed, but I predict that fewer people will participate than the repeater-based nets, and it may give the chance for more casual conversation. That said, Simplex will be a challenging reach between many points, so if you can help relay, that would be appreciated.

I will stay tuned until the designated ending time, even if there is no activity. If you don't hear anything, please call out!

Based on response, these nets may or may not become a permanent activity, and the times/days may change.

Pre-CCE22

posted Feb 9, 2020, 9:20 PM by Charles Boling

You might find this document to be of interest:

I originally received a copy via CAP. I don't see anything that would contraindicate public dissemination, but I also didn't see it on on any WA websites, so rather than post an actual copy of it here, I'm referencing the copy that ID ARES is hosting, so if someone tells them to take it down, it'll automatically break our link too. :-)

A few key points:
  • Gearing up for Cascadia Rising 2022
  • Comms is being separated a bit, because the biggest comm challenges are likely the first few days after a disaster, whereas the main exercise will focus on later response. (Y'know, we keep telling you not to expect the gov't to be there immediately? The exercises have realistic expectations!)
  • A big part of WA EMD's comms goal is to more fully/consistently use amateurs.
    • Amateurs (on average) have technical skills, i.e. we don't just wring our hands if the radio doesn't work
    • We're more useful if we train w/ served agencies and know common procedures.
      • Consider this a plug for ACS membership and ICS courses!
  • Camp Murray's getting a 220 repeater

Technician study classes in W. Longview

posted Jan 20, 2020, 4:24 PM by Charles Boling

Jeff Edgecomb (KB7PMO) is starting another series of classes to help people prepare to take the technician class amateur exam.  They're being held at 5PM every Tuesday at the meetinghouse at 1721 30th Ave, Longview, WA 98632. Contact Jeff (jmedgecomb at yahoo.com) for more info.

Rainier Stk net

posted Jan 17, 2020, 3:39 PM by Charles Boling

Rainier stake holds an ERC check-in net on a repeater system that includes Nicolai Mtn (146.76), an easy reach for many of us in the area. It's a brief net Sundays at 19:00. More details on the net calendar. We're a good link from the coast inland and in a good position to help each other, so just as we have people from Oregon that check into our nets regularly, it wouldn't hurt for a few of us to be familiar with their group.

FEMA youth camp in Alaska

posted Dec 29, 2019, 5:23 PM by Charles Boling

Region X is hosting a free (even transportation is provided) 6-day camp in AK for teens interested in disaster preparedness. To learn more and apply:

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