Saturday, March 31, 2018

The April 2018 Communicator Newsletter



Here is the latest Communicator 

In this edition you will find over 40 pages of Amateur Radio News from the South West corner of Canada and elsewhere.

We'll share several projects, tips and how-to's. You can download it directly from https://goo.gl/N15c1b .

If you print The Communicator, set your printer to ‘fit to page’
As usual, there are many hot links in the articles to websites as supporting material.

The last Communicator made it to 4 continents. As always, thank you to our contributors, and your feedback is always welcome. My deadline for the May edition is April 20th. If you have news, photos or projects from your Vancouver area club, events or other items of interest please email them to the communicator@ve7sar.net





Thursday, March 29, 2018

Surrey Amateur Radio Licensing Course



Last Chance... We Start Tuesday, April 3


The Surrey Amateur Radio Club generally offers two Basic licensing courses per year. Last year we graduated 27 members who attended our classes. These new 'Hams' came from all walks of life, some with technical backgrounds, most without. Many were interested in emergency preparedness and staying in touch if the BIG one hits.

We have set the start for the next class as Tuesday, April 3rd at 6:30pm. We use the excellent classroom facilities courtesy of the Surrey Fire Service at their training facility 14901 64th Avenue, Surrey, BC.

Have a look at what Amateur Radio can offer:

An exciting modern hobby



A useful emergency communications skill





Have a look at our Basic Course brochure and poster



GNUradio: Build Your Own Receiver








A bit of time and reading and you can enter this fascinating facet of the hobby (no license needed)

GNU Radio is a free & open-source software development toolkit that provides signal processing blocks to implement software radios. It can be used with readily-available low-cost external RF hardware to create software-defined radios, or without hardware in a simulation-like environment. It is widely used in hobbyist, academic and commercial environments to support both wireless communications research and real-world radio systems.

If you've never touched GNU Radio before, these pages will get you started with a running installation of GNU Radio and will show you how to take your first steps with this software radio tool.

The recommended way to get started with GNU Radio is to read the Guided Tutorials.

SARC members received a very interesting hands-on introduction in the fall of 2017. It was presented by Kevin VE7ZD. Here is a PDF of the slides.


A simple FM receiver in GNU



Wednesday, March 14, 2018

A Simple Field Strength Meter


A Communicator Reprise...

Summer 2011


Anyone use a field strength meter anymore?  It’s kind-of like a radiometer for RF energy.  Remember the radiometer?  It’s those little black and white squares that spin inside a glass ball when light shines at it; the brighter [or hotter] the light, the faster it spins. Cool “instrument” from the 1870’s.

Well a field strength meter is sort of like that, in that in its heyday, it was used by Hams and CB’ers to measure the transmitted signal strength of any antenna - from a distance usually  1, 3, or 30 metres or whatever measured distance you had.  As long as the meter was “calibrated”, one could set up the antenna, mount a FS meter X number of feet or metres away, pump 1, 5, 10 or 100 watts out of it and measure the “strength” of the RF field at that measured distance.  It was simple, you could tune for maximum meter deflection, usually meant your SWR was at its lowest. An OK tool if you didn’t have a sophisticated watt meter or new-fangled SWR bridge.

Today, it can be used by the Ham antenna experimenter to measure the gain of the antenna – in RF volts or Db or whatever scale you had labeled on your meter, even S-units.  A sensitive FS meter can pick up low power bugs, or any source of RF energy – guess what those ghost hunters use?   More useful if you spent big dollars and put a tuned circuit, attenuators or a pre-amp in the circuit, and of course lots of LEDs.
But of course, good RF meters are expensive and somewhat hard to find, not many at the swap meets these days… and they are usually combined with other types of measuring devices, watt or SWR meters, thus more money than the typical cheap Ham wants to dish out.

Solution, make your own!!  OMG! What a concept!  A simple FS meter is the simplest thing to make and is good enough to see if the antenna under test is radiating more power than your old ground plane, old mobile vertical or just radiating at all in a particular direction or in all directions.

Here is what you need:
  1. A digital voltmeter with a dc millivolt scale – every Ham should have a few in their shack.
  2. A Germanium diode, just about any one, as long as it’s Germanium, like 1N34, 1N270, 1N914 or 1N100. The best one, a non-North American standard. The super-sensitive OA91 from down under or Europe/UK  – Great for your crystal radio project too.
  3. A 3.3MΩ 1% resistor, 1/8 or ¼ watt.
  4. A 100 picofarad capacitor
  5. And a hand-made inductor [L1] of 7 turns on a ¼ inch coil form with a ferrite slug (some experimentation required to cover the North American FM Band) 24 to 28 AWG lacquered wire.
  6. Some miscellaneous parts like an antenna or antenna connection, a tiny box to put it all in, and some jacks that your DVM leads will insert into.
Using a digital multimeter, as opposed to an analogue meter has a few advantages in this circuit.

First, the impedance of a DVM is very high, around 10MΩ per volt on most meters.  This will not shunt or load down the tank circuit.  Second, compared to an analogue meter, very slight differences in signal strength can me more easily observed.  An third, a digital meter will have better linearity responding well to both weak and stronger signals.
All you want to see is the numbers, the higher the number, the more signal strength.  Just remember a few basic rules.  Keep the distance and power out the same for all your experiments, and turn off all your APRS trackers and digipeaters as they will want to add their 2-cents worth to your measurements.

If you have it in a hand-held configuration, you can “see” lobes, minimum and maximum RF fields as you walk around your test antenna. Oh, and then put a set of crystal ear plugs in place of your DVM and you might just hear the nearest AM broadcast station… well, until they all go digital.

Enjoy!

The original article appeared in the Communicator - Summer 2011 edition





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