Monday, 11 December 2017

The FA-VA4 Vector Antenna Analyzer (LF-100MHz)





For some time I had been considering the purchase of the MFJ259 antenna analyzer but after a little online sleuthing, came across this little beauty, the FA-VA4 Antenna Analyzer by Funk Amateur in Germany and available through their Box73 website here.





I liked the fact that the cost of the analyzer was about half that of anything else comparable ($140 US including shipping) and that it covered the new 2200 / 630m bands!

I think many amateurs planning on building a system for either of these new bands will find the very affordable FA-VA4 a handy piece of equipment when it comes to working on their LF / MF antenna since most available SWR meters do not cover these frequencies accurately.

Delivery time was fast and everything was very well packaged. The FA-VA4 comes in partial kit form and requires only a short amount of time to put together.


The necessary assembly consists of soldering pin strip connectors, switches, AA cell holders, and the BNC connector. All of the tricky SMD components have been pre-mounted ... total assembly time was less than 60 minutes and everything fired-up nicely, without problems, thanks to the well written instruction / user manual.


Included with the kit are three BNC connectors needed to calibrate the instrument for the highest accuracy. These consist of a 'Shorted' connector, an 'Open' connector and a 50 ohm 'Load' connector (SOL). A simple three-part calibration procedure for all frequencies takes about 15 minute to complete, while the instrument calibrates itself as it scans through all frequency ranges with each connector plugged into the output. Once this task is completed, the analyzer is ready for use.


If you're like me, I think the main use will be to check out and tweak some of your HF antennas using the SWR or Z sweep function. This allows you to set a desired 'center' frequency along with a + / - sweep range and have the display draw a nice plot of your system.

Had my 630m antenna not already been tuned and matched, I would have found the analyzer to be a great help but, thanks to my 'scopematch', that antenna has already been optimised.

All menu features and data entry is via three momentary-contact push switches. Although this might initially seem awkward, it is not, and operation is pretty intuitive.

The main modes of operation are:

Single Frequency SWR  Measurement

courtesy: http://www.box73.com/product/5

Single Frequency Impedance Measurement

courtesy: http://www.box73.com/product/5

Single SWR Measurement Run

courtesy: http://www.box73.com/product/5

Single Run For Impedance Measurement (Resistance and Reactance)

courtesy: http://www.box73.com/product/5

SWR Measurement On Five Frequencies (5 Band Measurement)

courtesy: http://www.box73.com/product/5

As well, all of the above can be viewed in a continuous 'cycle' mode, as inputs are changed and all screens can be saved for future reference.

Additional capabilities include use in an HF Signal Generator Mode (~ 1V square wave @50 ohms), the ability to measure C and L at a given frequency, as a 'dip meter' and to measure cable resonances and determine lengths.

The complete manual may also be downloaded from their website here.

I will soon put all of my antennas to the test and see what work might need to be done to optimize them, particularly my HF half slopers, which, in spite of their great performance, have always proven a bit of a mystery when it comes to pruning them to resonance ... I rather suspect that the sloping wires are more of an impedance tuning stub than a radiator and that most radiation comes from the vertical support tower, not the sloping wire.

All-in-all, the FA-VA4 appears to offer very good value for the money and is a well built, quality test instrument. I think it will become a popular choice among hams, especially those on LF / MF. The only thing different that I would have liked, would be to have a UHF (SO 239) connector rather than a BNC on the output, since most amateurs are using these on their HF systems ... or, the inclusion of a BNC-to-UHF adapter.

If you already use this device, please feel free to add your comments below!

Monday, 4 December 2017

Upcoming '29 BK QSO Party

courtesy: Lou, VE3AWA




This Saturday night as well as the next will be the annual Bruce Kelley 1929 QSO Party, otherwise known as the '1929 BK'.





Only transmitters that are 'era-appropriate' are allowed to be used. More specifically, transmitters must employ tubes that were available in 1929 or earlier, and transmitters must be self-excited. No crystals allowed! Crystals were new and largely unaffordable for most hams back in the depression days.

1929 marked a real turning point in amateur radio as governments finally cracked-down on things such as frequency stability, out of band operations and re-alignment of call districts. In short, hams were henceforth required to behave themselves and to clean up their signals and methods of operation.

courtesy: http://www.arrl.org/
Although the new rules did a lot to improve things when it came to 'signal purity', there was still a long way to go ... but the wheels of improvement had been officially set in motion. The next decade would see monumental changes in both transmitter and receiver architecture, as engineers along with some particularly gifted amateurs, strove to unlock the challenges of this relatively new technology.

If you tune across the CW bands during the next two Saturday nights, you will have the rare opportunity to hear exactly what the bands must have sounded like back in the early '30s'.

For the most part you will hear single tube Hartley, Colpitts or TNT oscillators along with a few two-tube MOPAs thrown in. Many of them will suffer the same problems encountered by the boys of '29 ... chirp, drift, buzzy notes and frequency instability from antennas swaying in the wind.

This year, signals should be a little louder as well, since the previous power limitation of 10W input has been increased to 25W.

The MOPAs will sound much better but some surprisingly nice-sounding signals can be heard coming from properly tuned and optimised single-tube oscillators. I recall being blown away by the lovely sounding signal I heard from such a rig when first tuning into the BK activity several years ago, only to learn that it was a self-excited Hartley using 1/4" copper tubing for the oscillator tank circuit!

The '29 watering-hole on 80m will be around 3550-3580 kilocycles (be careful not to confuse this with kilohertz!) while the early afternoon to post-sunset 40m activity will be found from 7100-7125 kc. There may even be a few on the very low end of 160m. Although many of these transmitter styles were used on 20m and higher, BK rule-makers have wisely decided not to inflict these sounds on the present populace as it would likely keep the 'Official Observers' busy for several days writing pink-slips.

You can learn more about amateur radio happenings leading up to and following the 1929 crackdown in my earlier series of 'Why '29' blogs here:

Part 1
Part 2
Part 3
Part 4

Those wishing to put something together for next year's event can find everything needed here:

Introduction To Building ... '29-Style

Building '29-Style - Part 1

Building '29-Style - Part 2

Heck, there me even be time to throw something together for the following Saturday if you have a few parts and an older tube or two ... the '27 comes to mind and is readily found in many junk boxes. Maybe you know an old-timer or two with lots of parts that could help you out.

Let's hope for good conditions for this event as the last few years have been adversely affected by geomagnetic storming. Poor propagation or not, I guarantee there will be plenty of '29ers busy calling 'CQ AWA' on the low bands.