Friday, October 11, 2019

FA-VA5 Vector Antenna Analyzer

FA-VA5 Vector Antenna Analyzer
For a long time I have been wanting an Antenna Analyzer that is better than my MFJ-259B which I have owned for many years.  The 259B covers 1.8 to 170 MHz and is a nice little hand-held unit to find the SWR and resonance of your antennas.  It can read SWR, return loss and reflection coefficients simultaneously.  It has two meters (one for SWR and one for Impedance) as well as a 2-line digital display.  In addition to those normal functions, I have even used mine to as a Time Domain Reflectometer to find where I had accidentally cut a feedline.  I believe I paid about $250 for this unit several years ago and feel I have received my money's worth over the years I have used it.

However, it has (for me) a major drawback.  It is NOT a graphing device meaning that you can not see a visual display of the SWR curve or other measurements.  Also, it takes 10 AA batteries and that gets expensive if you use it a lot.  I always remove the batteries after I use it so that takes a bit of time.

Components in the Kit
I was now looking for a unit that would interface to a computer and allow me to save graphical images.  I have had an N8LP LP-100 Digital Vector RF Wattmeter for many years and have used that to save graphs from the data it acquires.  I have really enjoyed being able to create those graphs and save them for later reference.  I can look back at how my antenna performed on a certain date and see if anything has changed.  However, the LP-100, as nice as it is, is not a portable unit, it is just a piece of shack equipment that is limited in where I can use it.  Also, it only covers 1.8 to 54 MHz with the one directional coupler I own so that limits its use as well.

Charlie, N8RR, purchased a SARK 110 a couple of years ago and helped me tune my 2-M EME antennas with it.  That's quite a nice little unit which operates between 0.1 and 230 MHz.  Current price for this unit is $389 and I seriously considered purchasing one for myself.  It can save and transfer measurements and graphs via its USB interface to a computer.  Just what I want.  It has an internal Li-Poly-1000 mAh battery that should run the unit for 2.5 hours but it can be charged over USB so you can extend the operating time by connecting it to a computer.  It has a 3" Color display which is 400x200 pixels but having it connected to a computer with a larger screen makes it much more useful.
Presentation Case + Adapters

In addition to the cost of the unit, you need to purchase at least an OSL (Open, Short, Load) Calibration Set plus some SMA adapters since the unit only has a female SMA connector as it's antenna connection.  $59 will get you the OSL Calibration Set, 4 SMA adapters plus a rubber case.
Suggestions for Adapter Placements

So I began researching what type of Vector Antenna Analyzers were available.  WOW!  Prices can be VERY low.  You can buy a Chinese NanoVNA for only $79.99 from Amazon!  It has a 2.8" LCD screen, built-in 400 mAh battery, and covers up to 900 MHz.  Plus it can export files to the PC.  This could be just what I need.  But, could it be too good to be true?

I began looking at the reviews on the NanoVNA and several other low-cost units and eventually came to the conclusion that these were actually NOT precision pieces of equipment.  Many reviews mentioned problems with some of these devices including those who received units that failed to work out of the box.  While the price points were super attractive, I came to my own conclusion that "you get what you pay for" and decided against going the "low-ball" route.

Turn On Look
More research and I found the DG8SAQ VNWA 3 Low Cost 1.3 GHz Vector Network Analyzer available from SDR-Kits.  I really, really liked this unit.  It is indeed a precision piece of test equipment and it would cover the 1296 MHz band which was one of the things I was thinking would be nice for future UHF work.  BUT, it is not really a "hand-held" unit, it has no display and MUST be connected to a PC to operate, it has no internal batteries, etc.  But, BOY, did I like this unit!  The software written for it is really extensive and impressive.  I spent a lot of time figuring out how I could get this unit which would run me about $565 for the DG8SAQ VNWA 3 unit, presentation case, OSL Calibration Kit, and a 165 page "Guided Measurements" book.  WOAH!  This is one SERIOUS piece of test equipment.

Dual-Band Antenna Measurement
But, while reading and viewing YouTube videos about the DG8SAQ VNWA 3, I became aware of the DG5MK FA-VA5 Vector Antenna Analyzer.  This is a truly portable analyzer AND it uses the SAME wonderful software as the DG8SAQ VNWA 3!  It only requires 2 AA batteries (which should allow it to work for up to 40 hours), and has a large display with good visibility.  The unit measures just 5.9 x 3.35 x 0.87 inches so it will fit easily in one hand.  It contains a real-time clock with capacitor backup so measurements can be time/date stamped and it has an audible buzzer alert for minimum SWR.  And you can connect it to a PC for real-time measurements on a larger screen.  Doing this gives full control of the FA-VA5 to the software (like the SARK 110) so that measurements can be made much more quickly than by using the analyzer's simple controls.

The FA-VA5's graphic display shows the complex impedance, standing wave ratio, complex reflection coefficient, capacitance and inductance.  Using the DG8SAQ VNWA software it can also be used as a Time Domain Reflectometer (TDR) to help find defects in antenna installations, measure the length of cables, and other similar applications. 

TDR Measurement
Since this is a one-port device (unlike the DG8SAQ VNWA 3 which is a 2-port device), it is limited to only measuring the S11 parameter.  S11 is a complex reflection coefficient, made up of a real and imaginary component. A lot of other values can be derived from S11 like Standing Wave Ratio (SWR) and impedance Z. Very often those values will be displayed using a special chart type, the Smith-Chart. The Smith-Chart does allow solving a lot of matching problems graphically.

The unit does only cover 10 kHz to 600 MHz so I lose the ability to use it on the 1296 band but it does add the 432 MHz band to my measuring ability.  And, this is a band the SARK-110 does not reach. But I gain a tremendous amount of accuracy as well as the ability to use it with some really great software.  And, the antenna connection port is a BNC connection.  In my experience this is MUCH easier to use than the SMA connector and can speed up the measurement process significantly by keeping me from not needing to fiddle with the SMA connection. 

It is a "Kit" which will require a bit of assembly (approximately 3 hours) but the process looks pretty straightforward.  You can CLICK HERE for a 3-minute video showing the assembling of the unit. And, no small feature, the cost is MORE than reasonable!  The basic unit can be had for about $225 including shipping.  I chose to purchase the basic unit, a "Presentation Case", a 600 MHz OSL (Open, Short, Load) Calibration Kit, 5 BNC adapters, a BNC to BNC cable and a BNC to SMA cable.  Total price was $270.72 including shipping.  Obviously, the price / performance ratio is outstanding!  It is essentially the same amount of money I paid for the MFJ-259B so many years ago and about $200 less than I would pay for a SARK 110.  AMAZING!  Click on any image in this Post to see a larger image.

So, based on the high accuracy, low-cost, portability, great software and excellent documentation for this analyzer, I decided to order the FA-VA5 from SDR-Kits. When I first decided to buy the unit it was shown as being out-of-stock due to high demand and they were taking reservations.  I made my reservation and just 2 days later received an email saying the unit was now available.  I immediately made the purchase (paid for with Pay-Pal) yesterday (10/10/2019) and today received a tracking number from Deutsche Post.  I am really looking forward to receiving this Vector Antenna Analyzer and learning to use it and the software.

Tuesday, October 8, 2019

Messi & Paoloni Coaxial Cable

Two years ago when first building my EME station, I purchased through GigaParts a 75-foot length of 400-UF cable with Male N-Connectors on each end which was built by ABR Industries and supplied to GigaParts.  This is cable which is apparently built for ABR Industries and is supposed to be "similar" to LMR400-UF but is actually marked as "ABR400UF" cable and NOT a Times Microwave LMR cable.  

This was to be the Receive cable from my preamp down to the shack.  It tuned out that the installed N-connectors were CRAP!  One of them was so difficult to screw on that I had to put a set of a double-female N-connector and a double-male N-connector on the shack end of the cable to allow the cable to be easily connected.

As I made more and more EME QSO's, I began to notice that quite a lot of the time I was receiving better signal reports than I was giving.  So, I tracked the QSO's where I had signal reports to see if my impression was true.

Out of 174 EME QSO's, 71.54% of the time I RECEIVED a better signal report than I gave.  That RECEIVED report was an average of 5.2 dB better than I gave.  21.14% of the time I GAVE a better report by an average of 3.0 dB.  7.32% of the time the reports were equal.  Now that I proved there was a substantial difference between signal reports received and sent, I began to suspect there was an issue with the ABR400UF cable and/or the N-connectors from ABR Industries.

Since I am now moving to an XPOL system with 2 preamps, I will need two receive coax cables.  I did not feel like using the current ABR400UF cable so I decided to look for something else.

Searching around I became aware of coaxial cable which was built in Italy by Messi & Paoloni.   They have been producing cables since 1984 and have received very good reviews.

In looking at the specifications on the M&P website, I decided to go with the "ULTRAFLEX 10" cable.  The main reason for choosing this cable is that it has a very high (Greater Than 105 dB) "screening efficiency" which is reported to reduce background noise more than other similar cables.  The shield effectiveness of the ABR400UF is Less Than 90 dB.  That's a BIG difference.  Loss per 100-feet at 144 MHz is 1.4 dB for the ULTRAFLEX 10 while the loss of ABR400UF at 150 MHz is 1.8 dB.  Not really a big difference considering I'm only using about 75-feet.

The N-connectors I chose for the M&P cables are their new generation ones with double sealing that protects even more from humidity, condensation and water.  The model is CO.N.10M-S and if you CLICK HERE, you can see the description of those connectors as well as a couple of videos showing how to install their connectors.  Also, you can click on any image on this page to see a larger version.

Currently two 75-foot lengths of ABR400UF with N-connectors costs $213.90 and GigaParts would ship them for free.  Today I purchased two 25m (82-foot) lengths of ULTRAFLEX 10 with SOLDERED N-connectors installed direct from Messi & Paoloni for a total of $259.50 including shipping and PayPal fees.  So for an extra $45.60 I will at the very least have peace of mind and possibly MUCH better receive cables.

UPDATE: My order was placed on October 8th, it was shipped on October 10th (from Italy) and UPS says I should expect it Monday, October 14th.  Not bad at all!