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Hi and thanks for including me in the group. I recently bought a FA-VA5 analyser 99% built with the standard 100Mhz calibration plugs and all went well in the assembly phase.
However, when I came to calibrate the analyser I couldn't find all the settings for? the SOL Master calibration ( there are the open and short settings in the manual but not the load? figure.) ?? So, I entered the Open and Short settings? in both Master and Actual settings and did the master calibration procedure. This took about half an hour as per the manual.?

However, when testing the analyser against my MetroVNA I find the measurements totally wrong , even to the extent of? a 1.13 :1 SWR on the MetroVNA showing as over 700 :1? with Z of 6500 and no J shown.?? So back i wnet and removed the Open and Short settings and did the master calibration again - same result.

I now wonder what it is I've done or not done and am prepared to be admonished from those who know more about Vector Network analysers than I do. All help gratefully received.

Thanks and regards

Lawrence G4GZG

Thanks all. It's an interesting little meter for the price. I think it's in the ballpark with a 30 dB attenuator at least for HF QRP measurements...

There is no calibration on the FA-VA 5 output power. The output power also depends on the selected frequency. For an antenna analyzer (or network analyzer) this is not a problem as any level of output power is included in calibration of the measurement. It still can be used as a signal source for your power meter. But you need a second device (spectrum analyzer) to measure the actual power.
Regards

Michael

It seems this device is built around the Analog Devices AD8307. Assuming this is a genuine AD product, I'd just go with the values from the datasheet, rather than use FA-VA5 as a calibrated source. Of particular interest, Figure 5 on page 6.

Also from the datasheet, Figure 7, we see the output voltage from the AD8307 is not linear across its entire range. I assume there's just a microcontroller with an ADC measuring this output on the power meter board. Depending on how the software is implemented, you may get additional errors outside the -65 to +16dBm range.

But there will be external components around the AD8307 that could have a significant impact on the performance of this power meter as well, and it'd be very interesting to see a detailed calibration with a monotonic source and step attenuator or similar.



73 de Magne LA1WUA

I suspect the Power is calibrated for a sine wabe
?Square wave will be way off.
--
VY 73,

Wes AE6ZM

Can anyone tell me if the 5.6 dBm square wave output of my FA-VA5 is a reasonable accurate signal level for calibrating my Aliexpress power meter?

K5BCQ had mentioned in another group.io forum that he had purchased one of these units and found it fairly accurate. It can measure up to 16 dBm directly and, with a 50 ohm attenuator, can measure even higher power levels.

When I connect my FA-VA5 directly to the Aliexpress meter, it reads 9.6 dBm. I would have expected closer to 6.21 dBm, taking in account the 3rd and 5th harmonics of the square wave.

When I connect my old MFJ-269, the Aliexpress meter reads 6.5 dBm, which is more in line with the suggest power output of 7 dBm of that unit. I am reminded of the saying "A man with a watch knows what time it is. A man with two watches is never sure."

Thinking about "condensed pages on certain critical aspects of FA-VA5 usage", it would probably be good to hear about those initial difficulties encountered by new FA-VA5 users.
We already know for example that one can be tricked by frequency displays in "kHz", where the frequency unit is displayed and "Hz" where the frequency unit is not displayed. This can happen when using different measurement modes.
The rule is that when no unit is displayed, the frequency is given in "Hz" which makes good sense but can still be a source of misinterpretation.

So, please feel free to state some initial "obstacles" you encountered on your way to FA-VA5 proficiency. :)

I had a few initial glitches myself, starting with not using the "master calibration" and not realising that "current calibration" values "are lost when changing the frequency and when switching off the analyser" (manual page 11). Upon realisation of my avoidable mistake, I always used "master calibration" (manual page 12) and never looked back.

73 & greetings from sunny Australia (32C)

Dieter, VK3FFB

I bought mine from sdr kits as well

Hi Dave,

I would refer to SDR-Kits in the UK. I bought mine from them.



73
Dieter, VK3FFB

Is there a source or sources for the FA-VA5 in Canada?
If not, where would be supplier and a website with
information to order for shipping to Canada?
VE1VQ/VA6NS

Thanks Mel.?

Hi Mel,

Good stuff. If you have a picture, please post.
thanks & 73
Dieter, VK3FFB

Fine work, Jacques. I'll convert it to pdf and upload in the "Files" section of our group.
73
Dieter, VK3FFB

Hello All,

Back in 2019 I did a presentation at the Boxboro convention which might be of interest.? I use my FA-VA5 to do many measurements.
¨Get the Most from Your Antenna Analyzer¨

Jacques,
VE2AZX

One thing that happened to me with other antenna analyzers, is whether the calibration was accurate.? So I did a test, a simple one with a termination of 50 ohms and a reactive load at a standard frequency 10 MHz.? Since most of my work is in the .5 to 30 MHz range, I felt that 10 MHz would be adequate.??

Configure this, on a BNC PCB male connector, you put a series 1206 50 ohm chip resistor on the flush center conductor straight up then a 318 pF calibrated chip from the 50 ohm chip to ground.? ?
At 10 MHz, it better read 50-j50 ohms, if the calibration is correct.? It is my quick check before making any measurements in the field.??

Mel, K6KBE

Yes, please do. VA5 users are in the best position to improve existing "how-to" instructions. Initially, I did not understand the SWR sweep settings (< > M) and had to read the manual a 2nd time.?

I also like my VA5 a lot. I have a "boatanchor" Agilent 8753 analyser and compared results with the VA5. I was surprised by the good agreement of both measurements in the HF and VHF ranges (did not check UHF so far).
I live pretty much in the main lobe of various VHF UHF high-power broadcast stations on a nearby mountain. My old MFJ-259B could never handle the induced RF during outdoor antenna measurements. It daunted on me when I got funny SWR results. Unlike the VA5, the old MFJ used broadband detection which meant that the induced RF is added to the reflected power during measurement. So, an SWR of 1.0 is never measured! The VA5 has no such problems as it effectively uses selective detection which is a big plus when you have strong RF near the test object.

Looking forward to hearing from you

73
Dieter, VK3FFB