BG7TBL FA1 and FA2 frequency analyzers

[Ringmodulator]

Here you can see both versions FA-2 and FA-3 to get an impression of the displays.

Chris

[burkm]

From what I have read the FA-3 and the FA-2 are identical except the larger size of the display, which leaves some questions about the current prices asked for the FA-3 versions...

[Ringmodulator]

More info here:

[Nargun]

G'day all.

Recent purchase of the BG7TBL FA-2.  The instrument appears to be working fine but I am having difficulties with the serial output.

I'd like to be able to use the unit with Timelab / Lady Heather etc, however all such software seem to require the test unit to output a continuous stream of measured data, which is the appropriately parsed, formatted and used in the relevant determinations.

My FA-2 can be connected to using any given serial terminal and responds normally to the documented commands such as '$S*' which prompts the output of the selected channel stats, or '$D*' which outputs the selected channel freq reading.

Unlike others in this thread though, my unit does not output a continuous stream of measurements, which software like Timelab needs to parse.

The unit needs to be polled with a command as above, before it outputs a single line of data.

I have a sneaking suspicion that there may be an undocumented command i.e. '$nn*' or similar that may configure the device for continuous output.
I'll be damned if I can find it on the inter webs tho - despite all manner of Google mashing.

Does this make any sense to any of the good folk on this excellent and informative site?

I'd be indebted to hear from you if it does!

Cheers & stay safe all - many thanks!

Nev. B
Canberra

[Ringmodulator]

Hi Nev,

that seems odd.
I have the FA-2 and FA-3 and both output a string of measurement for each gate period.

There might be different firmware versions for at least the FA-2, as we have reports of different output string format (mentioned in this thread).

If you use Chan 1, make sure, that there actually is an inputsignal, otherwise it might not output a measurement.
Chan 2 produces "measurements" without an input signal.
If the gatetime is 10 sec, you have to wait up to 10 seconds for the string to appear (I know that this is obvious, but fell into this trap myself, because I thougt, that I set a shorter gate time)

Sorry, I cant help with undocumented commands.

Chris

[FriedLogic]

Recent purchase of the BG7TBL FA-2.  The instrument appears to be working fine but I am having difficulties with the serial output.

Hi,

Was it like that from new, before you tried sending any commands to it?
If so, it might be worth checking with the seller to see if it's faulty since as far as I know they should normally just sent the data.

If there is a specific command to send data, it suggests that the continuous data can be turned off/on.

[Nargun]

Thanks all

Yes, has always been the same since purchase.  I've tried all gate times and pretty much every other setting that I can change, to little effect.

Sending $S* prompt an immediate output of the selected channel signal - but just one string/line.

On boot, the unit displays:

FA-2-6GP
FREQ COUNTER
1Hz-6.0GHz
BG7TBL V20210511

Fairly up-to-date firmware version there by the looks.

If any other owners have the same firmware version I'd love to hear if your unit behaves normally (i.e. outputs a continuous data stream).

Anyway - thanks again for the feedback - I'll try and get back to the vendor.

Nev.

[Nargun]

Apologies - I had my commands mixed up.

When using a loopback arrangement with the 10 MHz ref out as an input to Ch.1,

$S* outputs:

N:0000000025
AVG:0010000000.000026773
MAX:0010000000.000539217
MIN:0009999999.998921569
P-P:0000000000.001617648
READ STATIS DATA SOK

$D* outputs:

$F-CH1,0010000000.000637256,+0000000081,DOK

Nev.

[Ringmodulator]

This is my FA-3 output after startup:


ÿREAD EEPROM!

FA-3-6G       
1Hz-6.0GHz
FREQ COUNTER
BG7TBL V20210401
*FA0010000001.762987798
 FA0010000001.765365926
 FA0010000001.166358810
 FA0010000000.607329410
 FA0010000000.077409839
 FA0009999999.576813777
 FA0009999999.093665327
 FA0009999998.648740140
 FA0009999998.242994464
 .....




This is my FA-2 output after startup:


[00]READ EEPROM!

FA-2 PRECISION
FREQ COUNTER
1Hz-6.0GHz
BG7TBL V20191224
*  F:0010000079.335765709
   F:0010000077.721252453
   F:0010000076.413177439
   F:0010000075.100230553
   F:0010000073.777609762
   F:0010000072.439697556
   F:0010000071.089028763
   F:0010000069.720054912
   F:0010000068.335290743
   F:0010000066.940123780
   F:0010000065.531985956
   .....


Chris


 

[HighPrecision]

Hi,

last year I have got a used FA-2, this unit is working from several months 24/24 hours, yesterday made a test for counter noise feeding reference 10MHz to EXT-REF and CH-1 inputs from a frequency distributor, two outputs of a RACAL 9480 driven through 'DIV' option from HP5065A Rubidium (5MHz).

[RadioTube]

I received my FA-2 6G PLUS last week. It came with firmware V20210215. The only difference I noticed between PLUS and previous variants are 3 extra buttons on the front panel. So no new features, but easier to use, no double key presses necessary. The format of the serial output (FA...) is compatible with TimeLab, no tweaking of any settings was necessary to get it running.
CH2 input impedance is far from 50 Ohms, so I use this input with a 3dB attenuator to get some basic matching. Does anyone have a datasheet of the CH2 prescaler? I am interested in the input impedance and the specified power levels at various frequencies.

[Leo Bodnar]

It turns out I had FA-2 (V20190922) for quite awhile but never used it until today.

So I have connected two 10MHz Rubidium oscillators - one to FA-2 reference input and the other - to CH1.  Levels of both are about 7Vpp.

It seems that 0.1s gate results are very noisy and also offset by about 1.5E-10Hz.  1s gate frequency measurements are offset by around 2E-11Hz.

I have used 53230A and 53100A to verify the results: 10s gate FA-2, 53230A and 53100A agree pretty well.

Are these 0.1s and 1s gate FA-2 frequency measurement offsets deterministic and documented or do you, guys, just ignore them?

Cheers
Leo

[HB9EVI]

I always had the impression that those values with 5-6 decimal places behind the '.' the device spits out just pretend an accuracy that simply doesn't exist, especially on low gate times

Leo's chart seems to me the proof of that estimation

[Leo Bodnar]

I have swapped the input and the Ext. reference signals (both are 10MHz Rubidiums) and here's the result.
I would have assumed that in the perfect frequency counter they should be symmetrical around zero.

I have tried inserting variable attenuator in both CH1 and EXT.REF inputs but it has not visibly changed the outcome.

Feeding the same signal into CH1 and EXT.REF produces 2E-11 offset at 1sec gate (2E-10 at 0.1sec and 2E-12 at 10sec.)

Leo

[hgl]

That's interesting, thank you 
I measured Rubidium, HP10811, and a Samsung GPSDO with the FA2 counter against each other. In all combinations there was noise of this magnitude. Unfortunately I don't have another counter with this resolution to verify this.

[mino-fm]

Not knowing anything about FA2 internal operation but playing arround with different versions of high-res reciprocal counters, I always see a small positive offset doing linear regression using 64-bit double calculations. This offset doesn't appear if 128-bit integer calculations are used.
Maybe this helps.