Why is my Flex6300 doing this on receive?

Dave KD5FX

I'm trying to use my 6300 for the ARRL FMT (Freq Measure Test) and to improve my reading I just recently bought one of the Bodnar mini GPS Frequency Generators. It locks to the GPS sats and can generate a signal from 400 Hz to 810 MHz! This:http://leobodnar.com/shop/index.php?main_page=product_info&products_id=301

The plan is to set the Bodnar 500 Hz away from the FMT freq and use the fldigi software to calculate the difference for me.

So, I got the Bodnar mini GPS in last Saturday and it's been working since then and is fairly stable now. However, every few minutes there is a blip up or down in frequency that reads about .02 or more Hz. I'm using fldigi in the FMT mode to watch it. I posted on the FMT reflector and Leo Bodnar himself came on and asked about the problem. He tested one at his place using his Rubidium standard and just a 30 minute warmup and it was all rock solid. His email is copied below if you want to see the details. Below trace is from 1169000 Hz which is 1 KHz away from a nearby AM Digital station that is very steady. I've tried this on signal from 15 MHz down to this 1170 KHz and it does the same thing anywhere.

So.... I'm thinking there's something in my 6300 OR my PC that is doing this. Of course I'm using DAX to get the signal to fldigi. The 6300 has warmed up for almost two weeks, the Bodnar is on 5 days now. Is there something in how the Flex receives that can cause these blips?

Leo Bodnar leo@leobodnar.com via groups.io 

1:12 PM

to fmt-nuts

Here is what I have done: 

1) Turned on 10MHz Rubidium oscillator (Racal-Dana 9475 using Efratom FRK-H) and let it warm up for 30 minutes. It hasn't been on for at least a year.

2) Took a miniGPS clock unit that hasn't been on for at least half a year.

Loaded firmware 1.17 from the product webpage and left all settings as defaults (10MHz output.)

Antenna is inside a living room. Power is from a laptop.

Let it get GPS lock and settle for 30 minutes.

3) Used Microsemi 53100A Phase Noise analyzer to measure miniGPS output using Rubidium as the reference. Software is TimeLab v1.55b - current.

Frequency measurement intervals - 0.5sec, total time - 5min.

You can see that relative frequency deviation between the miniGPS clock and Rubidium reference is about +-2E-10 or 2mHz.

I have also adjusted the vertical scale to about +-0.05Hz to allow easier comparison to fldigi screenshot.

Please let me know if you want me to run other tests while I have it all powered up.

Thanks

Leo

Dave KD5FX

@Mike-VA3MW @Tim - W4TME