10MHz reference

joe camilli

I have the following 10MHz reference https://www.tindie.com/products/analysir/10mhz-ocxo-frequency-standard-module-or-kit/.

Output is HCMOS (5V square wave) on this unit. Looking for suggestions to get it to the 3.3V required by the Flex?

Joe N7QPP

KD0RC

Hi Joe, I don't think this will help you much. The TCXO in the Flex coupled with the calibration routine (Settings, Radio Setup..., RX tab) will get you spot on frequency. I would be surprised if this little $10 OCXO is more stable than the internal Flex TCXO. It looks like it is only +/- 2ppm (20 Hz at 10 MHZ...) where the Flex sets frequency in terms of ppb (3 orders of magnitude better).

I use a Leo Bodnar GPSDO (see link below), but the Flex is so stable, that I really don't need it. I got it to get more accuracy from my spectrum analyzer. Since I already have it, I use it on my Flex just for fun.

Precision Frequency Reference (GPSDO) : Leo Bodnar, Simulator Electronics

So if you just want to see what the OCXO does, it might be interesting to play with. If you are expecting a standard reference, I think you will be disappointed.

One experiment that you might want to try is to calibrate your Flex at 10 MHz using the internal TCXO, then listen to the IR OCXO on the Flex to see where it lands, and how well it stays put. From that info you will know whether you want to convert the voltage and actually use it on the Flex.

joe camilli

Any difference if I am going to add a 2M and 70cm transverters?

Joe N7QPP

joe camilli

Any difference if I am going to add a 2m and 70cm transverter?

Joe N7QPP

KD0RC

Hi Joe, not really. The TCXO or external reference for the Flex controls the Flex frequency used for the transverter IF (usually around 28 MHz). A good transverter will have a 10 MHz reference connection which puts the transverter on frequency very accurately. If the Flex and transverter are both operating from a GPSDO, you will be right on.

In my case, I have a cheap transverter that has no provision for a 10 MHz reference. So I used my spectrum analyzer with my Leo Bodnar GPSDO and adjusted the LO Error accordingly. You can find the adjustment in Settings, Radio Setup..., XVTR tab. My transverter oscillator was off by 250 Hz.

If you don't have an accurate spectrum analyzer or frequency counter, you can use a repeater to show you where your transverter oscillator is. This will get you to approximately the same accuracy as the repeater. YMMV on this, but generally, repeater owners keep their gear reasonably on frequency.