Ten-Tec Orion TCXO Fan Modification

I noticed a problem the other day with my Ten-Tec Orion 565 when I tuned to the 10 meter band and doticed everyone I heard was off frequency by approximately 110Hz! After getting some expert advice and pointers to a couple web pages at AA6E and N6IE, I decided I'd try this mod on my Orion and see what effect it will have on my radio. Visit those web page links above to read detailed information about the problem and solution. I present this page only to show how I implemented the modification and to document my results.

Jim K4CGY responded with the the following:
   Rig is within spec . Spec is +/- 3 PPM which is 45 Hz @ 15Mhz and 60 Hz @ 20 Mhz.  You have a maximum drift of 32 Hz @ 15 Mhz and 42 Hz at 20 Mhz. However the frequency starts off at  32 Hz
low so if the TCXO has a trimmer it likely can be touched up a little to be closer.

The trimmer on the TCXO is a bit touchy but you can adjust it with reasonable accuracy using a steady hand which is what I did after installing the fan and noting how much I needed to adjust the frequency after it stabilized. Below is a table showing the effects of the modification.

Frequncy measured at 80 degree room temperature
 
Before Modification
After Modification
 
15MHz WWV
20MHz WWV
15MHz WWV
20MHz WWV
Power On 14.999.968 19.999.956    
45 min 14.999.946 19.999.928    
90 min 14.999.939 19.999.919    
5180 min 14.999.936 19.999.914    

As you can see from the data, this simple modification is highly effective! I'm not sure just how quickly or when my Orion developed it's initial drift but it looks good now and I will keep an eye on it to see how stable it remains.

View of fan over TCXO

This is an overhead view of the installed fan. I positioned it so that I could reach through the fan between the blades and access the TCXO frequency trimmer with a jewelers screwdriver to adjust the oscillator frequency. The fan is secured to the wall with a "sandwich" consisting of two pieces of double-sided tape and a portion of unused make-up removal sponge stolen from my wife's make-up kit. This seems to have provided good vibration and noise isolation

 

Angled view of fan over TCXO

Here is a lower viewing angle of the installed fan.

 
Close-up of digital circuit board

HOn the end of my cable, I soldered a 2 pin header that plugs into the connector that came with the fan and covered the connection with shrink tubing.. If the fan ever needs replacing, I can easily just unplug it and swap it out. I also threw in a spare ferrite snap core around the extra fan wire just for the heck of it. The other end of the cable is snaked out the rear panel through the Data 2 connector openning and is terminated with a male RCA phono jack which plugs into the 12v supply plug on the rear of the Orion. The free end of the fan is held up with a tie-wrap around the small inner-connecting cable that terminates below the fan and travels through the gromet into the compartment behind.


Modified front panel

Yet another view of the fan.


Resistor shown soldered between RCA jacks

This is the resistor I used to slow the fan down. It is soldered between male and female RCA phono jacks so I could easily insert or remove it or change the value if needed.