[TenTec] DDS VFO as remote VFO?

[lee berman]

I am attempting to correct the thermal drift on my 580 Delta PTO, by using a Direct Digitally Synthesized VFO as a remote VFO.  The DDS output is said to be ~500mV P-P (I've not measured it myself).  To date, I had no success.  I wonder if anyone else on this reflector has successfully done this and can point me in the right direction.  The unit I'm trying is the one by N3ZI.
Other "fixes", such as PTO rebuild, and the K4DPK unit have worked well for many other hams, but not me.  The drift is definitely in the PTO, defintely thermally induced and does not settle out after hours of on time, so this is my latest effort at ending it.
thanks,  ~Lee, W1IDZ