[time-nuts] Fe-5680A -vs- LPRO

Bob Camp lists at rtty.us
Thu Feb 2 22:09:42 UTC 2012


They are pretty similar units.

They are both within about 7x10^-12 to 1.5x10^11 at one second. Both are
within about 1 to 3x10^-12 at 100 seconds. Good samples of both will get
much better than that out past 100 seconds. Bad samples of each, not so
much. You would have to test a pretty good sized sample to really tell who
pulls ahead on short term. Limited data says that the FE is *maybe* a bit
better than the LPRO. 

Both have a temperature coefficient in the 3x10^-10 vicinity over 0 to 70C
"worst case". Good samples of each do much better.

Both units age very little on a daily or weekly basis. You have to watch
them for months / years to see real aging. Good samples of each will get
down below 1x10^-11 per month. Poor samples do exist. 

The LPRO has a cleaner RF output spur wise. The power output on the FE's
seems to range from +3 to +10 dbm depending on which unit you look at. Power
output on the LPRO is a bit better unit to unit. Neither unit is in the
"rock star" category for either phase noise or spurs. 

The FE runs off of an easier to find supply voltage (+15 rather than +18). 

The monitor outputs and pps out on the FE are a bit weak. Not a problem if
you are driving CMOS logic. The LPRO is better at driving heavier loads.
FE's seem to show up without a pps output. I have not seen that issue on

Both units pull a major chunk of power at turn on, both get quite hot
without a heat sink (or fan) at room. Neither one is suitable for higher
temperature operation without some sort of thermal management. 

FE's right now are in the vicinity of $40 delivered. LPRO's were in this
vicinity a couple of years ago if you knew who to get them from. LPRO's are
more expensive now. The FE's are going up in price. 

The LPRO tunes with a voltage and a tuning pot, the FE has a cool serial
interface and an eprom.  

Both units warm up and lock in a similar amount of time. The LPRO lets you
look at a voltage to watch the VCXO tune, the FE lets you play with (often
undocumented) serial commands see what's going on. 

The FE interfaces through a DB-9 connector you can get pretty easily. The
LPRO uses something a bit less conventional, but still available.

Schematic and parts list on both units is a bit of a mystery. There is a bit
more on the LPRO simply because people have been reverse engineering them

Bottom line, they are very similar devices. The only big deal is the serial
interface on the FE vs the tuning on the LPRO. You could easily get a better
(or worse) unit buying either part. 


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Brucekareen at aol.com
Sent: Thursday, February 02, 2012 2:48 PM
To: time-nuts at febo.com
Subject: [time-nuts] Fe-5680A -vs- LPRO

Is anyone prepared to comment on the relative performance of the FE-5680A  
compared with the LPROs?
Bruce Hunter, KG6OJI
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