[time-nuts] Lucent RFTG-m-RB unit output level

[Robert E. Martinson]

Hi,

I have a pair of these units, that is an RFTG-m-X0 (10 MHz disciplined
crystal oscillator with a GPS receiver) and an RFTG-m-RB (10 MHZ disciplined
rubidium oscillator).  I have the two J2's and the two J5's interconnected.
These are very nice units and appear to function very well, despite what you
and others may have heard.  I also know three other Time-Nuts with properly
functioning pairs (one since damaged by a lightning strike).  As far as I've
been able to determine no info is available to us Time-Nuts (manuals, specs,
schematics etc).  The 15 MHz main outputs are derived from the 10 MHz
oscillators.  I understand its possible to bypass (or replace) the 15 MHz
filter to obtain a 10 MHz main output.  I have not done this as of yet.  The
10 MHz test Output (J1) on the RB gives a good strong 10 MHz source.  It's
also quite easy to tap the 10 MHz signal directly off the crystal or
rubidium oscillators internally.  I think an isolation amplifier might be a
good idea however.

I have no exact way of measuring the output impedances, however I made the
following 3 measurements on each output port with an HP436A power meter, an
8481A (50 ohm) head, and precision coaxial terminations of 50 or 75 ohms.
The measurements below are in the order of power meter alone,  with an
additional 50 ohm load  (using a BNC "T"), and finally with an additional 75
ohm load (using a BNC "T").

XO  15 MHz Out (J4)   17.71, 13.80, 14.93 dBm
RB 10 MHz Test Out (J1)   7.24, 12.80, 12.33 dBm
RB 10 MHz Ref Out (J2)  13.03, 9.54, 10.52 dBm
RB 15 MHz Out (J4)   17.45, 13.03, 14.28 dBm

If the output impedances were exactly 50 Ohms, the values with a second 50
ohm termination would be 3 dB less then the power meter alone readings.
Therefore I surmise the output impedances are around the 50-75 Ohms range.

The readings of the Test Out (RB J1) are rather strange, but that's what it
repeatably measures.


73,
Bob Martinson, N1VQR


  
-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Stuart
Sent: Wednesday, December 19, 2007 5:41 PM
To: time-nuts at febo.com
Subject: [time-nuts] Lucent RFTG-m-RB unit output level


Has anyone measured the 10Mhz output level of these units. How about the
output impedance?
Has anyone tried to tap off the 10Mhz from the OCXO on the XO unit? if so
what output level
did you get. I am looking for a GPSDO with an output level of at least 0dbm
into 50 ohms.

Stuart
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