[time-nuts] External 10Mhz referance levels

Ulrich Bangert df6jb at ulrich-bangert.de
Sat Mar 31 10:19:38 UTC 2012


Chris,

while there MAY be exceptions my rule of thumb is that none of the devices
that I have seen until today was unhappy at a +7 dBm  reference level. My
own distibution amp runs at +13 dBm (quite handy to drive a level 13 mixer
directly from a well isolated source) and I drive all my devices with that
which include

HP3330
HP3325
HP5370
HP5342
HP5359
HP8660
SR-620
DS-345
UA6200A
Wavetek 278
Racal-Dana 1996
Anritsu MS2601B

without experiencing any problems. Don't look at the problem with the eyes
of a ham: Unlike in most ham rf circuits a lot of these devices need to make
a square shaped signal from the sine input and are happy if you support them
with a not too small level. That is my experience but please don't take it
as an invitation to test if EVERY device may be fed with 13 dBm without
destruction. A look to the specs is never wrong.

73s de Ulrich, DF6JB

P.S.
Even if you consider that the reference input may have a 0805 50 Ohms chip
resistor for termination its destruction level will be well above +20 dBm.  

> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Christopher Brown
> Gesendet: Samstag, 31. Marz 2012 10:12
> An: Discussion of precise time and frequency measurement
> Betreff: [time-nuts] External 10Mhz referance levels
> 
> 
> 
> 
> So, going through a surplus HP 5087A.  All torn down, cleaned 
> and back together.  10Mhz input amp and 10 output amps.  
> Manual talks about setting for 3V rms into 50ohms, all 10 
> amps appear clean and a little extra time with a spec an 
> gives -55db at 30mhz and < -65 or better for the rest.  
> Dropping to 1V RMS and tweaking the balance pot gives -55 to 
> -60 at 20 and 30, rest in the noise.
> 
> All seems good, but what should I be feeding my gear.  All of 
> the manuals are pretty sparse on details, mentioning minimum 
> for a few, but no target or max.
> 
> 
> Will be feeding
> 
> 3596C
> 5335A
> 5370B
> 8657B
> 8395/E6380A
> 
> to start.
> 
> Maybe I am missing it, but the only mention of level I have 
> seen so far is > -10dbm.  The suggested 3v rms in the 5087 
> manual seems a bit high.
> 
> Comments, suggestions, guidance?
> 
> 
> BTW: Name is Chris, HAM since teens, playing with anything 
> technical for longer than I can remember, packet data 
> networking guy for last 18 years by day.  Getting around to 
> putting together a decent workbench opposite the HAM station. 
>  Never could stand owning/operating things I could not 
> properly service, fixing the issue but first I need to figure 
> out all the gear (and in some cases fix the gear that will be 
> fixing the other gear.).
> 
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