Checkin' out dummy loads with a VNA...
 

Hi Joerg,
Well I'm sorry to hear that. As an analogue guy, I don't much care for
PROMS and stuff. I can fix up anything analogue in good time, given a
schematic and a decent range of test equipment, but am off my territory
with digital stuff. But I'm still not sure what the problem is here.
Are you saying spares for the digital parts are hard to obtain or
rather that the encoding on those chips may be hard to reprogram?

Checkin' out dummy loads with a VNA...
 

Hello Paul,


Well I'm sorry to hear that. As an analogue guy, I don't much care for
PROMS and stuff. I can fix up anything analogue in good time, given a
schematic and a decent range of test equipment, but am off my territory
with digital stuff. But I'm still not sure what the problem is here.
Are you saying spares for the digital parts are hard to obtain or
rather that the encoding on those chips may be hard to reprogram?


Not sure yet what is broken. The analog sampling stuff and all seems to
work but is reads out garbage. The PROMs are really old style. They look
posh with gold plating and all but I guess that non-programmed spares
would be next to impossible to find. But again, maybe they are still ok.
Hopefully...

Regards, Joerg

http://www.analogconsultants.com

Checkin' out dummy loads with a VNA...
 

....noooo, you should not have any problems! these two connectors
units are actually attenuators, not loads. loads have only one input
connector.
ctually you can measure all the important characteristics of the load
by applying power through some kind of directional coupler an measuring
the applied (incident) power and the reflected power by using the VSWR
formula you can calculate the input real resistance in order to obtain
a curve relative to frequency. of course, in order tomeasure the
complex impedance, you need acces to equipment capable of measuring the
phase angle also, like a vector impedance meter or a vector network
analyzer: you measure reflections caused by mismatch in a 50 Ohms
environment, and translate them in complex impedance values.
Saandy 4Z5KS

wrote:
Hi all,

I'd like to see what this new dummy load I just bought on e-bay looks
like under test at its purported frequency limit of one Gig.
Problem is, all the documentation I have for my VNA shows devices to be

tested having *two* connectors (an 'in' and an 'out' if you will) like
filters for example. I can only connect to the *one* connection that
dummy loads typically have, since it'a a termination device rather than

a through one like a filter or attenuator. Does that mean I can't
analyse its
characteristics? Or is there a work around/special cable configuration
that would solve
this problem?
Thanks,
clueless paul