IFR 1200 SS
My company Logo, from around
Return Loss & Cable Fault Test Set
Once upon a time, part of my communications business
(See above logo) was manufacturing a small test set used to measure something known as
return loss and trace distance to faults in radio antenna cables. This was a
great little test set that made common communications test equipment
perform the functions of expensive and uncommon equipment. It was purchased by wireless communications
companies of all sizes, governmental agencies and by one large test
equipment manufacturer, Hewlett-Packard. HP bundled the test set with
another piece of equipment they sold at the time, which even had an optional
software package to automate the whole process: the HP8920A. It was a
slick setup, and the buyers loved them. From day one, I never had a single
return, warranty or otherwise--not even one!
I considered this a
moderately successful product, with serious production problems: Although
the basis for the test set was a readily available mass produced item,
they required many careful modifications and tuning to be useful as test
equipment. And, they were all empirically tuned by hand! The tuning was
so highly critical and time consuming that I could never find anyone else
able to do it with any success. I tuned them all myself--spending between two to
four hours each.
Picture of my RL test set demonstrating usage -
|Demand was high enough, and they were difficult
enough to build that I was afraid to advertise them widely for fear that I
would be unable to keep up with the orders. As it was, I had my share of ninety-hour
work weeks. When I sold my business in
the mid-nineties, I reserved the right to make these for any interested
parties and continued to sell them as long as there was a
demand. When the 8920 was discontinued by HP, the orders eventually dried
up. The fact that I never advertised the kit was obviously a factor. I
still have a few dozen in various states of assembly... any offers?
I updated the flyer for the last time around 1996, and had a request
for a new users manual several years ago. I took the opportunity to
correct a few things, which is why the copyright was updated.
My original test set required a spectrum analyzer and a
tracking generator to use-- common in typical communications service
monitors but not a universal option. I built this version as a demo for a large
paging company that included a built-in signal source to eliminate the
need for a separate tracking source. The fact that the signal source was
wideband noise made it useful for a whole new range of testing applications.
These were never developed, but could have included spectrum analyzer
calibration and noise figure measurements.
The demo was completed September 7th, 2001. As you can imagine, things changed
in the next few days. The paging
business took a dive and the demo was never delivered. I still use
it frequently in my work today--It's not for sale (unless you throw lots
of money my way :), and I'll never make
another like it.
Demo test set with internal noise source,
I wrote all the documentation and sales materials myself, and it was no
easy task. Well, it might have been easy for someone who started out
knowing more than I did, but I had to learn a lot in order to correctly
explain how the darned thing works! Even as I read it all today, I see
things that need clarification or correction. Feel free to make
- Sales flyer from Feb 1996
- The users manual for the RL kit
wlw_testset.pdf - I started
to write this for the self contained test set, and never finished.
My test set, circa 1993
|Do It Yourself Stuff
I wrote a few things years ago for various reasons:
- How to do Frequency Domain Reflectometry (FDR) with just a signal
generator and a signal level meter. I wrote this for a few friends in the
- Calculate directivity measurement error for a specific directional
coupler used to measure return loss. (Mouthful, eh?)
AntennaCalcV1_11.xls - Antenna
system power loss calculator I wrote to use in the paging industry.
- Build a simple noise source.
A few bits and pieces of my RL and noise stuff