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Airwave Inc.

I am no longer active in this hobby for the foreseeable future. 
I will no longer maintain or update the website, but I will leave it accessible to the web for as long as possible (years).


IFR 1200 SS
Cushman CE-5
Airwave Inc.

My Collection
Test Equipment
Model Rocketry
About Me


My company Logo, from around 1990

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 - 1992

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. 

Model Variations

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.

wlw_demo.jpg (73233 bytes)
Demo test set with internal noise source, 2001


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 suggestions. :)

flyer_feb1996.pdf - Sales flyer from Feb 1996
ReturnLossTestSet_2007-11-08.pdf - 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:

wlw_testingcables.pdf - 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 paging industry.
DirectivityErrorCalc-w-SWR.xls - 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.
BuildYourOwnNoiseSource.pdf - Build a simple noise source.

A few bits and pieces of my RL and noise stuff


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Copyright 2008 Bryan's Old Computers
Last modified:
October 16, 2009