I created this web page, not as much for you as for me. I wanted a place to store all my ham radio information, links, etc. This page is the result of my selfish effort. But, isn’t that the essence of the web – to share information?

Feel free to explore, comment and link to this blog. Or, better yet, contribute something!

Saturday, February 23, 2013

160 Meters - Size Matters

Drake L7 Linear Amplifier
Last year, I participated, or tried to participate, in the CQ Magazine 160 Meter contest. I used my Icom IC-756proIII radio into an inverted L antenna with a counterpoise. I ran barefoot with the 100w of the ProIII because my aging Drake L4B won't tune 160.

It was an exercise in frustration. Many of the weaker stations I tried to call couldn't hear me all that well, so multiple efforts were required. And, I just got buried by all the big signals.

This year, 2013, I bought a Drake L7, a later version of the L4B, that does full 1.5kw on 160. I like tube amps for a variety of reasons, but probably due to my background in broadcast engineering 35 years ago, the 3-500Z triodes were very common in drivers for AM transmitters. I know them to be efficient, hardy and, they glow. The only time solid state amps glow is when they melt down.

I had a much different experience this year, and worked nearly every station I could hear. I even tried a couple of CQs, and, at one point, had a bit of a pile up by stations wanting South Carolina. Same antenna, 9 db more power out.

Lesson learned - If you want to play with the big boys, you need big toys!

Wednesday, February 20, 2013

In Praise of Service Monitors

HP/Agilent 8924C Service Monitor
I like to fiddle with gear and antennas, so I have always dreamed of having a bench full of sophisticated, lab grade test equipment. What red-blooded tinkerer has not? My dream is to have a wide-band scope, an accurate RF generator, a multifunction AF generator, a wattmeter, frequency counter and lots of other gear. Throw in a sensitive receiver that goes from 30 Mhz to 1 Ghz, all modes, and you have the real deal. Oh, and a spectrum analyzer would be just dandy, as long as we are dreaming.

Trouble is, as you research the cost, each of these beasties can cost hundreds of dollars. And the amount of bench space they take up is mind boggling. Then, I discovered service monitors. A new one will set you back $25,000 and up, way up! But, after a bit of research, I found the HP/Agilent 8924C Service Monitor. This is an older piece of equipment, designed to serve the needs of the cell phone industry. It is computer controlled and has lots of features that are specific for the technical needs of CDMA cell phones.

8924C Display
But, but, but -- This baby is loaded with features that hams can use. In fact, it includes all the test gear I have mentioned so far, and a few others. It is programmable, so if you have a software bug (pun intended), you can create your own combinations.

Let me tell you what I have done with it in the few months I have had it. I fixed a UHF transceiver that was not putting out power. I set up 3 repeaters, including tuning the cavities. I have measured the output and frequencies of several dozen UHF handhelds I am working on. I also measured the sensitivity of the receive section. I plotted the SWR curve of a VHF/UHF J-pole antenna I built (needs some more work). And, just for kicks, I use it to tune around the HF, VHF and UHF bands, up to 1000 Mhz with great sensitivity. I can measure the tones generated by local repeaters.

Fantastic and unbelievable! What's that? How much did it set me back? $850 including shipping, and it weighs over 60#. There are variations of the HP/Agilent series of monitors, but the 8924C is the most complete. I did have to upgrade my input section, which was a maximum of 5w, to 100w (60w continuous). That cost another $125. I am under $1000 and it works perfectly. It is capable of doing much more than I am capable of doing with it. There is a learning curve, but there is lots of good info on operating these, including videos. Just plug 8924C into YouTube and you will find many good videos.
Here are a few:
Duplexer Tuning
HP 8920A Service Monitor and AW07A Antenna Analyzer
RX 40 meter band 7.075 Mhz SSB on HP 8920A Service Monitor
1 - RF Tools Antenna Return Loss.mp4