Tuesday, January 27, 2009

Microwaves: What's the Use?

I had an interesting exchange about microwaves and their usefulness with my friend and colleague, Chris Vanderkoy (KF9OP). Now just by way of background, Chris and I work for the same company, me as a lead test engineer for industrial controls products and Chris as the RF engineer in charge of designing the radio hardware for the company's wireless sensor and controls products (in the 2.4 GHz band.) So Chris is a die-hard microwave guy. In fact, he refers derisively to anything less than 500 MHz as "DC".

But that's just not me. I like HF a lot and am only just now getting turned on to VHF/UHF stuff. Some time ago I was asking Chris about feedlines. He stated:

I wouldn't buy LMR400 for less than 50mhz. At those frequencies, you can get by with a series of coat hangers for your feed line....(well, not really....)

His reply didn't exactly tick me off, but it did seem mighty uppity. So I shot back with a challenge:

Ya know, I realize that actually building the radios is more of a challenge, but the problem is that the darn microwaves don't do anything interesting. They don't bounce off anything in the ionosphere but they do get scattered by everything under the sun. They get sucked in by every water-bearing obstacle (spelled TREES) in their path. They don't even bend to give you just a teensy bit more than line-of-sight. So you have to build a 400 foot tower just to get out. What's the use?

I thought that would put an end to his smart alecky ways. But no, KF9OP shot back with a detailed list of 10 good reasons to look at microwaves Here you go:

Microwave's benefits.

1) Wide Bandwidth (lots of space for everybody)

2) Wide Bandwidth (hard for others to find you if they don't know where to look.)

3) Easy to build Hi gain antennas. (30dBi parabolic dish is reasonable)

4) Good for Satellite communications.

5) 1/f noise much less at these frequencies.

6) If you point your dish to the sky, you can get ultra low noise floors.

7) Awesome directivity (send the RF where you want it).

8) Can't moonbounce at HF.

9) Different freq's get absorbed by different gasses (this phenomenon is a benefit not a problem. CO2 sensors use this phenomenon to detect the gas.

10) You can use microwave energy to see through walls and penetrate concrete/earth/etc. (cool for discovery of underground caves, oil, etc...)

I guess I don't think of microwave frequencies as a place you call for CQ, but rather a frontier of research that has all kinds of gold nuggets waiting to be discovered.

Ham radio is cool because it is cutting edge... 300GHz is definitely an edge.

So there you go. Microwave communication and experimentation might not be your cup of tea. But that's the great thing about ham radio. There are myriad facets of the hobby and you can almost always find some other folks who are interested in doing what you're doing. (But they had better be close if you want to talk to them with those puny microwaves ;o)

The bottom line is, I'm learning more and more to never say never. I didn't ever think I'd be all that enthusiastic about VHF/UHF weak signal stuff, but here I am reading and planning on how to significantly improve my station in that area. Who knows? Maybe someday I'll be as big a microwave aficionado as KF9OP.

73 DE W9HQ

1 comment:

  1. If the Chris VanderKoy you reference here is a central Wisconsin native, I'd like to get in touch with him (a grade school/high school friend I haven't seen in a few years). Pass along to him that Brian (an old OM cronie) says hello.