March 01, 2005

High Gain Antenna Array

I consider it a blessing to have such a great source of massively diverse music as KDHX the public radio station here in St. Louis.

I consider it a torment that reception of KDHX in my cube is so problematic.

It's never been great, but with the boombox I used to have in here I could get a decent signal after about five or ten minutes fooling around with it. When that venerable old warhorse which someone had dug out of a dumpster, tinkered with till it worked, and given to me about nine years ago finally bit the dust I replaced it with a smaller but newer boombox which had been my wife's until I left it under the glass of the back hatch of our old Toyota Celica in a St. Louis summer several years back.

After that exposure to extreme conditions the top cover that flips down over the top-loading CD player part of the radio melted enough to distort under its own structural stresses and henceforth unable to close, the thing never played CDs again. After much 'discussion' Ruth told me to go ahead and take the thing to work.

The only problem was that it took a lot more work to get it to pick up KDHX. The reception was about the same as the old box, but due to an idiosyncrasy of the tuner of this particular system it was a matter of some frustration and fiddling to make the reception happen at all. Frequently the amount of fiddling rose to the point where I gave up in disgust.

It was after one of these very admissions of defeat last week that I hit upon the idea to haul the receiver I'd bought last summer to use out on the back porch in to work in hopes that its digital tuner would make it possible to get KDHX without problems.

Unfortunately, this plan was not an instant soultion.

Yes, tuning was much easier with a digital display to tell me that the frequency was set precisely to 88.1 MHz, but getting enough eletromagnetic radiation resonant at that frequency directed to the input circuits of the radio was still problematic at best.

The problem had shifted, though. In the past the problem was tuning. Now the problem was that, being at work, I find myself not free to stand stock still holding the end of the short, thin antenna wire coming out the back of the radio pinched between my fingers at the spot where Nijal our cat had gnawed a bit of insulation off so that my skin and natural body impedance and capacitance could be added to the input circuit.

Because when I was holding the wire reception was perfectly crystal clear but when I wasn't holding it- reception was almost nonexistent.

I knew that there was a square loop FM antenna in the box with the radio when I bought it, but subsequent searches of all likely spots at home did not turn up this antenna.

I was growing a little frustrated until I hit upon the idea of possibly adding a bit of wire onto the end of the antenna. Of course, it would have to be of some length to be of use but it might work.

I was about to make a scout around the back half of the building where the construction is drawing slowly to a close, but where there is still drywall dust on the new carpet and enough rough edges that I felt I ought to be able to find something of use.

About to, I say, until I thought to simply look under my desk where I found the treasure that would end my tribulation- an eight foot long piece of raggedy old Category five computer network cable which had been replaced at some point and which was currently unused.

It had RJ-45 connectors on each end but I pulled out my trusty pocket knife and quickly removed the connector off one of the ends (using a pair of big silver scissors since my pocket knife was too dull) and stripped one of the conductors in the wire. I twisted it around the bare spot on the antanna wire and presto!

No, the reception wasn't perfect, but it was much better without me touching the wire.

With a bit of configuration, though, the signal quality was much improved. As I ran the Cat-5 across the top of my shelves and down a cube wall reception improved and now after a bit more fiddling and getting all the loops out and making sure the wire running from the headphone jack of the receiver to the transmitter for my wireless headphones is laying just so- it sounds pretty good.

Posted by Roger at March 1, 2005 10:44 AM