The Radio Information Board

Recently I've seen a couple of instances where our TK-190s were not able to reach the dispatch center. So, I conducted a test to compare the relative radiated signal of the Kenwoods versus my trusty ol' MT-1000. Frequency is 46.42 MHz.

Test method: short clip lead on end of 6 foot coax connected to spectrum analyzer input. Set portables on desktop surface away from any encroaching objects. Mark the spot where the radio sits so that all radios are at the same position when transmitting.

The result was shocking: The Kenwoods were 6 to 10 dB LOWER than the MT-1000. I called the dealer to discuss this, and he is scratching his head over it. He did some experimenting with antenna lengths and found that an antenna about 1 inch longer gave better results.

Still, when repeating the tests with the "new" antenna the radiated signal is 2 to 4 dB worse than the MT.

Has anybody seen or heard anything about this? Perhaps cutting chart errors, or something?

Thanks in advance for any help or advice.

Joe

Here is an update on this situation:

I found out that Kenwood issued a bulletin that says something like "for best performance... tune the antenna to frequency..." They have a tuning procedure in which you program the radio to transmit on frequencies 1 MHz apart. Using an RF voltmeter or spectrum analyzer to monitor transmitted field strength, you can transmit in 1 MHz steps to see where the highest output is. Then you can clip the antenna one turn at a time and repeat the test to make sure you have the antenna peaked where you want it. The procedure starts you off by cutting the antenna per the chart supplied with the antenna.

Problem is, it appears that the antenna chart is wrong. I found that the antenna wants to be about 3/4 of an inch longer than what the chart calls for in order to resonate at the desired frequency. So I bought new antennas and tuned them up for "maximum smoke". The final length is about 7 9/16 inches.

Interestingly enough, the new antenna length is pretty darn close to that for the MT-1000.

Hope this is a help to someone.

JS