I can’t tuna fish, but perhaps an antenna?

by Bob Sauter on November 30th, 2010

So that we won’t be completely of- the-air in Watertown whilst we remove the old WSLJ transmitting antenna and install a new more better one (next week?), we’re planning to put up a temporary antenna at the site for a day or two. Fortunately, we’ve got our old Saranac Lake antenna to re-use… but as Saranac Lake is 90.5 and Watertown is 88.9, the antenna has to be re-tuned for the lower frequency. This involves lengthening each of the 1/4 wavelength arms by a little over a half an inch, then testing the antenna with a low power transmitter to determine if the adjustment worked.

re-tuning a Jampro JSLP-1 at NCPR labs (my garage)

5 Comments on “I can’t tuna fish, but perhaps an antenna?”

Hank says:

November 30, 2010 at 3:17 pm

Does this re-tuning procedure involve a hacksaw, by any chance?
Bob S. says:

November 30, 2010 at 3:22 pm

Nope, just a couple of 7/16″ (pretty close to your 11 mm) wrenches!
Mike Ludovici says:

November 30, 2010 at 5:50 pm

How can I determine the optimal antenna length for my portable radio when I am listening at different frequencies?
Thanks,
Mike
Craig Miller says:

November 30, 2010 at 8:02 pm

Looks Great, Bob.

I am sure you won’t make the mistake I made by tuning an antenna _inside_ a quonset hut at high altitude (it was cold outside). After moving the antenna outside I realized it was too short, the metal roof impacted the VSWR quite a bit.

Always a pleasure, Bob.

Craig…
[Former Chief Engineer of Hawaii Public Radio]
Bob Sauter says:

December 1, 2010 at 9:14 am

To Mike L (about determining the optimal antenna length for his portable radio when listening to different frequencies:) Mike, as you know there is a direct mathematical relationship between the frequency, wavelength and the speed of light for all electromagnetic radiation (radio waves, light waves, x-rays) V=Fλ. Then you could figure out the speed of light in air, and use a correction for the diameter of your antenna conductor…. OR use an on-line calculator like this one: http://www.crompton.com/wa3dsp/hamradio/antcalc.html OR best yet, just try different lenghts to see which works best. At any frequencies in the FM band a quarter wavelength is anywhere from 26 to 32 inches in length.

To Craig: my garage is wood!