antenna splint

[Butch]

Standing Wave Ratio (SWR) is a ratio of maximum voltage to minimum voltage along a feed line (Coax between the Transmitter and Antenna). Also... SWR involves how well the feed line impedance is matched to the antenna impedance; i.e. 50 ohm to 50 ohm. The latter should not be an issue if the antenna came with a factory attached coax feed line and the antenna is a marine antenna.

SWR is read by an inexpensive SWR meter in series between the transmitter and the antenna, with the meter being as close to the transmitter as possible.
With that being said, in a perfect world the SWR reading upon transmission should be 1:1. At a SWR of 1:1 100% of the RF signal sent from the transmitter is emitted by the antenna. Unfortunately, this ain't a perfect world and you'll get a SWR reading showing some of the RF power to the antenna is being reflected back to the transmitter along the feed line . Newer radios have limiting circuits that reduce output power when the SWR goes above 2:1... this is a life saver for expensive radio rigs . I believe this mentioned in the thread. When this happens... the range of the radio rig is reduced in proportion to the reflected RF and the reduction in the output power of the radio.
So if this is the case, how is the SWR reading affected by an antenna? Simply put... it is the antenna length. The length of an antenna is based on the frequency (Hz) of the bandwith utilized. Antenna lengths are based on incriments of the frequency; i.e. 5/8 wavelength, 1/2 wavelength, 1/4 wavelength, ect. Normally, one would lengthen or shorten an antenna to match the corresponding desired wavelength by monitoring the SWR meter during transmissions. An antenna that is well matched to the output power and frequency of the transmitter is said to be tuned and resonant at that frequency. Not much RF signal is reflected back down the feed line and thus the SWR is low.

Fiberglass antennas are factory pretuned to the frequency of the corresponding radio, such as the 11 meter CB band and the 10 and 12 meter Ham bands. You can use a 10 meter antenna on an 11 meter frequency, however, that could be hard on the transmitter and besides the performance (ability to be heard beyond one's shadow) will certainly suffer.

In your case... I'd suggest buying or borrowing an SWR meter and a short PL-259 jumper coax to measure SWR [u]after the you do the CPVC or PVC splint antenna fix. The reason is... a high SWR is an indication your transmission range may be severely limited.

I have witnessed SWR readings on marine radios so high the transmissions were not making it across a small marina... . One in particular was a 8' fiberglass with the last foot at the top duct taped on. At 25 watts radio output the feed line would heat up before the radio's SWR limit switch kicked in... I don't think that guy's RF signal; made it past his stern less than 20' away....

Hope this helps.... Butch KB30JO

[dotnmarty]

OK Butch- I'll get the SWR meter and the jumper coax. I'll try Radio Shack. I checked on the Metz 3 foot antenna and I think it's too expensive for me. West Marine has a 4 footer for about $100 which I will get if my reading is above 2:1. Thanks for taking the time to guide me. Marty

[Butch]

No problem Marty ... and good luck on repairing your antenna . Butch