K6STI: Baluns for 88-108 MHz

"....An incoming electromagnetic wave illuminates both an antenna and its feedline. Current induced on the outer surface of a coax shield may enter the feedline at the feedpoint. Common-mode signals induced on parallel transmission line may become differential at the receiver. Either makes the feedline an unintended part of the antenna structure, which can degrade the directive pattern and forward gain. A current balun can attenuate unwanted coax shield current. A current or voltage balun can attenuate common-mode signals on parallel line...."

Baluns for 88-108 MHz

K6STI: Busting a Pileup Calculations

Busting a Pileup

"I've (K6STI) long wondered about the value of small improvements in transmit signal level for an amateur station. This includes trading pattern quality for higher forward gain during antenna design, or increasing antenna size or height. What does being 0.5 dB louder really do for you? ....".

Read the full explanation here:
Busting a Pileup

K6STI 50 ohm to 75 ohm Matching

If you play with FM stereo receivers these matching networks may be useful.

"...Most signal generators have an output impedance of 50Ω. To align an FM tuner or measure its performance, it's best to match this to the tuner's 75Ω input impedance. Mismatch loss is only 0.2 dB, but a source impedance that differs from the design value may alter the RF input circuit bandwidth or resonant frequency. This can degrade front-end tracking and affect intermod or desensitization measurements.....".

http://ham-radio.com/k6sti/match.htm

80M to 20M Loop Antenna Design by N4TPP

Here is a good web page on the design and operation of low frequency HF loop antennas. It has some very good information on components.


N4TPP 80M-20M Loop Design