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Old 21st Apr 2021, 6:06 pm   #8
Skywave
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Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
Arrow Re: Spectrum Comms. Active Antenna problem

The classic method to determine the cause of the problem - considering that you have two active antennas - is to devise a method of comparing the gain of the two active antennas. There are many ways of doing that, generally determined by what test equipment you have available.

Ideally, you need to set up both antennas in the garden, pointing in the same direction, each fed with coax cable of the same type and length, fed into your workshop / listening room. At that point, you need the instrumentation to discover the signal levels arriving at the end of each cable - terminated in the appropriate load resistance - probably 75 or 50 ohms. A spectrum analyzer would be ideal for that comparative measurement.

Having said all that, my suspicion is that the offending antenna simply has excessive gain for the radio you are connecting it to and the 'front end' of that radio is simply becoming overloaded. A series of measurements with a switched, variable attenuator, alternatively connected to each antenna, should confirm - or otherwise - that suspicion.

Al.
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