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MFJ-269 Sign of Reactance

It is good to know that you have been directly involved with several technical sessions ("Circuits in Motion", "Capacitors and Oscillators"....) where building circuits was an enjoyable task.
I read your question about the physical introduction of a small capacitive reactance in series with a transmission line terminated with an antenna using the MFJ-269 Antenna Analyzer. A series reactance smaller than the reactance read by the analyzer should be considered. The variation of the absolute value of the phase angle or the reactance read by the 269 could be then used to determine the sign of reactance.
I do not know the bands that you are considering for your 30 feet away antenna. I guess that it could be in the 80 m to 10 m bands.
Probably you have available ceramic trough hole capacitors from a 10 pF to 8200 pF range in your lab. At the same time I guess that you considered too the series inductance option easy to do with a simple short wire.
 As you know it is relatively easy to hook up the short leads of a through hole part (THP) to an N or BNC connector.
Then the procedure to physically  add a series reactance while making a reliable measurement could be:
  269 female N connector + THP + Adapter
The Adapter could  be terminated in a female BNC or N at one end, and the required for your coax at the other one.
The 269 female N connector and the connector Adapter grounds must be connected (practically "just touching" could be acceptable).
Joaquin Bonilla ( JB )
Project Engineer 
MFJ Enterprises Incorporated 
----- Original Message -----

Sent: Thursday, May 15, 2003 10:29 PM

Subject: Determining Sign of Reactance


I  have a MFJ-269 HF/VHF/UHF antenna analyzer with version 1.24 software.
Section of the manual discusses measurement of impedance. In
order to determine the sign of the phase it is suggested to add a small
amount of capacitance in series with the load and watch the angle
change. My antenna is 30 feet in the air so I have to add the
capacitance at the connection to the analyzer. How can I best physically
do this while making a reliable measurement? Thank you.


Article details
Article ID: 67
Company: MFJ
Date added: 2017-01-12 14:27:24
Views: 29

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