Types of Interference
- Intermod or receiver overload - This is caused by transmitted signals mixing externally
or internally in the receiver, or the receivers input being overloaded by a transmitter
or strong signal in close proximity.
- Accidental - This is caused by operators (us) accidentally bumping or sitting on the Mic
button. Or when we push it to see if the battery still has enough power to turn on the
Tx light. Or when someone transmits on one frequency, when he thinks he is on another.
- Malicious - This is caused by someone, with the intent to interrupt normal communications
or to attract attention to what he is doing.
The person who causes malicious interference might do it for one of
- He has a grudge or score to settle with someone who owns, maintains, or uses the repeater.
- He is bored, has nothing to do, and wants to amuse himself. He thinks it is also amusing
When malicious interference occurs, the main desire should
be to eliminate the interference. Finding the person and talking to, or reprimanding him may
not be the best way to solve it. He may continue, trying not to get caught the next time.
The best way to remove the interference is to discourage the person doing it, so that he
does not have the desire to continue. Many times he does it to get attention. If he is
ignored, he may go elsewhere to play or quit altogether.
Guidelines for handling a jammer on the air:
1) DO NOT ACKNOWLEDGE INTERFERENCE OR THE INTERFERER.
Do not talk to him or
about him. If he is unlicensed, talking to him is against the law. If possible continue your
QSO as if the interference didn't exist. If that is not possible, move to another freq or
tell the other person you've got things to do and will contact him/her later. Do NOT let the
interferer know you have even noticed him. If his audience goes away, so will he.
REASON: Most "malicious" interference is done to get attention. When you acknowledge
the interference, you have given him the attention he wants, which encourages him to
continue. If he doesn't get noticed, he'll go somewhere else where he will get noticed.
2) WAS THERE A COUTRESY BEEP? Did you hear the repeater's courtesy beep after the
interference? Did it sound normal, or was it from a link?
REASON: On many linked systems, the courtesy tone changes depending on where the
transmission originated. On ARA systems, two beeps of the same tone indicate the transmission
was from that repeater. If the tones are different (hi-lo, etc.) then it came from one of the
link repeaters. Try and note this information for the interference report. If you don't hear
a courtesy tone after the interference, it is probably originating on the output frequency.
It could even be caused by intermod.
3) LISTEN ON THE INPUT FREQUENCY to see if you can hear the interference direct. Make
note of your findings for the interference report.
REASON: This is one of the most important pieces of information to pass on to the
interference committee. If the above methods fail to control the interference and we have to
locate the interferer, we need to know where he can be heard on the input frequency. With
hams in every part of the state, someone will be able to hear the interference directly.
With that information, we can put mobile Doppler and Transmitter Fingerprinting in that
4) RECORD THE INTERFERENCE on tape if possible. Label the tape, then seal it in an
envelope. Date and sign the envelope.
REASON: We need to have as many samples of the interference as possible to aid in
locating and eliminating it. If action proceeds beyond the local level, we may need to
demonstrate the chain of custody of the tape. That is where the sealed envelope comes in.
5) CONTACT THE INTERFERENCE COMMITTEE, immediately if possible. Then fill out and file
an interference report, including your tape. If you are submitting a tape, it is better to
hand carry both it and the interference report to an interference Committee person. That
prevents breaking the chain of custody. The Interference Committee will replace any tapes
REASON: Very little can be done about interference that occurred yesterday. We need
to get to work on the problem while it is happening. The follow up report goes into the
database, and as they come in from different sources, they paint a picture of the problem.
It is these reports that drive the Interference committee.
The following was found as one of the guidelines for the ZIA Connection.
It also represents ARA’s policy and that of most repeater systems:
If you hear a jammer, IGNORE HIM. Resist the temptation to 'set the jammer straight'.
Simply don't acknowledge his presence. If the jammer has no audience, he will soon be gone.
Arizona Repeater Association - Local Interference Committee
Send interference reports to:
A.R.A. Interference Committee
Dennis Bietry - KE7EJF Chairman
Phone: (602) 274-3732