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Transponder / DME Interference

I revently noticed a degraded ADS-B 1090 MHz performance when operating the DME in our aircraft. Today I did some reading and to my surprise the DME of the aircraft is supposed to transmit on 1090 MHz when the VOR/DME is tuned to 113.90. Am I missing something or is this interference really just accepted without any protection mechanism for the important 1090MHz frequency?

www.ing-golze.de
EDAZ

Sebastian_G wrote:

I revently noticed a degraded ADS-B 1090 MHz performance when operating the DME in our aircraft. Today I did some reading and to my surprise the DME of the aircraft is supposed to transmit on 1090 MHz when the VOR/DME is tuned to 113.90. Am I missing something or is this interference really just accepted without any protection mechanism for the important 1090MHz frequency?

The Wikipedia article on DME states:

Not all defined channels/frequencies are assigned. There are assignment ‘holes’ centered on 1030 and 1090 megahertz to provide protection for the secondary surveillance radar (SSR) system. In many countries, there is also an assignment ‘hole’ centered on 1176.45 megahertz to protect the GPS L5 frequency. These three ‘holes’ remove approximately 60 megahertz from the frequencies available for use.

ESKC (Uppsala/Sundbro), Sweden

Suppression lines installed correctly?

To create a suppression interface, the suppression lines between the units must be connected. However, this can only be done if the connected units are compatible. Before attempting to connect the suppression circuits, the compatibility of the units must be confirmed. If improperly matched, the suppression interconnect does not work and damage occurs to the circuitry. The units can be incompatible due to the unit’s suppression pulse, which can be bilateral or unilateral depending on the unit. Both connected units must have the same suppression pulse.

Last Edited by Vref at 10 Jan 16:06
EBST

Many aircraft use a suppression bus that the DME and transponder (and TCAS if you have it) are connected to. This ensures they don’t use the frequency at the same time. Do you have that and/or perhaps it’s not working correctly?

Top Farm, Cambridgeshire, United Kingdom

Suppression compatibility is an issue, the GTX33 is compatible with the KN63 but not the KN62 or 64.

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