Stratux 1090 MHz + 978 MHz Diplexer Now Available
Recently the company Stratux released a new ADS-B/UAT diplexer PCB. This is useful if you have a single antenna and want to feed two RTL-SDR dongles, with one receiving 1090 MHZ ADS-B and the second receiving 978 MHz UAT. The filter consists of a splitter and two SAW filters.
ADS-B is short for Automatic Dependant Surveillance Broadcast and is used to help track aircraft in the sky. It is transmit at 1090 MHz and the signal contains aircraft data such as the location, speed, altitude and aircraft call sign. ADS-B is utilized worldwide.
UAT is short for Universal Access Tranceiver and is transmit at 978 MHz. Like ADS-B it is used to keep track of aircraft, however UAT is only available in the USA and only for aircraft that fly below 18,000ft. It is a little cheaper and unlike ADS-B, UAT transmissions can also contain weather and traffic data.
US aircraft owners/operators that fly below 18,000ft can choose to install either UAT or ADS-B transmitters in their aircraft, so in the US a complete monitoring solution needs to monitor both 1090 MHz and 978 MHz.
The Stratux Diplexer board is currently available on Amazon for $24.99.
Any chance to have such for 1090 and 868MHz ?
Did anyone find some real information on the filter besides just the quoted insertion loss like e.g.
– filter bandwidth,
– how fast the filter drops off,
– the max. attenuation or
PS: I remember that UAT on 978 MHz was implemented by FAA so far in the US only for operational use in the Alaska region. It was just recently announced to be extended to other states.
Here’s some specan images that he gave:
So yeah it’s not a “true” diplexer in that it still requires the power splitter which adds 3dB loss on top of the SAW insertion losses.
Probably an LNA in front would help.
Thank you for the curves. Imho the insertion loss representation at amazon is quite misleading to potential buyers, since it does not clearly identify the total insertion loss
– 978 MHz insertion loss (above 3 dB): 2.73 dB @amazon vs. total insertion loss of 5.78 dB @978 MHz
– 1090 MHz insertion loss (above 3 dB): 2.88 dB @amazon vs. total insertion loss of 5.88 dB @1090 MHz
Can you confirm if I identified the logo correctly for 1090 MHz as Tai-Saw Filter, possibly TA1090EC (insertion loss 2.3 dB typ. 3.0 dB max) and the 978 MHz saw filter could be a TA0395a (insertion loss 2.2 dB typ. 3.5 dB max) since there don’t seem to be to many manufacteres for 978 MHz.
If you check the filter curves they are quite wide and provide not much more attenuation than 10 dB 20 to 30 MHz above and below the center frequency.
Depending the frequencies in use on your location signals can exceed -40 dBm (meassured) on multiple/many channel from e.g. :
– cell phone base stations below 960 MHz
– ground and aircraft transmitter
– L-Band PSR between 1215 MHz and 1400 MHz
Aside from the comment on high loss due to PCB design, this duplexer can also function as a band-pass filter by using only one port at a time, with the other terminated. This may come in handy to reduce some level of interference. Not sure I would want to use an LNA with this board though.
Very bad PCB desig, and high losses …