@Lothar’s 1090 MHZ Cable Data
The 3 dB maximum cable loss length is a general recommendation ONLY for RTL SDRs that have a Sky7510 amplifier and Taisaw 3 dB loss SAW filter after the Sky7510.
Beware: Some SDR’s have the 1090 filter in front of the amp. This increases losses before the amp and thus increases the system noise figure, and for example if you use an AirNav Radar box “green” Flightstick or a Flight Aware Pro Stick Plus, you should cut the cable lengths in half to be equal in losses,given that the best SAW filters have 3 dB loss.
You have to balance the cost of other more exotic SDRs and LNA combinations for really long cable runs vesus keeping it the lowest possible installation costs.
You can run longer cabling by using a lower loss 1090 filter, and still keep the same loss before the SDR amplifier. Example: a cavity filter has a maximum of 0.9 dB loss while the best SAW filters are 3 dB loss.
This means that you can accept 5 dB of cable loss if you use a cavity filter and an unfiltered amplified SDR like the Airframes.io “Orange stick” RTL SDR.
If you stick to 3 dB cable loss and use a cavity filter, you get more sensitivity and better ADS-B decodes at lower signal levels, and a better system noise figure
This is general guidance only. High RF field environments must consider other factors.
Important: make sure whatever cable you decide to use has structural return loss data available to above 1000 MHz. Garden variety CATV cables are rated to I GHz. Satellite rated RG cables are SRL rated to at least 1.5 GHz. The best are rated to 3 GHz.
| Brand (Country | Type | 3dB loss footage | Notes | |
|---|---|---|---|---|
| Times Microwave Systems (US) | LMR-240 | 32' | ||
| MR-400 | 62' | |||
| LMR-600 | 96' | |||
| HDG Telecom (CN) | KMR-240 | 28' | 1,2,4 | |
| KMR-300 | 30' | 1,2,4 | ||
| KMR-400 | 92' | 1,2,4 | ||
| KMR-500 | 94' | 1,2,4 | ||
| KMR-600 | 96' | 1,2,4 | ||
| Belden (US) | (RG-8) 9914 | 65' | 1 | |
| (RG-6) 1694A | 44' | 1,3 | ||
| (RG-6) 7916A | 42' | 1,3 | ||
| CommScope (US) | (RG-11) 2287V | 55' | 1,3 | |
| (RG-6) 2227V 38' | 1,3 |
Notes
1 -Linear Interpolated from known manufacturers data frequency points.
2 - Includes corrections found from real tests. KMR is NOT equal to LMR.
3 - Includes 0.14 additional loss for 75 ohm mismatch.
4 - Metric data converted to imperial
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Lothars_cable_guide.pdf (433.0 KB)