Thread by @M0SKN_SA5IKN

LNA / preamp is an unpopular topic of the portable SAT discourse. Noise figure (NF) is assumed to be low due to absence of long cables. But what if NF of the system inherently is not top tier? Any benefit in using LNA with FT-817 & FT-818? 🧵
#hamradio #amsat #amateurradio #hamr

NF & MDS are determined by the quality of the signal chain and the venerable FT-818 is not a star in that department. Under exact same conditions (antenna, cable etc) a very weak signal readable from IC9700 would not be copyable from FT-818. 2/7
#hamradio #amsat #hamr

The comparison of NF & MDS of IC705, IC9700 and FT-818 assumes favourable IMD performance of the FT-818 with a 500 Hz filter. In the field this is rarely true and even less so with a passband of 3 or 2.7 kHz in SSB. 3/7
#hamradio #amsat #amateurradio #hamr

A number of portable/rover operators successfully employ LNAs for SAT work. @KG0D_Dave uses JG-ULNA70VOX, @PRStoetzer uses High Sierra Microwave preamp, @w1pa uses ARR LNA with RF VOX to name a few. 4/7
#hamradio #amsat #amateurradio #hamr #preamp

Most of the LNAs mentioned above have a very low NF. I use LNA432JXX without RF VOX with NF=0.28 borrowed from my EME system. This is an overkill. Any LNA with NF<2 would significantly improve NF of the system. 5/7
#hamradio #amsat #amateurradio #hamr #preamp

Ideally, LNA needs to be installed at antenna. This is impractical with Arrow. My LNA is fastened to the FT-818. The combined insertion loss of LMR-240, Amphenol connectors and filter (0.8 dB) is outweighed by the improved NF of the front end. 6/7
#hamradio #amsat #hamr #preamp

I only use LNA for 7200+ km contacts on RS-44. In most other cases a bare FT-818 is sufficient. A pair of FT-818 is still my choice for a portable SAT rig due to their form-factor and weight (if only there was a panoramic display). 7/7
#hamradio #amsat #amateurradio #hamr #preamp

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