ISS FM Repeater

| May 23, 2021 | 0 Comments

SWLs may have a lot of fun monitoring the new FM voice repeater on the International Space Station. ‘I heard it on 21st May 2021 at 20:05 UTC for an 11-minute pass’, says VARC member Bob Houlston (G4PVB).

‘The Doppler effect is quite noticeable, so I tuned my receiver high to 437.810 MHz and gradually detuned to the original downlink frequency of 437.800 when the ISS was directly overhead then continued down tuning to 437.790 as it passed me by. I clearly heard callsigns G1AAK & G0ABI along with many others.’

‘SatPC32 is my free satellite prediction software. My aerial is a homebrew 1/4 wave ground plane hoisted to the inside apex of the loft. RG58C/U feeder and a PL259/SO239 connector. Not the best quality components if transmitting but sufficient for reception methinks.’

Bob’s antenna is based on a design by John M0UKD (https://m0ukd.com). Scroll down to the 1/4 Wave Antenna Calculator section.

Bob advises that his element lengths are 2∙5mm2 stiff, single-core, insulated copper wire from mains installation power cable: Driven element = 16.5 cm soldered to the centre pin of upside-down SO239, four ground plane elements = 17.5 cm bent at 45 degrees to enable 50 Ohms impedance. YMMV. They are attached to the panel mount SO239 with wire ring crimp connectors, nuts, bolts, and serrated shake-proof washers. He found the shake-proof washers to be essential. Apart from SO239, PL259 & RG58C/U feeder typically e-Bay you can source all the parts from DIY stores.

Category: Club News, Interesting, ISS, Short Wave Listening

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