Verulam Amateur Radio Club

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ISS FM Repeater

Posted: 23 May 2021 04:58 AM PDT
http://www.verulam-arc.org.uk/posts/iss-fm-repeater/







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.




Bobs 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.






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