RadCom May 2020, Vol. 96, No. 5

News and Reports Around Your Region – Club events calendar 84 Around Your Region – Events roundup 88 New products 14 News 12 RSGB Matters 6 Special Interest Groups News 16 Regulars Advertisers index 93 Antennas, Mike Parkin, G0JMI 54 ATV, Dave Crump, G8GKQ 53 Contesting 22 GHz bands, Dr John Worsnop, G4BAO 64 HF, Martin Atherton, G3ZAY 60 Members’ ads 94 Propagation, Gwyn Williams, G4FKH 91 Rallies & events 95 The Last Word 96 VHF / UHF 62 Technical Features Decibels without the logarithmic calculations, Roger Paskvan, WA0IUJ 66 Demystifying SDR FM modulation, Mark Atherton, ZL3JVX 30 Design notes, Andy Talbot, G4JNT 46 Educational WSPR transmitter, Anthony Le Cren, F4GOH/KB1GO H 37 TVI – a case history, Geoff Budden, G3WZP 44 VDSL interference – Call to action 18 What is the function of an antenna, Dr David Kirkby, G8WRB 68 Amateurs’ role in disaster communications, Richard Thomas, G4JJP 76 Battle of the Radio Beams, Dr Bruce Taylor, HB9ANY 80 Bhutan, the land of the Thunder Dragon, Adrian Ciuperca, KO8SCA 42 Build a Radio Workshops, Steve Hartley, G0FUW 26 Features RadCom THE RADIO SOCIETY OF GREAT BRITAIN’S MEMBERS’ MAGAZINE Managing Editor: Elaine Richards, G4LFM, elaine.richards@rsgb.org.uk Technical Editor: Giles Read, G1MFG, giles.read@rsgb.org.uk Layout and Design: Kevin Williams, M6CYB, kevin.williams@rsgb.org.uk All contributions and correspondence concerning RadCom should be emailed to: radcom@rsgb.org.uk . Alternatively by post to RadCom Editor, 3 Abbey Court, Fraser Road, Priory Business Park, Bedford MK44 3WH Phone 01234 832 700, fax 01234 831 496. RadCom LV SXEOLVKHG E\ WKH 5DGLR 6RFLHW\ RI *UHDW %ULWDLQ DV LWV RIÀFLDO MRXUQDO DQG LV sent free and post paid to all Members of the Society. The June 2020 edition of RadCom is expected to arrive with most Members by 22 May 2020 although this can take up to a week longer in some cases; international deliveries can take longer still. © Radio Society of Great Britain All material in RadCom LV VXEMHFW WR HGLWLQJ IRU OHQJWK FODULW\ VW\OH SXQFWXDWLRQ JUDPPDU OHJDOLW\ & taste. Articles for RadCom are accepted on the strict understanding that they are previously unpublished and not currently on offer to any other publication. Unless otherwise indicated the RSGB has purchased all rights to published articles. No responsibility can be assumed for the return of unsolicited material. See www.rsgb.org/radcompix for info on taking photos for publication. The online RadCom is at www.rsgb.org/radcom/ RadCom Plus is available to RSGB Members online at www.rsgb.org/radcom-plus RadCom Basics for Members new to the hobby can be found at www.rsgb.org/radcom-basics/ Abbreviations and acronyms we use are listed at http://tinyurl.com/RC-acronyms January 2016 5 Contents May 2020 The RSGB is on Twitter @theRSGB Find us on Facebook at www.facebook.com/theRSGB Cover image: The Lelantos program and VDSL interference. Photos courtesy RSGB EMC Committee. Design Kevin Williams. 18 Ascel AE20401 frequency counter and power meter kit, Andrew Barron, ZL3DW 72 bhi NES10-2 Mk 4 noise reduction speaker, Mike Richards, G4WNC 24 Book review 79 Reviews 42 RadCom ISSN: 1367-1499 is published monthly DV LWV RIÀFLDO MRXUQDO E\ WKH 5DGLR 6RFLHW\ RI *UHDW Britain, 3 Abbey Court, Priory Business Park, Fraser Road, Bedford MK44 3WH. Periodicals Postage Paid DW 56*% 8. DQG DW DGGLWLRQDO PDLOLQJ RIÀFHV