The vertical scale only goes to 15 MHz…..the chart is for the performance of the bent over whip, so lower angle radiation is attenuated. I am sure that there is skywave produced by the bent over whip it run at 20 MHz but this chart is to show NVIS and NVIS only happens in the lower HF spectrum, as described in the full manual. There is no NVIS from about 8 Megs up.
From: BVARC [mailto:bvarc-boun...@bvarc.org] On Behalf Of Michael Wrenn via BVARC Sent: Wednesday, November 04, 2015 10:08 AM To: BRAZOS VALLEY AMATEUR RADIO CLUB <bvarc@bvarc.org> Cc: Michael Wrenn <michael.k5...@gmail.com> Subject: Re: [BVARC] Re-SEND Correction -- NVIS -- Near Vertical Incidence Skywave and the BVARC Rag Chew Net Rick, I don't understand the chart. Is it the shaded area that encompasses each of the propagation types? If so, why doesn't the skyway extend to at least 28 Mhz? Seven Three, Michael - K5WRN http://www.qrz.com/db/K5WRN On Wed, Nov 4, 2015 at 10:03 AM, Rick Hiller via BVARC <bvarc@bvarc.org <mailto:bvarc@bvarc.org> > wrote: Resent for graphics correlation correction. Thanks, Michael…….Rick Recently, thanks to Jeff, AA(zero)ST, I received an installation/user manual for the Stealth Telecom Mobile Antenna System NVIS Whip Accessory. (PDF attached) It is an add-on 14 foot whip that is pulled down at the tip end to make it more horizontal. There are some user notes on the page that I thought interesting for antenna aficionados. One chart, shown below, shows the effects of using the NVIS whip, but more to the point and BVARC oriented, the chart shows the propagation that we experience on the BVARC Wednesday Night 75 Meter Rag Chew Net…..what we affectionately refer to as “the Donut Hole”. The Donut Hole (circle in red on the chart) is the (varying) area were line of sight and ground wave (if any) stop and then NVIS takes over a few miles more away. The dotted line is 3910 KHz. If you would like to read more about the NVIS and the Rag Chew Net…find it here… BVARC Tech Articles page. http://www.bvarc.org/index.php?page=tech and read the article by Larry, K5LJ: “Shortened Dipole Study for Conditions On BVARC’s Rag Chew Net” Thanks to Jeff for the inspiration. Enjoy….Rick – W5RH _______________________________________________ BVARC mailing list BVARC@bvarc.org <mailto:BVARC@bvarc.org> http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org
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