[VHFcontesting] Ionosphere Scatter

Paul Rollinson Paulrollinson at sbcglobal.net
Mon Oct 24 16:13:59 EDT 2016

This has me very intrigued.

Do you know of any software that could project an arc 800-1000KM from my
QTH? That way, I can look for a station that would theoretically, be in the
target area to experiment with.


Paul Rollinson, KE1LI
Rollinson Associates
860-928-3844 Fax
860-208-8814 Cell/Text
Paulrollinson at sbcglobal.net

Representing Component Part 
Manufacturers for over 35 years

-----Original Message-----
From: VHFcontesting [mailto:vhfcontesting-bounces at contesting.com] On Behalf
Of Keith Morehouse
Sent: Monday, October 24, 2016 3:38 PM
To: vhfcontesting at contesting.com
Subject: Re: [VHFcontesting] Ionosphere Scatter

There is a considerable amount of path loss, so, in theory, all the "good
things" you would want for long-haul troposcatter (or sporadic-E)  are
useful for ionoscatter.  High ERP, low angle take-off and low environmental
noise.  Research says scattering occurs around 80-90 KM up, so more-or-less
the same ionospheric height as some sporadic-E.  Because there is refraction
in the ionosphere, there will be a minimum distance for Ionoscatter of
approx 800-1000 KM ("skip zone"), with a maximum distance based on your
ability to get a signal into that 80-90 KM high sweet spot (just like Es).
Distances shorter then 800-1000 KM can be covered (somewhat unreliably) with
troposcatter.  Studies show there is a diurnal
(daily) variation in ionoscatter signal strength of around 10 dB, with
minimum attenuation (maximum signal strength) occurring at mid-path noon.

Note that path attenuation increases rapidly as frequency increases.  The
optimum traffic frequency (FOT) for ionoscatter was calculated many years
ago as 50-60 MHz, taking into account path loss vs typical band noise
levels.  At low and mid-band frequencies, path loss increases about 5 dB for
every 10 MHz upward change of frequency.  This is why ionoscatter at
144 MHz is much more difficult.

Jay W9RM

Keith J Morehouse
Managing Partner
Calmesa Partners G.P.
Olathe, CO

On Mon, Oct 24, 2016 at 11:32 AM, Mark Spencer <mark at alignedsolutions.com>

> Hi this is interesting.   From a practical perspective I'd be curious in
> knowing if there is much difference in what needed to be successful 
> using long haul tropo scatter versus iono scatter on 50 MHz ?
> Presumably bigger antennas, higher power levels and a clear view of 
> the horizon will all be useful ?
> The comments about the K index and time of day for iono scatter are of 
> particular interest to me.
> 73
> Mark S
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