Topband: Topband Digest, Vol 196, Issue 19

[Vic]

Steve VE7WZ, that recording is of *G3OQT* calling cq dx on topband.

Listed on QRZ.COM but page managed by G3PGN.

More I know not.

73

Vic

G4BYG (G6M)

On 21/04/2019 17:00, topband-request at contesting.com wrote:
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> Today's Topics:
>
>     1. Re: Fresnel Zone (donovanf at starpower.net)
>     2. Horizontal Waller Flag Modelling (David Needham)
>     3. Brief EU open from SW US (W7RH)
>     4. Re: Brief EU open from SW US (VE6WZ_Steve)
>     5. Re: Brief EU open from SW US (uy0zg)
>     6. Re: Brief EU open from SW US (Richard McLachlan)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 20 Apr 2019 12:09:20 -0400 (EDT)
> From: donovanf at starpower.net
> To: topband at contesting.com
> Subject: Re: Topband: Fresnel Zone
> Message-ID:
> 	<1812038113.10243265.1555776560791.JavaMail.root at starpower.net>
> Content-Type: text/plain; charset=utf-8
>
> Hi Sinisa,
>
>
>
> See the last paragraph in this email for a very specific answer to
> Ray's original question...
>
>
> Your comments about applying this 57 year old classic publication
> are exactly correct.
>
>
> First determine the desired elevation angle(s), t hen select the antenna
> height that optimally illuminates the Fresnel zone.
>
>
> HFTA does a good job of performing this basic analysis, although it
> doesn't perform Fresnel zone analysis. Instead HFTA leaves it up to
> the user to analyze several azimuth offsets to adequately analyze the
> full width of the Fresnel zone over which the antenna's elevation
> pattern is formed.
>
>
> The width of the Fresnel zone is 5.66 times the height of the antenna
> at a distance of approximately the height of the antenna (for antennas
> at the optimal height of the desired elevation angle) divided by the
> tangent of the elevation angle.
>
>
> For an elevation angle of ten degrees the Fresnel zone reaches its
> maximum width approximately six wavelengths in front of the
> antenna, the near edge of the Fresnel zone is approximately one
> wavelength in front of the antenna and the outer edge of the
> Fresnel zone is approximately 30 wavelengths in front of the
> antenna.
>
>
> Detailed Fresnel zone analysis of vertical antennas is impractical
> because of the variability of soil conductivity within the large
> Fresnel zone. Fortunately s oil conductivity isn' t a significant factor
> for horizontal polarization except for very dry, low conductivity soils.
>
>
> The location of far edge of the Fresnel zone for vertically polarized
> antennas (related to Ray's original question) is highly dependent on
> soil conductivity in approximately the outer 75% of the Fresnel zone.
> The outer 75% of the Fresnel zone can add 3 dB or more to the
> low angle performance of vertical antennas if most of the soil
> (or water) within the outer 75% of the Fresnel zone is highly
> conductive.
>
>
> The specific answer to Ray's original question regarding a
> 160 meter 1/4 wavelength vertical is:
> For a 10 degree elevation angle -- f or each specified azimuth angle --
> more than half of the low angle radiation is formed in an area
> approximately 500 feet wide located 3000 to 15,000 feet in front
> of the vertical.
>
>
> 73
> Frank
> W3LPL
>
> ----- Original Message -----
>
> From: "shristov" <shristov at ptt.rs>
> To: topband at contesting.com
> Sent: Saturday, April 20, 2019 8:16:37 AM
> Subject: Re: Topband: Fresnel Zone
>
>> donovanf at starpower.net wrote:
>> The classic source for Fresnel zones as they apply to HF site
>> selection is NBS Technical Note 139:
>> https://nvlpubs.nist.gov/nistpubs/Legacy/TN/nbstechnicalnote139.pdf
>
> This indeed is a classical source, but it should be noted that the derivation
> assumes that the elevation angle actually used for communication
> is equal to the elevation angle of the peak of lowest ground reflection lobe.
>
> This may or may not be the case.
>
> In amateur operation, communication is often done using elevation angles
> well below the peak of the lowest lobe, because of inability to erect very high antennas.
> In such cases, the first Fresnel zones extends much further than the
> equation 3.4-4 predicts. Correct formulas may be derived using the same
> procedure, while separating communication angle from lobe peak angle.
>
> Using vertical antennas additionally complicates matters.
> I am not aware of any work on this topic.
>
>
> 73,
>
> Sinisa YT1NT, VE3EA
>
>
>
> _________________
> Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
>
>
>
> ------------------------------
>
> Message: 2
> Date: Sat, 20 Apr 2019 15:37:35 -0400
> From: David Needham <k4aja73 at gmail.com>
> To: topband at contesting.com
> Subject: Topband: Horizontal Waller Flag Modelling
> Message-ID:
> 	<CAL6LObYW820Se9NF0A11XzOQ1wViHkCCKLhNpip3DavSaD9YYA at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> Hello Top Banders,
>
> I am collecting the parts to make my Horizontal Waller Flag. I am not up to
> speed on EZNEC modelling and need to figure out the proper terminating
> resistor values. Is there anyone able to help me complete the calculations?
>
> It will be sharing the same boom as my 7 element Loop Fed Array for 6m, so
> I ended up with the following design dimensions:
> - Two 11' x 28' Loops made of aluminum tubing, including the end loops.
> - Loops 14.5' apart on a 36.5 foot boom, 2" OD.
> - 95 foot above ground
>
> More info available by contacting me off list at K4AJA73 at gmail dot com.
>
> Any help is greatly appreciated.
>
> 73,
> Dave K4AJA
>
>
> ------------------------------
>
> Message: 3
> Date: Sun, 21 Apr 2019 00:18:14 +0000
> From: W7RH <midnight18 at cox.net>
> To: Topband <topband at contesting.com>
> Subject: Topband: Brief EU open from SW US
> Message-ID: <f093bf31-bb5a-9c47-4760-6cfa29f0978b at cox.net>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> Now two days old due to mail bounce.
>
> Last evening a brief pre-greyline opening occurred to western Europe on
> 160m from the SW. I was able to work G3PQA at 03:33 UTC. This late in
> the season makes this type of contact rare. Propagation at the time
> favored southern east coast. At that time solar wind was below 250m/sec
> and proton density was less than 2cm squared.
>
> A side note. 40m was popping with S9 plus EU during this time period.
>
> 73
>
> Bob, W7RH
>