+++++++++++++++ From: "Mike McCoy" To: "Kevin Rock" , Cc: Subject: Re: [Elecraft] Critical frequency Date: Sat, 23 Nov 2002 20:44:34 -0600 There is a handy dandy 'aid' I really like called dxatlas. I like it because it shows a map of the world with greylines, has prefix lookup, etc. All sorts of worthwhile goodies to play with. For those interested in propagation the latest version also overlays ionospheric data (MUF, F2 layer critical frequency, F2 layer height, E layer critical frequency, D layer peak density. Auroral activity). and geomagnetic data (Geomagnetic latitude; Corrected geomagnetic latitude; Magnetic dip; Modified magnetic dip; Magnetic dip latitude.) data. It's all updated based on your PC clock time & date. www.dxatlas.com They also just released IonoProbe. its function is to "Monitor space weather indices and helps you learn what those indices mean" and "IonoProbe downloads near-real time satellite and ground station data, stores information for future use and displays it in a user-friendly way." www.dxatlas.com/IonoProbe/ I have no connection with tha author other than admiring his work. Enjoy Mike K5PU ----- Original Message ----- From: "Kevin Rock" To: Cc: Sent: Saturday, November 23, 2002 6:37 PM Subject: [Elecraft] Critical frequency > Being a curious sort I looked up critical frequency. This is what I found: > > Near-Real-Time F2-Layer Critical Frequency Map > > The following image is a recent high-resolution global map of F2-layer critical frequencies. This corresponds to the maximum radio frequency > that can be reflected by the F2-region of the ionosphere at vertical incidence (that is, when the signal is transmitted straight up into the > ionosphere). It is also a map showing the current location of the auroral ovals, the sunrise/sunset terminator and the regions of the world > where the sun is 12 degrees below the horizon (which estimates the gray-line corridor where HF propagation is usually enhanced). This is > one of a plethora of constructable maps that is produced by PROPLAB- PRO Version 2.0 (formerly known as SKYCOM PRO), a very > powerful radio propagation software package for IBM or compatible computers, ideal for amateur or professional radio communicators. > Instructions on how to use this map follow below. > > This was found on : http://www.spacew.com/www/fof2.html > > 73, > Kevin. KD5ONS > ++++++++++++++++++ Reply-To: "Bob Lewis (AA4PB)" From: "Bob Lewis (AA4PB)" To: Subject: Re: [Elecraft] Thinking out loud again... Date: Sat, 23 Nov 2002 20:06:55 -0500 According to the ARRL Handbook, the "critical frequency" is the highest frequency that returns echoes at vertical incidence. +++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: "'Kevin Rock'" Cc: Date: Sat, 23 Nov 2002 19:33:15 -0800 Subject: [Elecraft] RE: Critical frequency Quite right, Kevin. I was confusing "Critical Frequency" with "Maximum Useable Frequency". The Maximum Useable Frequency is, I understand, about 3 to 5 times the Critical Frequency, but that is an estimate and it is effected by the geometry of the propagation as well as the frequency. In my original post I mentioned, in passing, the Maximum Useable Frequency and didn't realize that when Earl responded with a comment about the Critical Frequency that he had changed subjects! As Earl pointed out, the CF is defined by a signal being sent vertically upward and measuring the frequency at which there is no reflection back to the point of origin. It's normally measured with an ionosonde - a sort of specialized HF radar set - that gives the CF and measures the effective height of the ionosphere. Sorry about that! Ron AC7AC K2 # 1289 +++++++++++++++++ From: "Frank LaFranco W6NEK" To: Subject: Re: [Elecraft] Changes from 100 watts to 10 watts Date: Sat, 28 Dec 2002 12:13:31 -0800 Hello all, The statement that beacon station 4U1UN is operating on 28.200 MHz is an over simplification because the NCDXF beacon station referred to is only one of 18 beacon stations, spread through the world, which rotate transmitting on this assigned frequency. On 28.200 MHZ, the New York beacon station 4U1UN transmits 40 seconds past the hour for a period of 10 seconds. It then repeats the 10 second interval every 3 minutes. During that 3 minute period, 17 other NCDXF world wide stations are transmitting on this frequency. Each of them also transmit for 10 seconds. Therefore, in one 3 minute period, you have 18 worldwide beacons each transmitting ,one at a time, for 10 seconds. This is very useful for determining propagation openings to various parts of the world in real time. Each beacon will send its call sign (at 22WPM) followed by 4 one second carriers at 100W, 10W, 1W and 0.1Watt. In addition, the same 18 world wide beacons transmit on other HF bands. These include 20 meters (14.100 MHz), 17 Meters (18.110 MHz), 15 Meters (21.150 MHz), 12 Meters (24.930 MHz) and 10 Meters (28.200 MHz). If you tune to these frequencies, be sure to place your rig in CW mode to ensure you are listening to the displayed frequency. The NCDXF HF Beacon Network is a very valuable operating aid. For more info on this network go to: http://www.ncdxf.org/beacon.htm 73... Frank - W6NEK ----- Original Message ----- From: To: Sent: Saturday, December 28, 2002 8:08 AM Subject: [Elecraft] Changes from 100 watts to 10 watts > This is a critique of the Elecraft K2/100 > > Here are approximate changes on the NCDXF beacon > going from 100 watts to .1 watts. The station is 4U1UN > New York City on 28.200. Antenna is a 4 element beam. > > S9 100 watts > S8 10 watts > S5 1 watt > S3 .1 watt > > You are invited to listen to the NCDXF/ IARU beacon > network and listen for yourself the actual change in > signal level as the beacon goes fm 100 watts to 10 watts, 1 > watt and 100 mW, +++++++++++++++++++