# Ham radio: Certain signals at roughly sunset **URL:** \ **Category:** Factual Questions\ **Created:** [April 6, 2008, 3:41am UTC](https://boards.straightdope.com/t/ham-radio-certain-signals-at-roughly-sunset/444149 "2008-04-06T03:41:29Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Tripler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripler/32/21807_2.png) [@Tripler](https://boards.straightdope.com/u/Tripler)\ **Post date:** [April 6, 2008, 3:41am UTC](https://boards.straightdope.com/t/ham-radio-certain-signals-at-roughly-sunset/444149/1 "2008-04-06T03:41:29Z")
A quick question–with a part theory of mine: I am a nerd [sub]father is geek, and mother nerd. I got his brains, and her looks[/sub], who built a shortwave listening radio, and enjoys ‘catching’ [WWV](http://en.wikipedia.org/wiki/WWV_%28radio_station%29) out of Fort Collins, CO so I can double check the clock on my workbench. Over the past few weeks, I’ve noticed I can get it relatively well around/just after sunset, and I have a theory on this. I think, because I’m at sunset, my atmospheric conditions change (deionization of the sky), and I can receive signals well. Further, because sunset hasn’t reached WWVB _yet_, it’s still broadcasting strong at it’s daytime power\* and I can receive the signals at my location easier. However, after a few hours or so, I can’t get WWV anymore–and I think it’s because sunset passes from GA over to CO, and WWV drops its broadcast power to the point that I can’t receive it anymore (too weak). My theory is that the best time to SWL is just after sunset, where stations to the west of me are blastin’ out waves at daytime power, but I can receive them easier in nighttime conditions. So, does anyone else notice this, and does my theory hold water? Tripler Yes, I’m a nerd. I logged signals from CO, OH, and some Voice of Russia too. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [April 6, 2008, 4:13am UTC](https://boards.straightdope.com/t/ham-radio-certain-signals-at-roughly-sunset/444149/2 "2008-04-06T04:13:39Z")
I don’t believe that WWV drops their power. They may, but I’ve never heard any say that they did. The reasons broadcast stations reduce power at night is because most stations, AM that is, share frequencies and reduce power to reduce interference with their “sister stations”. WWV is not sharing frequencies with any other US stations. Their website [WWV](http://tf.nist.gov/stations/wwv.html) doesn’t mention any power cutbacks. > [@](#): > > WWV operates in the high frequency (HF) portion of the radio spectrum. The station radiates 10,000 W on 5, 10, and 15 MHz; and 2500 W on 2.5 and 20 MHz. Each frequency is broadcast from a separate transmitter. Although each frequency carries the same information, multiple frequencies are used because the quality of HF reception depends on many factors such as location, time of year, time of day, the frequency being used, and atmospheric and ionospheric propagation conditions. The variety of frequencies makes it likely that at least one frequency will be usable at all times. Radio reception on the HF bands is enhanced when both the transmitting and receiving station are on the greyline. This means the area of sunset/sunrise would be connecting the two points. If I find a better online explanation I’ll post it. ---
**Author:** ![Tripler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripler/32/21807_2.png) [@Tripler](https://boards.straightdope.com/u/Tripler)\ **Post date:** [April 6, 2008, 8:49pm UTC](https://boards.straightdope.com/t/ham-radio-certain-signals-at-roughly-sunset/444149/3 "2008-04-06T20:49:22Z")
[QUOTE=GaryM] I don’t believe that WWV drops their power. They may, but I’ve never heard any say that they did. The reasons broadcast stations reduce power at night is because most stations, AM that is, share frequencies and reduce power to reduce interference with their “sister stations”. WWV is not sharing frequencies with any other US stations. [/quote] Obviously, I need to string up a higher antenna then–the one I’ve got now is 75’ of speaker wire (tied together at one end with a wire cap, so it’s more like 150’) strung up through the rafters of my attic. I’m going camping soon, and am gonna try to hoist one up on a baloon. . . > [@](#): > > Radio reception on the HF bands is enhanced when both the transmitting and receiving station are on the greyline. This means the area of sunset/sunrise would be connecting the two points. If I find a better online explanation I’ll post it. Is that because the transmitting station is still broadcasting daytime power, and the reciever is in nighttime conditions? Hey, if you do find more info, I’ll owe you one! 😉 Tripler Still a nerd. ---
**Author:** ![Rico](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rico/32/3582_2.png) [@Rico](https://boards.straightdope.com/u/Rico)\ **Post date:** [April 6, 2008, 9:10pm UTC](https://boards.straightdope.com/t/ham-radio-certain-signals-at-roughly-sunset/444149/4 "2008-04-06T21:10:08Z")
You’re experiencing what is known as [grey line propagation](http://dx.qsl.net/propagation/propagation.html) (scroll down - there is a map showing the current grey line). From the link: > [@](#): > > The grey line is a band around the Earth that separates the daylight from darkness. Radio propagation along the grey line is very efficient. One major reason for this is that the D layer, which absorbs HF signals, disappears rapidly on the sunset side of the grey line, and it has not yet built upon the sunrise side. Ham radio operators and shortwave listeners can optimize long distance communications to various areas of the world by monitoring this band as it moves around the globe. Uh…you did want the official geek answer, didn’t you? ETA: **GaryM** had the answer first. Damn you, **GaryM**! (shakes fist angriliy) ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [April 6, 2008, 9:28pm UTC](https://boards.straightdope.com/t/ham-radio-certain-signals-at-roughly-sunset/444149/5 "2008-04-06T21:28:47Z")
[QUOTE=Rico] You’re experiencing what is known as [grey line propagation](http://dx.qsl.net/propagation/propagation.html) (scroll down - there is a map showing the current grey line). From the link: Uh…you did want the official geek answer, didn’t you? ETA: **GaryM** had the answer first. Damn you, **GaryM**! (shakes fist angriliy) [/QUOTE] Ah, but I didn’t have a Greyline link, so we both win. And **Tripler** , my greyline experience is on the ham bands, and we don’t normally cut our power at all. QRO all the way, which means 1.5 KW on sideband. ---
**Author:** ![Vlad\_Igor](https://avatars.discourse-cdn.com/v4/letter/v/7feea3/32.png) [@Vlad\_Igor](https://boards.straightdope.com/u/Vlad_Igor)\ **Post date:** [April 6, 2008, 11:50pm UTC](https://boards.straightdope.com/t/ham-radio-certain-signals-at-roughly-sunset/444149/6 "2008-04-06T23:50:32Z")
Man, **Tripler** , you’re this \>\< close to getting your license. Bone up on the FCC rules and operating procedures, take the test and get your ticket. We need more geeks like you. And yeah, you’re experiencing greyline propagation. I’ve talked to at least a station in Argentina on greyline prop. KF4VCC ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [April 7, 2008, 12:06am UTC](https://boards.straightdope.com/t/ham-radio-certain-signals-at-roughly-sunset/444149/7 "2008-04-07T00:06:49Z")
[QUOTE=Vlad/Igor] Man, **Tripler** , you’re this \>\< close to getting your license. Bone up on the FCC rules and operating procedures, take the test and get your ticket. We need more geeks like you. [/QUOTE] x2. At least take the tech exam. It’s super easy. -jngl Amateur General Hijack! Anyone else going to [Dayton](http://www.hamvention.org/) this year? ---
**Author:** ![Tripler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripler/32/21807_2.png) [@Tripler](https://boards.straightdope.com/u/Tripler)\ **Post date:** [April 7, 2008, 12:19am UTC](https://boards.straightdope.com/t/ham-radio-certain-signals-at-roughly-sunset/444149/8 "2008-04-07T00:19:45Z")
**Rico** , that link is awesome, thank you! . . . and an amateur license had been on my “when-I-‘settle down’-and-have-time-to-actually-have-hobbies” list of things to do. . . my private pilots license being on the list too. But being too damn busy with work and all, I just haven’t gotten to it yet. I’m loving SWL-ing, I just gotta get the gumption to go and invest some money into some used equipment (maybe next year’s b’day present). Are the tests really that easy? I was under the impression I had to learn Morse Code, pick a band, study for that particular band, and pass that band’s test. I know the ARRL sponsors training, but is it just a matter of literally taking the test? Tripler I’m such a nerd, I GeoCache, and even know how to wind a decent helical antenna. ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [April 7, 2008, 12:54am UTC](https://boards.straightdope.com/t/ham-radio-certain-signals-at-roughly-sunset/444149/9 "2008-04-07T00:54:36Z")
[QUOTE=Tripler] Are the tests really that easy? I was under the impression I had to learn Morse Code, pick a band, study for that particular band, and pass that band’s test. I know the ARRL sponsors training, but is it just a matter of literally taking the test? [/QUOTE] They really are that easy. The tech license in particular is about one third common sense questions. I think you could read through a study guide one time and pass it right off the bat. Tech is (I think) 35 questions, multiple choice. The license classes to get on HF (General and Extra) used to require morse code but this was dropped. There’s no band licenses or anything like that. The General ticket gets you most of the HF band. ---
**Author:** ![Vlad\_Igor](https://avatars.discourse-cdn.com/v4/letter/v/7feea3/32.png) [@Vlad\_Igor](https://boards.straightdope.com/u/Vlad_Igor)\ **Post date:** [April 7, 2008, 1:56am UTC](https://boards.straightdope.com/t/ham-radio-certain-signals-at-roughly-sunset/444149/10 "2008-04-07T01:56:28Z")
[QUOTE=jnglmassiv] Hijack! Anyone else going to [Dayton](http://www.hamvention.org/) this year? [/QUOTE] I’m going to try, since I missed it last year. It’s worth the drive for the outdoor flea-market alone.