Space Wave help

[biferi]

I just need some help if anyone can give it about the types of Waves that are used.

1. wave is the Ionishperic Wave
is when wave bounce back and forth between the Earth and the Ionishper till it gets to the Radio and these wave would be the HF witch is shortwave and MW witch is Mediumwave.

2. Wave is the Serface Wave and it goes on the ground till it gets to the Radio am I right that this is just the AM Wave?

3. Wave is the Space Wave and it goes in a Streat Line to the Radio and it is Transmitted many FREQ above the ground.
Now this is what I don't get what do these Books meen that the Space Wave is transmitted at FREQ higher then the Serface Wave? and it never comes in contect with the Earth?
And is space wave UHF/VHF??

Please help in your own words and do not give me a Link to a web site I have been all over and they all say something diferant??

 

[Moleculo]

I think you're getting different types of propogation confused with the different frequency spectrums.

Certain frequency ranges are more likely to bounce off of the atmosphere back down to earth. The HF spectrum is where this tends to happen.

Certain frequency ranges can propogate along the ground - called groundwave. The MF spectrum is where this happens, which is typically where AM broadcast radio stations are located.

Other frequency ranges tend to be more line of sight and don't usually bounce back off the atmosphere - VHF/UHF is where this happens. Becasue of that, these frequency ranges also work well for satellites since they are just outside the atmosphere.

Hope that helps.

 

[Captain Kilowatt]

If I am understanding you correctly (use spellchecker please) you want to know what a "space wave" is. It is another name for "direct wave". It is a signal that travels through space from point A to point B DIRECTLY without propagating along the ground or bouncing off the ionosphere. A "Surface wave" is also known as a ground wave and propagates in contact with the ground. What most people call ground wave is in fact NOT ground wave but rather direct wave propagation.Most people use the term ground wave to describe a non-skip signal when in fact a true ground wave signal only occurs on much lower frequencies than CB radio covers and is quite short range except those occuring on the very low freqs VLF bands.

 

[C2]

there was a guy experimenting with vlf ground wave. he was monitoring something for earthquakes...

so, why don't i pick up AM broadcast stations from around the globe?

For example, I hear folks on 80M from quite a distance and quite regular like. But even just a few hour drive takes a big radio station, such as KGO, off the air, and then there is a lot of dead air out in the boonies.

 

[dudmuck]

so, why don't i pick up AM broadcast stations from around the globe?

Because all the AM broadcast frequencies are re-used.
Usually every night you're able to receive AM broadcast DX on any ordinary AM radio, but the problem is the I.F. filter is not of sufficient quality to reject the adjacent signals.

For example, WLW in Cincinnati has exclusive use of its 700KHz frequency. But the local adjacent stations on 690 or 710 can wipe it out. In a nearby country, there could be another station on 700KHz also wiping it out.

WLW is an exception, most other clear channel stations share with another station, but its so far away that the clear channel stations can usually be heard over half the country.

there is a list Clear-channel station - Wikipedia, the free encyclopedia

 

[W5LZ]

C2,
Several reasons for that. One is the particular range of frequencies the AM broadcast band falls in is lower than 80 meters so has less range. Another is that many broadcast stations are directional, and reduce power during periods of the day/night, no idea about the one you listen to. One of the local stations used to change broadcast directions after dark. So, there's several possible reasons for what you hear/don't hear not really directly connected with propagation. And then again, sometimes 'Momma Nature', who IS in charge of propagation, just doesn't give a squat about what you wanna hear, she's gonna make you listen to what she want's you to hear! (And no matter what anyone tells you, She's da'boss!)
- 'Doc

 

[Captain Kilowatt]

C2, another simple answer is similar to why you don't hear everyone on ch 19.The freqs are immensely occupied and the strongest one is the one you will hear if in fact any of them get above the noise. You also need to have very good filters and a good antenna connected to a good receiver to hear stations around the world. Also bear in mind that here in north America we start the AM band at 530 and each channel allocation is spaced 10 KHz apart. In most other parts of the world the band starts at 531 KHz and channels are spaced 9 KHz apart on 531,540,549,558 KHz etc. that can be a good thing actually because some foreign assignments are halfway between North America assignments such as Norway on 1314 KHZ. Being here on the east coast I have logged 1 Kw stations in Central America and the northern part of South America as well as higher power stations in Europe, North Africa and the Middle East all on either longwave or the standard AM broadcast band.It's tough and you need good gear as I said before but it can be done.

 

[C2]

I was just making a comparison of what I hear, usually 80 meters has a lot of distant stations from the US, AM broadcast usually has a lot of local stations.

I understand that I will only hear the dominant station on a particular frequency, but I would expect a lot more DX stations to come through on "dead channels"

For example, KGO in San Franfreako, Californica is on 810, WBAP in Fort Worth, Texas is on 820, but I never hear 820, just static.

I'll play with my old Collins some and see what else I can pick up. It has about 50 feet of wire antenna just thrown up on the roof...

 

[C2]

I ploted the MW received spectrum. Lots of gaps...

1 = signal, no meter movement above noise, and no inteligibility
2 = signal, no meter movement above noise, inteligibility
3 = signal, meter reading, inteligibility
4+ = meter reading, good inteligibility

noise level was 2dB

meter scale from 0dB to 100dB

 

[W5LZ]

One of the local stations is on 1150, and you're hearing them off the scale! Dang!
- 'Doc

 

[C2]

That is 1170 and they are hitting me at +42dB.

The Wiki reports:

1170 KFAQ Tulsa, Oklahoma
1170 WWVA Wheeling, West Virginia

It must be another local station, which I'll look up. IIRC, it was either spanish or another asian language...

I also measured a reference, +10dB is -64dBm. So I'm guessing the meter is somewhat calibrated for -74dBm for 0dB and the measurements would be the typical "over S9"

 

[Captain Kilowatt]

I'll play with my old Collins some and see what else I can pick up. It has about 50 feet of wire antenna just thrown up on the roof...

If you could add another zero to that antenna length then you would have a very good antenna for broadcast band DX'ing. I currently use a 300 foot wire but at my previous QTH I managed to have a 600 foot long wire about 15 feet high. I swear I could hear static crashes in Mongolia on that thing. :w00t: Unfortunately I could also hear the driver feedthru power from the LF naval communications station 12 miles line of sight away.Their 10 Kw driver was copied at S-9+15 and that was just the leakage thru the finals. When they keyed the 250 Kw finals........well you know where the S-meter went.