Ground Wave - How far does it propagate ?

[Glenn NY4NC]

You got da muddy water slapper on big country?? 

Answer:

He'll never do it on any channel I'm on. When I put the maul down, all you hear is me - WHIRLWIDE.

Get these mud ducks outta here!

[Steve - WB3HUZ]

Hey Glenn. Yes, I'm on the air from the new 20 - since just before TNXgiving. This included the ham bands too. Hope to hear you on soon. We're pretty much the southern front on 75 meter AM. Where in NC have you settled? I might be able to lend antenna raising assistance.

[Glenn NY4NC]

Howdy Steve!

10-4 on the new 20!    I thought you moved there already during the summer? That's interesting because I was listening to the 75m round table you were in (late last night?) with K2DK, KB3AHE and AA3WH. I was listening on my bedside receiver (Lowe HF-150 w/15ft hunk of wire thrown around the bedroom), tuned in to hear Frank, then Dave transmit.. good signals... then it was your turn... HOLY CANOLI!!  what a strapping signal!! I couldn't believe how loud you were. DFQ old man FB!.. I have a strong feeling we're gonna have a pipeline between us once I get setup!.  Thanks for the Ant rasing offer but I have a feeling it would be a bit of a drive for you. I'm in Winston Salem, aprox northern mid-state. Not that far from the VA border but I think you're on the coast side.

Right now, my shack is the unfinished part of the basement. I going to start the building very soon and plan to be on the air by spring. The ant for 75 will be a pair of phased dipoles.

Whats your ant for 75? Moonraker or PDL? 

Hey Glenn. Yes, I'm on the air from the new 20 - since just before TNXgiving. This included the ham bands too. Hope to hear you on soon. We're pretty much the southern front on 75 meter AM. Where in NC have you settled? I might be able to lend antenna raising assistance.

[Steve - WB3HUZ]

Ah yes the ever more popular Moon Raper. Using an Antron 99 here.

The ant situation right now is a 75 meter coax-fed dipole at 70 feet. It's broadside NE-SW. A 160 dipole is in the works.

W-S looks to be about 213 air miles from here in a WSW direction, so you are in a main lobe of the antenna. The other stations in the Q last night were about that same distance from here. All were strapping (some as loud as I've ever heard), so conditions were premo! That said, I've received quite a few good reports from stations in that 150-250 mile range, so we will likely have a pipeline quite often.

I moved in August but just got around to the radio stuff in the last month. I can see why it will be a while to you are ready. Anyway, despite the distance, if things work out right, I could still head down your way. So let me know. The phased dipoles should kick A and take names!

[Warren]

Tom,

  As Bill pointed out ground wave is always vertically polarized.  Ground Waves are radio waves that follow the curvature of the earth. Ground waves are always vertically polarized, because a horizontally polarized ground wave would be shorted out by the conductivity of the ground. 


   As far as I know ground wave keeps incresing in distance as the frequency goes down. That's why VLF is used for world-wide coverage even in the daytime. Case in point last January the Alexanderson Alternator in Sweeden (a mechanical transmitter!) fired up on 17.2 kHz at 12:00 noon U.S. East Coast time and was copied up and down the East Coast on ground wave!
73 Warren K2ORS/WD2XGJ

[Warren]

Hmmm..... 30db improvement difference from 4mhz to 1.8mhz. and another 30 db improvement from 1.8 to the middle of the BC band.

You can see the tremendous ground loss improvement that the VLF guys enjoy. It's like almost 100 db better ground propagation down there...

T

  Tom,
      Keep in mind the curves are for 1kW radiated power. As you get down to 10kHz it becomes mighty hard to radiate 1kW!
     A 200ft tower even at 137 kHz (2200 meter wavelength) is approximately the equivalent of a 160 meter mobile antenna!
  73 Warren K2ORS/WD2XGJ

[K1JJ]

  Tom,
      Keep in mind the curves are for 1kW radiated power. As you get down to 10kHz it becomes mighty hard to radiate 1kW!
     A 200ft tower even at 137 kHz (2200 meter wavelength) is approximately the equivalent of a 160 meter mobile antenna!
  73 Warren K2ORS/WD2XGJ

Hey Warren,

Is it my fault you can't get up a 1,650' tall 1/4 wave vertical tower, huh?   

Yeah, good point, OM. Again, a good example of no free lunches. Ya think ya got it made with ground loss propagation and physics kicks ya in the BA's again.

T

[Jim, W5JO]

Hey Warren,

Is it my fault you can't get up a 3,300' 1/4 wave vertical, huh?   

Yeah, good point, OM. Again, a good example of no free lunches. Ya think ya got it made with ground loss propagation and physics kicks ya in the BA's again.

T

T if you decide to put up a 1/4 wave for that frequency, let me know.  I would like to see and take pictures of it.

JPW

[Ian VK3KRI]

Hey Warren,

Is it my fault you can't get up a 1,650' tall 1/4 wave vertical tower, huh?   

The guys down the road at the Omaga site make it look easy.

I was some distance away from the tower when I snapped this. Supposedly its 430m (~ 1400') tall. The 'lumps' in the guys appeared to be VERY big insulators

[Warren]

Thanks Ian for the Omega tower pic.


I guess you can look at the groundwave vs. wavelength argument another way. The greatly improved propagation at LF is what makes it possible for amateurs with tiny antennas to get on the air and make contacts. My pal W4DEX in North Carolina was recently copied in New Zealand on 137kHz!
I've gotten a QRO TX now running FB, but I've burned up the first two iterations of my antenna tuner!

Another look at how the pros do it - NAA in Culter Maine runs 2 Megawatts on 24 kHz. The antenna is 26 1000' towers ! The towers support a massive capacity top hat, the whole thing is clearly visible on Satellite photos from space.  NAA photo attahed.

73 Warren K2ORS/WD2XGJ

[Glenn NY4NC]

Antron 99 haaaaa!! 

Sounds good. Yea, Tom j-umbo j-oint suggested the phased dipoles, I believe thats what Gary INR is using..
Should blast a good signal up your way and beyond. Not sure about how I'm going to setup the phasing/switching yet, we'll see how much coax I can afford 

Make a post when you get the 160 ant up... I'm curious to see how loud you'll be here on 160. Don K4KYV has been blasting in here as of late. I'll also be putting up a 160 ant, probably coax fed perverted vee.

Ah yes the ever more popular Moon Raper. Using an Antron 99 here.

The ant situation right now is a 75 meter coax-fed dipole at 70 feet. It's broadside NE-SW. A 160 dipole is in the works.

W-S looks to be about 213 air miles from here in a WSW direction, so you are in a main lobe of the antenna. The other stations in the Q last night were about that same distance from here. All were strapping (some as loud as I've ever heard), so conditions were premo! That said, I've received quite a few good reports from stations in that 150-250 mile range, so we will likely have a pipeline quite often.

I moved in August but just got around to the radio stuff in the last month. I can see why it will be a while to you are ready. Anyway, despite the distance, if things work out right, I could still head down your way. So let me know. The phased dipoles should kick A and take names!

[Glenn NY4NC]

Hi Warren;

I'm curious about your VLF setup... I did a lot of experimenting in the 160-190khz "lowfer band" back in the mid 80's. I checked out your friends website, I see he has an experimental license for 137khz. I believe the rules for 160-190khz are still 1 watt and a 50ft antenna. Once and a while we would up the power for DX tests.. My beacon was heard in Ohio and Florida (nightime skywave) during one of those tests.
Hopefully hams will someday have fulltime use of an LF band.

The greatly improved propagation at LF is what makes it possible for amateurs with tiny antennas to get on the air and make contacts. My pal W4DEX in North Carolina was recently copied in New Zealand on 137kHz!
I've gotten a QRO TX now running FB, but I've burned up the first two iterations of my antenna tuner!

[Warren]

I'm curious about your VLF setup... I did a lot of experimenting in the 160-190khz "lowfer band" back in the mid 80's. I checked out your friends website, I see he has an experimental license for 137khz. I believe the rules for 160-190khz are still 1 watt and a 50ft antenna. Once and a while we would up the power for DX tests.. My beacon was heard in Ohio and Florida (nightime skywave) during one of those tests.
Hopefully hams will someday have fulltime use of an LF band.

Glenn,

   Most of the rest of the world has the 137 kHz band asssigned to ham radio. In the U.S. you have to go through the extra hurdle of an experimental license. My experimental license call is WD2XGJ, and I asked for and received permission to operate 136-140kHz.  If you want to see part of my setup, check out my LF webpage. It shows my first TX, a 250 watt rig. (The new 1.2kW rig is not on the web).
www.w4dex.com/wd2xgj.htm

Other good pages to look at:

http://www.qsl.net/on7yd/136khz_main.htm
www.wireless.org.uk
http://www.mlecmn.net/~lyle/
http://www.g0mrf.freeserve.co.uk/
www.lwca.org

73 Warren K2ORS/WD2XGJ

[K1JJ]

Wow... twenty six, 1000' towers.

Is that for submarine comm?  I guess there's no limit when it comes to military hardware.

Just think of the elaborate stacked sterba curtain arrays you cud put in various directions on 75M.  You cud fit in eight half wave stacks and make them 2 wavelengths wide with reflectors - stretched between towers.  Into Europe that would be 15db!!  louder than a single 3el Yagi. The take off angle wud be too low, however, unless you cud switch it higher. Man o man.

BTW, I think you told me you were using MosFETS for the VLF QRO rig.  How much power does it run when working OK, is that the  1.25kw rig?  So, with the low eff ant, you get out 50W ERP or so?

T

[Warren]

Wow... twenty six, 1000' towers.

Is that for submarine comm?  I guess there's no limit when it comes to military hardware.

Just think of the elaborate stacked sterba curtain arrays you cud put in various directions on 75M.  You cud fit in eight half wave stacks and make them 2 wavelengths wide with reflectors - stretched between towers.  Into Europe that would be 15db!!  louder than a single 3el Yagi. The take off angle wud be too low, however, unless you cud switch it higher. Man o man.

BTW, I think you told me you were using MosFETS for the VLF QRO rig.  How much power does it run when working OK, is that the  1.25kw rig?  So, with the low eff ant, you get out 50W ERP or so?

T

Tom,
   NAA at Cutle,Me is for submarine comms and it is worldwide no doubt!
NAA from space:
http://maps.google.com/maps?q=cutler,me&ll=44.644659,-67.274609&spn=0.029935,0.082191&t=h&hl=en

   Yes both of my TX's run power MOSFETs. The one on my web page runs a pair of IXYS 500 volt 55 amp  FETs, currently running 250 watts out. The bigger TX runs IRF 250s, a total of 12 FETs - three full bridge PA's going into a combiner. The big TX is a converted DECCA (European version of LORAN) so it is brick outhouse construction.
  The antenna efficiency kills you though. I calculate my antenna to be 0.1% efficient. So 250 watts out = 250 milliwatts erp, 1.2kW out =1.2 watts erp. On LF a 1 watt ERP signal makes you a 'big gun' and is good for world wide communications. I don't feel too bad about the erp, the Navy ran an ELF transmitter in Wisconsin on 77 Hz, a three  megawatts of  transmitter output and 8 watts erp!
http://www.elfrad.com/clam.htm

73 Warren K2ORS/WD2XGJ

[K1JJ]

I didn't know the power loss was that drastic down there.  That's like -30db or so. I can see why the big capacity hats are used.  So, 1W ERP is a big gun there. Just like the deaf man being king in the land of the blind. Or is it the one eyed man is king in the land of the deaf?

I remember once when I stayed in Maui, HI -  we took a drive around the island and all of a sudden in the distance I saw this huge dipole stretched between two mountains! It had some kind of feedline in the center going down to a large building. I mean, this antenna was at least five miles away but still looked big.  Just imagine two widely spaced and separate mountain peaks with a dipole between them... cheez.

I was later told it was some kind of submarine deal too.

T

[Glenn NY4NC]

Hi Warren;

Thanks for the info.... why are you using a loop for transmitting vs a vertical?...

[Warren]

Hi Warren;

Thanks for the info.... why are you using a loop for transmitting vs a vertical?...

Hi Glenn,
    I live on very wooded lot with rocky soil. This gives me two problems: 1) Difficult to get a good ground radial system 2) Electrically short verticals have  very high impedance above the loading coil which causes very high environmental loss such as absorption by the trees. For  good background reading on low frequency transmitting loops see Bill Ashlock's articles:
http://bill.have-my.info/
  Bill has demonstrated that a loop will outperform a vertical if the vertical is surrounded by trees.

  I may try a vertical in the future if I can get it far enough away from trees buildings etc.

73 Warren K2ORS/WD2XGJ

[Glenn NY4NC]

Hi Warren;
We found after some testing, that a vertical outperformed a loop on transmit if the vertical employed several long capacitive top hat wires. This placed the voltage/current nodes at different points along the antenna, vs a straight vertical. It was also more efficient because of the capacitive loading vs just a loading coil. I'll check out the link... probably refering to the fact that a vertical is an E-field device (voltage/high impedance) and a loop is an H-field device (current/low impedance). I would think also, a loop has less of a vertical component making it less effective for ground wave use.
 

Hi Warren;

Thanks for the info.... why are you using a loop for transmitting vs a vertical?...

Hi Glenn,
    I live on very wooded lot with rocky soil. This gives me two problems: 1) Difficult to get a good ground radial system 2) Electrically short verticals have  very high impedance above the loading coil which causes very high environmental loss such as absorption by the trees. For  good background reading on low frequency transmitting loops see Bill Ashlock's articles:
http://bill.have-my.info/
  Bill has demonstrated that a loop will outperform a vertical if the vertical is surrounded by trees.

  I may try a vertical in the future if I can get it far enough away from trees buildings etc.

73 Warren K2ORS/WD2XGJ

[Steve - WB3HUZ]

For some pix of the old NSS on 21.4 kHz (now gone) in Annapolis, MD, see the URL below. This site was decommissioned because the Cutler station could do the job. NSS was considered redundant. IIRC, it ran close to 1 MW into the antenna system and the ERP was around 30 kW.


http://www.amwindow.org/pix/htm/nss1.htm

[Warren]

Hi Warren;
We found after some testing, that a vertical outperformed a loop on transmit if the vertical employed several long capacitive top hat wires. This placed the voltage/current nodes at different points along the antenna, vs a straight vertical. It was also more efficient because of the capacitive loading vs just a loading coil. I'll check out the link... probably refering to the fact that a vertical is an E-field device (voltage/high impedance) and a loop is an H-field device (current/low impedance). I would think also, a loop has less of a vertical component making it less effective for ground wave use.
 

Hi Glenn,

    I'd be very interested in hearing about your testing and the results. Ashlock and others have found that even top loaded verticals have to be well clear of trees to be equal to a loop. It's all in part 1 of the Ashlock loop article which I posted earlier. But I'm certainly open to all arguments on the loop vs. vertical subject.  I plan on trying a top loaded vertical sometime this winter for comparison.
  You hit the nail on the head, a vertical has extremely high voltages above the loading coil, 20+kV with a few hundred watts out of the transmitter (think Tesla coil). The loop on the other hand is high current, 30 amps of RF in the loop when running 1.2kW out.
 
 B.T.W., you should easily hear Dex's (W4DEX) transmissions at your location, I hear him FB here  in Massachusetts!
73 Warren K2ORS/WD2XGJ