My Special QRZ deal

[kl7aj]

For a mere $29.95 (the price of an Earl Scheib paint job!) I will model your antenna with 4nec2 and give you a genuine 3D pattern!


No...actually I'll do it for free, because it's a lot of fun. If you want to know what your antenna pattern looks like, give me all your dimensions, and what you think your ground conductivity is in your area, and I'll give you a pattern. You might be surprised~!

Eric

[k7mh]

$29.95... What? No ups? No extras?? :D

[KA7RRA]

I can get it from K-MART for 9.95

[W4INF]

Walmart for $7.95 but Ill take the freebie.

I have a 70ft longwire. At the base on ground, a 4:1 balun which is grounded right at the balun. The wire runs at about a 45 deg angle up for 40 feet, then the last 30 feet is level in the trees. Orientation is base at W and tip at E. I am operating 80 - 10 on it, 17 does NOT tune very well all others almost flat.

Thanks for your service, I have no idea how to run NEC et al.

If you dont mind, Ill have more in the future that I would like to have done!


Andrew

[KB3LIX]

Here is one for ya Eric.

Basically a doublet, center fed with 450 ohm ladder/window line.
Dimensions as follows:

Length 88' (44' per side)
Installed as an inverted "V"
Apex of V at 25 feet above ground level
Doublet is oriented North-South
North end of doublet anchored at about 6 feet above ground level
South end of doublet anchored to a cinder block, 18" above ground level.

Fed with 450 ohm ladder line approx 40 feet long.

The FCC ground conductivity chart indicated a "4" conductivity for my area, SouthWestern Pennsylvania.
What this translates to in millisemens or micromhos (or whatever the measurement is, I don't remember the terminology), I have NO idea.

KB3LIX@Comcast.net

I have tried to model it with Eznec, and have been unsuccessful.

I know the antenna works, sometimes to my amazement. I picked up a new DXCC entity this morning, Tajikistan on RTTY.
# 174 from this homemade P.O.S.

bill

[kl7aj]

Here is one for ya Eric.

Basically a doublet, center fed with 450 ohm ladder/window line.
Dimensions as follows:

Length 88' (44' per side)
Installed as an inverted "V"
Apex of V at 25 feet above ground level
Doublet is oriented North-South
North end of doublet anchored at about 6 feet above ground level
South end of doublet anchored to a cinder block, 18" above ground level.

Fed with 450 ohm ladder line approx 40 feet long.

The FCC ground conductivity chart indicated a "4" conductivity for my area, SouthWestern Pennsylvania.
What this translates to in millisemens or micromhos (or whatever the measurement is, I don't remember the terminology), I have NO idea.

KB3LIX@Comcast.net

I have tried to model it with Eznec, and have been unsuccessful.

I know the antenna works, sometimes to my amazement. I picked up a new DXCC entity this morning, Tajikistan on RTTY.
# 174 from this homemade P.O.S.

bill


LIX

Your ground is 4 milliSiemens per meter.....just about average. If you have an ARRL antenna book, there's a nice map of ground conductivity. (In my 1991 edition, it's on page 3-3). You'll notice Alaska isn't even on the chart, it's so bad up here!

I'll get back with you with some plots before noon if the creek don't rise. :)

Eric

[KA4DPO]

For a mere $29.95 (the price of an Earl Scheib paint job!) I will model your antenna with 4nec2 and give you a genuine 3D pattern!


No...actually I'll do it for free, because it's a lot of fun. If you want to know what your antenna pattern looks like, give me all your dimensions, and what you think your ground conductivity is in your area, and I'll give you a pattern. You might be surprised~!

Eric


OK, I have a G5RV at 20 feet and it works real good. I can hear signals from across town and sometimes even farther. I have to wear a rubber glove to use the mic cause when I transmit it burns me. That's how I know it's working cause lots of RF is comming off of it everywhere.

Can your model show my SWRs and where they are so I can remove them? Can it also show how many pounds are comming off of my antenna? Thank you.....:D

[kl7aj]

Walmart for $7.95 but Ill take the freebie.

I have a 70ft longwire. At the base on ground, a 4:1 balun which is grounded right at the balun. The wire runs at about a 45 deg angle up for 40 feet, then the last 30 feet is level in the trees. Orientation is base at W and tip at E. I am operating 80 - 10 on it, 17 does NOT tune very well all others almost flat.

Thanks for your service, I have no idea how to run NEC et al.

If you dont mind, Ill have more in the future that I would like to have done!


Andrew


INF:

I see that 4 land also has average ground conductivity....I would have thought it would be much better! Even southern Florida is only 6 mS/meter...I thought it would be more like the coast of L.A (15)

Anyway....could you describe your ground connection? This is crucial for modeling an end-fed wire. Is it just a rod or some radials or what?

Eric

[W4INF]

INF:

I see that 4 land also has average ground conductivity....I would have thought it would be much better! Even southern Florida is only 6 mS/meter...I thought it would be more like the coast of L.A (15)

Anyway....could you describe your ground connection? This is crucial for modeling an end-fed wire. Is it just a rod or some radials or what?

Eric

Sure sir. Ground is 6 ft copper clad ground rod. Sorry I omitted that. NO RADIALS.

If you could model it with the ground rod AND 4 radials 50 ft long N-E-S-W it would help also!

Thanks much!
Andrew

[kl7aj]

Here is one for ya Eric.

Basically a doublet, center fed with 450 ohm ladder/window line.
Dimensions as follows:

Length 88' (44' per side)
Installed as an inverted "V"
Apex of V at 25 feet above ground level
Doublet is oriented North-South
North end of doublet anchored at about 6 feet above ground level
South end of doublet anchored to a cinder block, 18" above ground level.

Fed with 450 ohm ladder line approx 40 feet long.

The FCC ground conductivity chart indicated a "4" conductivity for my area, SouthWestern Pennsylvania.
What this translates to in millisemens or micromhos (or whatever the measurement is, I don't remember the terminology), I have NO idea.

KB3LIX@Comcast.net

I have tried to model it with Eznec, and have been unsuccessful.

I know the antenna works, sometimes to my amazement. I picked up a new DXCC entity this morning, Tajikistan on RTTY.
# 174 from this homemade P.O.S.


Eric



bill


LIX

On 80 meters, your inverted vee is indistinguishable from a dipole, as far as radiation pattern is concerned, from a first pass. I'll see how it looks on 40 and 20.

One reason you probably had trouble modeling this is common to any vee antenna. You have to "cheat" the feedpoint a bit. Put a small horizontal wire between the two legs...just three segments, and put your voltage source on the middle of that. If you have enough segments, this little "jumper" will be unnoticeable in your pattern. The alternative (probably more "official" method) is to use TWO volage sources in series. one at each upper segment. But you absolutely HAVE to be sure to get the phasing right on these!

[kl7aj]

Walmart for $7.95 but Ill take the freebie.

I have a 70ft longwire. At the base on ground, a 4:1 balun which is grounded right at the balun. The wire runs at about a 45 deg angle up for 40 feet, then the last 30 feet is level in the trees. Orientation is base at W and tip at E. I am operating 80 - 10 on it, 17 does NOT tune very well all others almost flat.

Thanks for your service, I have no idea how to run NEC et al.

If you dont mind, Ill have more in the future that I would like to have done!


Andrew

Here's patterns for 40 and 20m

[kb7nmu]

If someone could tell me how to model the isores coils on my Alpha Delta DX-CC I can do the rest. 4nec2 is an amazing program. Have you worked with ItsHF for propagation forecasting yet?

[kl7aj]

If someone could tell me how to model the isores coils on my Alpha Delta DX-CC I can do the rest. 4nec2 is an amazing program. Have you worked with ItsHF for propagation forecasting yet?


Yip...i've been playing with itsHF. Still learning some features. :)


Do you have a data sheet on your Alpha Delta?

eric

[N2RJ]

My antennae:

4 element MonstIR 4 element yagi (3 elements on 40 and 30) @ 72ft

Hustler 6BTV vertical

If you need anything specific let me know

[kl7aj]

Here's patterns for 40 and 20m


By the way, these are for TOTAL field, polarization independent. I'll put together some H and V patterns if you want. :)

[kb7nmu]

Yip...i've been playing with itsHF. Still learning some features. :)


Do you have a data sheet on your Alpha Delta?

eric

The best info I have found is here http://www.alphadeltacom.com/pg1.html. You can download the PDF instructions from there, but no, no real datasheet. I keep hoping to find something out there though. I was hoping that someone that KNOWS radio might have better luck than I at deciphering the design of the coils.

[kb7nmu]

Woops... I have a DX-EE, the 40 through 10 model, not the DX-CC. My excuse is that I am sick today.

[kl7aj]

The best info I have found is here http://www.alphadeltacom.com/pg1.html. You can download the PDF instructions from there, but no, no real datasheet. I keep hoping to find something out there though. I was hoping that someone that KNOWS radio might have better luck than I at deciphering the design of the coils.


NMU:

My GUESS is that the isores coils are using the self resonance (due to parasitic capacitance)as a trap. They look pretty closely spaced turns.

Do you have a grid dip oscillator? If you can tell me the actual resonant frequencies of these, I can do a lot.

Eric

[kb7nmu]

NMU:

My GUESS is that the isores coils are using the self resonance (due to parasitic capacitance)as a trap. They look pretty closely spaced turns.

Do you have a grid dip oscillator? If you can tell me the actual resonant frequencies of these, I can do a lot.

Eric

Oh boy. Now I have to figure out how to use the MFJ-259B for something other than SWR measurements. Not to mention climbing on the roof. Luckily I have the accessory pack to let me use the MFJ as a grid dip oscillator. So, will I need to disconnect the coils from the antenna to get an accurate reading?

(Yes, I know, licensed 17 years and no idea how to use a grid dip oscillator. Sorry, just got into HF the last two years or so. Much more fun than repeaters.)

[kl7aj]

Oh boy. Now I have to figure out how to use the So, will I need to disconnect the coils from the antenna to get an accurate reading?



Yes. You want the coils pretty well isolated from everything. It's a lot easier if you put them on a table (not a metal one!)

Eric

[K8MHZ]

My antenna: A double bazooka formerly 35 feet to it's inverted V configuration now about half way down the tree, making it look like a 'W'. The tree is down the hill in our back yard which now puts the apex at about 5 feet above the level of our front yard. We live on dune sand, but there is a creek in the back yard with some topsoil made mostly from compost. A 60 foot ground rod in the sand presents around 1300 ohms of impedance as measured by our electrical inspector. It's so bad that lightning has to stop and ask for directions on the way down. Oh, I forgot to mention that the feedline to the antenna is now almost horizontal. I have an RF choke 1/2 wave down the feedline wrapped around a stick. One leg of my 40 meter wire dipole is holding the choke and the feedline up just far enough so our dog can't jump off the upper deck and fetch the stick. As such, I assume the teeth marks in the stick are from squirrels. When first installed as an inverted V I managed a 1.1 to 1 match in the center of the band, with a 1.6 to 1 at the band edges. Now, in it's 'W' configuration I have an SWR of about 18,000 to 1 which drops to 6 to 1 when the squirrels are on it.

My question is, would my SWR get into the workable range if I figured out how to get the squirrels wet before they started climbing on my antenna?

[kl7aj]

Ah...now where was I? Oh yes...just got done with INF's model. Lemme see what we can do with this here invertolated Vee. :)

[kl7aj]

My antenna: A double bazooka formerly 35 feet to it's inverted V configuration now about half way down the tree, making it look like a 'W'. The tree is down the hill in our back yard which now puts the apex at about 5 feet above the level of our front yard. We live on dune sand, but there is a creek in the back yard with some topsoil made mostly from compost. A 60 foot ground rod in the sand presents around 1300 ohms of impedance as measured by our electrical inspector. It's so bad that lightning has to stop and ask for directions on the way down. Oh, I forgot to mention that the feedline to the antenna is now almost horizontal. I have an RF choke 1/2 wave down the feedline wrapped around a stick. One leg of my 40 meter wire dipole is holding the choke and the feedline up just far enough so our dog can't jump off the upper deck and fetch the stick. As such, I assume the teeth marks in the stick are from squirrels. When first installed as an inverted V I managed a 1.1 to 1 match in the center of the band, with a 1.6 to 1 at the band edges. Now, in it's 'W' configuration I have an SWR of about 18,000 to 1 which drops to 6 to 1 when the squirrels are on it.

My question is, would my SWR get into the workable range if I figured out how to get the squirrels wet before they started climbing on my antenna?

MHZ. I think I'd have an easier job modeling a ball of steel wool..but I'll try. :)

eric

[kl7aj]

OK, I have a G5RV at 20 feet and it works real good. I can hear signals from across town and sometimes even farther. I have to wear a rubber glove to use the mic cause when I transmit it burns me. That's how I know it's working cause lots of RF is comming off of it everywhere.

Can your model show my SWRs and where they are so I can remove them? Can it also show how many pounds are comming off of my antenna? Thank you.....:D


DPO

Here's looking straight down on your antenna on 20 meters, modeled over average earth.

[kl7aj]

DPO

Here's looking straight down on your antenna on 20 meters, modeled over average earth.

Well, here's the SWRs on you antenna. As you can see, you've got some BIG ones. I recommend a hammer to beat them into submission.

:)

eric

[kl7aj]

Here's your horizontal radiation pattern on 40 meters

[kl7aj]

And here's yer vertical polarized pattern.

[kl7aj]

LIX

On 80 meters, your inverted vee is indistinguishable from a dipole, as far as radiation pattern is concerned, from a first pass. I'll see how it looks on 40 and 20.

One reason you probably had trouble modeling this is common to any vee antenna. You have to "cheat" the feedpoint a bit. Put a small horizontal wire between the two legs...just three segments, and put your voltage source on the middle of that. If you have enough segments, this little "jumper" will be unnoticeable in your pattern. The alternative (probably more "official" method) is to use TWO volage sources in series. one at each upper segment. But you absolutely HAVE to be sure to get the phasing right on these!


LIX:

For what it's worth, your antenna is self resonant at exactly 5 MHz. It has a feedpoint resistance of 56 ohms at that freq.

eric.

(If you have a noise bridge, I'd like to see how close this comes to reality!)

eric

[kl7aj]

My antennae:

4 element MonstIR 4 element yagi (3 elements on 40 and 30) @ 72ft

Hustler 6BTV vertical

If you need anything specific let me know

RJ....I'm really surprised that New Jersey has ground conductivity from average to very poor. Intellesting.


eric

[kl7aj]

My antennae:

4 element MonstIR 4 element yagi (3 elements on 40 and 30) @ 72ft

Hustler 6BTV vertical

If you need anything specific let me know

This is an optimized 3 element pattern for 20 meters....scaled to 35 foot tower height. This can be done with reasonable confidence. I chose "moderate" for your ground conductivity.


I'm not sure if the steepIR automatically seeks best F/B or best gain. Do you know?

eric

[KA7RRA]

I have to wear a rubber glove to use the mic cause when I transmit it burns me. That's how I know it's working cause lots of RF is comming off of it everywhere.

I know where my RF is going!! it is going into my neighbor's TV, lights stereo telephone and all of the other cheap electronics that he has

he threaten to report me to the FAA

[KE7HQY]

I have to wear a rubber glove to use the mic cause when I transmit it burns me. That's how I know it's working cause lots of RF is comming off of it everywhere.

I know where my RF is going!! it is going into my neighbor's TV, lights stereo telephone and all of the other cheap electronics that he has

he threaten to report me to the FAA

RRA - I'm sure the Federal Aviation Administration would get right on the case :p

Seriously though, is your radio, amp (if you have one), etc. grounded? Mic bite and radio splatter reek of an ungrounded system.

[W4INF]

By the way, these are for TOTAL field, polarization independent. I'll put together some H and V patterns if you want. :)

Please do, and if you or someone else can... on the picture post for my longwire, can you explain what Im looking at? I dont understand the visual.

I understand graphs like this: http://zievid.com/W6OT/Hex/EZNEC17mElevation.gif


Thanks for any help-
Andrew

[KB3LIX]

LIX:

For what it's worth, your antenna is self resonant at exactly 5 MHz. It has a feedpoint resistance of 56 ohms at that freq.

eric.

(If you have a noise bridge, I'd like to see how close this comes to reality!)

eric


That is why the chosen length. It was not chosen because of any book, or article I read, it was chosen to be a 1/2 wave dipole at 60 meters.
That way, in theory, it would exhibit 0 db gain at 60 meters, and I would not have to sweat the maximum ERP requirements at 5 mhz.
I just remember to reduce the transmitter power to 50 watts, subtracting any inherent tuner loss and feedline loss (very minimal) I am right at 50 w ERP on 60m.


Patterns are VERY interesting.
Sure explains why I seem to get into Europe well on 40m.
20 should be interesting.



After a few minutes of digesting the models/photos,
on 40, it looks like this antenna has both a decent east-west horizontal component and a decent north-south vertical component.
I honestly expected most of the radiation to be horizontal in polarization with very little vert component.

Obviously, I was also VERY wrong !!!!!!!

[kl7aj]

That is why the chosen length. It was not chosen because of any book, or article I read, it was chosen to be a 1/2 wave dipole at 60 meters.
That way, in theory, it would exhibit 0 db gain at 60 meters, and I would not have to sweat the maximum ERP requirements at 5 mhz.
I just remember to reduce the transmitter power to 50 watts, subtracting any inherent tuner loss and feedline loss (very minimal) I am right at 50 w ERP on 60m.


Patterns are VERY interesting.
Sure explains why I seem to get into Europe well on 40m.
20 should be interesting.



After a few minutes of digesting the models/photos,
on 40, it looks like this antenna has both a decent east-west horizontal component and a decent north-south vertical component.
I honestly expected most of the radiation to be horizontal in polarization with very little vert component.

Obviously, I was also VERY wrong !!!!!!!

LIX

Without a ground, you would be correct...the inverted vee would be strictly horizontal, biecause the vertical components would be in common mode (assuming a perfect balance).

However the presence of the ground changes EVERYTHING. It was eye-opening for me too. :)

eric

[kl7aj]

Please do, and if you or someone else can... on the picture post for my longwire, can you explain what Im looking at? I dont understand the visual.

I understand graphs like this: http://zievid.com/W6OT/Hex/EZNEC17mElevation.gif


Thanks for any help-
Andrew


INF:

What you are used to is 2D graphs. If you take a SLICE through the red blob, what you see will match your more familiar graph. 4nec2 has a really great slicer...you can do it in any direction you want. :)

I can send you a few of these tonight if you like.

eric

[kb7nmu]

Yes. You want the coils pretty well isolated from everything. It's a lot easier if you put them on a table (not a metal one!)

Eric

Good thing I have to relocate the antenna anyways. At five watts it interferes with my cable TV. The cables run parallel 4 feet below the antenna in the roof. Time to move it to some trees.

[N2RJ]

I'm not sure if the steepIR automatically seeks best F/B or best gain. Do you know?

eric

Both, according to them, because they aren't limited by bandwidth.

[N2RJ]

RJ....I'm really surprised that New Jersey has ground conductivity from average to very poor. Intellesting.


eric

I am surprised too. Maybe you're looking at the wrong part of NJ

Where I live -

- The water table is about 11 ft below ground
- The soil is rich in iron (and so is the ground water)

I am in northwest NJ, closer to EPA rather than NNJ.

[kl7aj]

Good thing I have to relocate the antenna anyways. At five watts it interferes with my cable TV. The cables run parallel 4 feet below the antenna in the roof. Time to move it to some trees.


Another thing that would be nice to know is the L/C ratio. You need an extra KNOWN VALUE capacitor to do that. I can tell you how to figure this out, if you get that far. :)

eric

[kl7aj]

I am surprised too. Maybe you're looking at the wrong part of NJ

Where I live -

- The water table is about 11 ft below ground
- The soil is rich in iron (and so is the ground water)

I am in northwest NJ, closer to EPA rather than NNJ.

I just downloaded a more detailed map. I will take a closer look at your bailiwick. :)

eric

[kl7aj]

New Joisey Ground Conductivity

[kl7aj]

New Joisey Ground Conductivity



New Joisey

[W6GQ]

Is it possible to give info on the "slinky Antenna"

http://www.nonstopsystems.com/radio/frank_radio_antenna.htm

[K8MHZ]

MHZ. I think I'd have an easier job modeling a ball of steel wool..but I'll try. :)

eric

Steel wool? Like from an iron sheep?

But you do have me thinking.....

A garden hose stuffed with steel wool. Or steel wool at the end of a vertical to be used as a cap hat. How about a big ball of steel wool as an isotropic radiator?

The possibilities are endless.

[n2jso]

New Joisey

What are the numbers on the map?

N2RJ and I live right under the "2" in the Northwest corner of NJ - Sussex County. In fact, the lower left corner of that "2" is pretty much right over my QTH. It's very rocky here, lots of granite. A lot of iron, too, as Ryan mentioned. Don't know if iron ore affects ground conductivity much.

[KA4DPO]

Well, here's the SWRs on you antenna. As you can see, you've got some BIG ones. I recommend a hammer to beat them into submission.

:)

eric


Gee thanks Eric, now maybe I won't have to wear that stupid glove anymore..:D

[kl7aj]

What are the numbers on the map?

N2RJ and I live right under the "2" in the Northwest corner of NJ - Sussex County. In fact, the lower left corner of that "2" is pretty much right over my QTH. It's very rocky here, lots of granite. A lot of iron, too, as Ryan mentioned. Don't know if iron ore affects ground conductivity much.

JSO

The numbers are ground conductivity in milliSiemens/meter. (A Siemen is 1/ohm). The standard is derived by driving two one meter copper rods in the ground, one meter apart, and measuring the resistance between them. It's actually a VOLUMETRIC measurement, but by using the standard above, one dimension "cancels out."

Eric

[kj3n]

The numbers are ground conductivity in milliSiemens/meter. (A Siemen is 1/ohm). The standard is derived by driving two one meter copper rods in the ground, one meter apart, and measuring the resistance between them.

I'll assume that the higher the number, the better?

[W4INF]

INF:

What you are used to is 2D graphs. If you take a SLICE through the red blob, what you see will match your more familiar graph. 4nec2 has a really great slicer...you can do it in any direction you want. :)

I can send you a few of these tonight if you like.

eric

Yes, please do. And if you could give me your opinion on the antenna, that would be nice. w4inf at yahoo . com

I downloaded 4nec2 and for the most part, 99%, Im lost. :-)

Thanks,
Andrew

[kl7aj]

I'll assume that the higher the number, the better?

Yes that is correct. Unless you're building a Beverage :)

[kl7aj]

Yes, please do. And if you could give me your opinion on the antenna, that would be nice. w4inf at yahoo . com

I downloaded 4nec2 and for the most part, 99%, Im lost. :-)

Thanks,
Andrew


For the space you have, it's probably about as good as you're going to do. You might go ahead and put in the four radials...if you can elevate and resonate them, you'll be a little better off.\


Now, as far a 4nec2 goes....where are you lost? I can help unlose you.

Have you looked at the examples antennas?

ERic

[kl7aj]

I just downloaded a more detailed map. I will take a closer look at your bailiwick. :)

eric


I'm not sure why New Jersey shouldn't be more conductive....apparently the iron doesn't help. What's really amazing is that Long Island (Lawn Gyland in New Yorkese) is only .5, and it's IN the water!

Mysteries still abound. :)

eric

[kl7aj]

Here are some files for you. The first is the data file, the second your vertical plane radiation pattern (at maximum azimuth) and your horizontal pattern (at 0 degrees elevation.


ERic

[kl7aj]

Here are some files for you. The first is the data file, the second your vertical plane radiation pattern (at maximum azimuth) and your horizontal pattern (at 0 degrees elevation.


ERic

Here they are

[AC0FP]

Hi Eric,

Where did you get your soil conductivity map? The only one I find is linked below.

http://www.fcc.gov/mb/audio/m3/

In EZNEC I typically use 15 mS/m for conductivity and 20 for the dielectric constant.

By the way, have you found any inconsistencies between the answers given in 4nec2 and EZNEC?

73,

Frank

[kl7aj]

Hi Eric,

Where did you get your soil conductivity map? The only one I find is linked below.

http://www.fcc.gov/mb/audio/m3/

In EZNEC I typically use 15 mS/m for conductivity and 20 for the dielectric constant.

By the way, have you found any inconsistencies between the answers given in 4nec2 and EZNEC?

73,

Frank

I'm using the M3 file....zipped it's 6.8 MB

[kl7aj]

I'm using the M3 file....zipped it's 6.8 MB

There shouldn't be any major inconsistencies between EZNEC and 4NEC2. EZnec is based on the mininec3 engine, which was written in BASIC, but very similar algorithms to NEC2. (Method of Moments).

Where you'll see the difference is modeling ground wires IN CONTACT with the Earth, super close spaced wires of different diameters, and tapered conductors. For wires, I've never run into any differences.

w4rnl goes into some detail in the different flavors.

eric

[kl7aj]

Hi Eric,

Where did you get your soil conductivity map? The only one I find is linked below.

http://www.fcc.gov/mb/audio/m3/

In EZNEC I typically use 15 mS/m for conductivity and 20 for the dielectric constant.

By the way, have you found any inconsistencies between the answers given in 4nec2 and EZNEC?

73,

Frank

FP:

15 mS is the average conductivity for the whole continent. :)


eric

[kl7aj]

Is it possible to give info on the "slinky Antenna"

http://www.nonstopsystems.com/radio/frank_radio_antenna.htm

GQ:

For all practical purposes the slinky antenna has the same radiation pattern as a dipole of the same linear length. (not the length of the spiral
!)

So if you have a slinky that happens to work on 40 meters, but it's only stretched to 8 feet total, the pattern and radiation resistance will be the same as an 8 foot antenna on 40 meters. The reactance, however, is distributed over the length, which can, depending on the pitch between the turns, be a very efficient or very inefficient process. Also, the "ohmic" resistance of a Slinky isn't a real issue. Yes, it would be better if it was made out of copper or brass...but steel is okay.

eric

[kl7aj]

By the way, ages ago, someone did extensive testing on the slinky, using different combinations of pitch...more compressed at the ends, or the middle, or the center, for example, to see which was the better. I forgot the results, though. (They even went so far as to have a Slinky made with a REVERSE twist, to see if that made a difference when used as pairs. (It didn't, by the way)).

[kl7aj]

I guess everyone's happy. I'll send my invoice of $0.00 to everyone who availed themselves of my special offer!

:)

eric

[AC0FP]

FP:

15 mS is the average conductivity for the whole continent. :)


eric

Thanks, I used that number because the map indicates the soil is 15 to my East and 30 to my West. The antenna model doesn't change enough when using either number that would justify trying to measure it myself.

My latest antenna is a vertical 20 meter doublet fed with ladder line in the middle. The bottom of the antenna is 9' above ground and the top is 43' above ground. Antenna is 12 ga. copper wire.

73,

Frank:)

[n4bfd]

I've been speculating on making a Jpole for 20 meters that I can hang from a tree. I have a few branches that stick out from one in the back yard that may be just long enough to keep one off the ground if it is under 60 feet long.

Modeled after this one..
http://www.hamuniverse.com/slimjim.html

But making it out of wire and using 1 foot PVC spacers.

[kl7aj]

Thanks, I used that number because the map indicates the soil is 15 to my East and 30 to my West. The antenna model doesn't change enough when using either number that would justify trying to measure it myself.

My latest antenna is a vertical 20 meter doublet fed with ladder line in the middle. The bottom of the antenna is 9' above ground and the top is 43' above ground. Antenna is 12 ga. copper wire.

73,

Frank:)

Yer antenna is about 60 ohms at the feedpoint. How long is your transmission line? If you're only using this on 20 meters, cut the transmission line an exact multiple of a half wavelength, and you can feed it directly from a rig with a 1:1 balun.

Eric

[AC0FP]

Yer antenna is about 60 ohms at the feedpoint. How long is your transmission line? If you're only using this on 20 meters, cut the transmission line an exact multiple of a half wavelength, and you can feed it directly from a rig with a 1:1 balun.

Eric

I am presently using approximately 59' of 450 ohm ladderline hooked to a SGC-239 autotuner. My calculations show the Z @ the tuner as 88 -j 147. EZNEC says the feed point of the antenna is 75 +j 16 @14.2 MHz, however 20 meters is the only band from 80 through 10 meters that the tuner has trouble tuning.

[KB3LIX]

I guess everyone's happy. I'll send my invoice of $0.00 to everyone who availed themselves of my special offer!

:)

eric


Yes, I AM a PITA.......

Did you by chance model mine for 20 and higher ????

[kl7aj]

Yes, I AM a PITA.......

Did you by chance model mine for 20 and higher ????

PITA> Not at all...as long as youre MOVING in the direction of self-reliance. :)

eric

[kl7aj]

PITA> Not at all...as long as youre MOVING in the direction of self-reliance. :)

eric


Here's the composite pattern for 20 meters....very cute looking

[n2jso]

I guess everyone's happy. I'll send my invoice of $0.00 to everyone who availed themselves of my special offer!

:)

eric

Well, I'm happy....

Because of the interesting discussions in this thread and the pretty pictures you posted, I downloaded a copy of 4nec2. It is an excellent package. The geometry editor is nice!

However, I stayed up way too late last night playing with antenna models. Now I'm tired and wish I could take a nap.

[kl7aj]

Well, I'm happy....

Because of the interesting discussions in this thread and the pretty pictures you posted, I downloaded a copy of 4nec2. It is an excellent package. The geometry editor is nice!

However, I stayed up way too late last night playing with antenna models. Now I'm tired and wish I could take a nap.

The geometry editor IS nice indeed. Ya don't even have to know any trig with that puppy!

eric

[KB3LIX]

Here's the composite pattern for 20 meters....very cute looking


For lack of a better term, it looks like a set of lungs !!!!!

Don't get GROSS guys !!!!

[AC0FP]

For lack of a better term, it looks like a set of lungs !!!!!

Don't get GROSS guys !!!!

Hi Eric,

Can you give me a plot of my vertical dipole with 4nec2 on 20 and 10 meters? I have the 3D plots in EZNEC, I would just like to see what they look like in 4nec2.

73,
Frank