A Calculator for HDB Loop dimensions

[Egil]

I had forgotten all about this program, originally made some years ago using MiniBASIC. But today I converted it into CB code.
The original antenna description can be found at: http://www.wz4c.com/Hdoublebay1.htm.
The antenna was built and found working ok on 50MHz.
As you can see, I am using the same recipe as for all the other antenna calculators I have been playing with. For frequencies outside the given range, change frequency limits at will.

Good luck!

[Techno]

I had forgotten all about this program, originally made some years ago using MiniBASIC. But today I converted it into CB code.
The original antenna description can be found at: http://www.wz4c.com/Hdoublebay1.htm.
The antenna was built and found working ok on 50MHz.
As you can see, I am using the same recipe as for all the other antenna calculators I have been playing with. For frequencies outside the given range, change frequency limits at will.

Good luck!

Hi,

How can I change the frequency with the mousewheel?. I'm try to convert it with IWBasic professional v3.0

Kind regards

[Egil]

Only used the mousewheel once in my code, and that was with MiniBASIC....

But since you are going to convert the code to IW Basic, here is the way to do it: http://www.ionicwind.com/forums/index.php?topic=1212.msg11480#msg11480
Using Barneys method, increase or decrease frequency as needed.

Good Luck!

[Egil]

While thinking of it, adding  mousewheel functionality with CB is rather easy.

Here is the HBO Loop Calculator modified to include changing frequencies with the mousewheel.

The extra lines are clelarly marked.


Good Luck!
Egil

Code Select Expand

'
' hdb-loop.cba 
'----------------------------------------------------------------
' The N4PC "H Double Bay" loop antenna calculator by Egil-LA2PJ
' Original description: http://www.wz4c.com/Hdoublebay1.htm
'
autodefine "off"
DECLARE calc(fq:float)

' **************  THIS LINE IS NEW  *****************************
setid "IDMOUSEWHEEL", 522
'****************************************************************

DEF win:WINDOW
DEF a,b,c:float
DEF fq:float
DEF handle,run:int

fq = 50

WINDOW win,0,0,380,620,0,0,"    LA2PJ's HDB-Loop Calulator",main
CENTERWINDOW win
setprecision 3
FRONTPEN win, RGB(128,0,64)

' Before making an EXE file file remember to add GIF and ICON files using the Resource menu
' handle = LOADIMAGE (2500, @IMGSCALABLE) :' use when making an EXE file

handle = LOADIMAGE ("hdb.gif", @IMGSCALABLE) :' rem out when making exe
ShowImage win,handle,@IMGSCALABLE,100,20

FRONTPEN win, RGB(128,128,160)
move win,45,535
print win," Use PG_UP, PG_DOWN and ARROW Keys"
move win,108,550
print win," to change frequency."
move win, 120,570
FRONTPEN win, RGB(128,0,64)
print win,"All lengths in Meters"

calc(fq)

run = 1
WAITUNTIL run = 0
CLOSEWINDOW win
END

'¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
SUB main

SELECT @CLASS

CASE @IDCLOSEWINDOW
run=0

' *************  THIS SECTION IS NEW  *******************************************
CASE @IDMOUSEWHEEL                  :' Mouse Wheel rotated
IF @CODE & 0x10000000    :' Mouse Wheel rotated forwards
fq=fq+0.01 :' increase freq 0.01 MHz
if fq >= 450 then fq = 450 :' Upper frequency limit
if fq <= 28 then fq = 28 :' Lower frequency limit
calc(fq)

ELSE                          :' Mouse Wheel rotated backwards
fq=fq-0.01 :' decrease freq 0.01 MHz
if fq >= 450 then fq = 450 :' Upper frequency limit
if fq <= 28 then fq = 28 :' Lower frequency limit
calc(fq)
ENDIF
' *******************************************************************************


CASE @idkeydown
if GETKEYSTATE(0x1B) then run=0 :' ESC is pressed - program terminates
if GETKEYSTATE(0x21) then fq=fq+10 :' PG UP pressed
if GETKEYSTATE(0x22) then fq=fq-10 :' PG DOWN pressed
if GETKEYSTATE(0x26) then fq=fq+1 :' UP ARROW pressed
if GETKEYSTATE(0x28) then fq=fq-1 :' DOWN ARROW pressed
if GETKEYSTATE(0x25) then fq=fq-0.1 :' LEFT ARROW pressed
if GETKEYSTATE(0x27) then fq=fq+0.1 :' RIGHT ARROW pressed
if fq >= 450 then fq = 450 :' Upper frequency limit
if fq <= 28 then fq = 28 :' Lower frequency limit
calc(fq)

ENDSELECT
RETURN

'
'¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
' Calculate and print antenna dimensions
'
SUB calc(fq)

def h,w:float

h=(365/fq)*0.3048
w=(110/fq)*0.3048

FRONTPEN win, rgb(128,0,64)
move win, 220,135
PRINT win, USING("#.###",h)+" "
move win, 220,340
PRINT win, USING("#.###",h)+" "
move win, 150,25
PRINT win, USING("#.###",w)+" "
SetFont win,"Ariel",32,800
move win, 50,480
PRINT win, USING("####.##",fq)+" MHz "
SetFont win,"Ariel",10,700

RETURN



[aurelCB]

Hi Egil
I don't know how your calculation formula work but i have different results
In fact it looks to me that your 7.5 cm on 450 Mhz is Lambda/8 not L/4
do i have a right?
anyway thanks on program...this type of antenna i use for my wifi 2.4GHz
but as i say my design is L/4 with two additional loops which gives cca - 8dB gain.
Tomorrow i will build TV UHF antenna with your calculation to test how work
as you can see i will connect coaxial cable in the middle of loop.

[Egil]

Hi Zlatko,
I agree. But the drawing you have supplied is showing an antenna very different than the HBO Loop. So it is quite natural that the dimensions also are different.
I have never seen that construction before, but once I saw an antenna very like yours with still more loops added on a french survey vessel visiting the harbour here. I do not know what it was used for, but the dimensions indicated upper part of the UHF public bands.

The formulas I used for calulation was taken from  the publication I referred to in my first post: http://www.wz4c.com/Hdoublebay1.htm.


Egil

[Bill-Bo]

Bill,

I just downloaded and ran you program in CBasic 1.153. The mousewheel has no effect.

Bill

[aurelCB]

Hi Egil
Yes i see..
I use old good formula
LEN(L/2) = const / freq
where LEN is size of ordinary dipole
const is 142.5 , freq is in MHz
your calculation give 7.5 cm and i get 7.9 which can be ok if we agree
for edge efect that must be less 5%..right.
Design is simple and of course more loops can be added to increase gain of antenna.
This type of antenna is in fact some sort of fractal antenna.



PS. I use CB 1 and mouse work fine 
Egil ..why is limited to 450Mhz ..in my case?

[Egil]

Bill:
I use the same CB version here, and the mousewheel works ok. (On 64 bit Windows 7 Pro). So have no idea why it does not work with you. Also tried v.1.0 right now with same result.

Zlatko:
The high frequency limit on 450 MHz is set in the software by me, but you can set it to whatever you  want by changing the lines:

Code Select Expand


if fq >= 450 then fq = 450 :' Upper frequency limit
if fq <= 28 then fq = 28 :' Lower frequency limit


The formulas for calculating the dimensions of this antenna is given i the mentioned reference article. I have used the same formula, but since the original formula gives dimensions in feet, I multiply by 0.3048 to get the dimensions in meters.

And this antenna is NOT a dipole antenna, so dimensions will be quite different. And the nature of loop antennas do that the loopantennas always have larger dimensions compared to the wavelength than a dipole.
The wave velocity in a loop antenna is such that a full wavelength loop allways is longer than  the physical wavelength. This fact can be found in any antenna textbook. The length also become  longer with increasing frequency, as the practical element thickness then always increase with frequency.

If you do some practical experiments and have the proper equipment to check antenna resonance, it is easy to see this effect yourself.

[aurelCB]

Hi Egil ...
thanks for tip where to change freq limitation 

But this one simply cannot be true:

The length also become  longer with increasing frequency, as the practical element thickness then always increase with frequency

as far as i know this is the rule:
The length of antenna become  longer with decreasing frequency
Or in another  words :
Longer antenna mean lower frequency and contra.

[Bill-Bo]

Egil,

I don't know. I have a Toshiba laptop with 64-bit Win 8.1. Still does not work.

Bill

[Egil]

Sorry to hear about that Bill.
I do not have Win 8.1 myself, so maybe someone else with win 8.1 can try on their computers.
As far as I understand, "st4range" things happen every now and then with that OS. Things that have worked for years, do not work with 8.1.
Lets hope that things change to the better with the coming Win10.


Egil

[Egil]

Hi Egil ...
thanks for tip where to change freq limitation  

But this one simply cannot be true:

The length also become  longer with increasing frequency, as the practical element thickness then always increase with frequency

as far as i know this is the rule:
The length of antenna become  longer with decreasing frequency
Or in another  words :
Longer antenna mean lower frequency and contra.

Now I think you misunderstand me intentionally. And I am not willing to discuss further under such terms.
All I can say, is buy an antenna textbook and read about loop antennas. They are what antenna specialists call special cases.
Unfortunately we can not change physical laws.

End of disussion!



Egil

[aurelCB]

sorry Egil
but i don't understand what i say wrong
ahh forget

[Egil]

Zlatko:
Sorry for being so grumpy, but I assumed you knew about the difference between loops and other antennas.

So I'll try once more...
At elementary school, we learnt that radio waves travels by the speed of light.
The formula for a wavelength is the speed of light divided by frequency, e.g. 300/f(MHz) gives wavelength in meters.

So for  a half-wavelength dipole the formula ought to be 150/f(MHz).
But this is not true due to the fact that in such an antenna, the radiowaves travel slower than the speed of light, so the formula for ressonance becomes approximately 142.5/f(MHz) to get the dipole length in meters, which is 5% shorter than half a wavelength.
Such an antenna is only effective over a bandwith of less than 1% of the design frequency.

Loop antennas behave quite different. And in a closed loop antenna with a length of one wavelength or more, the actual circumference of the loop becomes almost 3% LONGER than a wavelength.
Which means that in such an antenna, radio waves travel FASTER than light.
And this kind of loopantennas are wideband devices, and can be effective over at least two octaves.

For both antenna types the actual lengths must be adjusted when the element thickness becomes larger than approximately 1% of the design wavelength. This will be increasingly noticeable the higher the frequency becomes.

Then we have the kind of loop antenna that has a circumference that is very much smaller than a wavelength. But we are already way out of topic here, so if you want to know more about these, do a Google search for "Magnetic Loops".

And if you really want to learn about antennas, get a good textbook. Or still better, download an antenna simulation programme and start experimenting. I once suggested that you could download the freeware MMANA-GAL, which is a very good and instructive antenna simulation programme. But you answered then that you found it very ackward to use. But fact is that all you have to do, is to specify the start and end coordinates plus the diameter for each antenna element. And finally specify the feedpoint. The results are very accurate.
And just by experimenting with the supplied examples, you'll learn a lot.

It is pretty much the same procedure if you want to repair your house.  You have to obtain the dimensions before you can order the materials needed for the repair.


Egil

[aurelCB]

Hi Egil
I have read all possible resources on internet about wi-fi 2.4 GHz antennas.
And some about TV antennas not about ham or shortwave antennas .
I agree with you that loop antenna is different than open dipol but then
what if we have closed dipole( some sort of loop-right? )
Many  times i see some super design in theory but in practical things are different.
Also fractal antennas are also very different than loop antennas or just directional
yagi antennas  then there are patch ant(resonator ant) etc..etc..

[Egil]

Hi Zlatko,

The antenna theory is the same wheter it is for 0.1MHz or 2.4GHz. But for the higher the frequency, the more important the element diamenter become for calculating the antenna dimensions.

I agree with you that loop antenna is different than open dipol but then
what if we have closed dipole( some sort of loop-right? )

That's right, but since the distance between the upper and lower part of the folded element is very small when compared with a wavelength, you can consider a folded dipole dimensions the same as for the non-folded counterpart, with one important exeption: the feed impedance is around four times higher than for the non-folded dipole antenna.

The "higher efficiency" with fractal antennas, is obtained mainly by making the antenna elements very long. That is the main reason that such antennas are mainly used on GHz frequencies. You can do exactly the same on  shortwave frequecies, but the you'll need an enormous property to erect your antennas in addition to high masts...

And again, all this can be tested with the MMANA-GAL software I have recomended before. And if you by using this program to experiment with dimensions manage to construct a high efficiency antenna with the radiating diagram you want to obtain, you can use that dimensions to build that antenna and try it "on the air" with only slight adjustments for impedance matching. I have experienced this many times.