Making a Magnetic LOOP-antenna with a Variabel VACUUM-Condenser                             10.10.2012              UPDATED: 12-08-2013   minor

Conclution:

Gerlev, near Frederikssund, 12- 08-2013

  A MAG-LOOP is NO competition to a full size dipole!

Is it an antenna ?, Maybee, but only a if you have NO other option.

In test with a nearby HAM, OZ3SW, Steen, we tested with full 1 K PWR to a full size dipole, and listening on a SDRadio i Holland on the 80 meter band, and with 1 full K PWR on the MAG-LOOP, we found a diffence in signal level between 6 - 8 db in favor of the full size dipole.

The loop was placed at the point on the picture herunder, and the full size dipole was elevated into 30 feed above GND.
The differance in HIGHT over GND, could make some difference, but the very small bandwith on 80 meter, 2,5 KHz, just enougt for SSB, make it impossible to adjust fast enough in contest, so... the MAG-LOOP will NOT be mounted on my house ruf.

I will NOT recommand this kind of antenna, if you in any way have the possibility to make a dipole, even a shorted dipole will perform better.

END of STORY
De OZ6YM, Palle

 


The EXPERIMENT

Planning a MAGNETIC LOOP-ANTENNA for use on 80, 60, 40 and 30 meter... ???

This page is my documentation on a project to make a MAG LOOP.

Reading all stuf on the internet, to find the best solution...
This is a good place to start:
     http://www.nonstopsystems.com/radio/frank_radio_antenna_magloop.htm

This page has a lot of Refferencis to other descriptions of small Magnetic Loop-antennas, and a lot of "how to..."

Consulted K8NDS, Richard Fusinski about his phantastik project...
More here:
     http://www.hlmagneticloopantennas.com/

Richard has a some videos available on YOUTUBE - Access some of them from his QRZ.COM...  Thanks for your input, Richard!!

Some tecnical reading about LOOP-Antenna is
      Small Loop Antenna Efficiency in PDF.

First thing first... Get some material...

New PICTURES:

Picturen from 11.21.2012

The final MAG LOOP will be this setup.
I turned the antenna upside-down, and my expirience say, that this is the best setup.
The received noice is 20 db lower, and comparred with another HAM on WEBSDR in
Holland, say signal is 6 to 10 db less than a full size antenna.

Now, I still have some noice-problem.
When I switz the power on to the REMOTE, I get clearly a increces noice, so have to
find the problem there.

I also have to figure out, how to the remote wire must go down to the shak.

In this setup it is more easy to find the perfect match-point for the feeding-loop,
placed in the buttom of the loop.

  The REMOTE-BOX in place.
  A look from EAST.

  The antenna is directed NORTH - SOUTH.

This is the point on my ruff, with a quart wave dipole for 30 m.. is in place.

My ruff is made of steel, making a good ground for any kind of antenna, and I am realy
exited to put the MAG LOOP on my ruff on this spot, but the wether must be dry.

The MAG-LOOP will then be about 6 meter higher op then now on the ground.

 

   
A used Jennings Variabel VACUUM-Condenser:  
This VACUUM-Condenser is:     (copy from Jennings homepage)
(CVV) UCS-375-16 rated Permanent front flange, US$
10 - 375 pF
   16kv (20kvp)  
55 amps   1/2" shaft
985.00

Measured: MAX: 381 pF

Measured: MIN:   10 pF

Lenght:  217 m.m. without STUB for the shaft

Width:     75 m.m.

Video:  A MOTOR to drive a Vacuum-Condenser 2 minuttes of video shoving the KURSMOTOR running

Video:  The finished REMOTE STEERING of the VACUUM Condenser

4 minuttes of video shoving the finished remote steering and how it works.
A HAM-friend in spirit have offered me this little engine from World War II.
Used in German figther-fly to correct the kurs.

This engine have a very fine GEAR, using 24 Volt and 75 watt,
it must be abel to turn the VACUUM-Condenser.

Now, must get it to fit.

Was in STOCK in the local HAM-club, for Dkr: 200,00 (40 US$).

 

Need a little cleaning before use. 

 

Cleaning is DONE!!!

 

Wave-guide cabel:

 
The local HAM-club had some picies of WAVE-GUIDE cabel.
I got 6 meter for free...

There was some grizy stuf between the isolation and the cobber.

Easy to remowe with Terpentine.

 

Measured 16 m.m. X 26 m.m.

This cabel is very light and still flexible and strong.

As I expectet, this cabel have possibility to hold the loop by it self.

Here just supported with some STRIPS...

I will have the VACUUM-condenser mounted in the bottom, and make the the feed-point and
match at the top.

The bottom-mount of VACUUM-condenser will lower the weight-point, and make it possible to experiment.

Now... Have to do some motor-experiments...


Servo stearing of the LOOP-Antenna

Planning the Stearing:

 
A = LOOP Connecting point 1
B = LOOP Connecting point 2
C = Vacuum Condenser
D = PLEXIglass Wahl, 2 pcs.
E = 10-turn Potentiometer, for frequensreading scala on instrument
F = 1:2 Gearwheel
G = Insolatated driveaxel with m.m. gevind
H = Clutch
K = KURSMOTOR
L = Electric connetion Point
M = PLEXIglass mounting rod
The princip would be, that when the K-motor is turning ON, one way or the other, and turn the rod of the 
VACUUM Condenser, a Gearwheel F:, 1:2 lower the 16 turn of Vaccum-Condenser to 8 turn on the E: 10 turn-Potentiometer, used to show a scala for relativ frequens, and to kipe an eye on where we are on the
VACUUM-Condenser.

The future plan will be, that a PIC-processor will take care of logik, start and stop of K-motor, mounted 
in a steeringbox in the shack. The PIC-processor  will be able to "know" where it is, and how long to the STOP-point.

Addition to this project would be, to put a display on the control-box, READ the frequens, and auto-TUNE the LOOP-antenna. The PIC-processor would be able to read tuning frequens, knowing last frequens, then change
motordirection to new frequens, change motor-speed from FAST to SLOW, and make a full STOP with the best
SWR. This will be possible, if I can find a way to pull out the SWR-signal from my SPE ITALIEN EXPERT 1k-fa,
QRO-transmitter.

Always good to have a PLAN... We must se what the time will bring.... 

10.17.2012 - 
For the moment I am working on the LOOP-Connection point 1 and 2.

DONE!

10.23.2012 -
Her is the PLAN-SETUP.

Nothing is finished yet, but only the plan.

The board of plexi-glass is 42 cm long, and 10 cm width.

 

Just for the PLAN...

 

The gearwheel just fit...

Just enough room on the board...

Still to come -
1: The insulated axel between VACUUM-Condensator and the KURSMOTOR
2: The holder of the KURSMOTOR
DONE

Holder of the KURSMOTOR could bee like this:

 Material:   PLEXI-GLASS  14 m/m

Now, the LOOP-RODS is finished.

Just to get a pic. of kobber, with indside diameter of a half inc. 22 m.m. kost me

90 D.kr. ( 18 US$ ), to fit on the TOP of Vacuum-Condenser, is a lot of money for
nothing.

I hope it is worth it...

 
A close-up foto of Vacuum-Condenser with LOOP-connection rods.

 

 

 

 

 

In TOP of PAGE you will find a video of the finished remote steering af th vacuum-condenser.

No I just have to VATERPROFF the BOX before I make the LOOP-Antenna.

 

Experimenting with REMOTE CONTROL, the beginning...

This is the way I made the REMOTE-Control for the
KURSMOTOR.

The KURSMOTOR need a supply-current on the stator,
pin 1 and 2, and then a variabel current to the ancor,
3 and 4, to work the way I want it to work.

Therefor I put 2 stabiliced regulators in the box.

  1. 1 for 10 volt continuing current to stator and the
    control-potentiometer,
  2. and 1 regulated 5 volt, with rugulation up to
    21 volt, for controlling the speed of the motor.

The crosswired switch is selecting left and right motor-run.

The push-button after the 7805 regulator, ingage the motor.

The voltmeter gives me a scala - 5 - for the VACUUM-
condenser, going from 380 to 10 pf - left to right - and will
later be frequens-calibrated.

Simpel but working.

It will be fun to se what frequens the LOOP can span over.


The Control BOX

I used an old box from another project, with a meter build in, and some hulls in the
frontplade.

The 500 Volt meter will later be calibrated with frequens-bands. An inside resistor
is removed, and the full scala is 1 mA.

Black NOP is a 1K potentiometer to vary the voltage to the KURSMOTOR from app.
5 Volt to 21 Volt.

Right to the POT. is POWER-ON button.

In the bottom-left is the cross-coubled switch for LEFT/RIGHT turning af the
KURSMOTOR, and the PUSH-BOTTON in the right corner is "INGAGE the MOTOR".


 

 

 

Just now, I works with some ACRYL to pak the REMOTE in, for WX-protection.

 

 

 

This is the Balance-point, and the way it must be mounted on the mast.

 

  FINISHED to day, 12.11.2012

 

 

 

  NEXT THING will be to setup the LOOP....

 

 

  This is my TEST-SETUP, just for a TRY....

 

 

 

 

   Experimenting with the cublings-link

 

(this is NOT good...)

 

 

 

  This is much better, but not the best....
  Must be a little closer to the loop...

 

  More pictures later... with more experiments...

On the REVERSE BEACON NETWORK
I can follow which station arround can hear my signal.

This i result of 100 watt to the antenna - FIRST TRY - Places 1 meter over ground in the garden.

The antenna is placed EAST - WEST.

SWR say 1.05 on my Italian EXPERT 1K-fa, but I think the antenna is to close to my window, only 3 meter away from the shack, so 300 watt is MAX effekt, on 80 meter until The antenna get his place on the ruff.

Today i got a glass-fiber rod.

Originally a commercial antenna, 4 meter long, used for the band 450 - 460 MHz Mobil-band.
After I have remowed all inside the antenna, I have a fine rod, to put on the ruff, when all experiment is finished.

 

 

 

More to come...

More to come....