SOME QUESTIONS  

160cm Loop for 40m


 

 WHY LOOPS?


 - IF YOU HAVE SERIOUS SPACE LIMITATIONS

- IF YOU WANT A PORTABLE ANTENNA

- IF YOU LIKE TRYING NEW SOLUTIONS

AND DO NOT EXPECT TO TRANSMIT VERY HIGH POWER SIGNALS

THEN YOU HAVE AT LEAST ONE GOOD REASON TO TRY GOING FOR LOOPS. 


 

SINGLE BAND OR MULTI BAND?


SINGLE BAND ANTENNAS WILL BE OPTIMISED FOR THE BAND WOU WANT TO USE

MULTIBAND ANTENNAS WILL DO THEIR BEST FOR YOU ON ALL BANDS. BUT DO NOT EXPECT MIRACLES


 

VACUUM OR AIR CAPACITORS?


 VERY GOOD QUESTION

FOR MULTIBAND ANTENNAS 

A VACUUM CAPACITOR 

WILL PROBABLY BE THE ONLY PRACTICABLE WAY

BECAUSE THEY REQUIRE HIGH CAPACITY VARIATIONS

SINGLE BAND LOOPS REQUIRE LOWER CAPACITY AND VERY LOW VARIATION

SO THE BEST SOLUTION WILL BE A FIXED CAPACITOR IN PARALLEL WITH A SMALL VARIABLE CAPACITOR

HARD TO FIND ON THE MARKET, THIS IS EASY TO ACHIEVE IF YOU LIKE DOING THINGS YOURSELF


 

WHAT DIMENSIONS?


 IN GENERAL TERMS, THE LOOP DIAMETER AND THE PIPE SECTION SHOULD BOTH BE AS LARGE AS POSSIBLE.

OF COURSE THERE ARE LIMITATIONS.

THE LOOP HAS TO RESONATE ALSO AT THE HIGHEST FREQUENCY YOU INTEND TO TRANSMIT, AND THIS LIMITS ITS DIAMETER.

INDICATIVE DIAMETERS FOR A SINGLE BAND LOOP ARE:

10 METERS BAND:  40-50 CM

20 METERS BAND: 80-120 CM 

40 METERS BAND: 150-300 CM

AND WILL DEPEND MOSTLY ON THE RESIDUAL CAPACITANCE OF THE CAPACITOR, PLUS THE INTRINSIC CAPACITANCE OF THE LOOP ITSELF.

PIPE SECTION LIMITATIONS ARE MAINLY INDUCED BY THE DIFFICULTY OF OBTAINING A CIRCULAR SHAPE WITHOUT NEED FOR SPECIAL MECHANICAL TOOLS.          

 

Home


 SCOPE OF THIS WEBSITE IS TO SHARE EXPERIENCE WITH OTHER HAMS WHO FOR ANY REASON WISH TO TRY MAKING A MAGNETIC LOOP ANTENNA THEMSELVES, AND WITH THOSE WHO ALREADY HAVE DONE IT.

THERE ARE NO FORMULAS HERE, NOR CALCULATION PROCEDURES. THERE ARE MANY GOOD SITES ALREADY ON THE WEB ABOUT THIS.

MY AIM IS ONLY TO MAKE MY EXPERIENCE AVAILABLE TO OTHERS, WHO MAY HAVE DIFFICULTIES IN INSTALLING TRADITIONAL ANTENNAS, HOPING TO BE HELPFUL.


FOR DETAILS ABOUT THE RESULTS OBTAINED WITH MY LOOPS, PLEASE VISIT:     www.qrz.com/db/IU2DHM

This is not a sponsored Website. Any Banner or other Advertisement is published by Virgilio, who kindly provides free Webspace and Website Wizard to guest users.

 

                           My Logo and my Transceiver

                   50 cm Magnetic Loop for 15-12-10 meters

                 80 cm Two-Turns Magnetic Loop for 40 meters

                90 cm Magnetic Loop for 20-17-15 meters


 


  MORE QUESTIONS
 

   45cm Loop for 10m


 

ALUMINUM OR COPPER?


 ANOTHER GOOD QUESTION

COPPER IS BETTER CONDUCTOR, BUT ALUMINUM IS NOT BAD AT ALL

AND THE DIFFERENCE IN CONDUCTIVITY IS PARTIALLY COMPENSATED BY THE DIFFERENCE IN SKIN EFFECT DEPTH.

THE RESULT IS STILL IN FAVOUR OF COPPER, BUT WHEN YOU CONSIDER OTHER PARAMETERS SUCH AS WEIGHT, COST, AND DIFFICULTY IN BENDING,

IN SOME CASES ONLY ONE OF THESE PARAMETERS WILL DRIVE THE DECISION IN FAVOUR OF ALUMINUM. IN GENERAL THE THREE REASONS WILL ALL HAVE SOME EFFECT AND THE CONCLUSION WILL PROBABLY BE:

ALUMINUM UNLESS THERE IS A VERY GOOD REASON FOR GOING COPPER.


 

WHAT TYPE OF ALUMINUM PIPE SHOULD I BUY?


 THERE ARE ON THE MARKET MULTI-LAYER PIPES USED IN DOMESTIC WATER DUCTING. THEY ARE QUITE CONVENIENT AS PRICE IS VERY LOW. THEY ARE MADE OF THREE BASIC LAYERS:

THE OUTER AND INNER LAYERS ARE GENERALLY MADE OF PVC OR PE (POLYETHYLENE). THE INTERMEDIATE LAYER IS MADE OF ALUMINUM AND GENERALLY HAS A THICKNESS OF HALF MILLIMETER OR SO, WHICH IS ENOUGH TO OUR SCOPE.

THIS IS THE ONLY LAYER WE REALLY NEED, BUT THE OTHER TWO LAYERS WILL ALSO BE VERY USEFUL, AS THEY WILL NOT ONLY PROTECT THE ALUMINUM PIPE, BUT ALSO HELP MAINTAINING THE CIRCULAR SECTION WHEN THE PIPE IS BENT TO OBTAIN THE DESIRED SHAPE OF TE LOOP.


 THESE PIPES ARE GENERALLY SOLD EITHER IN STRAIGHT SECTIONS 2 TO 5-6 METERS LONG, OR IN COILS WITH 40-60CM DIAMETER, AND 20-50 METERS LENGTH, IN PLUMBER SUPPLY SHOPS. PRICES ARE PROBABLY THE LOWEST YOU CAN FIND (SOMETHING LIKE 1-1.5  EUROS PER METER).


 SOME DO-IT-YOURSELF SHOPS ALSO SELL THEM, IN STRAIGHT SECTIONS 2-3 METERS LONG, OR COILS OF SIMILAR LENGTH, OBVIOUSLY AT MUCH HIGHER PRICES (TWO TO THREE TIMES HIGHER PROBABLY) STILL REMAINING A QUITE CHEAP MATERIAL.

I NORMALLY BUY A 5 METER SECTION AND I CAN MAKE ONE OR TWO ANTENNAS.