N4MQ Magnetic Loop and STUFF Site
Under construction: To detail various antenna systems including my 12 ' diameter loop antenna for 160 meter operation at 1 kilowatt power level
This video shows the high power tuner I assembled to tune the 12 foot loop Iam running for 160 thru 80 m. I plan on adding a series cap so that I can get back on 40 m where its performance was really great. It is mostly a receiving antenna as the reception is sooo good but is all honesty the transmit side is below my 160 m windoms performance. With a rotor I have NOT been able to see a difference in reception, though on transmit the other stations do report a significant "peak" as it is rotated ( up to 10 db - their words). I have no way to direct it toward them (my boy scout compass), as the signal reception gives me no directional reference information.
That thar be the unvarnished truth about my experiments, I will be making more small loops as they are more directional and the reception is so much better. Please see the third video for that one. Woody
Here is a video of the attempt to raise the antenna, Poof
"160 meter signal response on air (1) "
Showing the noise rejection of the magnetic loop antenna compared to the 160 OCF windom antenna. Factually it works better on 40 m than on the lower bands, I will be doing more receiving loops, and xmit on the windoms. I do plan investigating a 160 meter full size horizontal loop, to be continued. 6/19/2017
This is a fun video of a vacuum capacitor, on opening day!! August 2017
Horizontal loop antenna and DEICER !
I have been planning and finally installed a large horizontal loop antenna for all band operation on HF. The loop goes around the house from 100' hi to 60' hi using trees and 2; 40'poles and is about 860 feet in length using #14 cadillac style stranded wire. The feed line is 6" spacing 600 ohm #13 ladderline copperweld going up to the 100' apex of an oak tree.
The two 'tree' supports were installed using my Quad copter to pull a thread into the crown of the tree to pull up 3/16" dacron line with pulleys at all supports to reduce stress ( allowing shifting ) when the wind blows strongly. Antenna tension is provided by a spring loaded rope with another pulley. The wire is rated at 128# of tension strength and 16# of spring tension on the rope holds the feed line and antenna at the desired elevation giving a safe catenary shape.
Operation on 160 meters and up is possible with use of a 1:1 balun. The use of the 4:1 balun did not allow the MFJ autotuner to match several segments of the lower ham bands, and I believe that the low impedance was the problem. The balun is mounted on an exterior wall in a relay cabinet that isolated the rig and grounds the antenna when the shack is NOT powered up for lightning safety.
The relay box has the earth ground connections along the right side. 600 ohm ladder line enters into the box on the right side and is controlled by the two internal antenna relays. The internal balun is 1 : 1 and connects the rig to the antenna. The dark cable feeds the low voltage transformer power (<50 VAC) into the loop to circulate current warming the antenna wire during icing conditions.
The upper right relay normally grounds the ladder line and passes the "antenna" to the left hand relay when it is energized. If the left relay is off, the loop antenna is connected to the low voltage power source to heat the antenna wire.
Powering up of the ham rig energizes both relays passing the "antenna" to the balun and the rig for normal operation.
Here is the photo of the ladderline support and its connection to the relay control box. Grounding for safety is by the vertical #6 copper wire going down to the array of ground rods and radial wires below.
The controller below shows my antenna control boxes. The grey box grounds all of my coax antennas when both station locations are off the air. When either station is on this cabinet feeds the antennas up stairs or downstairs as needed. The grounded cabinet is for static removal as all the coax lines entering the house are buried, ranging from 75' to about 125' in the lawn and tied to a large driven ground rod array using #6 copper for interconnection; more lightning protection
The center cabinet controls a low voltage 50 v AC supply and provides it to the 860' loop antenna when the antenna is loaded with ice The weight of the ice on the antenna support pulley would force an outdoor mounted strain switch to turn "close". This function is automatic when needed, and insures protection nites and times I am not home. The right cabinet enables the loop antenna, as its leads are grounded outside when the stations are off the air. If Ice is indicated it directs the loop to the low voltage supply and runs about 12 amps into the #14 gauge antenna loop for defrosting. November 2017
Testing of my 7, diameter RECEIVE only loop antenna. Shows the directivity and sensitivity when tuned for resonance.
Some follow up information on the deicer
Here are the photos of the ice formation on my antenna feed line. The heater circuit cleared the ice in about 30 minutes with a circulating current of 17 amps of 60 cycle power. The antenna is powered thru the relay control box when the lawn ice control switch closed because of excessive spring tension due to the ice formation. This switch is just to the right of the large tree and looks like a small white 'stick'. A mercury switch senses the ice strain on the support rope and pulley, closing the control circuit.
I calculated that 1/4" of ice would add significant weight to the 860 foot horizontal loop antenna risking support failures. The defroster WORKED, Yeah !