The UltraLight Magnetic Loop QRP antenna ver. 4 by OM0ET

3,195.00 kr

Beskrivning

Designed for 7 shortwave bands + CB
 
4th version of the QRP UltraLight Magloop antenna has the foldable construction designed for easy carry in the 17″ laptop bag. This antenna was designed for 40m to 10m bands + CB. The main loop is almost 1m in diameter and is almost 1,3m hight. I have used a solid PVC tube on foldable boom. This all caused higher efficiency on all bands, especially on 40M band which was missing in the 3th version of UltraLight MLA. By using a new variable capacitor with bigger capacity and almost 1m wide loop I am able to reach the 10M band also. Capacitor is connected in serial fashion because of very low resistance in a whole antenna circuit what is very important to secure a high Q and high efficiency of my loops.
 
The tuning box is made of the solid ABS plastic with sealing aginst the dust or humidity. But the tuning box is not waterproof in any case! For the SWR measuring I use the QRP transceiver XIEGU X5105. The SWR on all bands is better than. 1:1.5
 
This v. 4 MLA is working from 7MHz to 28,8MHz continuisly and the CB band is covered too.
 
Total weight is only +/- 1kg. No switch is needed.  It’s a QRP version for 0 to 20W (max. 10W CW / 20W SSB) depends on the desired band.
 
Please do not exceed the power limit of 20W! It may cause a fire on the capacitor plates or demage PA in your transceiver.
The Main Loop system
The Main Loop is made of an excellent quality coaxial cable BELDEN H1000 (made in Holland) which is 10,3mm thick in outer diameter. Inner conductor is made of solid Bare Copper 2,62mm thick core which allows to hold the perfect circular shape of the loop without deformation of gravity. In all my Magloops is connected only the inner core. Outer shield is disconnected for improve SWR results and less sensitivity of nearby objects.
 
 
 
In the middle of the Main Loop lenght is located the mark (heatshrink) which inform you where the Loop have to be inserted in to a Plastic Holder on top of the Magloop Antenna Boom.
 
The Coupling system
Quick installation of my Magloops is my priority and therefore I made the small coupling loop with a BNC socket. Clamp on the Coupling box allows you to attach the small loop on antenna boom in a second.
 
 
Great for Experimentators
The ”small” coupling loop is made of 2,5mm thick solid copper wire attached with a mounting eyes on both ends, which allows you anytime to do your own modifications or easy exchange the other experimental loops.
 
The Tuner
The heart of all the Magloop Antennas is a Variable Capacitor, which is located in the Tuner box. In my antennas was used the enclosure made of ABS plastic with sealing against the rain shower or dust (but the Tuner box it self is not fully waterproof). The Main Loop is connected to the Tuner box with two SO-239 connectors (sockets) and two PL-259 on Main Loop with goldened center poles, which improves connection and reduce loses. Tuner box is also equipped with two clamps for very quick installation on the antenna boom.
 
 
Capacitor
Variable capacitor used in my Magloops is connected in serial fashion due to a minimal loses in the antenna circuit, which improves Q-value and efficiency of the Antenna on all bands. The second positive thing is that the Antenna will not change the SWR value when human hand is close to the tuning knob. For more comfortable tuning is this Capacitor equipped with the 1:3 gear reduction.
 
 
Wide frequency range
Up to 7 bands + CB with only one small antenna (40m/30m/20m/17m/15m/12m/CB/10m). All the bands are countinuously tunable for the best SWR on all frequencies in this range. In addition to HAM you can count also with the AM broadcast, Air, Maritime mobile or Military service shortwave bands. Here are the minimum and maximum frequency range SWR chart:
 
 
The Feed line
Connection between the Antenna and Transceiver is done by the very soft and flexible Coaxial cable HELUKABEL C/U RG58 with waterproof BNC male (clamp system) connector. Usable lenght of this cable 4,5m is sufficient to operate in the safe zone of 2 or 4m away from the Magloop when we are transmitting (If we use max. 20W).
 
 
Connectors
On the Feed line coaxial cable and on the Main Loop coaxial cable I use waterproof BNC and PL-259 connectors with the clamp system.
 
 
The Mounting adapter for Camera tripod stands
With help of my friend Lev – OK2PLL we have designed and made this CNC machined 1/4′ camera tripod mounting adapter.  Is suitable for any standard camera tripod stands. With this adapter is very easy to mount entire antenna on the tripod and also very comfortable 360 degree rotating this antenna on it.
 
Portable Antenna to most as possible
The priority of my Magnetic Loop Antennas design is to be portable as much as it gets. And therefore is this small multiband antenna completely foldable and composed of a many dismountable or exchangable parts. Antenna fit’s in to a bag for 17″ Laptops. The longest part is only 477mm long. Complete setup of this antenna will take you only 2 min. on the tripod.
 
 
Dimensions
Large loop diameter: approx. 1m ( coax lenght is 3000 mm )
Small loop diameter: approx. 23cm ( wire lenght is 720 mm )
Capacitor: air type with ELTRA 380+320pF with a small gearbox reduction 1:3 – used in split stator fashion
Large  loop is made of Belden Venlo H1000 microwave coaxial cable (can be used  RG213U but it’s not hold the shape of ring as good as Belden H1000)
Small loop is made of 2,5mm thick copper wire (black PVC isolation)
The foldable boom is made of 3 pieces, 25mm in diameter, PVC tubes
Total weight: +/- 1kg
How to use this antenna
 
Important information:  
Never transmit in to the antenna before you don’t listen the background noise peak while tuning, it may demage your transmitter!
 
1.  Set the desired frequency on your transceiver and rotate antenna knob to resonant frequency until you will listen the noise peak.
2.  After you listen the noise peak start measure the SWR in carrier mode (FM/AM) with 5 – 15W and carefuly tune antenna for the best value ( ideally SWR 1:1,1 or 1:1,5 ).
3.  Now switch to desired modulation mode and you can transmitting.
4.  If you move from this frequency away you will need tune the antenna again (point 1-3).
 
Some close metalic objects may disturb SWR, if so you have to place antenna more away from this object or rotate the main loop to the another direction.
The elevation will improve efficiency of your magnetic loop antenna. Higher – better. Please consider the hight of your tripod stand.
This antenna doesn’t need the counterpoise.
 
I wish you have fun with QRP activities and this antenna!