Discussion in 'Ham Made Gear' started by KX4CY, Jul 7, 2017.

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  1. KX4CY

    KX4CY Ham Member QRZ Page

    When I started searching for practical antennas for my restricted HOA apartment community the Magnetic Loop was a clear choice.

    However most commercial magnetic loop antennas are for low power operation or QRP.
    I ended with a design of my own and have had so much fun, that thought it may benefit other HAMS with similar needs, so decided to advertise it in Gear made by Hams. The antenna is light, portable, serviceable, handles a tremendous amount of power, high Q rejects some interference, and is capable of detecting some weak signals.

    The High power magnetic loop handles 100W PEP easily. (Model SML-1000-1)

    38 inch loop down.jpg

    Magnetic Loop Antenna Parts/Assembly video
    : SML-1000-1
    (sorry, no music)
    Picture Shown with Active loop down. It can easily be reconfigured for Active loop Up

    38 inch loop up.jpg Horizontal Polarization.jpg 24 inch loop up.jpg SML-1000-1 Parts.jpg

    I designed this antenna to be easily serviceable and made from commonly available materials, so that you could enjoy a robust and solid performing antenna that allows Dx to the far places of the world on a minimal footprint, portable, light configuration, discrete form and reasonable power handling.

    Currently with 100W PEP , rain or shine, I routinely make contact with HAMS across the USA and other countries in South America and Europe.With the SML-1000-1 QRP is optional.

    Interestingly, even tough we are geographically located at the tip of the Florida peninsula, with the antenna in a north-south orientation, reaching to Texas, California to the west and Spain and Italy to the East has been normally achieved. And as a matter of normal course the states directly to the north all the way to Canada and to the south Puerto Rico, Venezuela & Brazil. This on 20 and 40 mts. The current tested rig is a YAESU 857D + MFJ-939 automatic antenna tuner. The Yaesu maximum power output is 100 watts PEP on SSB HF.

    The process of tuning the antenna for Dx is straight forward and is as follows:

    1.- Turn OFF the auto-tuner and choose the desired frequency on the Transceiver.
    2.- Turn on the volume on the transceiver and turn over the capacitor on the antenna and find the spot where maximum noise is heard.
    3.- Turn on the auto tuner and proceed to auto tune the antenna. This process usually results in a 1:1 swr or very close to it.
    After this tuning process, when you search for other stations to Dx, you do not need to perform auto tune until you are ready to transmit on a chosen frequency. Once the frequency is chosen, you press auto tune and get your SWR down to 1:1 or very close to it. Then transmit. (If the auto tune does not tune satisfactorily after a frequency change, go back to No.1 above and repeat.)

    Usually the big capacitor on the antenna will have to be moved two or three times only to cover the entire band. And only an arc of one or two 1/16 of an inch on the 4 inch diameter turning knob!.
    Yaesu 857.jpg
    (The combination tested is YAESU 857D + MFJ-939 Automatic tuner. NOT INCLUDED )


    This antenna design lends itself to experimental applications if you are so inclined.

    For example, you may want to change the diameter of the radiant loop or the diameter of the tube forming the loop. Or the material of the radiant loop. Or double up a large loop for operation on 160 Mts.

    Also you can also play with the plane of the loop, vertical or by relocating some portions of the PVC, lay it on a table and have a horizontal polarization.

    Or maybe you would like to compare the propagation differences between active loop up or down. Which can be made by adding a pvc coupling and a pipe extension to the top to provide support for the newly reconfigured radiant loop.

    I hope you find this information interesting.

    The High power SML-1000 MAGNETIC LOOP Antenna only PRICE is $145.00 Plus shipping. Shipped USPS to any of the contiguous states of the Continental USA.

    What you get for $145.00 plus shipping:

    Fully assembled ready to use High voltage air core variable capacitor. ( Aluminum Fins & Zinc plated steel rods and nuts)
    Qty (1) carefully coiled 38" Diameter and Qty (1) 24" Diameter 3/8 Diameter copper Radiant loops
    Qty (1) 7"Diameter 3/4 wide Aluminum plate and Qty (1) 5"Diameter 3/4 wide Aluminum
    4.-Coaxial Wire (Coaxial Wire is for limited time only JULY 2017!)
    Qty (1) 33 Ft 50 Ohm Coaxial wire with PL 259 male connector for the radio and Caiman Clamps for the active loop.
    5.- PVC Frame:
    PVC frame with Qty (10) 3/4 PVC T joint and Aprox. 14 Ft of 3/4 PVC pipe cut in several segments. Qty (10) 6 inch electrical nylon ties.
    6.- Instructions:
    Assembly and use instructions.

    (The combination tested is YAESU 857D + MFJ-939 Automatic tuner.)

    a. Cash in Advance. We currently accept Money orders or personal checks.
    b. Estimated shipping is 5 Days after reception of payment if by personal check.
    c. Orders are final. No returns accepted after antenna is shipped.
    d. Antenna is custom built. If you need any additional features or only parts please contact us for additional or reduced pricing.
    f. We reserve the right to make any modification to improve the design.
    e. User assumes all responsibility for use of this antenna and fitness of purpose.

    Please contact me: prior to mailing (Sending) any confirmed order or payment. We need to send you a confirmed Fedex ground estimate to your zip code and you must attach your signed purchase order with your payment.

    All the best and happy DX.
  2. KX4CY

    KX4CY Ham Member QRZ Page

    I have been receiving some questions about the Capacitor numbers:

    Here are the answers....

    1.-Capacitor is estimated at around 6 Kv breaking dielectric tension.
    (One equation predicts (100W) can possible raise the capacitor tension to around 5Kv.)
    2.-Capacitor Fixed blades are Qty (14) 4x3 Inches
    3.- Capacitor Rotating blades are Qty (14) 4X5 Inches
    4.- Estimated Capacitance: 208 pf.

    All the best.
    KX4CY. 73!
  3. KX4CY

    KX4CY Ham Member QRZ Page

    SOLD !. We continue to take orders but will deliver an improved antenna featuring:

    1.- Only Qty (1) 38 Inch radiating loop 5/8 Copper instead of 3/8 (Additional 24 inch loop only on request will be an added co$t).
    2.- Mechanically balanced capacitor.
    3.- Capacitor protective enclosure.
    4.- 1/4 inch Gold plated connectors instead of caiman clamps.
    5.- 33 Feet Marine Grade coax cable and PL 259 Male connector for transceiver.

    Due to this changes there will be slight price increase as soon as the new add is published.

    Thank you for your interest!.

    Happy DX!.

  4. N1KTJ

    N1KTJ Ham Member QRZ Page

    Roberto - am interested. am good on QRZ email. - N1KTJ Have a Kenwood TS570D with internal tuner and 100W. Also have a low power W4OP Loop from LNR Precision, but would like to compare to your loop solution on high power. Thanks for having this available.

    Never mind I see your email and your terms of purchase. So basically pay what you ask, and get it shipped in five days, with no returns possible.

    Would like to see some third party reviews and testimonials that it works great, and will not be a hazard to use. Somehow read that you really need to not be in the same room as this (20 feet away or more) if you intend to use it at all. 100W in a loop is some pretty serious RF power in the loop center.
    Last edited: Jul 18, 2017
  5. KX4CY

    KX4CY Ham Member QRZ Page

    Hello N1KTJ,

    Thank you for your posting. The antenna is custom made, and is basically a big High voltage capacitor directly attached to a copper Loop. The inner active loop is aluminum.

    100 Watts is very serious power indeed. One mistake trying to couple directly without Automatic antenna tuner and could result in a PUFF!, if the radio has no tolerances/protections for that kind of mistake.

    The Automatic antenna tuner also works as safeguard for the radio from mistakes, accidents etc.

    And yes, you are responsible for complying and following the ARRL guidance on the allowed/permissible station radiation quotas.

    Having said that, we just improved the antenna and will publish a new add in 24 to 48 Hrs.

    We now accept Paypal and will accept a return with a 20% restocking fee, if item is returned in as new condition ready for sale.

    But we still require you to sign "Buyer assumes all responsibility for use of this antenna and fitness of purpose".

    This is the same for all antennas anywhere, but it serves as a reminder to everyone of their personal responsibility when dealing with radio waves.

    It is a straight forward, honest Magnetic loop antenna whose behavior can be modeled, and users may start experimenting with other size loops, materials and configurations, as they advance their knowledge in the art of the Magnetic Loop Antennas.

    It finds a very interesting application as a ready portable antenna, easy to use and store, requires no counterpoise or radials, and allows HF in areas where users are constricted by a number of reasons. RV's, camping, Dxpedition, Apartments, Townhouses, Penthouses, Restricted HOA communities, and emergency communications or situations where fast deployment, and quick pick up are a premium, with not much real state to expand your dipoles, yaguis or verticals. NOT that there is anything wrong with those, but the discreet profile of the Magnetic Loop has its charm and applications. Specially one with reasonable power handling characteristics.

    I hope you decide to give it a try and become another happy Magnetic Loop Dxér.

    All the best,

    Roberto. KX4CY,

    N1KTJ likes this.
  6. N1KTJ

    N1KTJ Ham Member QRZ Page

    Excellent professional reply. Thanks for being so clear and for now accepting returns with 20% restocking. Looks like a interesting and proactive solution for the persons trapped in apartment life. Looking at some other robust automatic tuner configurations for a future purchase. Hope your design does not get bought out by a big name distributer too soon.
  7. K1ZYM

    K1ZYM Ham Member QRZ Page

    I am intrested it trying this antenna for motorhome applacations, I am on several HF motorhome nets as well as other nets including YL net, Nightwatch net, Brothers net and a couple others. I also write for a couple blogs related to antennas and ham radio on the road and at the campsite. I do tell it like is is. email @
  8. KX4CY

    KX4CY Ham Member QRZ Page

    Hello Ken,

    Thank you for your note.

    Probably for your application The HIGH POWER Magnetic Loop Antenna for 40 Mts to 10 Mts is more appropriate.(80 and 160 for the road would require some very elaborate and imaginative solutions, none of which is truly ....portable). It will be a more rugged and designed with a purpose in mind. Not like the original posting, intended to share my excitement at the success of the design and see if anyone shared my enthusiasm for that solution. Let me know...

    For fellow hams who ordered the original, we upgrade it to a full enclosure and some other technical improvements. So the first design is already phased out and we are yet to post the new antenna design. simply no time...

    The HIGH POWER Magnetic Loop Antenna for 40 Mts to 10 Mts will be the same high power as the original but fully enclosed and and better overall. And tough as nails...for the road.....

    We have not yet posted this antenna for sale and you would be among the first to receive one as soon as we finalize testing and get it out... So your comments and review would be greatly appreciated.

    This week we are literally SWAMPED filling some orders from the original posting, but we will be back with new products and updated postings soon...

    You can send me email at:

    All the best,

    Roberto. KX4CY.

    N1KTJ likes this.
  9. N1KTJ

    N1KTJ Ham Member QRZ Page

    nice on the design being more robust for the road and able to handle 40M well. Think about an RV parked in a space. they have no room to put up a massive inverted V or inverted L antenna for 40M. So they can just put up your mag loop on the roof, and start doing communications.

    Any way to show a quick comparison in efficacies of antennas (in theory) between a MAG LOOP, INVERTED L or V, HAM STICK, END FED, RAISED DIPOLE in a small chart with 10M, 15M, 20M, 40M ? Have not found any chart yet but would think someone would have built that.
  10. W1CEW

    W1CEW XML Subscriber QRZ Page

    I love the Alpha loop I run, but I have arc-ing above QRP power. Are you still building these?


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