Category Archives: Antennas

Guest Post: Building a magnetic loop antenna & broadband amplifier for your SDR

Many thanks to SWLing Post contributor, Dave Gahimer (K9ZCE) for the following guest post:

Small Magnetic Loop Antenna with Broadband Amplifier for SDR Reception

by Dave Gahimer (K9ZCE)

Those with limited space, or antenna restrictions, might find a small 1 meter loop antenna a solution.

My son lives in an apartment. One Loop leaning against a wall gives him acceptable reception with the SDRPlay RSP on the ground floor–2nd or 3rd level flats should have very good reception.

Ten meters off the ground outside should give reception equal to any SWL antenna. We all with SDRs fight the image problem. Normal resonate ham band antennas show too strong reception of unwanted bands/stations. Did I mention noise? Loops are well known for –6 db noise reduction.

Then there is the possibility of SDR chip damage from your 1.5 KW station! In researching Loops we came across LZ1AQ. A Brilliant design /engineer (http://www.lz1aq.signacor.com/). Deep reading sometimes, but a great understanding of what makes a good receiving loop antenna.

Those who chase DX know that sometimes fading is caused by the signals’ polarization changing in the Ionosphere. Having both vertical and horizontal loops, and the ability to combine both signals diminishes this fading problem. Being able to filter the powerful, commercial FM transmitters diminishes image problems. Clipping strong signals at the antenna from very near powerful antennas/transmitters could save the SDR receiver from damage.

The LZ1AQ broad band Amp solves all these problems. http://active-antenna.eu/amplifier-kit/.

My son Ted and I built three, one meter loops from soft ½ inch copper plumbing tubing. One for his apartment, two for my crossed loops antenna. We weather proofed the Copper from corrosion by coating with outdoor clear spar varnish. We shaped the circle by drawing the tubing around a round glass top patio table.

The soft copper loop in held by white PCV plastic plumbing pipe. 1” or 1.25 inch schedule 40. Be careful to check that the PVC is schedule 40, thick wall. The thin wall pipe is not strong in the wind and will crack when you try to drill it.

Drill up to a 3/8 hole for the ½” copper tube to go through, then file out to fit. Here are some photos (click to enlarge):

Check out these links (all courtesy of LZ1AQ) to acquaint yourself with the loop construction and amplifier installation:

http://active-antenna.eu/tech-docs/2_ActiveAA_Mount_20.pdf

http://active-antenna.eu/tech-docs/1_ActiveAA_DandS_20.pdf

http://active-antenna.eu/tech-docs/3_ActiveAA_Antena_11.pdf

Many SDR receiver owners have seen improved noise and Image reduction by placing the plastic cased SDR unit on a small shielded/ grounded case.

The Amp needs 12VDC from in the shack. The Amp has two relays that you can switch, from in the shack, to select Vertical or Horizontal loops, or a dipole. The loop amp connects back to the shack via a shielded Cat 5 cable, Make sure you get shielded CAT 5 to reduce noise pickup. Make sure you provide an adequate good Ground below the antenna, less noise pickup and lightening protection.

Have fun!
Dave, K9ZCE
Retired from EE Dept @ Rose-Hulman Institute of Technology
Terre Haute, Indiana

Thank you so much, Dave!

Readers: yesterday I saw Dave’s loop antenna photos on the SDRplay RSP Facebook page. I was fascinated by his horizontally/vertically oriented loops and asked if he would write up a short guest post. He kindly obliged in a matter of hours!

If you have an antenna project you’d like to share, please contact me. So many SWLs and ham radio operators live in areas with restrictions and pervasive RFI–projects like Dave’s can revive one’s radio life!

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GODAR antennas

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Many thanks to SWLing Post contributor, Mario Filippi (N2HUN), who writes:

[Check out] this site I came by accidentally, small company, USA made antennas, most are OTA TV but he has a few shortwave antennas, quite reasonable. […] Also has old vintage pics. A little of this and that on the website, quite interesting company. He sells on Ebay too.

GODAR USA

Thanks for the tip, Mario. I love supporting mom-and-pop manufacturers like Godar. It appears–based on his eBay rating–that Michael Godar has very satisfied customers and produces quality antennas.

Thanks for the tip!

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Guest Post: Jerry’s Mediumwave DXing Powerhouse Mini FSL Antenna

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Many thanks to SWLing Post contributor, Jerry Popiel, for the following guest post:

A MW DXing Powerhouse Mini FSL Antenna

by Jerry Popiel

In late February 2016 I completed construction of a modified version of Gary DeBock’s excellent 3 inch Mini FSL design (click here to view).

This new antenna is nothing short of a AM DXing powerhouse with unbelievable sensitivity for receiving stations across the entire AM Bandwidth both day and night. The tuning of stations is razor sharp and it has stunning nulling qualities. Consultation assistance was provided from DXing experts Steve Ratzlaff and Gary DeBock on the project.

Construction Details:

The Antenna was constructed using 9 – 100 mm Ferrite Bars wound on a 2.75 inch diameter x 4 inch styrofoam cake dummy form custom made by in Vancouver, B.C. Canada – ([email protected]) for $3.50 plus shipping.

The Coil wire consisted of 38 turns of high gain 660/46 Litz Wire. (Note: As can be seen 38 turns of the thicker Litz Wire left only 5/8” of room on each side of the Styrofoam Form to wire wrap the coil to the ruler frame. A longer Form ie 5” long would work much better for this build).

The insulation spacer used was 2 layers of 1/8 inch Aerotape self adhesive tape which also helped hold the 100 mm Ferrite Bars onto the Styrofoam Coil Form. Inductance measured 356 uH using a DM 4070 Meter which is well within the requirement of over 300 uH for AM Band Reception.

Side View Of 9-Bar FSL Antenna with 2.75” Diameter Styrofoam Cake Dummy.

Because of the extra thickness of high gain 660/46 Litz Wire which is a bit too big to solder to the inside terminals of the Tecsun PL-380 Radio, a 2 Position Terminal Block was superglued to the outside of the Ruler Frame to act as an interface connection point.

2 Position Terminal Block Superglued To Back Of Antenna Frame

Testing Results:

Both daytime and evening AM station captures have been spectacular. Stations as far away as KKOB / 770 kHz Alberquerque, New Mexico 1130 Miles from here in Winnipeg, Manitoba, Canada have been received. Country music station WSM / 650 kHz in Nashville, Tennessee 1082 miles distant is a daily evening pickup.

Station KKOB / 770 kHz Alberquerque, New Mexico 1130 Miles distance.

Station WSM / 650 kHz in Nashville, Tennessee 1082 miles distance.

Two Stations Received At 600 kHz 90 Degrees apart at the same time:

The amazing Nulling and Razor Sharp Tuning quality of this FSL was demonstrated when 2 stations at 600 kHz were received at the same time by rotating the Radio with attached FSL 90 degrees. In the North / South direction Station KSJB / Jamestown, North Dakota (219 miles distant) was received with a strong signal strength of 50 / 23. Then by rotating the Radio 90 degrees to the East / West direction Saskatoon, Saskatchewan station CJWW (442 miles distance) was captured with a similar strong signal strength of 44 / 24.

600 kHz Station KSJB / Jamestown, North Dakota.

600 kHz Station CJWW / Saskatoon, Saskatchewan.

Daytime Reception of 600 Watt Station 137 Miles Distant:

A major daily AM reception capture during the afternoon illustrating the amazing sensitivity of this antenna is 600 Watt station KKXL Sports Radio 1440 kHz (137 miles).

All Indoor Reception – For Now!

Due to winter conditions here in Winnipeg, all of the amazing station reception captures in this report were done inside the House facing towards the South window. Fortunately the red ruler platform sides can he used as handles when pointing the radio in the direction of best reception. Exciting times are ahead to see how well this mini 3” FSL will perform outdoors for likely even better AM DXing.

Summarizing:

The design of this new FSL Antenna attached to the Tecsun PL-380 Ultralite radio by Gary DeBock is a major breakthrough in AM DXing since the Radio is attached to the FSL. This new FSL Antenna needs to be constructed to be really appreciated. The application described here requires a bit more skill to construct and is also heavier than the original construction – but at least it is portable. For beginners Gary’s original 3” FSL Heathkit Design is highly recommended and can be reviewed in his You Tube Video posted at: https://www.youtube.com/watch?v=VY9u8MReGjk

Thanks,
Jerry Popiel
Winnipeg, Manitoba, Canada

Thank you, Jerry! It’s amazing what performance you and Gary DeBock have gotten out of these homebrew FSL antennas! Thank you so much for taking the time to share your construction details and performance notes!

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Portable power for active antennas

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CPI1000 mit Powerbank

Many thanks to Dennis at Bonito for sharing a link to an article he recently published on the Bonito blog:

Autonomous power supply of our active antennas via USB and power bank

It is getting to be more and more difficult to procure reasonably priced analogue external plug-in power supplies because just like old light bulbs they are no longer allowed to be produced due to power consumption restrictions. We are spending a lot of time to find and buy remaining stock so that we can offer our customers noise-free external power supplies. But for years, there has been an alternative.

Our MegaLoop ML200, ML052, the MegActiv MA305 as well as the GigActiv GA3005 can be operated internally with as little as 5V and so can be powered by the supplied CPI1000DP / CPI3000DP bias tee via a USB cable. In light of the annoying switching power supplies, PowerLAN and heightened mobility of listeners, this is a very practical alternative and offers much more flexibility for the customer. Unfortunately, this fact is not well known and that is why I would like to shed some light on this subject.[…]

Continue reading at the Bonito website.

Thanks, Dennis!

I should note that there are a multitude of 5 VDC powerblocks on the market. I have two made by Eton Corp (see above) that even have hand-crank power generation. I recently used one to power my Raspberry Pi (Raspberry Pirate!) for several hours.

As Dennis states, using a DC source certainly cuts down on interference from noisy power supplies.

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Free webinar on receiving antennas

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Many thanks to SWLing Post reader, Tim Anderson (KF7JBM) who writes:

You may have seen this already, but I ran across this at the ARRL site and thought it might be of interest to your readers:

Receiving Antennas Will Be Focus of Free Webinar

“High Performance RX Antennas for a Small Lot” will be the topic of a free webinar by Jose “JC” Carlos, N4IS, and sponsored by the World Wide Radio Operators Foundation (WWROF).

Carlos will explore basic concepts of receiving antennas and share his experiences with low-band receiving antennas on a small lot, including the Waller Flag.

The webinar will take place on March 4 at 0200 UTC (the evening of Thursday, March 3, in US time zones). It will run for about 1 hour.

Registration is required. — Thanks to Ken Claerbout, K4ZW, via The Daily DX

Many thanks, Tim! I may try to attend this next week.

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MegaLoop ML052: Bonito’s new portable mag loop antenna

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(Source: Bonito Press Release)

At the beginning of the model year 2016, there is good news in the range of our MegaLoop Active Loop Antennas:

New Model: MegaLoop ML052

The new Active Loop MegaLoop ML052, which is available end of February, is the successor to our MegaLoop 060. Based on the proven technology of theMegaLoop 200 platform, an additional low pass filter with an extra FM-band-stop was integrated. Thus, the ML052 is especially suitable for operation near strong FM-stations and higher frequencies , where, because of its broadband capacity, the ML200 could be overloaded by strong signals.

Frequency range:
Low Gain: 9kHz – 52 MHz
High Gain: 9 kHz – 36 MHz
Suppression on FM (88 – 108 MHz): max. 40 dB

Intercept Point
IP:3: typ. +40dBm
IP2: typ. +84 dBm

The effect of the integrated filter can be seen very good on these two images:

ML052 in High Gain Mode

ML052 in Low Gain Mode

Like the ML 200, the amplification of the ML052 can be changed internally with a jumper:
a) High Gain: 0-36MHz
b) Low Gain: 0-52 MHz (-7dB)
Suppression of the FM band: (88-108MHz): max. 40dB

Outstanding intermodulation surpression, with only 5 volts!

CPI1000 with a standard Powerbank

The MegaLoop ML052 achieved outstanding values regarding intermodulation suppression even at a low supply voltage from only 5V. It can be powered either by a conventional plug power supply or even via USB. Powering via USB has the advantage that no external power supply is needed and that the antenna can be used autonomously and noise-free with a separate USB power bank. A appropriate dual power input adapter (CPI1000) is already included in the standard package.

The MegaLoop ML052 can now be pre-ordered in our eShop underwww.hamradioshop.net. In the UK at Taylor Made RF.

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Intergalactic DX: Detecting gravitational waves

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NASA illustration of LISA--spacecraft that will form an extremely large antenna system for detecting gravitational waves.

NASA illustration of LISA–spacecraft that will form an extremely large antenna array for detecting gravitational waves.

Many thanks to SWLing Post reader, Dan H, who writes:

The biggest news during the last week is not the Republican or Democratic national party debates, the surrender of the last Militia Man at Malheur National Wildlife Reserve in Oregon or falling stock prices for Tesla. The biggest story of the week involves some lasers enclosed in huge vacuum tubes.

The recent proof for gravity waves is something that should have a lot of appeal to readers of SWLing Post. This story involves very weak waves originating billions of years ago, measuring distances with lasers and old-style vacuum tube tech (albeit four 2.4 mile-long tubes located 1,900 miles apart). It sounds like DXing to me and DXing is interesting. But, this story describes changes in spacetime and that is really significant.

I get it, at least on a layman basis. I think that many SWLing Post readers would get it too.

This link to an older article is the best that I can provide to describe it all. The recent discoveries involved LIGO sites in Hanford, Washington and Livingston Parish, Louisiana.

http://www.nola.com/environment/index.ssf/2013/05/ligo_captures_gravitational_wa.html

I heard over 90 minutes of programming on this subject during the last seven hours from BBC. I heard it locally on SW in northern California at 7445 and 9740 kHz. The programs were featured on the Newsday and Science Day BBC programs. Yes, I was listening to two different BBC relays from different parts of the world on my apparently outdated and uncool Sangean ATS-909X.

You’re right, Dan! I had planned to post an item about this, but have been been a bit behind due to travels. I believe you can’t find any weaker DX than gravitational waves from distant colliding black holes! It’s a fascinating idea, too, to use a laser antenna to detect these waves across space/time.

I also enjoyed this article and video from the New York Times.

Oh, and regarding your Sangean ATS-909X? I think it’s one of the coolest looking portables on the market! Glad to hear it’s serving you well.

Thanks for sharing, Dan!

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