Category Archives: Antennas

Tom’s field portable HF antenna snags VOK’s summit broadcast

Tom’s field portable car roof HF antenna.

Many thanks to SWLing Post contributor, TomL, who shares a recording he made of the Voice of Korea on June 14, 2018. This English broadcast focuses on the Singapore summit and is, no doubt, historic in its content. [Note that we’ve posted other recordings on the Shortwave Radio Audio Archive.]

TomL notes:

Recorded on my noisy Lenovo laptop, SDRPlay RSP2, and an unamplified 18.5 foot antenna on the roof of my SUV.

I’m most impressed with the quality of his recording–VOK is not the easiest station to snag in the US midwest:

Click here to download the audio recording.

Thank you for sharing, Tom! I love your field portable vertical–obviously, it’s doing a fine job and your car must make for a decent ground plane!

Guest Post: Backpack Shack 3 – Part 2

Many thanks to SWLing Post contributor, TomL, who shares the following guest post as a his Backpack Shack 3 evolves:


Backpack Shack 3 – Part 2

by TomL

Wanting MOAR options for my recent amplified whip antenna experiment, I decided to add a second antenna input to the kitchen cutting board (can I call it a “Breadboard”? – Ha, that’s an electronics joke!).  The idea behind it came from realizing that I might not want to spend all my time outside at a picnic table or on the beach, especially if it is drizzly and windy. And I still wanted a better ground for the antenna.  So, I thought I could use more Trucker Parts and put an antenna on top of the roof of my vehicle so I could listen in the relative comfort and safety of my small SUV (or even a friend’s car).

Breadboarding

Here is the crowded “Breadboard” with some extra items added.

I thought of the vertical antenna as a short longwire and had an old, original RF Systems Magnetic Longwire Balun.  That device allows for an improvement in signal/noise ratio (in theory) if used on a longwire. Perhaps it works on this, too??  You can see the gray cylinder connected right beneath the trucker mirror mount on the left (this will not be tested at this time, see External Antenna below).  The output goes to a greenish Daiwa switch on the right.

A large amplified antenna has the real possibility of overloading the amplifier.  With the Magnetic Balun, I am hoping the VHF band is attenuated enough to preclude any problems because its response naturally tapers off past 40MHz.  But Mediumwave is well within its bandpass. I remembered an old Kiwa Electronics Broadcast Band Rejection filter not being used for a long, long time, so I connected that right after the Daiwa switch (the metal box with red plate).

This output then goes to an RF choke just before entering the pre-amp.  I figure I will be using my SDRPlay RSP2 and noisy laptop and wanted to try to reduce any interference traveling on the outside coax braid before it gets amplified.

External Antenna

OK, now for the other Daiwa switch selection.  The external antenna will be connected and disconnected as often as I use it.  I attached two right-angle coax adapters to be the connection point for the antenna.   This is so that the physical switch threads do not have to handle that wear-and-tear. You can see it as the fuzzy out of focus thing sticking up out of the left side switch position.

The wire going out the top of the Breadboard goes to a Firestik K-11 magnetic mount placed on top of the roof of the SUV.  I also wanted this to be connected to a magnetic balun. I just happened to have a nearly unused Palomar Engineers Magnetic Longwire Balun.  It has its own ground lug for use with a counterpoise. Temporarily, I left the 18 feet of wire that came attached to the K-11 Mount and attached an adapter and BNC test lead; on the other end is connected the spade lugs to the Balun (red wire to the lanyard nut, black wire to the ground lug).  It all fits neatly inside a Sistema 3 liter container.

The magnet and box self-clamp easily onto the roof of the vehicle.  I added a new 18 inch section to the Trucker Antenna Shafts creating a full 72 inch antenna, complete with mag mount, ground plane (car body), and magnetic balun.  It is very easy to put up and take down and the box helps keep everything contained.

I am pushing things a bit here.  Magnetic Baluns are not really meant to be used on vertical antennas.  It probably breaks some sort of Cosmic Electrical Law somewhere that causes electromagnetic waves to get very confused and die a horrible, twisted, circular death.  But I figure that it is an unbalanced “line” similar to a longwire antenna; it’s just a little short and goes straight up instead of horizontal! I like the idea, so I am going to run with it.

Warnings!

It goes without saying that the Antenna Shafts, magnet mount, and magnetic balun are weatherproof (but NOT lightning proof!).  Take proper lightning precautions and take it down.  Even so, I might add a small drainage hole to the box since it did rain a tiny bit during testing.

Secondly, this setup is ONLY FOR STATIONARY VEHICLES!!!!  DO NOT TRY TO DRIVE DOWN THE ROAD OR HIGHWAY!!!! The magnetic mount will NOT stay on the car and will damage your vehicle and maybe a vehicle travelling next to you!

Performance

As you can see from the picture, my new Tecsun S-8800 is getting a workout while connected to the Cross Country preselector (not shown behind it) and to the backpack next to the back seat window.  The Tecsun S-8800 is a nice radio. My copy has a couple of quirks that I might have to send it back (the AM band tunes incorrectly 2 kHz lower than it should and the SW SSB tunes 140 Hz higher than indicated and I have to compensate using the fine-tuning dial for these modes–FM seems correctly tuned).

Other than this, the actual performance is really quite good!  DSP does have sharp cutoffs to the IF bandwidth (especially resolving strong station interference when selecting 3 kHz vs. 4 kHz).  With all my filters/balun/choke, I did not notice any MW or FM breakthroughs and signals on those bands were nicely contained and “normal”.  Interference from my cell phone while looking up internet frequency listings was minimal – seems like the cable shielding, choke, and car roof are doing a good job.

The audio output jacks have very thin clearance between the jacks and the housing of the radio. So for the second time, I will not have recordings since the cable I wanted to use has home theater style construction with very thick plug outer connectors and will not fit!

From an RF-quiet “Forest Preserve” (County park), there were a variety of stations received from the 25 through 19 meter bands (Local time 11am-1:30pm). A few stations I have never heard before until now:

  • Radio Free Asia in Korean on 11985 KHz (Tinian Island)
  • Radio China International in Esperanto on 11650 KHz (Xian China)
  • Radio Farda in Persian on 12005 KHz (Wooferton England) – broadcast opposite my direction
  • Radio Bible BCI in Somali on 15310 KHz (Nauen Germany) – Strange sounding but interesting  Christian Somali music
  • Radio Free Asia in Chinese on 13675 KHz (Dushanbe Tajikistan)
  • Voice of Hope Africa in English on 13680 KHz (Lusaka Zambia) – had to use ECSS USB to get away from strong interference from RFA on 13675, fairly good intelligibility (including music)!  I wish there was a 6 KHz option for SSB mode since the audio was slightly muffled and could not compensate much with the tone controls. That kind of feature usually comes with radios costing 3X more, however.
  • Voice of Korea in French (Kujang North Korea) being squashed by Radio China International (Kashi China) in English on 13760 KHz

It was so nice not to be on a beach and have people walk by STARING at me with my weird radio/antenna setup.  And I was dry and comfy sipping a cool drink while there was a drizzle of rain pelting the windshield. Downside might be that the car setup cannot always be located optimally if I want to be next to that Very Large Body of Water (Lake Michigan) to help enhance reception but this is not a bad alternative.   The next test will have to be during early evening when signals are booming into my location and see if performance holds up under those conditions!

Happy Listening,

TomL

Modified Parts List

Parts Repeated from Part 1 article


As always, Tom, a most impressive setup powered by home-grown ingenuity! Thanks so much for sharing the evolution of your field kits with all of us here at the SWLing Post!

By the way, you still have me chuckling about your use of the term, “breadboard!” 🙂

Guest Post: Tom’s Backpack Shack 3

Many thanks to SWLing Post contributor, TomL, who shares the following guest post:


Backpack Shack 3 – Amplified Whip Antenna

by TomL

So, having enjoyed using the Ferrite Sleeve Loop I created last year, I have wanted something a little more sensitive and less bulky.  I will eventually create a much BIGGER FSL antenna on the order of 2 feet long and perhaps 18 or 24 inches in diameter for indoor/attic use.  But that is not a priority at the moment.

Since I already have the DX Engineering Pre-Amplifier and the very nice Cross Country Preselector from the loop project, I thought it might be useful to create an active whip antenna for it.  And the cool looking Solar Red backpack needed something to do!

Power

Now that the bulky loop was not taking up the main compartment of the backpack, I could think about what else to put in there, like a larger power pack.  I scoured FleaBay for ideas and stumbled upon this contraption for backup power to network systems, the CyberPower CyberShield for Verizon.

This has 12 spaces for D-cell batteries and was mounted inside the demarcation terminal to provide backup power for things like cable systems and Copper-to-Ethernet networks.  It is not waterproof, so would be inside the premises of the customer getting the internet/cable service. But my Pre-Amp needs 12-18Volts and would love to have nearly unlimited power.  So, I bought a used one, cut the end off of the power lead and put on my own 2.1×5.5mm plug (carefully glued down and tie-wrapped). Then I filled it with 1.2Volt Tenergy D-cells.

Everything was just fine until I forgot to double check the polarity of the plug that I had wired onto the end.  Plugged it into the DX Engineering Pre-Amp, flipped the power switch and fitzzz…. The Pre-Amp light went on, then off (permanently!).

So, my expensive mistake is that I start using the FREE multimeter I got from Harbor Freight and check the polarity before I connect homemade battery packs to anything!!

DX Engineering charged me $60 to fix my mistake and it is working fine now after I swapped the wires on the plug. Yes, their Pre-Amp is NOT reverse-polarity protected! Disappointing, since the price tag for that device is $148!!!  The CyberShield now sits comfortably inside the bottom of the backpack.

Antenna

Now that the drama was over regarding the Power pack, I could think about the whip.  I did not want a wimpy whip! (No one should rightly aspire to this, in my opinion). More FleaBay searches found me looking at Trucker parts.  Loaded whips, magnetic mounts, 10 foot tall MFJ telescoping whips, etc was looking a bit expensive.

Besides that, I cannot fit a 10 foot tall telescoping whip into the backpack, I am limited to at most 18 inches (and that is at an angle to fit it in there).  But I found an old-fashioned mirror mount that looked promising since it had a nice SO-239 connector at the bottom and standard CB antenna fitting on top of 3/8”-24.

Then I found the 44 inch SuperAntenna with the same threads; then found the replacement Stainless Steel Shafts for a Wilson antenna in different lengths (I ordered the 10 inch version to test).  With a couple of rod coupling nuts and I was ready for testing!

Test Locations

I had already scheduled a short vacation to Sleeping Bear Dunes on the thumb of Northwestern Michigan, so I took this test setup with my Sony ICF-2010. This area is a very nice remote National Lakeshore with minimal noise.  I tried a beach setting and a couple of hilltop picnic areas (including meeting a local Porcupine) and had very nice reception at all locations. The hilltop locations are approximately 400 – 600 feet above the Lake (yes, the Dunes are THAT big there!).

Meeting a local Porcupine

Later on, I went to Grand Haven, MI on the way home and stopped at their very lovely beach.

Reception was just as good as the hilltop locations at Sleeping Bear! In both areas, I was next to a large body of water (in this case, Lake Michigan) and makes for an advantageous place for DXing!  I had also stopped at a Rest Area off the highway and that was a terrible place even though it was electrically quiet but nowhere near the big Lake. I guess the rumors are true about being near a large body of water somehow enhances reception of weak signals–?

I will submit recordings later since I lost the mini-B cable for the Sony digital recorder and had to order a replacement.  However, this was a nice project that freed up some space inside the backpack. I will add an 18 inch extension to the whip that will give me a total length of 72 inches.  Plus, it is mounted 12 inches up on the poly cutting board and I place the backpack on a small hunters folding chair that is about 24 inches tall. So, the tip will be about 9 feet off the ground.

Not pictured but I was also able to easily fit inside a used CCrane Twin Coil Ferrite antenna for mediumwave use that also performed very well.  I noticed that the picnic benches at some locations are made of metal, so that gives me a future idea of trying to leverage that to use as a ground plane somehow.  The battery pack is heavy but also gives great ballast to the backpack and will not tip over. Cannot wait for the Tecsun S-8800 to arrive so I can try leaving the radio inside the bag and just use the remote control to tune!

Happy Listening,

TomL

Parts List


As always, I’m so impressed with your spirit of radio adventure, Tom! I love the fact that your goal is to make a field-deployable DX kit that isn’t cumbersome or time-consuming to set up on site. I imagine you only need a couple of minutes to open the pack and have it on the air. 

Those DXing spots are stunning! I had no idea one could find 400-600′ dunes in NW Michigan–! With that said, I’ve heard that part of the state is one of exceptional natural beauty.  If you could somehow turn the lake into a body of salt water–thus increasing ground conductivity–you’d really enhance that already impressive reception! I’m guessing that sort of project would be a bit outside your budget! Ha ha!  That and the freshwater fish might protest!

To me, there is no better way to enjoy radio than finding a nice RF quiet spot in the great outdoors…no matter where you live in the world. On top of that, Tom, you’re constantly building, experimenting, documenting and sharing your findings–you’re a true radio zealot! Huzzah!

Post readers: Read Tom’s past contributions and articles by clicking here.

Ham Radio Friedrichshafen 2018 Vendor Photos

Many thanks to SWLing Post contributor, Mehdi Asgari (DF2HF / NM9A), who shares photos from the Friedrichshafen ham radio convention this year. Tomorrow, we’ll post his photos of the flea market area!


Ham Radio Friedrichshafen 2018

by Mehdi Asgari (DF2HF)

Mehdi is a software engineer and SDR lover working in Berlin. He’s a licensed ham (DF2HF & NM9A) and also a member of EP2C club.

Test the MegaDipole MD300DX wideband active dipole via a KiwiSDR

In reply to our post about the Bonito MegaDipole MD300DX wideband active dipole antenna, SWLing Post contributor, Mark, comments:

Dennis from Bonito kindly sent me a sample megadipol and I’m truly impressed with it. The SNR is amazing right through the shortwave spectrum and really helps pull out weak signals.

I was particularly impressed to be able to pick up World Music radio on 5840 kHz all the way here in Ireland with just 100 watts in the evenings.

It’s also quite excellent on LW/MW.

See for yourself on my KiwiSRR just check out the SNR !!!

Click here to load Mark’s KiwiSDR in a new web page.

Thanks, Mark, for hooking the MegaDipole up to your live KiwiSDR!