Tag Archives: Antennas

Larry’s variation of the W6LVP amplified magnetic loop antenna

Many thanks to SWLing Post contributor, Larry Thompson (WPE8EKM), who writes:

I’ve just finished building a variation of the W6LVP amplified magnetic loop antenna. I was able to purchase the preamplifier, power inserter, and the power supply separately. I then created my own loop antenna using LMR400Max coax and designed my own knock-down PVC support. I wanted something extremely compact and portable to take on sae-kayaking expeditions and to DXpeditions to Africa.

I spent many years teaching in the DRC Congo and hope to return.

I’ve used a 6’ loop, a 9’ loop, a 12’ loop, and an 18’ loop. All do very well, but the 6’ and the 9’ seem to do the best. I’ve been using the 9’ length of coax doubled into two loops and that seems be be doing extremely well.

The signal strength from the W6LVP variation is equal to my Parr EF-SWL End-Fedz 45’ dipole, but the reduced noise level on the bands is amazing. I live in a central city high-rise with no possibility of an exterior antenna. The EF-SWL is strung out a 5th floor window down the side of the building. It performs well, but with a high degree of noise. My QTH is rampant with QRM and RFI noise. The W6LVP amplified magnetic loop has really resolved that in a big way.

The bands are horrible at the moment, so evaluating the loop antenna is difficult. But the cleaner, stronger signals of CHU Canada on 3339 kHz and 7850 kHz, as well as WWV on 10,000 kHz is impressive.

I’m impressed with the reduced noise level on the bands tuning across them, as well as the noise-free signal once you lock into a station. I’ve heard hams on the 17 mb for the very first time.

So far, I’m very impressed with the performance of this amplified magnetic loop.

Very cool Larry! You’ve build a compact loop that can bring the RFI down to a tolerable level–I’d say that’s a complete success. Thanks for sharing!

Click here to read our previous article about the W6LVP loop.

Antenna installation: John would like to use home satellite TV/RG6 port

Many thanks to SWLing Post contributor, John Minor, who writes:

I am going to set up a rig to start DXing, and getting my technical license. My plan is to buy a Kenwood TS-590 SG transceiver and a discone antenna.

My home’s previous owner had satellite TV, and my question to you is, can I use the existing cabling for my antenna?

There is a connector in my living room, and the cable runs to the connector/splitter box for the dish. Could I run a cable from the end of the existing cable at the splitter box, to the antenna?

I’ve attached some pictures to show you what the existing cables look like.
Picture 6 has a circle drawn on it to show where I’d like to mount the antenna.

I remember back when I was 9 or 10, laying under the covers at night slowing turning my AM transistor radio dial and seeing what I could pick up. It was a thrill to hear stations from Chicago, Cincinnati or Little Rock. I look forward to the same thrill listening to voices from across the country and around the world……

Thank you for your time, and for the wonderful website.

Thank you, John, for your question and for the kind compliment!

I’m publishing this question here, though, in hopes the SWLing Post community can help you.  I have very little experience matching antenna impedance this way especially when transmitting will be involved–there will be a mis-match, I’m pretty sure. With that said, I know many mag loop receive-only antennas actually use RG6. It would certainly be great to use an existing penetration for this application.

Post readers: If you can help John, please do comment. Quite frankly, this isn’t the first time I’ve been asked this question, so I’ll follow comments as well.

John, I’m sure you’ll soon have your radio on the air receiving the world just like when you were nine–or even better!  Great choice in that Kenny TS-590SG–it has a brilliant general coverage receiver for broadcast listening!

Video: Paul’s large aperture “Volleyball Net” loop antenna

Many thanks to SWLing Post contributor, Paul Walker, who shares the following video and notes:

Here is a 10 minute narrated, detailed video on my 25 foot long by 10 foot tall “Volleyball Net” Loop antenna using a Wellbrook ALA100LN amp control head and antenna interface.

Click here to view on YouTube.

Great job, Paul!

I like how Paul is using the antenna space he has so effectively. Though he has no antenna restrictions, his mag loop can be deployed and taken down quite easily; it’s obviously serving him well on both the HF and mediumwave bands. As he mentions, it’ s also manually steerable.

Those of you with the Wellbrook ALA100LN amplifier might try building this loop as well.

I also like how Paul is using the Tecsun ICR-100 recorder. Not only does it provide an easy way to record line-in audio from his radio, but the built-in speaker serves as an excellent monitor. It’s pretty affordable, too.

I agree with Paul about the Emtech ZM-2 ATU: it’s an exceptional little tuner that can be used for both QRP and SWL applications. I recently purchased the ZM-2 after having borrowed one from my buddy Eric (WD8RIF). Great value, in my opinion.

Thanks again, Paul!

Post readers: If you have an antenna design you’d like to share, please comment or contact me.

Eric seeks advice: Building a directional mediumwave antenna for the RSP2 SDR

Many thanks to SWLing Post contributor, Eric McFadden (WD8RIF), who writes with the following question:

A request for assistance.

After comparing the reception of the RSP2 and 1/2 doublet to the reception of the County Comm GP-5 SSB and its little external ferrite-bar, I’ve decided I probably want to make some sort of directional antenna to use on AMBC with the RSP2. A wire loop, perhaps, or some sort of ferrite-bar thing, that connects to the RSP2’s Hi-Z input.

[Perhaps SWLing Post readers can suggest] options and then I can get the needed bits at the 2017 Hamvention.

Post readers: if you can offer Eric suggestions, or point him to antenna plans, please comment! I do believe he would rather build an antenna than simply buy one and he’s looking to permanently mount this antenna outdoors.

Tony performs a quick LNA4ALL test

Many thanks to SWLing Post contributor, Tony Roper, who shares the following guest post which originally appeared on his blog, Planes and Stuff:


Quick LNA4ALL test

by Tony Roper

Despite the best efforts of the Royal Mail service, I have been able to get my hands on a Low Noise Amplifier created by Adam at LNA4ALL. The Royal Mail showed just how useless it is, when the parcel arrived here in the UK in just 11 hours from Croatia on February the 14th, but then not getting delivered to me until March the 14th – yes, one month! There is no surprise that courier companies such as DPD and Hermes are getting more business than the Royal Mail – they are bloody useless.

Anyway, the reason for the purchase is for a later review on an AIS dongle that I will be testing, but which has unfortunately been possibly damaged before getting to me.

So, as I had some time to spare I thought I’d run a quick test on how the LNA performs against the claims that is shown on the LNA4ALL website. For the test I used a quickly built 12v to 5v PSU that was connected to a Maplin bench PSU and also a Rigol DP711 Linear DC PSU where I could ensure a precise power input. As it was, it was good that I used the DP711 because my quick PSU was only chucking out 1.2v at connection to the LNA4ALL, despite an unconnected output of 5v – some work needed there I think.

Despite this lower power the LNA4ALL still worked with just the 1.2v input, though the results where not as good.

Other equipment used were a Rigol DSG815 Signal Generator and a Rigol DSA1030 Spectrum Analyser (no longer available), along with various Mini-Circuits shielded test cables. The Rigol equipment I purchased from Telonic Instruments Ltd last year.

Below then is a table that contains all the relevant data. As you’ll see the Gain claim is pretty much spot on with some being over. Just a couple of frequencies are below that which is claimed, especially at 28 MHz.

LNA4ALL Frequency data

A couple of things to note.

Firstly, somehow I managed to miss testing 1296 MHz. I obviously didn’t put it in the table in Excel before I started ? Also, the DSG815 only goes up to 1.5 GHz so I couldn’t test above that.

Secondly I ran a test for the AIS centre frequency of 162 MHz, for which there was no comparison to the LNA4ALL data. A gain of over 24dB though shows that the LNA would be perfect for those of you with AIS receivers that may want to get better reception. To prove the theory I compared the LNA reception against data without it connected to the NASA Engine AIS receiver that I currently use. In ShipPlotter I average a max range of around 15nm without the LNA, but with it connected this increased to around 22nm. The number of messages received also tripled as it was able to dig out the weaker signals.

The NASA Engine isn’t a bad receiver, but it is a frequency hopper rather than a dual monitor, and so it changes between the two AIS frequencies every 30 seconds (161.975 MHz and 162.025 MHz). I suspect a dual monitor would give better message numbers and range.

Below is a graph made using the excellent software by Neal Arundale – NMEA AIS Router. As you can see the message numbers (or sentences) for over an hour are pretty good – well, it is a vast improvement on what I used to get with my current “temporary” set-up, with 419 messages received in an hour. The software is available at his website, for free, along with various other programs that you can use with AIS. If you’d rather not use ShipPlotter he has created his own AIS Decoder which can be linked into Google Earth and such like. Visit his website for more information.

My antenna isn’t exactly top-notch. It is at a height of just 4 metres AGL in the extension loft, and it is made from galvanised steel angle bead used by plasterers to strengthen corners prior to skimming – this I cut down as a dipole for a target of 162 MHz. As usual with my trimming of antennas, I cut just too much off and ended up with it cut to 161.167 MHz. It gives a VSWR of 1.018 and Return loss of 40.82dB, with 162 MHz being approx. 30dB Return loss which equates to 1.075 VSWR – that will do.

Also, as I live right on the coast, about 50 metres from the sea, I’m practically at sea level, which doesn’t help much with range and signal reception either. Despite this the antenna produces great results, though it is just temporary until I can get a new homebuild up on the roof.

VSWR reading for the homebrew loft AIS Antenna

The LNA4ALL retails at various prices depending on what option you go for. I went for the aluminium box version so it was around £54 including the delivery. I had looked at a Mini-circuits equivalent, and when it looked like the LNA4ALL was lost I did actually order one. But this was nearly twice the price, and seeing as the LNA4ALL contains many components from Mini-Circuit I doubt it is any different really.

All in all the LNA4ALL is all you need to boost your weak signals – couldn’t get any more all’s in ?.


Many thanks for sharing your quick test of the LNA4ALL, Tony! Post Readers: if you’d like to read more of Tony’s work, check out his blog, Planes and Stuff.