Category Archives: AM

Bill tweaks his AM loop antenna for optimal mediumwave performance

Many thanks to SWLing Post contributor, Bill Hemphill (WD9EQD), who writes with the following update to his previous post:

As you may remember, back in May, I picked up a beautiful home-made loop antenna. It was 25 inches on a side with 23 turns of wire. My initial testing showed that it would tune from 280 kHz to 880 kHz. While I was familiar with loop antennas, I had never tried using one.

My initial tests were disappointing. So I spent some time on the internet reviewing AM loop antenna designs. I came across a reference to an AM Loop Antenna Calculator by Bruce Carter:

http://www.earmark.net/gesr/loop/umr_emc_calc.htm

I first measured the tuning capacitor and found that it tuned from 25 to 400 pF. Entering the data into the calculator:

This matches closely to what I was experiencing.

I then proceeded to calculate various Number of Turns to see the effect on tuning range. My goal was to tune the entire AM broadcast band.

I settled on ten turns which gives the following from the calculator:

Perfect. I removed 13 turns (which left ten turns) and then added a two turn secondary loop which would be connected to the radio. The results were fantastic.

I have created three short videos showing the difference between using the Tecsun S-8800 without the loop on a weak station and then using it with the loop.

[Note: If you’re viewing this post via our email newsletter you might need to view this post via a web browser to see the following embedded videos.]

Without the loop

With Loop

As you can hear, a very noticeable difference.

[After making these videos] I tested the of reception of 1510 kHz on the Panasonic RF-2200:

The results are amazing.

I have logged three stations on one frequency. Just peak the one station, then tune the loop and peak the second, then turn the loop some more and peak a third station.

I’m having a lot of fun with the loop. When it gets a little cooler, I plan to take it to the park where there is zero noise and really put it through its paces.

Excellent job, Bill! You’ve proven that doing a little research and making small adjustments to an antenna design can yield impressive results! Thank you for sharing!

Jason gives a favorable review of the Sangean DT-120

Sangean DT-120

In reply to Olivier’s post about the Sony SRF-M95, SWling Post contributor, Jason, notes:

Another amazing AM ultra light performer, the Sangean DT-120 or DT-180

I have the DT-120 in my pocket and it has got many hours of use. Travelling in outback Australia in April/May I was very impressed with it’s performance on AM.

Camped at the Devils Marbels 412km north of Alice Springs, I could receive it’s 783 kHz AM signal OK, weak obviously but definitely listenable. Of course the signal from Radio National at Tennant Creek on 684 AM was stronger, since it’s only 100km to the north of Devils Marbles.

Very happy with the little Sangean. It’s by far and away the pocket radio with the best DX reception I’ve ever owned, but the Tecsun R-209 and the Sangean SR-35 are probably the two best AM DX pocket radios with a speaker.

One day I will pick up a Sangean DT-250, but it’s probably not much better than the Sangean DT-210 I already have, which is another good choice with a speaker.

Thanks for sharing your comments, Jason! And, wow, I’d love to make that camping pilgrimage to the Devil’s Marbles–sounds remote and fantastic!

If you like ultralight radios like the Sangean DT-120, check out our endurance test of the Sangean DT-160CL and Sony SRF-39FP.

Links:

Gary shares some catches from the first day of the Rockwork 5 DXpedition

FSL Antennas poised to grab DX! (Photo: Gary DeBock)

Many thanks to SWLing Post contributor, Gary DeBock, who shares an update from the latest Rockwork (Utralight) DXpedition. Gary notes (in bold):

First day FSL antenna setup at the Rockwork 5 ocean cliff near Manzanita, Oregon (Craig Barnes in the photo)– outstanding conditions for 558-Fiji and 1017-Tonga!

558 Radio Fiji One Suva, Fiji Awesome signal with island music and medley song ID on the half hour at 1230 (including “Radio Fiji One, Na Domoiviti” at 1:36) :

Click here to download audio.

765 Radio Kahungunu Napier-Hastings, NZ The usual S9 signal from this 2.5 kW overachiever with distinctive Maori music at 1218:

Click here to download audio.

1017 A3Z Nuku’alofa, Tonga Monster signal with island music at the start of the session at 1221:

Click here to download audio.

Monster signal with island music near the close of the session at 1314 (in other words, all session long):

Click here to download audio.

Wow! Impressive catches, Gary! Someday I would love to join your team as you snag signals from the edge of the Rockwork cliff.

Thanks for sharing, Gary and good DX!

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Guest Post: A DSP Hi-Fi “Stupid Radio Trick”

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


Stupid Radio Trick – DSP “Hi-Fi”

by TomL

If you can remember the 1960’s, there was an audiophile rage going on called Hi-Fi.  The base unit consisted of a ponderous piece of furniture consisting of a rectangular cabinet and equally large mellow sounding speaker of fairly smooth frequency response, say in the range of around 40 – 15000 Hz.  They would have a built-in radio (using vacuum tubes) with large analog scale. Most would also have a “record player” embedded on the top to spin some vinyl discs (78 or 33 rpm).

For pedestrian consumers, it became a decision of how to keep up with the Joneses, so-to-speak.  And that meant a trip to Sears to look at the latest offerings. When the decision finally came to purchase, of course no one could buy it outright.  So, to add to the suspense, one had to put money down on “Lay-A-Way” plan that did not allow you to take possession of your prized choice until the last monthly payment!  One had to visit or mail in a check every month.

So where am I going with all this?  Well, as you can see from the photo [above], I have purchased three portable radios for three very different purposes.   All three were painstakingly studied and reviewed and weighed against all other possible choices. All are highly rated by the usual reviewers like RadioJayallen, SWLing Blog readers and other internet personalities.  The Sangean is for home use and listening to baseball games when I did not want to fire up the stereo hooked up to the Grundig Satellit 800. The small Sony ICF-19 is a phenomenal knock around radio for the car and listening while out to lunch or a walk in the park.  The large Tecsun S-8800 is a possible replacement for my ailing 20+ year old Sony ICF-2010 for shortwave use.

Well, I was tired of listening to any one of them in terms of sound quality.  The Sangean has too much upper bass/lower mid range, the small Sony is very carefully maximized for total speech clarity, and the Tecsun seems to lack a little in the mid range frequencies (compared to highs and lows).  Staring at them, I thought to self, “What if I turn on the Sangean and Sony together???” What ensued was a revelatory sonic experience (it sounded pretty good)! One seemed to fill in the other in certain ways. But it was not perfect.

Duh, I had the new Tecsun in a carry case while trying to decide if I send it back for a tuning quirk and dug it out and plopped it on top.  Turning it on, I heard more lows and highs, just like a Field Radio should have but with the mid range filled in! After very careful volume adjustment, I now have something that could rightly be called DSP Hi-Fi.  At least, that is what I am calling it for now. ?

Violin and piano pop-out of an orchestra but not too harsh sounding.  Rock & Roll sounds loud and punchy without that boombox effect. Bass lows are there (could be better, now all I need is a small subwoofer connected to the Tecsun line-out ???).  Highs are there too but well controlled. Mid range voice clarity is stunning, as if someone is in the room with me but not sounding too forward! It is not room-filling but acts more like a near-field monitor.  I like that I can line-up the speakers over each other.

The really fortunate thing is that all three radios have complete DSP for FM and receive my favorite over-the-horizon station with very similar reception quality.  Also, they process DSP with a similar delay before output to its respective speaker. The sound is fairly coherent and even though it is still mono output, the full range of musical fidelity can be appreciated better.  It is not audiophile quality but it is very satisfying and I can actually hear more details in the music than with any one of the radios by themselves. Just goes to show you that you CAN teach a new Radio dog old Tricks (LOL)!

Happy Listening,

TomL


I love it, Tom!  Thanks for pointing out that sometimes it takes a “stupid radio trick” to really produce some amazing audio fidelity! This reminds me that in the early 90s, I used to have a Zenith Transoceanic and RadioShack DX-440 on my radio table in my room.  If I recall correctly, the Zenith was on my left and the DX-440 on the right. I used to tune to shortwave, MW and FM stations and produce a makeshift “stereo” effect by playing both at the same time. Sometimes, on shortwave, it actually helped me discern voices in weak signal work!

Thanks again, Tom!