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FSL Antenna Tuning Course Video


Gary DeBock
 

For the benefit of Todd, Paul, Chris or any other Oz (or worldwide) DXers who wish to try out a compact FSL antenna to track down exciting DX, a video showing detailed the tuning procedures for the getting the best inductively coupled gain boost from any FSL has been posted at  https://youtu.be/uIvNdYdbxg4

Three daytime DX fringe stations (on 620, 1070 and 1700 kHz) are tuned in on a stock CC Skywave and 3" Baby FSL, while the fanatical instructor shows you how to track down the best gain boost every time. The FSL antenna does have a reputation for being somewhat tricky and mysterious, but hopefully this tuning course will dispel some of the mystery, and prepare some DXers for an exciting new way to enjoy the hobby! Once you get past the Yankee accent the rest should be easy...

73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)


Les Rayburn
 

Thank you for taking the time to produce this training course for the use of FSL’s. Very helpful! 

One question I have that would only apply to DSP ultralights like the CC Skywave. Does the effect of narrowing the bandwidth of the receiver have any impact on tuning the antenna? What bandwidth setting were you using in the video? I assume the stock 6 KHz setting. 

Your craftsmanship is something to behold. 


73,

Les Rayburn, N1LF
121 Mayfair Park
Maylene, AL 35114
EM63nf

NRC & IRCA Courtesy Program Committee Chairman
Member WTFDA, MWC

Perseus SDR, Elad FDM-S2 SDR, AirSpy + Discovery, SDRPlay RSP-2 Pro, Sony XDR-F1HD [XDR Guy Modified], Dennon TU-1500RD, Sangean HDT-1X, Ray Dees RDS Decoders, Korner 9.2 Antenna, FM-6 Antenna, Kitz Technologies KT-501 Pre-amps, Quantum Phaser, Wellbrook ALA1530 Loop, Wellbrook Flag, Clifton Labs Active Whip. 

“Nothing but blues and Elvis, and somebody else’s favorite song…” 

On May 25, 2020, at 12:39 AM, Gary DeBock via groups.io <D1028Gary@...> wrote:

For the benefit of Todd, Paul, Chris or any other Oz (or worldwide) DXers who wish to try out a compact FSL antenna to track down exciting DX, a video showing detailed the tuning procedures for the getting the best inductively coupled gain boost from any FSL has been posted at  https://youtu.be/uIvNdYdbxg4

Three daytime DX fringe stations (on 620, 1070 and 1700 kHz) are tuned in on a stock CC Skywave and 3" Baby FSL, while the fanatical instructor shows you how to track down the best gain boost every time. The FSL antenna does have a reputation for being somewhat tricky and mysterious, but hopefully this tuning course will dispel some of the mystery, and prepare some DXers for an exciting new way to enjoy the hobby! Once you get past the Yankee accent the rest should be easy...

73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)



Chris Rogers
 

Thanks Gary. The FSL is very easy to master on radios like the 2010, 803A, 880 etc and similar. The later DSP chip radios like the Skywave etc requires some skill to hear the "peak" as they are quite slow to react to the increase in signal level and can be quite frustrating to those who are used to the older style radios.


Todd
 

Thanks Gary for both the instructional video, and informative technical construction details.

Based on all the factors involved, I suggest that building an FSL antenna is much more challenging than operating the finished product.

The critical FSL tuning is largely overcome by using a 8:1 reduction drive 384p variable capacitor. The tuning sharpness in the video is similar to my 40 inch PVC box loop. Of course the tuning is even sharper down near the bottom of the MW band, e.g. 531 KHz. But I have never had issues re quickly finding the loop resonant signal peak.

Like any loop, the optimum induction distance is a function of RF frequency. At first, I position the portable radio a little too far away from the loop, carefully tune to resonance, then gradually position the radio closer until the loudest signal is obtained. The tuning sharpness tends to be greater with distances marginally too far for the loudest signal.

With the 40" air core loop, all my portable radios receive stronger signal induction when positioned center broadside to the loop. Directly back or front of the wires also works, but the signal level is not as strong.

I gather your backyard 9 foot air core PVC loop is the benchmark antenna for comparing all your other antennas. Is it possible for say a 7 inch FSL to match the 9 foot PVC loop? The benchmark is daytime stable groundwave. But with all the recent metro stay-at-home resultant consumer electrical noise, the bigger 9 foot loop may only produce more signal and noise. Hence the law of diminishing returns kicks in.

Kevin Schanilec's FSL optimization paper states that the FSL antenna can provide the same level of performance as an air-core loop 12 times the size. Hence a 7 inch diameter FSL could be expected to approximately perform to a 7 foot air-core loop. The Belrose equation says the air-core loop will provide more signal. But the equation doesn't factor in all the variables. It is only by trial that the more efficient antenna can be determined.

Regards,

Todd


Todd
 

Thanks to Steve Ratzlaff for notifying me re the March, 2012 Gary DeBock FSL article. I uploaded the file to the antenna section.

Regards,

Todd

https://ultralightdx.groups.io/g/main/files/5%20Antennas%20and%20Equipment/DeBock%202012%20FSL%20Antenna%20Design%20Optimization.pdf


Gary DeBock
 

Thanks Gary. The FSL is very easy to master on radios like the 2010, 803A, 880 etc and similar. The later DSP chip radios like the Skywave etc requires some skill to hear the "peak" as they are quite slow to react to the increase in signal level and can be quite frustrating to those who are used to the older style radios.

Thanks Chris (and Todd),

Todd, prior to our joint Kauai (Hawaii) DXpedition in November I provided Chris with the latest 5 inch "Frequent Flyer" FSL model, but he found it a little tricky to find the gain peaks because of the delayed response of the CC Skywave's DSP chip, which always tries to compensate for any antenna frequency changes. Broadband receivers like the PL-880 and ICF-2010 do not have this quirk, and are much easier to use with a razor-sharp tuning FSL. Despite this a DXer can become pretty skillful at using a CC Skywave with a 5" Frequent Flyer FSL if he practices continuously, and masters the DSP chip quirks.

<<<   Based on all the factors involved, I suggest that building an FSL antenna is much more challenging than operating the finished product.   >>>

Any DXer's first attempt at constructing an FSL will probably be challenging, but once you get used to the quirks they are very simple and straightforward.

<<<   The critical FSL tuning is largely overcome by using a 8:1 reduction drive 384p variable capacitor. The tuning sharpness in the video is similar to my 40 inch PVC box loop. Of course the tuning is even sharper down near the bottom of the MW band, e.g. 531 KHz. But I have never had issues re quickly finding the loop resonant signal peak.   >>>

Actually the tuning sharpness of the latest FSL's (tweaked for the maximum gain) is quite a bit trickier than that of an air core loop, Todd, but with some practice a DXer can adjust to it. On an FSL the sharpest tuning is on the high band, and the low band frequencies (530-600 kHz) tune more broadly (i.e., easier to peak the gain boost).

<<<   I gather your backyard 9 foot air core PVC loop is the benchmark antenna for comparing all your other antennas. Is it possible for say a 7 inch FSL to match the 9 foot PVC loop? The benchmark is daytime stable groundwave. But with all the recent metro stay-at-home resultant consumer electrical noise, the bigger 9 foot loop may only produce more signal and noise. Hence the law of diminishing returns kicks in.   >>>

The signal boost from the 9' air core loop is pretty impressive, but the Monster FSL's (15 inch and larger) can match it in S/N ratio. FSL antennas have a natural tendency toward lower noise reception, so a compact FSL design can usually compete with a much larger air core box loop. The latest model 5 inch "Frequent Flyer" FSL's can usually outperform my 4 foot air core box loop in S/N ratio, primarily because of lower noise reception on the weakest signals. Even the latest "Baby FSL's" can sometimes compete with the 4' air core loop in weak signal reception, especially on the extreme low band frequencies when domestic splatter is an issue.

73, Gary

  

 



 


Max Italy
 

I noticed that passive coupling of a 20" air loop antenna with capactitor to a DSP radio gives better signal than removing the internal ferrite and wiring it directly. Although the DSP chip has an automatic tuning circuit.

This makes me think that the automatic tuning is not so accurate and it may be the main reason why hard wiring a FSL is not even considered an option?

However I did the test with a cheap radio. 


Gary DeBock
 

On Wed, May 27, 2020 at 07:53 PM, Max Italy wrote:

I noticed that passive coupling of a 20" air loop antenna with capactitor to a DSP radio gives better signal than removing the internal ferrite and wiring it directly. Although the DSP chip has an automatic tuning circuit.

This makes me think that the automatic tuning is not so accurate and it may be the main reason why hard wiring a FSL is not even considered an option?

However I did the test with a cheap radio.

Hi Max,

Actually there have been quite a few FSL's hard wired into DSP-chip Ultralight radios, and some of them work quite well. Most of the attempts have been with the Tecsun PL-380, which seems to tolerate an FSL's powerful RF output as long as a small coil is used (3" or less diameter). 

I've attached a construction file for the hard wired 3 inch FSL Tecsun PL-380, of which about 10 were made by me and other DXers back in 2016. A couple of 2 inch FSL Tecsun PL-380's were also made, one of which I sent to Hiroyuki Okamura in Japan. These hard wired FSL experiments were attempted with the CC Skywave Ultralight, but their Si4735 DSP chips were fried pretty quickly. A PL-380's Si4734 DSP chip was also fried when a larger (5 inch) FSL was hard wired in place of the loopstick. 

The hard wired 3" and 2" FSL Tecsun PL-380's work quite well, but the main drawback is that they require the very rare Russian surplus 100mm x 20mm x 3mm ferrite bars, which haven't been available commercially since 2012. These are the same lightweight ferrite bars used in the 5 inch "Frequent Flyer" FSL antennas, so the demand for these rare ferrite bars is extreme.

73, Gary DeBock (in Puyallup, WA, USA)


Max Italy
 

Thanks Gary, your explanation is very clear as always.