Discovery of FSL Antenna Phasing for Front to Side Rejection


Gary DeBock
 

After many dual FSL antenna experiments I've finally determined how to effectively cancel out QRM from a local pest that is off to the side (90 degrees different) from a weak DX station, although I'm not quite sure of the theory behind this discovery.

This experiment was an attempt to cancel out QRM from a local pest, 950-KJR in Seattle, WA (35 miles/ 56 km to the north) and chase 950-KKSE in Parker, CO (1005 miles/ 1617 km to the southeast) during the early morning hours. The receiver was a basic (non-SSB) C.Crane Skywave, and two identical 5 inch ferrite rod FSL antennas were used. Please refer to the attached photo to follow this description.

Step 1)  Null out the pest station with the portable radio's loopstick (away from the FSL antennas). Set the radio down in this nulled position, so that the pest station is as weak as possible, while ensuring that there is space to set up the FSL antennas to the back and side (see photo).
Step 2)  Take the "Reception FSL" and use it to peak the pest station's frequency, setting it up parallel to the portable radio as shown, at the position providing the maximum inductive coupling gain. This will temporarily boost up the pest station, which previously was nulled.
Step 3)  Take the "Nulling FSL" and pretune the frequency to that of the pest station. You can do this either by adjusting the variable cap plates to match those of the "Reception FSL," or by temporarily peaking the pest station's signal in a position in front of the portable radio. After setting this frequency, set the "Nulling FSL" off to the side of the portable radio as shown, with the spacing identical to the spacing between the radio and the "Reception FSL."
Step 4)  Slowly and carefully tune the "Nulling FSL" until you hear the pest station's signal take a sharp drop. This setting will be very sharp, but once you find this position you will have nulled out the pest very effectively, and if another station is on the frequency, it may suddenly become dominant, even if it is far away (like 950-KKSE in Denver).

Some MP3's from this morning's experiments:

950-KJR in nulled position with the portable only  https://dreamcrafts.box.com/s/c2hkjl979oz12m3dcbcr9uz73ziid2y3
950-KKSE generally dominant over the local pest KJR when the "Nulling FSL" is peaked  https://dreamcrafts.box.com/s/5ctshbrf5tk9duwyruimgq85ml7ngn8c

More experiments will be conducted with identical FSL antennas in an attempt to provide a front-to-back ratio for the nulling of domestic splatter, and front to side nulling of the same splatter. If successful, this would dramatically increase the effectiveness of FSL antennas on flat ocean beaches, where domestic splatter from both the back and side is routine.

Gary DeBock (in Puyallup, WA, USA)   
    


Michael.2E0IHW
 

Yep, this works.
I've been applying the same principle with an external ferrite rod to squash QRM and QRN for many years now.

Michael UK
.........................................................................................

On 23/09/2020 12:38, Gary DeBock via groups.io wrote:
After many dual FSL antenna experiments I've finally determined how to effectively cancel out QRM from a local pest that is off to the side (90 degrees different) from a weak DX station, although I'm not quite sure of the theory behind this discovery.

This experiment was an attempt to cancel out QRM from a local pest, 950-KJR in Seattle, WA (35 miles/ 56 km to the north) and chase 950-KKSE in Parker, CO (1005 miles/ 1617 km to the southeast) during the early morning hours. The receiver was a basic (non-SSB) C.Crane Skywave, and two identical 5 inch ferrite rod FSL antennas were used. Please refer to the attached photo to follow this description.

Step 1)  Null out the pest station with the portable radio's loopstick (away from the FSL antennas). Set the radio down in this nulled position, so that the pest station is as weak as possible, while ensuring that there is space to set up the FSL antennas to the back and side (see photo).
Step 2)  Take the "Reception FSL" and use it to peak the pest station's frequency, setting it up parallel to the portable radio as shown, at the position providing the maximum inductive coupling gain. This will temporarily boost up the pest station, which previously was nulled.
Step 3)  Take the "Nulling FSL" and pretune the frequency to that of the pest station. You can do this either by adjusting the variable cap plates to match those of the "Reception FSL," or by temporarily peaking the pest station's signal in a position in front of the portable radio. After setting this frequency, set the "Nulling FSL" off to the side of the portable radio as shown, with the spacing identical to the spacing between the radio and the "Reception FSL."
Step 4)  Slowly and carefully tune the "Nulling FSL" until you hear the pest station's signal take a sharp drop. This setting will be very sharp, but once you find this position you will have nulled out the pest very effectively, and if another station is on the frequency, it may suddenly become dominant, even if it is far away (like 950-KKSE in Denver).

Some MP3's from this morning's experiments:

950-KJR in nulled position with the portable only  https://dreamcrafts.box.com/s/c2hkjl979oz12m3dcbcr9uz73ziid2y3
950-KKSE generally dominant over the local pest KJR when the "Nulling FSL" is peaked  https://dreamcrafts.box.com/s/5ctshbrf5tk9duwyruimgq85ml7ngn8c

More experiments will be conducted with identical FSL antennas in an attempt to provide a front-to-back ratio for the nulling of domestic splatter, and front to side nulling of the same splatter. If successful, this would dramatically increase the effectiveness of FSL antennas on flat ocean beaches, where domestic splatter from both the back and side is routine.

Gary DeBock (in Puyallup, WA, USA)  


Sudipta Ghose VU2UT
 

Thanks Gary. Must keep a hard copy.
Regards,
Sudipta


On Wed, Sep 23, 2020 at 5:08 PM Gary DeBock via groups.io <D1028Gary=aol.com@groups.io> wrote:
After many dual FSL antenna experiments I've finally determined how to effectively cancel out QRM from a local pest that is off to the side (90 degrees different) from a weak DX station, although I'm not quite sure of the theory behind this discovery.

This experiment was an attempt to cancel out QRM from a local pest, 950-KJR in Seattle, WA (35 miles/ 56 km to the north) and chase 950-KKSE in Parker, CO (1005 miles/ 1617 km to the southeast) during the early morning hours. The receiver was a basic (non-SSB) C.Crane Skywave, and two identical 5 inch ferrite rod FSL antennas were used. Please refer to the attached photo to follow this description.

Step 1)  Null out the pest station with the portable radio's loopstick (away from the FSL antennas). Set the radio down in this nulled position, so that the pest station is as weak as possible, while ensuring that there is space to set up the FSL antennas to the back and side (see photo).
Step 2)  Take the "Reception FSL" and use it to peak the pest station's frequency, setting it up parallel to the portable radio as shown, at the position providing the maximum inductive coupling gain. This will temporarily boost up the pest station, which previously was nulled.
Step 3)  Take the "Nulling FSL" and pretune the frequency to that of the pest station. You can do this either by adjusting the variable cap plates to match those of the "Reception FSL," or by temporarily peaking the pest station's signal in a position in front of the portable radio. After setting this frequency, set the "Nulling FSL" off to the side of the portable radio as shown, with the spacing identical to the spacing between the radio and the "Reception FSL."
Step 4)  Slowly and carefully tune the "Nulling FSL" until you hear the pest station's signal take a sharp drop. This setting will be very sharp, but once you find this position you will have nulled out the pest very effectively, and if another station is on the frequency, it may suddenly become dominant, even if it is far away (like 950-KKSE in Denver).

Some MP3's from this morning's experiments:

950-KJR in nulled position with the portable only  https://dreamcrafts.box.com/s/c2hkjl979oz12m3dcbcr9uz73ziid2y3
950-KKSE generally dominant over the local pest KJR when the "Nulling FSL" is peaked  https://dreamcrafts.box.com/s/5ctshbrf5tk9duwyruimgq85ml7ngn8c

More experiments will be conducted with identical FSL antennas in an attempt to provide a front-to-back ratio for the nulling of domestic splatter, and front to side nulling of the same splatter. If successful, this would dramatically increase the effectiveness of FSL antennas on flat ocean beaches, where domestic splatter from both the back and side is routine.

Gary DeBock (in Puyallup, WA, USA)   
    



--
One of those ... ...


C B
 

Hi Gary,

Great work phasing the FSLs producing effective results! One DXer's pest nulled to receive another DXer's pest! :-) Well done.

73,

Craig Barnes
Wheat Ridge, CO

On Wednesday, September 23, 2020, 08:08:38 AM MDT, Sudipta Ghose VU2UT <oneghose@...> wrote:


Thanks Gary. Must keep a hard copy.
Regards,
Sudipta

On Wed, Sep 23, 2020 at 5:08 PM Gary DeBock via groups.io <D1028Gary=aol.com@groups.io> wrote:
After many dual FSL antenna experiments I've finally determined how to effectively cancel out QRM from a local pest that is off to the side (90 degrees different) from a weak DX station, although I'm not quite sure of the theory behind this discovery.

This experiment was an attempt to cancel out QRM from a local pest, 950-KJR in Seattle, WA (35 miles/ 56 km to the north) and chase 950-KKSE in Parker, CO (1005 miles/ 1617 km to the southeast) during the early morning hours. The receiver was a basic (non-SSB) C.Crane Skywave, and two identical 5 inch ferrite rod FSL antennas were used. Please refer to the attached photo to follow this description.

Step 1)  Null out the pest station with the portable radio's loopstick (away from the FSL antennas). Set the radio down in this nulled position, so that the pest station is as weak as possible, while ensuring that there is space to set up the FSL antennas to the back and side (see photo).
Step 2)  Take the "Reception FSL" and use it to peak the pest station's frequency, setting it up parallel to the portable radio as shown, at the position providing the maximum inductive coupling gain. This will temporarily boost up the pest station, which previously was nulled.
Step 3)  Take the "Nulling FSL" and pretune the frequency to that of the pest station. You can do this either by adjusting the variable cap plates to match those of the "Reception FSL," or by temporarily peaking the pest station's signal in a position in front of the portable radio. After setting this frequency, set the "Nulling FSL" off to the side of the portable radio as shown, with the spacing identical to the spacing between the radio and the "Reception FSL."
Step 4)  Slowly and carefully tune the "Nulling FSL" until you hear the pest station's signal take a sharp drop. This setting will be very sharp, but once you find this position you will have nulled out the pest very effectively, and if another station is on the frequency, it may suddenly become dominant, even if it is far away (like 950-KKSE in Denver).

Some MP3's from this morning's experiments:

950-KJR in nulled position with the portable only  https://dreamcrafts.box.com/s/c2hkjl979oz12m3dcbcr9uz73ziid2y3
950-KKSE generally dominant over the local pest KJR when the "Nulling FSL" is peaked  https://dreamcrafts.box.com/s/5ctshbrf5tk9duwyruimgq85ml7ngn8c

More experiments will be conducted with identical FSL antennas in an attempt to provide a front-to-back ratio for the nulling of domestic splatter, and front to side nulling of the same splatter. If successful, this would dramatically increase the effectiveness of FSL antennas on flat ocean beaches, where domestic splatter from both the back and side is routine.

Gary DeBock (in Puyallup, WA, USA)   
    



--
One of those ... ...


Gary DeBock
 

On Wed, Sep 23, 2020 at 09:38 AM, C B wrote:
Great work phasing the FSLs producing effective results! One DXer's pest nulled to receive another DXer's pest! :-) Well done.
Thanks Craig,
     That's true about one DXer's pest was nulled to receive another DXer's pest, but my pest is a 50 kW Mega Pest, while yours is only a 5 kW mini pest!

Gary


a a
 

I have been using a fsl and a long wire to good effect on 1.8mhz to null nearby solar panel interference,its been a relevation i can use the band again...love the fsl. hail gary... de alec g8gon

On Wednesday, 23 September 2020, 23:20:08 BST, Gary DeBock via groups.io <d1028gary@...> wrote:


On Wed, Sep 23, 2020 at 09:38 AM, C B wrote:
Great work phasing the FSLs producing effective results! One DXer's pest nulled to receive another DXer's pest! :-) Well done.
Thanks Craig,
     That's true about one DXer's pest was nulled to receive another DXer's pest, but my pest is a 50 kW Mega Pest, while yours is only a 5 kW mini pest!

Gary


radiojayallen
 

Gary,

That is very cool and your description with the picture makes perfect sense...great idea! I have tried similar things with some positive results in the past using two Twin Coil Antennas and it did work to some extent. 

Jay


Max Italy
 

Good job Gary but now you have a problem bringing 2 FSL along on DX-peditions :D


Paul Blundell
 

Great work as always.

Paul


Gary DeBock
 

Thanks Michael, Sudipta, Craig, aa, Jay, Max and Paul,

Your comments are all very much appreciated!

This dual FSL nulling procedure has been tested over and over with many pest stations, and works very well once you get the hang of it, and follow the instructions. I have some recommendations for the best results (please refer to the attached photo).

1)  The stronger the pest station, the more razor-sharp will be the null, both with the radio loopstick and with the "Nulling FSL's" variable cap setting. Best results will be obtained by placing the radio down in the exact null position (however "hair trigger" that might be).
2)  You can still null out a pest when DXing conditions are poor, but you may not receive any weak DX station in the null position. On the other hand, when conditions are good, you may end up with two or more DX stations fighting it out with the pest in its null position.
3)  Make sure that you have the exact same inductive coupling distance between the radio and the two FSL antennas (although the two FSL's will be perpendicular to each other, as shown in the attached photo). If you are familiar with using an FSL antenna, you should have some practice determining the best inductive coupling distance on different frequencies (such as around 2 inches for 1700 kHz, around 4 inches for 1000 kHz, etc.). Or, you can simply listen for the best gain boost when you move the "Reception FSL" up to the radio-- that will be the best inductive coupling distance.
4)  So far these experiments have concentrated on receiving DX stations on the same frequency as a pest station. Although this procedure should be effective in nulling out domestic stations on frequencies like 540, 630, 720, 810 (etc.) when chasing transoceanic DX, further experimentation will be conducted for nulling out domestic splatter on slightly different frequencies than a transoceanic target station. If those experiments prove successful, the compact FSL antenna will become far more effective for transoceanic DXing on flat ocean beaches, where domestic splatter runs wild (unlike at ocean cliffs).

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