why does my 7.5" loopstick favor one direction above 1000 KHz?


Ryan Martin
 

I just noticed my pl-380 w/7.5" loopstick mod favors one direction above(roughly) 1000KHz instead of the typical figure-8 reception pattern. Does anyone know why that is?
Ryan


josephrot
 

Because the "classic" figure 8 reception pattern isn't the "same uv (microvolt) signal at both lobes of the figure 8"...one lobe, the one pointing more to your desired signal, will be seen (say on RF scope, spectrum analyzer, etc.) to be the "stronger" of the two, and the opposite lobe will be seen to be the lesser -- but not by much, in general.
 
What you are seeing is both "lobe centric" behavior, and also a result of the antenna's place in the response curve, likely meaning that the ferrite antenna's size, wire, inductance is slightly more sensitive, or making the resulting circuit it feeds, on the curve at 1000 kHz or above.
 
Joe Rotello / Knoxville, TN / USA


Andy Gardner <ceo@...>
 

Maybe it's the proximity of certain components in the radio to the loop, or the windings being offset on the ferrite bar towards one end.

On 12/01/2014, at 6:26 AM, rmartin100@... wrote:

I just noticed my pl-380 w/7.5" loopstick mod favors one direction above(roughly) 1000KHz instead of the typical figure-8 reception pattern. Does anyone know why that is?
Ryan


chutton12000
 

I agree with Andy. A ferrite loop figure 8 is normally very close to a figure 8. If something is wrong to the point where you notice it casually, something is  badly wrong. This can also be confirmed if the nulls are not 180 degrees apart. The normal culprits are nearby objects and a lot of pickup (contamination) between the loop and the radio.


One question I'd like to know the answer to is the performance of a proper 7.5 inch replacement to the PL-380 rod. As far as I know, no one has reported the values for standard pattern skewing tests.


Chuck


Gary DeBock
 

Andy and Chuck,
 
The 7.5" loopstick PL-380 antenna design has a completely symmetrical coil (not offset to one side,) and is well isolated from the receiver circuitry (much more so than the internal stock loopstick), as shown in the attached photo. It has also been successfully built and/or used by at least a dozen DXers (including Patrick Martin, not a member of our Ultralight Yahoo group), all of whom have reported good results with it. None of the users have reported any issue with nulling or loopstick directivity, as Ryan has mentioned. The evidence would indicate that Ryan either has nearby metallic objects (indoors) which are skewing the symmetrical loopstick reception pattern, or a unique issue related to his own loopstick construction.
 
Ryan, as I recall, you originally had asked me to build the 7.5 loopstick PL-380 model for you. I have a couple of the models finished now, neither of which have any loopstick directivity issue (like you describe). As a final check, I would recommend that you get outdoors and check to see if your loopstick directivity issue still exists. If so, you may either send your finished model here for loopstick replacement, or simply exchange your finished model for one of the two finished MW test models here (both of which operate normally).
 
73, Gary DeBock (in Puyallup, WA, USA)  .  

-----Original Message-----
From: charlesh3
To: ultralightdx
Sent: Sun, Jan 12, 2014 7:30 pm
Subject: Re: [ultralightdx] why does my 7.5&quot; loopstick favor one direction above 1000 KHz?

 
I agree with Andy. A ferrite loop figure 8 is normally very close to a figure 8. If something is wrong to the point where you notice it casually, something is  badly wrong. This can also be confirmed if the nulls are not 180 degrees apart. The normal culprits are nearby objects and a lot of pickup (contamination) between the loop and the radio.

One question I'd like to know the answer to is the performance of a proper 7.5 inch replacement to the PL-380 rod. As far as I know, no one has reported the values for standard pattern skewing tests.

Chuck


Andy Gardner <ceo@...>
 

Yes, that certainly looks completely symmetrical.

Cross THAT off the list. :^)

On 13/01/2014, at 6:14 PM, D1028Gary@... wrote:


Andy and Chuck,

The 7.5" loopstick PL-380 antenna design has a completely symmetrical coil (not offset to one side,) and is well isolated from the receiver circuitry (much more so than the internal stock loopstick), as shown in the attached photo. It has also been successfully built and/or used by at least a dozen DXers (including Patrick Martin, not a member of our Ultralight Yahoo group), all of whom have reported good results with it. None of the users have reported any issue with nulling or loopstick directivity, as Ryan has mentioned. The evidence would indicate that Ryan either has nearby metallic objects (indoors) which are skewing the symmetrical loopstick reception pattern, or a unique issue related to his own loopstick construction.

Ryan, as I recall, you originally had asked me to build the 7.5 loopstick PL-380 model for you. I have a couple of the models finished now, neither of which have any loopstick directivity issue (like you describe). As a final check, I would recommend that you get outdoors and check to see if your loopstick directivity issue still exists. If so, you may either send your finished model here for loopstick replacement, or simply exchange your finished model for one of the two finished MW test models here (both of which operate normally).


Jay <jaypolicow@...>
 

What you say makes perfect sense. I have read discussions about this before and in my experience loops are generally very equal from one lobe to the other. However, in a few very isolated circumstances I have noticed some differences from one lobe to the next which I attributed to local conditions (local meaning quite close to the radio), because those effects were impossible to duplicate in another spot. If a particular radio or loopstick seems noticeably asymmetrical I also suspect something is wrong.

Jay
http://radiojayallen.com

--- In ultralightdx@..., D1028Gary@... wrote:


Andy and Chuck,

The 7.5" loopstick PL-380 antenna design has a completely symmetrical coil (not offset to one side,) and is well isolated from the receiver circuitry (much more so than the internal stock loopstick), as shown in the attached photo. It has also been successfully built and/or used by at least a dozen DXers (including Patrick Martin, not a member of our Ultralight Yahoo group), all of whom have reported good results with it. None of the users have reported any issue with nulling or loopstick directivity, as Ryan has mentioned. The evidence would indicate that Ryan either has nearby metallic objects (indoors) which are skewing the symmetrical loopstick reception pattern, or a unique issue related to his own loopstick construction.

Ryan, as I recall, you originally had asked me to build the 7.5 loopstick PL-380 model for you. I have a couple of the models finished now, neither of which have any loopstick directivity issue (like you describe). As a final check, I would recommend that you get outdoors and check to see if your loopstick directivity issue still exists. If so, you may either send your finished model here for loopstick replacement, or simply exchange your finished model for one of the two finished MW test models here (both of which operate normally).

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


-----Original Message-----
From: charlesh3 <charlesh3@...>
To: ultralightdx <ultralightdx@...>
Sent: Sun, Jan 12, 2014 7:30 pm
Subject: Re: [ultralightdx] why does my 7.5" loopstick favor one direction above 1000 KHz?







I agree with Andy. A ferrite loop figure 8 is normally very close to a figure 8. If something is wrong to the point where you notice it casually, something is badly wrong. This can also be confirmed if the nulls are not 180 degrees apart. The normal culprits are nearby objects and a lot of pickup (contamination) between the loop and the radio.


One question I'd like to know the answer to is the performance of a proper 7.5 inch replacement to the PL-380 rod. As far as I know, no one has reported the values for standard pattern skewing tests.


Chuck