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New style of FSL........I think ?

Dean wayman
 

Because of the rising cost in Ferrite and Litz wire I have been thinking for some time about building a FSL that uses less .
It seemed to me that the wire part of the FSL is mostly fixed ,so maybe less ferrite in some way would be cause less stress on the pocket book?
After looking at everything on the net ,Pics of loops ,Gary's massive collection ,other peoples builds and all ,I decided to see if a spider weave or Basket weave was practical?

I made a 3 inch circle from wood and put 9 ,8x80mm Ferrite rods M400  on it , I have no pic of it . To this was added some turns of 1200/46 litz, And a variable tuning cap of 14-465 pF .This tiny loop worked very well giving a good boost in signal strength ,The nulls were very deep and sharp.

So I cut a plastic pipe of 4 inch size ,and installed 15 of the same size rods on it. Again 1200/46 Litz was wound on this .

I also wanted a pickup loop to set next to the radio ,because this loop would need to be mounted to some thing in the vertical plane ,so that it could be rotated to line up with different stations on the compass.

2 configurations were tried the first was 

This winding proved to be very difficult to produce and ,not of much benefit ,seemed to make the tuning on the loop mushy even adding bass to the signals,so it was abandoned.

The next was this, 4 turns at the center and then the loop winding and finally 4 more turns over that to complete the pickup coil.

A inner and outer winding was made of 660/46 Litz, terminated to a 1/4 inch Mono phone jack so the pickup loop could be removed for mutual coupling or transport etc.


Up to now I had  used 2 weeks of nearly full days testing, building ,rebuilding etc.but one more thing needed to be explored ,on this loop do you need space between the Ferrite and litz?  I'M not trying to start any arguments etc. but I needed to know ,So this was unwound and spacers were added to the Ferrite ,clear plastic hose worked just right .Everything was re-assembled for testing ,And a second loop was wound directly on the Ferrite rods ,this part of the whole experiment needs more work but so far I see no difference in gain.

Another test loop was also built on wood dowels and a center circle to use as a control to test Ferrite vs non Ferrite .As we would think the ferrite gave more boost of signal.

Several days later it was taken to a quiet location ,in testing it has very good nulls which are deep and gives plenty of boost to signals.
Comparable boost with my 6 inch flat wound loop ,,and easier to use because the radio sits near me and  needs no lazy-susan .

So I leave it to you ,If your looking to spend a bit less and have a decent antenna maybe give it a try ?

Test radio's
Tecsun PL 600
Sangean 909 X

Dean

Tony Magon
 

Hi Dean

How many turns of litz is required - or what is the length of Litz wire required


Regards

Tony VK2IC



On Mon, Dec 2, 2019 at 11:41 AM Dean wayman <dx_plains@...> wrote:

Because of the rising cost in Ferrite and Litz wire I have been thinking for some time about building a FSL that uses less .
It seemed to me that the wire part of the FSL is mostly fixed ,so maybe less ferrite in some way would be cause less stress on the pocket book?
After looking at everything on the net ,Pics of loops ,Gary's massive collection ,other peoples builds and all ,I decided to see if a spider weave or Basket weave was practical?

I made a 3 inch circle from wood and put 9 ,8x80mm Ferrite rods M400  on it , I have no pic of it . To this was added some turns of 1200/46 litz, And a variable tuning cap of 14-465 pF .This tiny loop worked very well giving a good boost in signal strength ,The nulls were very deep and sharp.

So I cut a plastic pipe of 4 inch size ,and installed 15 of the same size rods on it. Again 1200/46 Litz was wound on this .

I also wanted a pickup loop to set next to the radio ,because this loop would need to be mounted to some thing in the vertical plane ,so that it could be rotated to line up with different stations on the compass.

2 configurations were tried the first was 

This winding proved to be very difficult to produce and ,not of much benefit ,seemed to make the tuning on the loop mushy even adding bass to the signals,so it was abandoned.

The next was this, 4 turns at the center and then the loop winding and finally 4 more turns over that to complete the pickup coil.

A inner and outer winding was made of 660/46 Litz, terminated to a 1/4 inch Mono phone jack so the pickup loop could be removed for mutual coupling or transport etc.


Up to now I had  used 2 weeks of nearly full days testing, building ,rebuilding etc.but one more thing needed to be explored ,on this loop do you need space between the Ferrite and litz?  I'M not trying to start any arguments etc. but I needed to know ,So this was unwound and spacers were added to the Ferrite ,clear plastic hose worked just right .Everything was re-assembled for testing ,And a second loop was wound directly on the Ferrite rods ,this part of the whole experiment needs more work but so far I see no difference in gain.

Another test loop was also built on wood dowels and a center circle to use as a control to test Ferrite vs non Ferrite .As we would think the ferrite gave more boost of signal.

Several days later it was taken to a quiet location ,in testing it has very good nulls which are deep and gives plenty of boost to signals.
Comparable boost with my 6 inch flat wound loop ,,and easier to use because the radio sits near me and  needs no lazy-susan .

So I leave it to you ,If your looking to spend a bit less and have a decent antenna maybe give it a try ?

Test radio's
Tecsun PL 600
Sangean 909 X

Dean

Dean wayman
 

Hi :
The length will depend on what value of capacitor your going to use but these loops have been around 60 ft of litz.
the count 1200/660/275 etc. isn't so important as the AWG ,46 is best for MW.
Dean

Tony Magon
 

Hi Dean


Thanks for the info - all ok

Regards

Tony VK2IC



On Mon, Dec 2, 2019 at 12:53 PM Dean wayman <dx_plains@...> wrote:
Hi :
The length will depend on what value of capacitor your going to use but these loops have been around 60 ft of litz.
the count 1200/660/275 etc. isn't so important as the AWG ,46 is best for MW.
Dean

Dean wayman
 

A little more info:

Spider weave coils or basket weave coils are very high Q that's why the crystal set radio builders use them .Combine a high Q tuning cap (ceramic insulators) and this loop has very sharp tuning ,enough so that even at BFO setting like in LW you get a very crisp tune .

Also the basket weave coils have very little distributed capacitance ,some thing that has been talked about a lot when the first FSL builders were tweaking their designs.

Used inside most houses this loop suffers from noise as any very sensitive antenna does ,as far as i know nothing can be done about that ATM.

Dean

Dean wayman
 

As far as I know this is the first time Ferrite has been used in a spider web coil ?

Dean

Tony Magon
 

Thanks Dean

Yes I would think that would be the first time ferrite has been in a loop this way

I do have a loop that I bought years ago that was made up in a basketweave style

It looks it was made up in a jig then fishing line was threaded through where the small sticks were to keep it all together - it used normal enameled wire. - Think it was about 9 inches diameter or thereabouts

I think the sticks on the jig were probably small skewers. Was modifying the amp that was originally in it - It is down in the garage somewhere - It worked very well.

Yes noise in the house is always a problem and Sydney - Australia is not a good location

Regards

Tony VK2IC



On Mon, Dec 2, 2019 at 1:04 PM Dean wayman <dx_plains@...> wrote:
A little more info:

Spider weave coils or basket weave coils are very high Q that's why the crystal set radio builders use them .Combine a high Q tuning cap (ceramic insulators) and this loop has very sharp tuning ,enough so that even at BFO setting like in LW you get a very crisp tune .

Also the basket weave coils have very little distributed capacitance ,some thing that has been talked about a lot when the first FSL builders were tweaking their designs.

Used inside most houses this loop suffers from noise as any very sensitive antenna does ,as far as i know nothing can be done about that ATM.

Dean

vbifyz
 

I am not an expert in ferrite antennas, just have a gut feeling: shouldn't the rods be moved more to the center, so that they are not sticking outside of the coil?
Intuitively, the magnetic material should be in the desired path of the magnetic field lines - inside the coil, not outside. The ferrite outside of the coil may actually "short circuit" the field lines and reduce the antenna effective height.
I am sure it still concentrates the field in the vicinity of the coil, but maybe not in the most efficient way.

Mike AF7KR