Reliable but reasonably priced sources of ferrite for FSLs?-FARMERIK


Rik
 

Searching on Ebay, I see lots of Ferrite rods and bars, but very little info on which are suitable for MW frequencies.

Also a question for FSL designers. Has any particular ratio of diameter to ferrite length stood out as being better, and in what way is it better.

For example how might a 12 inch diameter FSL with 4 inch rods compare to a 4 inch diameter FSL with 12 inch rods?

Also, has anyone intertwined the Litz wire over and under ferrite rods the way the 'peg' form for winding air core Diamond and Rook weave coils, but the ferrite stays in place?

-FARMERIK


Gary DeBock
 

<<<   Also a question for FSL designers. Has any particular ratio of diameter to ferrite length stood out as being better, and in what way is it better.
For example how might a 12 inch diameter FSL with 4 inch rods compare to a 4 inch diameter FSL with 12 inch rods?   >>>

Richard,

Extensive FSL antenna testing in 2012 revealed how all the variations in coil diameter, ferrite length and ferrite material (rods or bars) play out in the final determination of actual weak signal DXing gain. Seven different FSL test models were constructed and multiple A/B weak signal reception tests were run in order to definitively answer these questions. The result of the experimentation was the FSL antenna "sensitivity formula," which can accurately predict the actual gain of an FSL antenna prior to construction. Full details are in the article posted at     
   
http://www.mediafire.com/file/6oyoldllrbiwf91/FSL_Antenna_Design_Optimization.doc/file

Gary DeBock (in Puyallup, WA, USA)





-----Original Message-----
From: Rik <farmerik@...>
To: main <main@UltralightDX.groups.io>
Sent: Mon, Feb 4, 2019 8:23 am
Subject: [UltralightDX] Reliable but reasonably priced sources of ferrite for FSLs?-FARMERIK

Searching on Ebay, I see lots of Ferrite rods and bars, but very little info on which are suitable for MW frequencies.

Also a question for FSL designers. Has any particular ratio of diameter to ferrite length stood out as being better, and in what way is it better.

For example how might a 12 inch diameter FSL with 4 inch rods compare to a 4 inch diameter FSL with 12 inch rods?

Also, has anyone intertwined the Litz wire over and under ferrite rods the way the 'peg' form for winding air core Diamond and Rook weave coils, but the ferrite stays in place?

-FARMERIK


Max Italy
 

Hi Gary, i haven't seen your document before, very interesting, same area same performance, this makes everything much easier.
I have read that the length of the rod should not exceed too much the length of the coil in a single rod antenna but this doen't seem to apply here and the tests wipe out any doubt.
You mentioned some Russian rods with permeability 400, i think the others have permeability 125; did you notice any difference caused from different permeability of the ferrite (if you tested ferrites with the same size but different permeability)?

Also i would like to understand how much the type of wire makes the difference. If normal wire is used instead of Litz, can the lower performance be compensated increasing the diameter of the loop?


Gary DeBock
 

Hi Max,

<<<   I haven't seen your document before, very interesting, same area same performance, this makes everything much easier.
I have read that the length of the rod should not exceed too much the length of the coil in a single rod antenna but this doesn't seem to apply here and the tests wipe out any doubt.   >>>

Thanks for your comments on the FSL Design Optimization article, and I'm happy that it was useful for you. I have also uploaded the file to our Ultralight Experimenters group site, and hope that it will be helpful to other FSL antenna enthusiasts in understanding how the factors of coil diameter, ferrite length and ferrite shape work out in the gain determination.

<<<   You mentioned some Russian rods with permeability 400, i think the others have permeability 125; did you notice any difference caused from different permeability of the ferrite (if you tested ferrites with the same size but different permeability)?   >>>

At the time of the experimentation (2012) almost all of the ferrite rods and bars available on eBay (at least for the reasonably priced Russian surplus material) was of 400 permeability, so all of the 7 FSL test models were constructed with that ferrite. Currently there is a wider range of permeability in the ferrite rods up for sale, but ferrite permeability was not one of the variables tested during that 2012 experimentation. In 2012 we did have quite a selection of different Litz wire types available, but at that time the largest size commercially available was the 660/46 Litz wire, so that was the type used in all 7 of the FSL test models. In 2015 the new, higher (MW) sensitivity 1162/46 Litz wire became available, so all of my new FSL designs since then (including the "Frequent Flyer" miniature FSL's) use this higher sensitivity Litz wire.

<<<   Also i would like to understand how much the type of wire makes the difference. If normal wire is used instead of Litz, can the lower performance be compensated increasing the diameter of the loop?   >>>

In all cases the highest count of individual #46 strands in a Litz wire type will always result in the highest MW sensitivity. As such, the 1162/46 Litz wire will be superior to the 660/46 Litz wire, and the 660/46 Litz wire will be superior to the 330/46 Litz wire, etc. The use of solid conductor wire was actually Graham Maynard's original FSL coil material in 2011, but detailed testing among the three original Ultralight group experimenters (Steve R., Kevin S. and yours truly) revealed that it had significantly less sensitivity that 330/46 and 660/46 Litz wire. In 2012 our fanatical group of three were going all-out for maximum gain, and we shared information about how to achieve it (much to the delight of the Ukraine ferrite sellers on eBay, who must now be enjoying early retirement).

Gary

      

      


-----Original Message-----
From: Max Italy <max2013@...>
To: main <main@UltralightDX.groups.io>
Sent: Mon, Feb 4, 2019 7:58 pm
Subject: Re: [UltralightDX] Reliable but reasonably priced sources of ferrite for FSLs?-FARMERIK

Hi Gary, i haven't seen your document before, very interesting, same area same performance, this makes everything much easier.
I have read that the length of the rod should not exceed too much the length of the coil in a single rod antenna but this doen't seem to apply here and the tests wipe out any doubt.
You mentioned some Russian rods with permeability 400, i think the others have permeability 125; did you notice any difference caused from different permeability of the ferrite (if you tested ferrites with the same size but different permeability)?
Also i would like to understand how much the type of wire makes the difference. If normal wire is used instead of Litz, can the lower performance be compensated increasing the diameter of the loop?


Todd
 

I suggest that an unusually physically large FSL if left untuned (i.e. broadband) would produce sufficient signal output for serious MW DX purposes. But this is academic because such a physically large FSL would be impracticable to transport, operate, and set up at most listening sites.

In a resonant tuned circuit, a high Q factor (L/C ratio) is achieved by low resistance in the main tank coil, hence the advantage of using low as practicable resistance Litz wire. But as the voltage output increases, the RF output signal bandwidth decreases. This potentially can become an issue especially towards the low frequency end of the MW band. Even with my 40 inch tuned square PVC loop, peaking the tuning cap to say 558 KHz results in relatively muffled audio. Assuming the wire overall resistance was lowered, the signal output on 558 MHz would be increased, but the audio would be more muffled.

So like everything else in life, we have to deal with the law of diminishing returns. High voltage output comes with a drawback (decreasing signal bandwidth and associated subjective audio fidelity). A compromise needs to be reached.

Regards,

Todd.


Russ Edmunds
 

Todd, have you tried adding more capacitance in better tune the lower part of the band ? The late 1960's era Gordon Nelson 4' air core loop included the ability to switch in additional capacitance for just that purpose.


Russ Edmunds

WB2BJH

Blue Bell, PA

Grid FN20id


From: main@UltralightDX.groups.io <main@UltralightDX.groups.io> on behalf of Todd via Groups.Io <toddemslie@...>
Sent: Tuesday, February 5, 2019 6:35:41 AM
To: main@UltralightDX.groups.io
Subject: Re: [UltralightDX] Reliable but reasonably priced sources of ferrite for FSLs?-FARMERIK
 
I suggest that an unusually physically large FSL if left untuned (i.e. broadband) would produce sufficient signal output for serious MW DX purposes. But this is academic because such a physically large FSL would be impracticable to transport, operate, and set up at most listening sites.

In a resonant tuned circuit, a high Q factor (L/C ratio) is achieved by low resistance in the main tank coil, hence the advantage of using low as practicable resistance Litz wire. But as the voltage output increases, the RF output signal bandwidth decreases. This potentially can become an issue especially towards the low frequency end of the MW band. Even with my 40 inch tuned square PVC loop, peaking the tuning cap to say 558 KHz results in relatively muffled audio. Assuming the wire overall resistance was lowered, the signal output on 558 MHz would be increased, but the audio would be more muffled.

So like everything else in life, we have to deal with the law of diminishing returns. High voltage output comes with a drawback (decreasing signal bandwidth and associated subjective audio fidelity). A compromise needs to be reached.

Regards,

Todd.


lamontcranston17
 

In response to Gary's 2012 length to diameter conclusions,
there is another characteristic, I haven't found any information on.
That would be, how permeability affects the FSL.
I see R40C1 material has a ui of 40 vs 400 for the material
used in Gary's initial testing.
 I would like to see a shootout of identical size FSL's
that use the two different 40 vs 400 ui materials.

Hi Gary,
I'm poking at you!
You have the smaller FSL's to use in a comparison test.
The crystal radio guys love this material because of the
high Q's they get with it.

Maybe mkmak222 would give you a deal on enough ferrites to build a
small FSL to do the test, if R40C1 proved better, it would be great for
his sales.

https://www.ebay.com/itm/NiZn-Ferrite-Rod-R40C1-200x10mm-for-High-Q-Amateur-Crystal-Radio-Coils-AM-SW/151884949745?hash=item235d0c68f1:g:3QMAAOSwNSxU-kHM
                             Mikek


Rik
 

Gary- For some reason I could not get the link you posted open, but I found what appeared to be the same title in the files of this group. Now I see it is also in a new related group. I should join the experimenters group anyway.

I noticed in section 9 mention of Polydorof patents for a twin coil. I did experiment with some of his windings some years ago, and settled on the 3 coil contra I found to be sharply directional, but it does  not have too high a signal strength. The file seems to say that 2 coil Poly. beat a larger 3 coil in parallel, so maybe I should wind one of those.   So it's time for me to pick out a few designs and guess how much Litz to order. I still plan to try a higher count Litz than what was available in 2012 from Ebay.

Lots of info to digest. So far I have not found the section regarding the optimal Width to Length for an FSL, but I am thinking of [temporarily]  rewinding a four foot square air core  with the high count Litz, before experimenting with my stack of toroids, and  before starting on an FSL. It may only be in the file at the new io group as well, so lots of home work attempting to understand the info.

Thanks so much for your patient answers. - FARMERIK


Gary DeBock
 

<<<    Hi Gary,
I'm poking at you!
You have the smaller FSL's to use in a comparison test.
The crystal radio guys love this material because of the
high Q's they get with it.
Maybe mkmak222 would give you a deal on enough ferrites to build a
small FSL to do the test, if R40C1 proved better, it would be great for
his sales.

                             Mikek   >>>

Hi Mikek,

Thanks for the link, and the new R40C1 material does seem very interesting. I have been a regular Litz wire customer of Mkmak222 for about 10 years, and know him to be honest and reliable.

The main problem with this 200mm x 10mm ferrite rod is the price. At $14.00 shipped, the cost would be reasonable for loopstick construction, but pretty impractical for FSL's. The 200mm x 10mm rod size is one of the standard Russian surplus rod sizes, and many FSL's have been constructed here with that rod size. In fact, one of the test models in the 2012 FSL design article was a 3.5" Long Rod model, using 23 of the 200mm x 10mm ferrite rods. At the cost of $14 per rod (shipped) for the new R40C1 ferrite material, the construction cost of such a miniature FSL would be $322 even before the Litz wire, variable cap and PVC frame cost (which would raise it up to around $450). Even if such an expensive miniature FSL is built, almost nobody would be interested in duplicating it.

For loopsticks, though, it would be a completely different matter. $14 is a very reasonable cost for a high quality ferrite rod of that size, and there are already excellent loopstick designs popular in the DXing community for both MW and LW (such as at  http://www.mediafire.com/file/du3sr5cd9thqvau/7.5inch-LS-PL380.doc/file
Since there are already several PL-380 and XHDATA D-808 models here with that 7.5" loopstick design, it would be easy to substitute the R40C1 material for the Amidon Type 61 ferrite rod, and compare the relative performance on MW and LW. I'll probably order a few of the new R40C1 rods for such a test in the next few days, and then let the group know how everything shakes out.

73, Gary

  
  


-----Original Message-----
From: lamontcranston17 <nojunk@...>
To: main <main@UltralightDX.groups.io>
Sent: Tue, Feb 5, 2019 6:47 am
Subject: Re: [UltralightDX] Reliable but reasonably priced sources of ferrite for FSLs?-FARMERIK

In response to Gary's 2012 length to diameter conclusions,
there is another characteristic, I haven't found any information on.
That would be, how permeability affects the FSL.
I see R40C1 material has a ui of 40 vs 400 for the material
used in Gary's initial testing.
 I would like to see a shootout of identical size FSL's
that use the two different 40 vs 400 ui materials.

Hi Gary,
I'm poking at you!
You have the smaller FSL's to use in a comparison test.
The crystal radio guys love this material because of the
high Q's they get with it.

Maybe mkmak222 would give you a deal on enough ferrites to build a
small FSL to do the test, if R40C1 proved better, it would be great for
his sales.


                             Mikek




Max Italy
 

Gary thank you very much for your answer. All these tests made in the past are of great help, not just to replicate your great and well detailed projects but also to address experiments in the right directions.


Guy Atkins
 

Hi Mikek,
 
I'm not Gary, but I did wind an external loopstick with the R40C1 material for a CC Skywave (non-SSB model) a few years ago.
 
It worked very well, but I didn't do any direct comparisons with the Russian 200mm rods as Gary probably would have. Indeed, the $14.00 each price is a killer for FSL purposes! If I recall, mkmak222's price was $9.00 each when I bought one in 2016(?).
 
The peaking of signals with the R40C1 seemed a bit better than what I'd experienced with Russian 200mm ferrite, but this is just speculation. Someone would need to do a real A-B test to find out for sure if the higher price is worth it for this special ferrite.
 
73,
 
Guy Atkins
Puyallup, WA


Phillip Fimiani
 

$10.50 now

 
 
Best Regards
Phil
KD2HTN / WA2069SWL
Long: 34.210293 Lat:-78.057048
FM04xf 30dl
______________________________



From: Guy Atkins <dx@...>
To: main@UltralightDX.groups.io
Sent: Wednesday, February 6, 2019 10:42 AM
Subject: Re: [UltralightDX] Reliable but reasonably priced sources of ferrite for FSLs?-FARMERIK

Hi Mikek,
 
I'm not Gary, but I did wind an external loopstick with the R40C1 material for a CC Skywave (non-SSB model) a few years ago.
 
It worked very well, but I didn't do any direct comparisons with the Russian 200mm rods as Gary probably would have. Indeed, the $14.00 each price is a killer for FSL purposes! If I recall, mkmak222's price was $9.00 each when I bought one in 2016(?).
 
The peaking of signals with the R40C1 seemed a bit better than what I'd experienced with Russian 200mm ferrite, but this is just speculation. Someone would need to do a real A-B test to find out for sure if the higher price is worth it for this special ferrite.
 
73,
 
Guy Atkins
Puyallup, WA



--
73
Phil
KD2HTN / WA2069SWL
Long: 34.210293 Lat:-78.057048
FM04xf 30dl


Todd
 

Not yet, Russ. But adding additional (temporary switchable) capacitance to my 40 inch box loop would offer the following advantages:

1. Lower frequency coverage for long wave AITS stations, etc.

2. Lower circuit Q which corresponds to decreased muffled audio towards the bottom end of the MW band.

I assume higher loop or FSL Q selectivity response is obtained with higher inductance, lower capacitance, and lower coil wire resistance.

Regards,

Todd.


Russ Edmunds
 

The added capacitance will provide better low-end performance on an air core loop, and so it should on an FSL.

One other feature from the original 4' loop design was a Q-spoiling pot to add or remove resistance from the circuit and improve audio clarity. I never got to a point where I felt that I needed that with mine and I eventually removed it entirely from my 2' loop. If the audio isn't improved with the switchable capacitance, the pot may be another option to consider.


Russ Edmunds

WB2BJH

Blue Bell, PA

Grid FN20id


From: main@UltralightDX.groups.io <main@UltralightDX.groups.io> on behalf of Todd via Groups.Io <toddemslie@...>
Sent: Wednesday, February 6, 2019 5:57:20 PM
To: main@UltralightDX.groups.io
Subject: Re: [UltralightDX] Reliable but reasonably priced sources of ferrite for FSLs?-FARMERIK
 
Not yet, Russ. But adding additional (temporary switchable) capacitance to my 40 inch box loop would offer the following advantages:

1. Lower frequency coverage for long wave AITS stations, etc.

2. Lower circuit Q which corresponds to decreased muffled audio towards the bottom end of the MW band.

I assume higher loop or FSL Q selectivity response is obtained with higher inductance, lower capacitance, and lower coil wire resistance.

Regards,

Todd.


Rik
 

It sounds like several responses are from people who understand far more about Q than I do as it relates to MW loops.

I would think I should  aim for the highest Q possible, but it sounds like if too high speech is muffled which would hamper DXing  IDs. However, adding  some variable R could reduce Q. Is that correct? [non-inductive R I assume]

In one of the files I thought it said if either the coil or cap is lower in Q than the other, the tank circuit goes down perhaps to the lower value. So a high Q cap is also important in a resonated circuit?

Higher count Litz increases Q, if I understand correctly. If there is a limit for audio quality, it would be a waste to buy higher count Litz beyond that point, where ever it is.

Also in files here, I think I read increasing both Q or the number of turns of wire increase signal strength, but they are achieved in opposite ways, so you have to balance those factors for best all around performance. Is that correct?

Hoping for expert replies so I can better understand how to build a better portable  ferrite loop. - FARMERIK