Toroid Ferrite Loop Stick


Everett N4CY
 

Guys,
 
I just finished experimenting with a loop stick made up of 12 each 61 mix toroids. (The toroids are 2" in dia, with a 1" dia hole and are 3/4" thick). I slipped them onto a 1" dowel rod, thus ending up with a 9" long rod.
I covered the rod with 1/2" Poly foam, thus ending with a 3" dia. I then wound the loop stick with 26 turns of 660/46 Litz wire, ending up with a inductance of 212uH. Using one of the 8:1, 365 pf variable capacitors I was able to tune both to both ends of the AM BC band.
 
Using a Tecsun PL-660 radio I compared the loop stick to, my very high performance, 1 meter loop using several daytime stations. The loop stick performed as well, if not somewhat better, than the 1 Meter air loop. I was able to couple up very nicely to the loop stick with the radio 4" to 5" away. I was very impressed with the performance of the loop stick 
 
You can find the toroids on ebay and if you make a reasonable offer to the guy for several of them he will give you a better price than his listed price. I would think that 10 of them would make a very nice ferrite loop.
 
 
Everett N8CNP
 


Rik
 

I am impressed with a ferrite loop which compares so well to such a large air core loop. I have followed a number of articles available on line, including yours in the files section of this group about multi coil ferrite antennas. Do you have any conclusions that the stack of hollow ferrites is better than a single huge ferrite, or is it less expensive? - FARMERIK


Everett N4CY
 

Sorry, but since I don't have a solid ferrite rod that size to compare it to, nor would I want to pay the price such a rod, I can't answer you question. I can tell you that it is much better than the stack toroid rod that I wrote about that using the FT140-61 toroids. 
I was quite surprised at how well it the stacked toroid loop worked compared to 1 meter air loop. I probably will not do any more experiments with this as a receiving loop, as my plan is to experiment with using it as a transmitting loop.  I plan on placing the toroids on a copper pipe, rather than a wood dowel rod, so I can do some cooling. I have been operating a lot of JT65, which allows you to DX with very low power. I bough 46 of the toroids so I can build several ferrite transmit loops. 

I don't know how long the supply of the toroids will last. I think that if you offered the eBay supplier $35 to $40 delivered for 10 toroids he will take the offer. They are not a standard size, but are made by Fair-Rite, whom is a high end manufacture of ferrite. You would normally pay $10 a pice, or more for a toroid like that. The inductance for ten turns of wire on a FT240-61, which is the largest core that Fair-Rite makes in that mix, is 20uH and it weights about 106 gm, the toroids that the eBay seller is offering have a inductance of 36uH and weigh 136 gm.  

Everett N4CY (new call)


On Nov 6, 2015, at 9:47 AM, farmerik@... [ultralightdx] <ultralightdx@...> wrote:

 

I am impressed with a ferrite loop which compares so well to such a large air core loop. I have followed a number of articles available on line, including yours in the files section of this group about multi coil ferrite antennas. Do you have any conclusions that the stack of hollow ferrites is better than a single huge ferrite, or is it less expensive? - FARMERIK


Rik
 

I'm in. I just ordered 5 pairs of those toroids. I hope my repair guy will wind them for me.

How did you decide the thickness of the spacer between the winding and the toroids?

With Litz, are you getting high Q sharp tuning?

-FARMERIK


Everett N4CY
 

The spacing was the same that I used in the article that wrote and at the time worked out to be the best option. The tuning was sharp, indicating high Q and the loop rotation was quite sharp also. 

What price did you get them for?

Everett N4CY


On Nov 6, 2015, at 7:13 PM, farmerik@... [ultralightdx] <ultralightdx@...> wrote:

 

I'm in. I just ordered 5 pairs of those toroids. I hope my repair guy will wind them for me.

How did you decide the thickness of the spacer between the winding and the toroids?

With Litz, are you getting high Q sharp tuning?

-FARMERIK


Rik
 

Sounds like it should make a very interesting antenna for me. I should have enough 660/46 Litz left over from the special low uH antenna for the Fisher AM 80 which I am having made on a 12 inch X 1/2 inch ferrite. I sent your article from this site regarding multi coil antennas and Polydorf. I hope to get him to wind at least two coils I can parallel for a reasonable number of turns at around only  46 uH total for the Fisher. If he does that, I could also connect them in series for the Tropical bands + tuned with a cap.

If that works well, I may ask him to separate the toroids and space them apart with separate coils to see if it is more directional, but that is just a wild guess that it might be. Anyone have ideas about that?

I did not bother make a bid for a lower price.

-FARMERIK


Everett N4CY
 

A 2 coil Polydorff might be a good option. It will take a little more than just one coil. 

Everett N4CY


On Nov 6, 2015, at 7:43 PM, farmerik@... [ultralightdx] <ultralightdx@...> wrote:

 

Sounds like it should make a very interesting antenna for me. I should have enough 660/46 Litz left over from the special low uH antenna for the Fisher AM 80 which I am having made on a 12 inch X 1/2 inch ferrite. I sent your article from this site regarding multi coil antennas and Polydorf. I hope to get him to wind at least two coils I can parallel for a reasonable number of turns at around only  46 uH total for the Fisher. If he does that, I could also connect them in series for the Tropical bands + tuned with a cap.

If that works well, I may ask him to separate the toroids and space them apart with separate coils to see if it is more directional, but that is just a wild guess that it might be. Anyone have ideas about that?

I did not bother make a bid for a lower price.

-FARMERIK


Rik
 

Another question about your [Eversharp's] new anteena wound on Toroids, have you experimented with a pick up coil, and if so what worked best to connect directly to a radio.

I guess the usual way is 3-5 turns to match 50 Ohms or so, but what ever number of turns works best.

-FARMERIK


Everett N4CY
 

I did not experiment with a pick up coil on the one using that 2" dia toroids. However, if you will look back at some on my past articles I have info on using a coupling transformer using binocular cores BN202-73 using, I think, a 36:1 ratio. This keeps you from loading the tuned circuit, thus keeping you from screwing up the Q. 

Everett N4CY


On Nov 8, 2015, at 9:01 AM, farmerik@... [ultralightdx] <ultralightdx@...> wrote:

 

Another question about your [Eversharp's] new anteena wound on Toroids, have you experimented with a pick up coil, and if so what worked best to connect directly to a radio.

I guess the usual way is 3-5 turns to match 50 Ohms or so, but what ever number of turns works best.

-FARMERIK


Rik
 

I couldn't help myself and ordered 8 more toroids. My plan is to have 3 coils wound which will have a total uH in series for AM. I think those windings will cover 2 toroids, but 3 would be fine too. Those sets of 2 or 3 toroids I'll glue or tape together, and then use most of the rest as spacers which can be arranged in different patterns. For example, in one of Everetts tests he found a 5-6 inch spacing between coils worked best on a FSL. So I could slide one coil set on the core, then 3 spacer toroids, then the second coil the other side 'up' so the turns go in the opposite direction, then 3 more spacers and then the 3rd coil and finally one toroid with a pick up coil at the end. If all 18 toroids work very well together, that is fine. If the extra length is not that big an advantage, I could make a smaller version with a single coil out of the extras. It will be quite a while before I can get this all done. I like the fact it will be a test bed which can be modified easily by just rearranging the coils and spacers on a 1 inch rod.  - FARMERIK


Everett N4CY
 

You do not need to glue, or space the toroids, I have tried it both ways. Just get a 1" dia dowel rod and cut it just slightly shorter than the total length of the 18 stacked toroids. Then use wood, or plastic disk the ends of the dowel rod to hold and compress the toroids (The disk can be screwed on). 

Based on my experiments it appeared that, by doing the above, that the combined toroids looked as though they were one solid rod. I base this assumption on looking at the induction readings of a coil being moved from one end of the rod to the other. The induction is less on each end and higher in the middle of the rod, which is the same thing that I saw on a solid bar. 

When you wind the 3 coils, you will need to use less turns on the middle coil in order to try to keep the inductance the same for each coil. 

Everett N4CY


On Nov 9, 2015, at 2:58 AM, farmerik@... [ultralightdx] <ultralightdx@...> wrote:

 

I couldn't help myself and ordered 8 more toroids. My plan is to have 3 coils wound which will have a total uH in series for AM. I think those windings will cover 2 toroids, but 3 would be fine too. Those sets of 2 or 3 toroids I'll glue or tape together, and then use most of the rest as spacers which can be arranged in different patterns. For example, in one of Everetts tests he found a 5-6 inch spacing between coils worked best on a FSL. So I could slide one coil set on the core, then 3 spacer toroids, then the second coil the other side 'up' so the turns go in the opposite direction, then 3 more spacers and then the 3rd coil and finally one toroid with a pick up coil at the end. If all 18 toroids work very well together, that is fine. If the extra length is not that big an advantage, I could make a smaller version with a single coil out of the extras. It will be quite a while before I can get this all done. I like the fact it will be a test bed whi ch can be modified easily by just rearranging the coils and spacers on a 1 inch rod.  - FARMERIK


Rik
 

Would you think multiple coils in series are significantly better than one winding, or just a little better? -FARMERIK


Everett N4CY
 

If you are using the Polydoroff configuration, then YES. Now that you are increasing the length of the rod, you should be able to use a 4 coil Polydoroff configuration. If you are wanting to make it a dual band, then you would want 3 coils, however, you might get by with two coils for a dual band, in series for the lower frequencies and in parallel for the higher frequencies.
 
Everett N4CY
 
In a message dated 11/9/2015 7:42:19 A.M. Central Standard Time, ultralightdx@... writes:

 

Would you think multiple coils in series are significantly better than one winding, or just a little better? -FARMERIK


Rik
 

So it sounds like the 4 coil Polydorf would have all four coils about the target uH, giving lots of Litz to pick up signals, but I would have to choose one uH if I stayed with a series/parallel 4 coil connection.

I do want to use this antenna  both tuned by a cap and tuned by the PL-360 radio which wants a higher uH of 350. So I am thinking of dividing the 350 uH into 2 or 3 coils in series, and then connecting all 3, or only 2 or just one for the Tropical bands.

[ I don't happen to be interested in LW, as my BOG does that very well for EU broadcasters, and I am not interested in NDB where the directional ability of a loop would be welcome, but others here are.]

Connecting 2 coils in  series or in  parallel gives a 4:1 change in uH. I don't know, but I would think it more likely to end up with a gap in coverage. Choosing the number of coils in series gives much closer steps with more overlap.

If I had all the various coils I might like wound on a sleeve I could slide  it over the 'stack' of toroids, I could use the same set of ferrite for  many configurations.

My earlier plan was to attach the coils to just the toroids under them, and then I could completely remove unused coils, and try different spacings between coils with different numbers of toroids without coils wound on them. Also, by flipping over a coil I could reverse the winding pattern or not, and have all coils wind in the same direction, or every other one  change as Polydorf Patented.

If both schemes would work, I still would have to choose one way or the other.  So that is my question now. - FARMERIK


Rik
 

As I try to read articles here, it looks like combining coils is not like combining speakers. It looks like the uH does not change the same way, and I see no obvious way to predict results at all. Is it entirely determined by experimenting and measuring uH with a meter? - FARMERIK


John Bruckner
 

Rik;

 

For approx. $100, you can buy the same meter I use, AADE IIB for measuring inductance.

 

John

W0HII

 

 

From: ultralightdx@... [mailto:ultralightdx@...]
Sent: Monday, November 09, 2015 4:52 PM
To: ultralightdx@...
Subject: Re: [ultralightdx] Re:Toroid Ferrite Loop Stick

 

 

As I try to read articles here, it looks like combining coils is not like combining speakers. It looks like the uH does not change the same way, and I see no obvious way to predict results at all. Is it entirely determined by experimenting and measuring uH with a meter? - FARMERIK


Guy Atkins
 

One of the inductance meters I use is this this low cost, multi-function tester for only $21.97 with Amazon Prime shipping. At this price, anyone experimenting with antennas for their Ultralight radios can afford one:

Amazon.com: Yosoo GM328 LCD Display Transistor Tester ESR Meter Cymometer Square Wave Generator: Home Improvement

 

In the inductance range the unit measures from 0.01 mH to 20 H, and I have found it to essentially match my other inductance tester.

I've also used this for transistor identification and capacitor measuring, and it's great for that too.

73,

Guy Atkins
Puyallup, WA



---In ultralightdx@..., <jbruckner@...> wrote :

Rik;

 

For approx. $100, you can buy the same meter I use, AADE IIB for measuring inductance.

 

John

W0HII

 

 


Everett N4CY
 

It is s trial error process when using multi coils and with coils in parallel you will see a lower inductance than a single coil for the same frequency coverage. For coils in series the inductance will be about the same as a single coil. 

If you want different slide on coils you can take 1/2" thick poly foam and glue it together into cylinders using hot melt glue. The glue melts the poly enough that it will bond the two ends together. 

Everett N4CY


On Nov 9, 2015, at 4:52 PM, farmerik@... [ultralightdx] <ultralightdx@...> wrote:

 

As I try to read articles here, it looks like combining coils is not like combining speakers. It looks like the uH does not change the same way, and I see no obvious way to predict results at all. Is it entirely determined by experimenting and measuring uH with a meter? - FARMERIK


Rik
 

Thanks- I do have an LC meter to test with. I guess my problem is I don't have accurate use of my hands or sharp vision, and my Radio repair guy, who is an expert on antique  tube equipment has never had interest in these types of antennas, so I'd have to pay him to experiment and come up with something which works. Maybe I'll ask him to wind a relatively small coil, measure it, and then decide how many to make which might add up in series near the 350 uH, but I have no idea what the number of turns I should specify for him to wind. Anyone here have a guess? If the ratio of turns to uH was linear, I would start with about half of what Everett used and go for 3 coils, to total around 350 uH, but if it is not a linear relationship, I am lost.  - FARMERIK


John Bruckner
 

Rik;

 

Try this site: keisan.casio.com/exec/system/1258035720  for inductance in series and parallel.

 

John

 

From: ultralightdx@... [mailto:ultralightdx@...]
Sent: Tuesday, November 10, 2015 8:58 AM
To: ultralightdx@...
Subject: Re: [ultralightdx] Re:Toroid Ferrite Loop Stick

 

 

Thanks- I do have an LC meter to test with. I guess my problem is I don't have accurate use of my hands or sharp vision, and my Radio repair guy, who is an expert on antique  tube equipment has never had interest in these types of antennas, so I'd have to pay him to experiment and come up with something which works. Maybe I'll ask him to wind a relatively small coil, measure it, and then decide how many to make which might add up in series near the 350 uH, but I have no idea what the number of turns I should specify for him to wind. Anyone here have a guess? If the ratio of turns to uH was linear, I would start with about half of what Everett used and go for 3 coils, to total around 350 uH, but if it is not a linear relationship, I am lost.  - FARMERIK