Wave wound and plain coils, are they equal? - UK Vintage Radio Repair and Restoration Discussion Forum

Boater Sam · 27th Apr 2017, 5:14 pm

Had a IF transformer where both AM coils were scc on enameled wire and O/C.
As I can't wave wind I have rewound with 44 swg enameled, pile wound in the same place on the former and the same number of turns.
Will I get it to peak correctly?

Nuvistor · 27th Apr 2017, 5:29 pm

I don't know but this is some info from Surrey university. My guess is they would be different with the self capacity being lower in a wave wound coil.

http://info.ee.surrey.ac.uk/Workshop...ave/index.html
Frank

Boater Sam · 27th Apr 2017, 5:38 pm

So if the self capacity is greater, it will be a lower natural peak frequency?
There are padding caps across both windings, hopefully I will be able to reduce these to compensate?

The windings are only 222 turns, pile wound they take up less space than the scc wave winding.

Nuvistor · 27th Apr 2017, 5:43 pm

That is what I would expect, though you may be able to reduce the number of turns.

Frank

G6Tanuki · 27th Apr 2017, 6:40 pm

Wave-wound should have lower self-capacity, yes.

Though wave-winding uses a greater length of wire - so (unless your winding is made out of a superconductor) for a given inductance the resistance will be higher than a pile-wound coil and so the resultant "Q" will be lower.

I guess "Litz" is a reasonable way to try and get lower effective RF-resistance in a wave-wound coil.

Perhaps this is why - after WWII - things moved away from Litz-wave-wound IF transformers with a simple ferrite tuning-slug up the middle, to IFTs using pile-windings of ordinary enamelled wire but fitted into a 'pot core' to get the inductance up?

kalee20 · 27th Apr 2017, 7:08 pm

Wave winding should have a lower self-capacitance, as already said, but if there is a parallel trimmer then to a first approximation, all you need to do is reduce this.

It does use more wire! Though not much more. So Q is lower, because of this... Though as self capacitance is lower, this will act to raise Q (the self-capacitance in a close-wound coil is a bit lossy).

It does have the advantage that the coil is self-supporting, especially when wound with fabric-covered wire which doesn't slide over itself. Whereas a close-wound coil often needs some impregnation (wax, varnish, etc) to make it rigid, and this increases self-capacitance too.

Basically, I don't think you have much to worry about!

Boater Sam · 2nd May 2017, 9:01 pm

I removed and dismantled the IF transformer and discovered why it was O/C.

It had been well twiddled and the horrible thing had twisted the formers in the top and bottom mounting paxolin. I assume that these are Pye items, I'm not impressed. Coils snapped off all round.
Carefully worked out what and where, cut the through wire supports on one side to release the formers. Unwound the coils, and rewound with 48 swg enamelled wire. A pig of a job with my fat ol fingers. Glued the formers back in.
Put it all back together, now have anode volts but its still totally deaf. Fed up, leave it for another day.

Ed_Dinning · 3rd May 2017, 9:17 pm

Hi Sam, see if you can find a Q meter, the advance T2 can often be found for very little money, it is easy to use and will tell you all you need to know about coils like this.

Ed

David G4EBT · 4th May 2017, 10:08 pm

I'd have thought that the first requirement would be for the coil to have the correct inductance to resonate at the required frequency. Maybe with the same number of turns, a 'scramble wound' coil will have similar inductance, but lower 'Q' - maybe not. I made a little 'Gingery' hand wave winder from scrap which works very well, but depending on the setting of the angle at which the waves are wound, a coil wound with the same number of turns and the same cam, (which determines the width of the coil), but a different wave angle will have a markedly different inductance from another coil. The wave angle affects how close the turns lay next to each other and the number of turns per layer.

Ideally, if you had another (good) IFT on which you could measure the inductance, you could then simply wind coils of the same inductance by experimentation, however many turns that called for. I doubt very much that hand winding a coil with the same number of turns as the original will give a similar inductance. Obviously high 'Q' is to be desired, but there's not much point in having a coil which fortuitously turns out to be high Q but peaks at the wrong frequency.

Just thinking out loud really.

Good luck with it Sam anyway.

TrevorG3VLF · 5th May 2017, 10:19 am

If you know the resonating capacitors, then you can estimate the inductance. Coil capacitance will affect the result.
If it is an IF transformer, then the amount of coupling between coils will be difficult to get right.

Boater Sam · 5th May 2017, 10:31 am

Considering the bad construction of the formers and the lack of test equipment or expertise, I think I'll try finding another second IF transformer complete.
There is probably more than one fault with this PAM 713, its been well twiddled. The AF is OK but all the RF bits seem dumb. It was cheap anyway.

27th Apr 2017, 5:14 pm	#1
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Wave wound and plain coils, are they equal? Had a IF transformer where both AM coils were scc on enameled wire and O/C. As I can't wave wind I have rewound with 44 swg enameled, pile wound in the same place on the former and the same number of turns. Will I get it to peak correctly?

27th Apr 2017, 5:29 pm	#2
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: Wave wound and plain coils, are they equal? I don't know but this is some info from Surrey university. My guess is they would be different with the self capacity being lower in a wave wound coil. http://info.ee.surrey.ac.uk/Workshop...ave/index.html Frank

27th Apr 2017, 5:38 pm	#3
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Wave wound and plain coils, are they equal? So if the self capacity is greater, it will be a lower natural peak frequency? There are padding caps across both windings, hopefully I will be able to reduce these to compensate? The windings are only 222 turns, pile wound they take up less space than the scc wave winding.

27th Apr 2017, 5:43 pm	#4
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: Wave wound and plain coils, are they equal? That is what I would expect, though you may be able to reduce the number of turns. Frank

27th Apr 2017, 6:40 pm	#5
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,007	Re: Wave wound and plain coils, are they equal? Wave-wound should have lower self-capacity, yes. Though wave-winding uses a greater length of wire - so (unless your winding is made out of a superconductor) for a given inductance the resistance will be higher than a pile-wound coil and so the resultant "Q" will be lower. I guess "Litz" is a reasonable way to try and get lower effective RF-resistance in a wave-wound coil. Perhaps this is why - after WWII - things moved away from Litz-wave-wound IF transformers with a simple ferrite tuning-slug up the middle, to IFTs using pile-windings of ordinary enamelled wire but fitted into a 'pot core' to get the inductance up?

27th Apr 2017, 7:08 pm	#6
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,088	Re: Wave wound and plain coils, are they equal? Wave winding should have a lower self-capacitance, as already said, but if there is a parallel trimmer then to a first approximation, all you need to do is reduce this. It does use more wire! Though not much more. So Q is lower, because of this... Though as self capacitance is lower, this will act to raise Q (the self-capacitance in a close-wound coil is a bit lossy). It does have the advantage that the coil is self-supporting, especially when wound with fabric-covered wire which doesn't slide over itself. Whereas a close-wound coil often needs some impregnation (wax, varnish, etc) to make it rigid, and this increases self-capacitance too. Basically, I don't think you have much to worry about!

2nd May 2017, 9:01 pm	#7
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Wave wound and plain coils, are they equal? I removed and dismantled the IF transformer and discovered why it was O/C. It had been well twiddled and the horrible thing had twisted the formers in the top and bottom mounting paxolin. I assume that these are Pye items, I'm not impressed. Coils snapped off all round. Carefully worked out what and where, cut the through wire supports on one side to release the formers. Unwound the coils, and rewound with 48 swg enamelled wire. A pig of a job with my fat ol fingers. Glued the formers back in. Put it all back together, now have anode volts but its still totally deaf. Fed up, leave it for another day.

3rd May 2017, 9:17 pm	#8
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Wave wound and plain coils, are they equal? Hi Sam, see if you can find a Q meter, the advance T2 can often be found for very little money, it is easy to use and will tell you all you need to know about coils like this. Ed

4th May 2017, 10:08 pm	#9
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,766	Re: Wave wound and plain coils, are they equal? I'd have thought that the first requirement would be for the coil to have the correct inductance to resonate at the required frequency. Maybe with the same number of turns, a 'scramble wound' coil will have similar inductance, but lower 'Q' - maybe not. I made a little 'Gingery' hand wave winder from scrap which works very well, but depending on the setting of the angle at which the waves are wound, a coil wound with the same number of turns and the same cam, (which determines the width of the coil), but a different wave angle will have a markedly different inductance from another coil. The wave angle affects how close the turns lay next to each other and the number of turns per layer. Ideally, if you had another (good) IFT on which you could measure the inductance, you could then simply wind coils of the same inductance by experimentation, however many turns that called for. I doubt very much that hand winding a coil with the same number of turns as the original will give a similar inductance. Obviously high 'Q' is to be desired, but there's not much point in having a coil which fortuitously turns out to be high Q but peaks at the wrong frequency. Just thinking out loud really. Good luck with it Sam anyway. __________________ David. BVWS Member. G-QRP Club member 1339.

5th May 2017, 10:19 am	#10
TrevorG3VLF Rest in Peace Join Date: Apr 2011 Location: Matlock, Derbyshire, UK. Posts: 1,378	Re: Wave wound and plain coils, are they equal? If you know the resonating capacitors, then you can estimate the inductance. Coil capacitance will affect the result. If it is an IF transformer, then the amount of coupling between coils will be difficult to get right.

5th May 2017, 10:31 am	#11
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Wave wound and plain coils, are they equal? Considering the bad construction of the formers and the lack of test equipment or expertise, I think I'll try finding another second IF transformer complete. There is probably more than one fault with this PAM 713, its been well twiddled. The AF is OK but all the RF bits seem dumb. It was cheap anyway.