Re: Topband: [time-nuts] Minicircuits 10% discount in December
The 2873000202 73 material binocular core, I buy those by the hundreds from Newark and hand them out like a human Pez dispenser at local radio club meetings. They are amazing things. Not only do I use them for 160M and other RF applications, but I have using them in small step-up applications too up to the 10W level!!! Newark also sells them in single quantity. Again, the magic trick is to use the Fair-Rite part number in the search. http://www.newark.com/fair-rite/2873000202/ferrite-core-cylindrical/dp/02E8908?mckv=sLlWjcZh9|pcrid|54824053955|plid||[keyword_text]|match|pCMP=KNC-GUSA-GEN-SKU-MDC-FAIR_RITE One trick for the sharp-edged cores when used for HV step-up transformers, is to wind them with kynar wire-wrap wire. Tim N3QE On Thu, Nov 27, 2014 at 2:07 PM, Richard (Rick) Karlquist rich...@karlquist.com wrote: On 11/27/2014 10:57 AM, Tim Shoppa wrote: I would encourage that if you use part numbers on Clifton Labs website that cores/binocular cores of many mixes are stocked and sold in small quantities. If you start from a part number from a catalog, you may very well end up with one that is quantity-500 minimum. I would particularly encourage the 73-material binocular cores if you are doing anything in LF-MF-HF. The core in question was a 73 binocular core. I believe it was the one recommended on W8JI's website. Rick Karlquist N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: [time-nuts] Minicircuits 10% discount in December
On Thu,11/27/2014 11:14 AM, Tim Shoppa wrote: The 2873000202 73 material binocular core, I buy those by the hundreds from Newark and hand them out like a human Pez dispenser at local radio club meetings. They are amazing things. Not only do I use them for 160M and other RF applications, but I have using them in small step-up applications too up to the 10W level!!! The single turn resonance of this core is around 10 MHz, with a Z at resonance of about 120 ohms. Like any other ferrite core, winding turns will increase L as N squared, increase C as N, thus moving the resonance down in frequency. I'd guess that 8 turns would move the resonance fairly close to 160M with Z in the range of 4-5K ohms. The catch is that the i.d. is pretty small, so the choke would need to be wound with something like one pair out of CAT5 cable. Fair-Rite considers this a suppression part, not an inductive part, although it is widely used for winding transformers for MF RX antennas. The laws of physics don't change with what we call something, so this will be a fairly lossy transformer. For RX transformers, it may not matter (and the low Q may even help), but don't be surprised when you see the added resistance beyond what the turns ratio predicts. :) 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: [time-nuts] Minicircuits 10% discount in December
Anyone with proper test equipment can measure and verify what I say below is absolutely true. I'd hate to see anyone accept this information as factual or accurate: The single turn resonance of this core is around 10 MHz, with a Z at resonance of about 120 ohms. Like any other ferrite core, winding turns will increase L as N squared, increase C as N, thus moving the resonance down in frequency. I'd guess that 8 turns would move the resonance fairly close to 160M with Z in the range of 4-5K ohms. The catch is that the i.d. is pretty small, so the choke would need to be wound with something like one pair out of CAT5 cable. 10 MHz is the core resonance, not the combination of winding inductance and winding capacitance. Somewhere around 10 MHz the core, no matter how many turns are wound, crosses from having any inductive effects to capacitive. This is because the core becomes diamagnetic, not because of the winding. The dominant impedance anywhere above 2-3 MHz is resistive. If you wind one pass around the center (out and back to start through both holes) you'll find the reactive sign of core impedance crosses over to capacitance at around 10 MHz. If you wind five turns, it remains about the same. The capacitance effect does not matter much because core resistance dominates. As turns are added, the resistance shunting the winding increases with only a slight shifting of apparent resonance. It is the resistance that dominates and parallels the windings. The loading effect can be minimized by proper winding techniques. This core (or any 73 material) reaches X = R, or Q = 1, at around 2.5 MHz. In other words, at around 2.5 MHz, one pass (through the hole and back to start) is about 75 +j75 ohms, where inductance and resistance are equal. You want at least a two-pass (out and around and back two times) 50-75 ohm winding for 160 meters, and it will be good well beyond 30 MHz. Fair-Rite considers this a suppression part, not an inductive part, although it is widely used for winding transformers for MF RX antennas. The laws of physics don't change with what we call something, so this will be a fairly lossy transformer. The last sentence is incorrect. A typical primary-secondary modest impedance broadband transformer using that core, with minimal attention to winding style, has about 1 dB loss at 50 MHz. Loss decreases with a reduction in frequency, and is a fraction of a dB on 2 MHz. Without special care, this transformer material is easily much less than .5 dB loss across HF. With higher power you might have to move to a lower loss core, or with very high impedances you may want to choose a core that allows the winding to become resonant, but characterizing this core as fairly lossy (whatever that really means) is not correct unless we consider 1/2 dB fairly lossy. Generally, 1/2 dB (10% power loss) core loss becomes worrisome with a core this size at about 10-20 watts. At 20 watts the core will be dissipating about 2 watts on HF, less at the low end of HF or on 160 meters. At higher power, the core loss over the operating frequency range has to decrease or the size increase. The ALS1306, for example, uses a stack of 43 mix cores just like this style for the input transformer. That transformer has less than .2 dB loss from 1.8 to 100 MHz, and safely handles well over 100 watts. For receive, and if extreme impedances are not required, the 73 mix core is good to 60 MHz or so. For RX transformers, it may not matter (and the low Q may even help), but don't be surprised when you see the added resistance beyond what the turns ratio predicts. :) You will see a loading effect in high impedance applications, because even several thousand ohms core resistance shunting a winding will load a 400 ohm or higher resistance load. Broadband transformers almost always use a core material that is well beyond magnetic effects at the top end of the frequency range. That is what makes them broadband. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: [time-nuts] Minicircuits 10% discount in December
I had good results with a matching transformer for 50-800 ohms for a terminated KAZ receiving loop, that was wound on a binocular core of 73 material. Very modest turn count. I wound it as a conventional transformer with wire-wrap wire to accommodate the small core. The loop worked VERY well on 160, 80, 40 and 30m. I could hear lots on 160 that I hadn't even known was there before putting up the loop! It was a huge help on 160 on my small lot. The loop was terminated with an 820 ohm carbon composition resistor. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Thursday, November 27, 2014 7:20 PM To: topband@contesting.com Subject: Re: Topband: [time-nuts] Minicircuits 10% discount in December Anyone with proper test equipment can measure and verify what I say below is absolutely true. I'd hate to see anyone accept this information as factual or accurate: The single turn resonance of this core is around 10 MHz, with a Z at resonance of about 120 ohms. Like any other ferrite core, winding turns will increase L as N squared, increase C as N, thus moving the resonance down in frequency. I'd guess that 8 turns would move the resonance fairly close to 160M with Z in the range of 4-5K ohms. The catch is that the i.d. is pretty small, so the choke would need to be wound with something like one pair out of CAT5 cable. 10 MHz is the core resonance, not the combination of winding inductance and winding capacitance. Somewhere around 10 MHz the core, no matter how many turns are wound, crosses from having any inductive effects to capacitive. This is because the core becomes diamagnetic, not because of the winding. The dominant impedance anywhere above 2-3 MHz is resistive. If you wind one pass around the center (out and back to start through both holes) you'll find the reactive sign of core impedance crosses over to capacitance at around 10 MHz. If you wind five turns, it remains about the same. The capacitance effect does not matter much because core resistance dominates. As turns are added, the resistance shunting the winding increases with only a slight shifting of apparent resonance. It is the resistance that dominates and parallels the windings. The loading effect can be minimized by proper winding techniques. This core (or any 73 material) reaches X = R, or Q = 1, at around 2.5 MHz. In other words, at around 2.5 MHz, one pass (through the hole and back to start) is about 75 +j75 ohms, where inductance and resistance are equal. You want at least a two-pass (out and around and back two times) 50-75 ohm winding for 160 meters, and it will be good well beyond 30 MHz. Fair-Rite considers this a suppression part, not an inductive part, although it is widely used for winding transformers for MF RX antennas. The laws of physics don't change with what we call something, so this will be a fairly lossy transformer. The last sentence is incorrect. A typical primary-secondary modest impedance broadband transformer using that core, with minimal attention to winding style, has about 1 dB loss at 50 MHz. Loss decreases with a reduction in frequency, and is a fraction of a dB on 2 MHz. Without special care, this transformer material is easily much less than .5 dB loss across HF. With higher power you might have to move to a lower loss core, or with very high impedances you may want to choose a core that allows the winding to become resonant, but characterizing this core as fairly lossy (whatever that really means) is not correct unless we consider 1/2 dB fairly lossy. Generally, 1/2 dB (10% power loss) core loss becomes worrisome with a core this size at about 10-20 watts. At 20 watts the core will be dissipating about 2 watts on HF, less at the low end of HF or on 160 meters. At higher power, the core loss over the operating frequency range has to decrease or the size increase. The ALS1306, for example, uses a stack of 43 mix cores just like this style for the input transformer. That transformer has less than .2 dB loss from 1.8 to 100 MHz, and safely handles well over 100 watts. For receive, and if extreme impedances are not required, the 73 mix core is good to 60 MHz or so. For RX transformers, it may not matter (and the low Q may even help), but don't be surprised when you see the added resistance beyond what the turns ratio predicts. :) You will see a loading effect in high impedance applications, because even several thousand ohms core resistance shunting a winding will load a 400 ohm or higher resistance load. Broadband transformers almost always use a core material that is well beyond magnetic effects at the top end of the frequency range. That is what makes them broadband. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: [time-nuts] Minicircuits 10% discount in December
On Thu,11/27/2014 4:19 PM, Tom W8JI wrote: I'd hate to see anyone accept this information as factual or accurate: Are you suggesting that Fair-Rite's published data for this part is wrong? In extensive measurements of certain of their parts, I've not yet seen that. I stand by my comments. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: [time-nuts] Minicircuits 10% discount in December
To focus any discussion, could you be specific? It's rather hard to react to such a broad statement. Chuck Date: Thu, 27 Nov 2014 22:49:48 -0800 From: j...@audiosystemsgroup.com To: topband@contesting.com Subject: Re: Topband: [time-nuts] Minicircuits 10% discount in December On Thu,11/27/2014 4:19 PM, Tom W8JI wrote: I'd hate to see anyone accept this information as factual or accurate: Are you suggesting that Fair-Rite's published data for this part is wrong? In extensive measurements of certain of their parts, I've not yet seen that. I stand by my comments. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: [time-nuts] Minicircuits 10% discount in December
On Thu,11/27/2014 11:25 PM, Chuck Hutton wrote: To focus any discussion, could you be specific? I have been quite specific in the document referenced by the link, and in several others on my website. Perhaps you might study them. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
