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Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
Im building Steves mini and I want to switch from atenna to CT feed back.
I have been reading up on it but I just want to clarify.
CT gets the ground of the seconday ran through the center ?
CT amount of turns, I have seen a lot of 1:1000. Can I rewind a bobin on an E core and have the seconday gnd go through one of the spaces in the core? I dont see winding 1000 turns on a toroid.
I read that If there is high enough coupling between the pri and sec. it may be possible to use the primary grn lead for the CT . In this case the secondarys magnetic feild is absorbed by the primary and the CT will pick this up? Thats what I read but it doesnt sound right.
Since the SSTC primary ends up matching the sec. freq. via antenna feed back I dont think using the primary for the CT with this method will work.
Worse comes to worse I will just use the antenna method that the circuit calls for.
Registered Member #4074
Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
The 1:1000 CT's are most likely for DRSSTC circuits. They are placed over the primary coil where the peak current can easily exceed 1,000A. The primary circuit is tuned to match the secondary.
For a regular SSTC it will need to be placed over the secondary ground lead. You won't need anything close to 1,000 turns, 30 - 100 seems to be the common range. I'm about to wind a CT for my coil, I'm just using a wire from a cat5 cable and a relatively large ferrite toroid.
An E core and bobbin isn't recommended, but it might work. You would need to thread the ground lead through both holes, otherwise you will only have 0.5 turns.
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
GrantX wrote ...
The 1:1000 CT's are most likely for DRSSTC circuits. They are placed over the primary coil where the peak current can easily exceed 1,000A. The primary circuit is tuned to match the secondary.
For a regular SSTC it will need to be placed over the secondary ground lead. You won't need anything close to 1,000 turns, 30 - 100 seems to be the common range. I'm about to wind a CT for my coil, I'm just using a wire from a cat5 cable and a relatively large ferrite toroid.
An E core and bobbin isn't recommended, but it might work. You would need to thread the ground lead through both holes, otherwise you will only have 0.5 turns.
Awesome thanks!! As far as grounding what do i need to ground the coil too? Does what I ground it to effect the CT core ?
Registered Member #6038
Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248
I built this same SSTC and also switched from antenna to CT. Wound about 30 turns of cat-5 single strand wire on the torroid with the base of the secondary running through it to the ground. For the ground I connected everything to the mains ground. Here is my setup
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
Graham Armitage wrote ...
I built this same SSTC and also switched from antenna to CT. Wound about 30 turns of cat-5 single strand wire on the torroid with the base of the secondary running through it to the ground. For the ground I connected everything to the mains ground. Here is my setup
Thats good. I have a CT with 42 turns of small solid wire.
Mains ground really ? I was thinking more of either an earth ground or a pseudo ground ( large metal surface). Just in Case I want to move it about and taking it places that might not have a true ground. I do not want and RF going back into the mains and disrupting or harming sensitive equipment.
Can I use a filter on the mains input ? then I can use it for a ground.
What kind of filter would I need for a coil like this, they are frequency specific right ?
Probably gonna start a project thread to show the building process of it later. Thanks !!
Registered Member #6038
Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248
Yup - a line filter (matching the power input) is what is I use. Keeps the RF out of the house mains. I also want to be able to make it mobile and digging a hole in a school classroom for dedicated ground is not realistic. Never had any problem with RF filter and mains grounding. EM interference from the coil discharge is a much bigger problem.
I will add the connecting to mains ground and a dedicated RF ground could be problematic with ground loop issues. I try and avoid that.
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
Graham Armitage wrote ...
Yup - a line filter (matching the power input) is what is I use. Keeps the RF out of the house mains. I also want to be able to make it mobile and digging a hole in a school classroom for dedicated ground is not realistic. Never had any problem with RF filter and mains grounding. EM interference from the coil discharge is a much bigger problem.
I will add the connecting to mains ground and a dedicated RF ground could be problematic with ground loop issues. I try and avoid that.
Gotcha, you said matching the power input. Like in wattage ? I thought the the filter only blocked a narrow band of frequencies and need to be somewhat specific to the target RF.
Registered Member #54655
Joined: Thu Mar 19 2015, 05:56PM
Location: BC, Canada
Posts: 82
I built a small coil using Steve's sstc5 schematic but with a 1:80 secondary base current transformer and no line filter, just using the mains ground. It worked great and I never blew anything up.
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
Benjamin wrote ...
I built a small coil using Steve's sstc5 schematic but with a 1:80 secondary base current transformer and no line filter, just using the mains ground. It worked great and I never blew anything up.
Interesting I have heard lots of mixed things about SSTC. I have had working versions of this coil before and it seems to be a very forgiving and predicable coil. I think ill just run it with the mains ground and earth ground when I can.
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Question about CT for SSTC
