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eHam.net Forum : QRP : stabilizing a toroid

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stabilizing a toroid	Reply
by VE3VVF on October 20, 2009	Mail this to a friend!
I am building the Ten-Tec 1340 kit and the VFO toroid is quite sensitive to movements and I want to make it permanent on the frequencies of my choice. Is there a good way to keep the windings from moving? Nail polish , glue gun? Thanks for any suggestions Scott

RE: stabilizing a toroid	Reply
by W5FYI on October 20, 2009	Mail this to a friend!
The two old-fashioned ways were 1) Q-dope and 2) beeswax. Q-dope (polystyrene+solvent) was used to hold windings in place more-or-less permanently--the solvent evaporates and leaves the hard polystyrene plastic to hold everything together. Beeswax can also be used--it holds up well to moderately-high temperatures, but can be melted if necessary. A lot of sewing goods stores sell it. I've also used fingernail polish and hot glue with good results. Of the two, I'd favor the hot glue, since it can be remelted to add or remove turns, or change the toroid's orientation. My guess is it would also dampen microphonics somewhat better than fingernail polish alone.

RE: stabilizing a toroid	Reply
by VE3VVF on October 20, 2009	Mail this to a friend!
Wonderful. Thatns for the info.

RE: stabilizing a toroid	Reply
by AA4PB on October 22, 2009	Mail this to a friend!
Q-dope is still available. Supposedly it has minimal affect on the inductance. Google will get you lots of sources.

RE: stabilizing a toroid	Reply
by WX7G on October 23, 2009	Mail this to a friend!
An old issue of the ARRL Handbook said Q-dope can be made by desolving styrofoam in acetone. Might this harm the wire insulation? RTV works to secure toroids. A non-corrosive type is used in the electronics industry. The hot melt glue suggestion sounds like the best way to go.

RE: stabilizing a toroid	Reply
by W5FYI on October 24, 2009	Mail this to a friend!
"... Might this harm the wire insulation?" It might "melt" some plastic insulation, but it has virtually no effect on the insulation used on magnet wire. Acetone evaporates rapidly, and there might be health issues if too much is inhaled. I've used both acetone and MEK to dissolve styrofoam, and both work well and don't seem to harm PC board components. (MEK is the strong solvent methyl ethyl ketone).

RE: stabilizing a toroid	Reply
by K2QPN on October 26, 2009	Mail this to a friend!
I have been using a dab of hot melt glue. I have done this on several QRP rigs. Works so well that I 'borrowed' one of my wife's glue guns. 73, Bob K2QPN

RE: stabilizing a toroid	Reply
by VE3WMB on October 27, 2009	Mail this to a friend!
I raised a similar question about a year ago on the yahoo group for the KD1JV ATS-3A rig. It has separate band modules with 3 or 4 toroids each. To change bands you must swap modules and I was concerned that this would eventually take it toll on the toroids as a few are wound with #32 AWG. Someone in the group took it upon himself to wind a bunch of toroids and measure their characteristics and then use different methods to secure the toroids to a PCB (most have already been mentioned here in previous responses). He then repeated the measurements, noting any changes in the inductance and Q. The conclusion was that the hot glue method had the least impact on the electrical characteristics of the coil. The trick that I use was gleaned from the manual for the original KD1JV ALT Tuner kit sold by Hendricks QRP kits. Cut a small sliver of hot glue stick with an exacto-knive and wedge it under the toroid once it is mounted to the board. Heat gently with a heat gun or hair dryer just until the glue starts to melt, gently push the coil down into the melted glue. Let the board sit for a few minutes until the glue hardens. Best of luck with your Ten-Tec rig Scott. Michael VE3WMB

RE: stabilizing a toroid	Reply
by WB6BYU on October 27, 2009	Mail this to a friend!
Another option is to use a nylon bolt, nut and washer to secure the toroid to the PCB. Drill a hole in the board, pass the bolt through the board and the hole in the toroid, put on the washer and nut and tighten them down. You can add a small ring of glue under the washer (or between the toroid and the board) if you want to make sure the turns stay in the same places, but in many cases it won't be necessary.

RE: stabilizing a toroid	Reply
by AA4PB on October 28, 2009	Mail this to a friend!
I wonder how much affect the nylon bolt, hot glue, etc. has on the Q of a torid? Anybody ever do some actual measurements to see?

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