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JHGibson · 8th Mar 2004, 3:51 am

After winding a RF coil, I like to dope it to keep the winding tight. I finally ran out of the dope I bought many years ago and looked around to replace it. The only kind that seems to be readily available now is the polystyrene type which I found to be a poor substitute as it does not grip either the wire or the former very well.
I had some gloss polyurathane varnish left over from a hardwood floor refinishing project so thought I would try an experiment. I wound a coil and measured it on my Q-meter as 200 at 20 Mhz. Then I used the floor varnish on it and remeasured the Q after the varnish dried. Still 200, and the varnish gripped the wire and the coil former just like my old coil dope did.
So polyurathane varnish makes a satisfactory coil dope.
John.

8th Mar 2004, 3:51 am	#1
JHGibson Retired Dormant Member Join Date: Apr 2003 Location: Salt Spring Island, BC, Canada Posts: 368	Coil Dope Subsitute After winding a RF coil, I like to dope it to keep the winding tight. I finally ran out of the dope I bought many years ago and looked around to replace it. The only kind that seems to be readily available now is the polystyrene type which I found to be a poor substitute as it does not grip either the wire or the former very well. I had some gloss polyurathane varnish left over from a hardwood floor refinishing project so thought I would try an experiment. I wound a coil and measured it on my Q-meter as 200 at 20 Mhz. Then I used the floor varnish on it and remeasured the Q after the varnish dried. Still 200, and the varnish gripped the wire and the coil former just like my old coil dope did. So polyurathane varnish makes a satisfactory coil dope. John.