Tuning coil?

I can only guess from the information provided. They are probably assuming that the coil will be air core (it exact specifications for the core were not provided, you can assume this), and that the wire would be solid enameled copper wire (known as magnet wire at more surplus outlets). So, you should remove the bit.

Unless you have the test equipment to tune the circuit, you would be well advised to stay as close as possible to the original instructions.

Dean

Yes, leave the "plastic" (usually enamel) on, the adjacent turns of the coil must not short, and coils like this are usually wound with the turns physically touching.

You can't (to my knowledge) test the coil to see if it is tuned to 88mhz. The circuit is tuned to that frequency, not the coil itself. The coil is likely to be part of a filter. If your plans/schematic have an inductance (usually milli-henrys (mh) )you can use an LCR meter (or a digital multimeter with inductance measurement) to get the correct inductance for the part. If you have followed the build instructions for the part, the C and R components of the part should be close enough.

Depending on what the circuit is, the proper test equipment could a VOM meter, a dip meter, oscilloscope or spectrum analyser. With most RF circuits, you really have to watch out for your measurement setup affecting the circuit. Test probes (and body proximity) will cause oscillators to fail to start, or to start when they normally would not.

You might want to visit a book store/library and read a good intro book on RF circuit design/fabrication. It might save you 10's or 100's of hours of frustration. RF is not as simple, orderly and intuitive as digital (IMHO), but it just as much fun.

Dean

What are you trying to do with this coil? Sound interesting