How is a Grid Dip Meter used to measure a detector coil?

[kenny444]

Hello would some one please tell me how I can use a Dip Meter / Grid Dip oscillator to measure the frequency of a home made detector coil. I ask because I want to try building some coils that have an included damping resistor and so have a selection of coil sizes, that can be plugged directly into my Surf PI 1.2 to give flexibility. thank you.

[6666]

With PI, Remove damping R and feed line then dip meter against coil. look around 1.1 to 1.4 megs.

[kenny444]

Thank you, but in order to keep the coil water proof I have been winding coils (coated cables) with a feed line left on, if I lay it out straight, do you think that would be OK, or perhaps feed it through a ferrite core. again, thank you.

[6666]

I am not sure what you are asking about the ferrite,, but it sounds like your coils are already sealed up, I can remove all the feedlines off my coils and get my Kenwood gdo close the coil, while I have not tried it you could try putting a small coil of a couple of turns on the end of the feedline and see what the gdo tells you

[kenny444]

Yes, sorry to confuse you, when winding my coils I leave 3ft of wire on each end and twist them. so there are no joints in the coil housing for water ingress, I just thought a ferrite slipped over the feed cable down to the coil would stop any interference from the feed cable. I do though understand how to use the Dip meter now, thank you appreciated. Ken

[6666]

ok on the lead wire, the lead wire will reduce the res freq of the pi coil, just place the gdo coil near the pi coil and test.

[kenny444]

OK, thanks again

[6666]

When I add a twisted pair feedline (which has about 50pf of capacitance) to my basket weave coil the res freq drops from about 1.4 megs to about 1.3 megs.

[golfnut]

you may try shorting the coil at the lead. then offer up the GDO

[kenny444]

Thank you for that.

[golfnut]

If your coil is mounted on the detector and you had a scope you could see the small ring after the Tx an that would be the self resonance of the coil/lead combo

[kenny444]

Yes thank you. I have organised a dip meter for my testing. Grateful.