TGSL Coil will this work?

[andrew]

Wound the tx coil to match 14.5khz then wound the rx coil to 13.9khz tied them up which bunched the windings nice and tight then glued them in and oh dear! when dried i now have 14.1khz tx and 13.6khz for rx coil bugger i see making these coils are going to be very difficult? bit late tonight to see if it may work but shal try in the morning heres hoping it might? cheers all, andrew.......

[porkluvr]

Don't you have your relative frequencies backwards? The rx should be slightly higher than tx, and not the other way around.

I'm curious, how did you determine those frequencies to begin with, I mean what did you measure?

What are your coils inductances? It seems to me like you could use 13.1 for tx and then adjust the other coil's tuning to get something usable.

I think the ratio of tx to rx tuning is ideally around 1:1.1, but that ratio is for a tx frequency of 14.5 and might oughta be adjusted if you have a lower tx freq. Just a guess.

[andrew]

Don't you have your relative frequencies backwards? The rx should be slightly higher than tx, and not the other way around.

I'm curious, how did you determine those frequencies to begin with, I mean what did you measure?

What are your coils inductances? It seems to me like you could use 13.1 for tx and then adjust the other coil's tuning to get something usable.

I think the ratio of tx to rx tuning is ideally around 1:1.1, but that ratio is for a tx frequency of 14.5 and might oughta be adjusted if you have a lower tx freq. Just a guess.

Sorry porkluvr! the post was a little misleading! those are the frequencies of the coils connected to the tx oscillator and measured with a frequency counter so depending on the receive tuned circuit capacitor etc? i guess the rx could well be higher? i just wound the coils using .25mm wire to don bowers or ivconic's article ie tgsl 101! i have no idea what the inductances are so we will see how it comes out? initial depths and discrim without shielding are encouraging though! cheers andrew......

[dfbowers]

Sorry porkluvr! the post was a little misleading! those are the frequencies of the coils connected to the tx oscillator and measured with a frequency counter so depending on the receive tuned circuit capacitor etc? i guess the rx could well be higher? i just wound the coils using .25mm wire to don bowers or ivconic's article ie tgsl 101! i have no idea what the inductances are so we will see how it comes out? initial depths and discrim without shielding are encouraging though! cheers andrew......

You have it right.. When you remove your Rx coil from the oscillator and connect it back to the Rx circuit it will then resonate at 16.1kHz. It's just a cheap way to check for an inductance value of 6.5 mH.

[dfbowers]

Wound the tx coil to match 14.5khz then wound the rx coil to 13.9khz tied them up which bunched the windings nice and tight then glued them in and oh dear! when dried i now have 14.1khz tx and 13.6khz for rx coil bugger i see making these coils are going to be very difficult? bit late tonight to see if it may work but shal try in the morning heres hoping it might? cheers all, andrew.......

Don't throw your coils away! It's not overly important to match frequencies. What IS important is the difference in resonant frequencies. You can always adjust the value for C6!! I'll bet with a little experimenting you can get things to work.

BTW.. when I make my coils, things are correct but after adding shields it decreases frequencies a bit. Usually, not a problem!!

[porkluvr]

You have it right.. When you remove your Rx coil from the oscillator and connect it back to the Rx circuit it will then resonate at 16.1kHz. It's just a cheap way to check for an inductance value of 6.5 mH.

Ahhh, I see. That just goes to show that I don't know the right questions to ask.

[andrew]

Don't throw your coils away! It's not overly important to match frequencies. What IS important is the difference in resonant frequencies. You can always adjust the value for C6!! I'll bet with a little experimenting you can get things to work.

BTW.. when I make my coils, things are correct but after adding shields it decreases frequencies a bit. Usually, not a problem!!

Good tip don thanks! looking at the 15n cap im thinking of replacing it with some sort of trimmer? but values are a little difficult ie nf! i got plenty of small pf up to 100pf or so kicking around could try one in parallel see if that is enough to peak things so to speak? after i have found the best null with my coils! cheers andrew...