IGSL

[Wiltran]

ISGL

Ivconic, when tuning a TX coil to resonate at a freq. such as 14.5 KC, will it radiate power better if you use a smaller value tuning capacitor? In other words if you have two coils, one 100 turns, the other 110 turns, and they both have to resonate at 14.5 KC using differnt tuning capacitors , which one would be more efficient?

[ivconic]

Ivconic, when tuning a TX coil to resonate at a freq. such as 14.5 KC, will it radiate power better if you use a smaller value tuning capacitor? In other words if you have two coils, one 100 turns, the other 110 turns, and they both have to resonate at 14.5 KC using differnt tuning capacitors , which one would be more efficient?

The one which present less ballast for TX transistor!
More efficient will be the one with less damping, the one with lower resistance (at given frequency).
But that is subject to explore a bit more.
If LC tank is matched exactly to desired frequency - than efficiency will be maximal.
Meaning; it is more important to match LC than to worry only about one "component".
There are advantages and disadvantages at both cases: higher C and lower L, lower C and higher L.
My English is not so good to be able to properly elaborate these relations.
Therefore, my explanation may confuse you even more...than to help you!
Maybe some native English can do that instead?

[ivconic]

Mikebg is not native English.. but he is very literate, and he managing with technical terms much better than me.
I think he already elaborated this question very good, in details.
Use search function and list through his earlier posts..

[mikebg]

Mikebg is not native English.. but he is very literate, and he managing with technical terms much better than me.
I think he already elaborated this question very good, in details.
Use search function and list through his earlier posts..

Hi Wiltran, unlike ivconic, my English language is very bad. However for every my post, I use two machine translators and a program for spell checking. My spell check program shows that in above quote, ivconic uses two dots at end of the first sentence and the new sentence starts with lower letter.
In theory, your 100 turns coil will operate more efficient than 110 turns coil if both coils have equal weight of wire. This is because of better impedance matching at limited weight of TX coil. In practice, the difference is insignificant because the improvement of matching is relatively small.
To increase TX power 4 times, you should use center tapped TX coil. It can be connected in self-oscillating (Hartley) circuit or in driven oscillator circuit as in White's TM-808. The TX tank should have large capacitance, for example 1uF, formed by capacitors type MKP.

[der_fisherman]

Resonant frequency Calculations

Generally you don't need to worry about a few kHz oscillator frequency.

Maybe more important is relative resonant freq of Rx coil and C6 capacitor.

dfbowers TGSL 101 doc says Rx coil and Capacitor C6 should have resonance at about 16.1 kHz for configuration where TX oscillator is 14.5 kHz.

That means:

RXcoil,C6 res freq = 1.11 * Oscillator freq

That may be the most important tuning consideration, although I don't know if anyone has independently confirmed it as the optimum ratio. Basically, if the ratio gets closer to 1, you get more phase shift that can mess up your discrimination circuit, and possibly too much gain for your preamp. Alternatively, as the ratio goes higher than 1.1, you lose gain of your signal, although the phase shift is not changed too much.

You can tune to this rule by either changing your oscillator frequency, or tweaking C6 to a different value according to the formula:

Resonant Frequency = 1 / (2 * pi * sqrt(L * C))

Where L is Rx coil inductance and C is capacitance of C6. You just have to solve for C.

Regards,

-SB

Many thanks for your post, I will key it into my calculator for instant use, Can you just say as to whether the units are as I note here C in Farads? Inductance in Henries? Frequency is then in Hz?

Which cap (there are two if I remember correctly C1 and C2 in my diagram) or both in the Collpitts oscillator is the one that affects the Tx coil frequency?

In the Rx circuit, I guess I must add both C4 and C43 together?

Thanks for help in this matter.

regards

Andy

[ivconic]

Hi Wiltran, unlike ivconic, my English language is very bad. However for every my post, I use two machine translators and a program for spell checking. My spell check program shows that in above quote, ivconic uses two dots at end of the first sentence and the new sentence starts with lower letter.
In theory, your 100 turns coil will operate more efficient than 110 turns coil if both coils have equal weight of wire. This is because of better impedance matching at limited weight of TX coil. In practice, the difference is insignificant because the improvement of matching is relatively small.
To increase TX power 4 times, you should use center tapped TX coil. It can be connected in self-oscillating (Hartley) circuit or in driven oscillator circuit as in White's TM-808. The TX tank should have large capacitance, for example 1uF, formed by capacitors type MKP.

Initially there were 3 dots.. but one escaped!
Look! Happened again!!?

[der_fisherman]

IGSL Kit for TGSL DIY Coils has arrived from SilverDog

First impressions are really fantastic, the PCB artwork is good enough to hang on a wall in a den (sadly my wife would not alloow it on the lounge wall!!!!! )

All component positions clearly marked, even a complete beginner will have problems in placing a component wrongly orientated.

He has also added the wire links in as tracks on the top, so its really a double sided PCB, no wires to fit at all on the PCB....makes it even prettier.....

Two bags of components with attractive mini pots (easy to fit in any size enclosure) WITH KNOBS, which have a POINTER on them, sockets for all chips, clear extra marking on the paper strips which hold the resistors, no exscuse to get it wrong at all !!!

The reasonable price belies the the excellent quality of everything.

Thanks SilverDog and well done.

Regards

Andy

PS I have attached two pictures of the kit.

[ivconic]

........

PS I have attached two pictures of the kit.

Nice pictures!
A bit invisible... but nice indeed!

[der_fisherman]

Nice pictures!
A bit invisible... but nice indeed!

I just corrected that, I had to resize them to allow uploading.....

[ivconic]

[simonbaker]

Many thanks for your post, I will key it into my calculator for instant use, Can you just say as to whether the units are as I note here C in Farads? Inductance in Henries? Frequency is then in Hz?

Which cap (there are two if I remember correctly C1 and C2 in my diagram) or both in the Collpitts oscillator is the one that affects the Tx coil frequency?

In the Rx circuit, I guess I must add both C4 and C43 together?

Thanks for help in this matter.

regards

Andy

Yes, Henrys and Farads and frequency in Hz are the units.


I believe the two caps in the oscillator are combined in parallel, so both do affect the oscillator frequency. I think the oscillator frequency is approximately equal to:

1 / (2 * pi * sqrt(L * C))

where L is inductance of TX coil and C is C1 || C2 == C1 * C2 / (C1 + C2).

To adjust, I'd probably focus on the larger cap by either replacing it and/or add small caps in parallel, depending on whether you want to adjust the freq up or down.

Probably adding small caps across the TX coil leads would work too to lower the freq.

I probably confused people by talking about C6 in the RX resonant circuit, because in IGSL circuit Ivconic relabeled it to C4. In any case, I mean the .015u capacitor connected in parallel with the RX coil.

I don't see a C43 in the IGSL circuit... which do you mean?

Regards,

-SB

[simonbaker]

Ivconic, when tuning a TX coil to resonate at a freq. such as 14.5 KC, will it radiate power better if you use a smaller value tuning capacitor? In other words if you have two coils, one 100 turns, the other 110 turns, and they both have to resonate at 14.5 KC using differnt tuning capacitors , which one would be more efficient?

An interesting question I've been wanting to investigate for some time (and probably others already have). Maybe a little LTSpice will shed some light, although I agree with Ivconic that it is a more complex subject than meets the eye.

Ultimately you want a design that gives you the best tradeoff of qualities you are looking for... depth, battery life, stability, etc. So "radiated power" may not be the only criteria. Also the oscillator circuit you choose affects how important changes in the coil parameters are.

But it is a very good question and I hope to continue studying and discussing it.

Cheers,

-SB

[simonbaker]

First impressions are really fantastic, the PCB artwork is good enough to hang on a wall in a den (sadly my wife would not alloow it on the lounge wall!!!!! )

All component positions clearly marked, even a complete beginner will have problems in placing a component wrongly orientated.

He has also added the wire links in as tracks on the top, so its really a double sided PCB, no wires to fit at all on the PCB....makes it even prettier.....

Two bags of components with attractive mini pots (easy to fit in any size enclosure) WITH KNOBS, which have a POINTER on them, sockets for all chips, clear extra marking on the paper strips which hold the resistors, no exscuse to get it wrong at all !!!

The reasonable price belies the the excellent quality of everything.

Thanks SilverDog and well done.

Regards

Andy

PS I have attached two pictures of the kit.

The top jumpers are a very nice touch for sure!

Who will come up with a nice inexpensive coil-building kit, enclosure (box), and pole assembly?

-SB

[dfbowers]

The top jumpers are a very nice touch for sure!

Who will come up with a nice inexpensive coil-building kit, enclosure (box), and pole assembly?

-SB

Ha! I've been thinking about that one for some time. Those items seem to double the cost of the project. Especially good encapsulating epoxy

[WM6]

The top jumpers are a very nice touch for sure!

Who will come up with a nice inexpensive coil-building kit, enclosure (box), and pole assembly?

-SB

Ask Georgi Zhelev who sell coil housing here on Geotech. I am pretty aware that he can offer other building parts (as enclosure (box), and pole assembly) too.