DIY TGSL STEP BY STEP BUILDING AND TESTING

[chuubaba]

Recently have been trying to build TGSL ver.3 as posed in sticky post. Gave it three attempts but all failed. I conclude its time a step by step building and testing procedure is prescribed to facilitate enthusiasts with my level of experience (my level is -10) .
Contribution by seniors gurus will help me a great deal whilst members at large benefit from it too.

[dbanner]

My first TGSL build was successful.
I had problems with my first coil because I didn't use correct gauge wire, my inductances were off by miles.
The other problem I had was with FET's, I used incorrect pinouts the first time but realized the mistake and corrected it
The last problem was I couldn't get chatter, so I did small mod I found on TGS thread that gave chatter, so now had ability to tune to max sensitivity( just before chatter
The final problem I had was shielding, I eventually used very good shielding salvaged from cable used to bring cable signal from road to house. It was perfect diameter for wrapping coil longitudinally instead of spiral.
I used the Version 3 layout
I found that Tl082 work better for me in one of the chips.
Now I'm very happy with its performance

[dbanner]

Balancing the coils is a bit tricky at first, but now it's very easy to do even without oscilloscope believe it or not. I it small plastic bolt to fine tune coil after sealing with epoxy as I found the fine nulling always change after epoxy cured.

[dbanner]

Pay attention to type of epoxy, using a slow curing type and epoxy which doesn't "pull" as it cures.
I used epoxy resin of cheap fast cure and it pulled like ****.

[chuubaba]

I am yet to move towards coil building

[chuubaba]

Do you approve use of 2N5484 instead of BF245C. The IC on my circuit are getting hot as i attach the 100k G.Balance POT. The voltage at Tx is 4.58V while on Rx it is 0 millivolts no coils attached

[Nandor]

Hi
2N5484 is an amplifier Transistor, you need a switch! N-channel switch like J105, J106, J107 and others too. If something is getting hot it means you have short circuit! Tx amplitude should be around 12-14 volts AC!

[chuubaba]

Thank you Nandor.

[kt315]

Hi
2N5484 is an amplifier Transistor, you need a switch! N-channel switch like J105, J106, J107 and others too. If something is getting hot it means you have short circuit! Tx amplitude should be around 12-14 volts AC!

2n5484 is not switching transistor? did you open datasheet?

[Nandor]

This one says it's JFET VHF/UHF Amplifiers
http://pdf.datasheetcatalog.com/data...0/72258_DS.pdf

[kt315]

http://pdf.datasheetcatalog.com/data...ild/2N5484.pdf

[dbanner]

Hi
2N5484 is an amplifier Transistor, you need a switch! N-channel switch

[dbanner]

The 2N5484 is not recommended for Analog/Digital switching. This is according to Fairchild, Onsemiconductor document.
https://www.google.tt/url?sa=t&sourc...0Nk3IKUciG4Abr
This document is like Bible for jFET transistors

[dbanner]

What is needed is a n-channel general purpose Amp/SWITCH.

[dbanner]

Here is a good tip I use sometimes whenI am looking for substitute/replacement. Cross reference the part number to NTE cross reference. Then cross reference possible replacement to same NTE database. If they match, then she is a good substitute.
This is quicker and easier than reading a ton of technical information of datasheet, looking for max. min. specs etc.
It is fast way of knowing if what you have available will work or not.