RELIC HAWK

[Max]

Hi Fred,
I've found another mistake there... or two... maybe you're addicted to irish whiskey more than me...

At U2 I see the two pins that goes to GND that actually are floating... and the GND is at pin1 (output) of LM393 ???

Ok... no problem... I will cut and paste there... and LM393 works infinite time with output at GND... (...I have 50 of them to replace)

Anyway... I think last time I checked for this I was drunk...
cause I didn't see them.

You can solve moving the upside track that goes to pin1 to go to pin3.

Kind regards,
Max

[Fred]

Hi Max,

This is getting embarassing
I think we should both change of make of drinks...

You know, actually i only drink water. Maybe i should try something srtonger.

Below corrected PCB.The good thing is that there is no version nº
Thanks!
Regards,
Fred.

[nakky]

Hi Fred can't open it.Grt Nakky

[Fred]

Hi Fred can't open it.Grt Nakky

Hi,
It should open with Sprint Layout 5.0 ?
Regards,
Fred.

[Max]

Hi Max,

This is getting embarassing
I think we should both change of make of drinks...

You know, actually i only drink water. Maybe i should try something srtonger.

Below corrected PCB.The good thing is that there is no version nº
Thanks!
Regards,
Fred.

Hi,
no problem... I think at the end it will work... one way or another.

Kind regards,
Max

[VUJO]

Dear gentlemen, is there the possibility of posting the latest version without PCB components and with dimensions
Best regards
Vujo

[Max]

Hi,
I've a new recipe for tx coil:

WIRE GAUGE = 20AWG , 0.8125mm without varnish, about 0.85 with varnish
TURNS = 42
D SHAPED like in Ivconic's design for TGS, same former about DD255x137, for a single halve

Wire Resistance/1000m = 33.292ohm

Actual lenght = 27.4m
Resistance = 0.912ohm
Inductance = 1mH (exact, with strong tightened wires)

Though not so thin boundle is still acceptable and coil works very nice on RH oscillator, giving strong signal.

I'm awaiting for more wire to check for other config as well but will require some time.

Kind regards,
Max

[ivconic]

Reffering coil doubts,
yesterday i asked friend to bring professional resistance meter to me and we measured again original RH coil resistances.
TX= 3.1 ohms (including cable)
RX= 41.3 ohms (including cable)
So...
I do have few unimeters and we checked resistances with all. My meters showed approx. same values with minor drifts.
I think catch is in the last TX transistor. On original pcb that (only that) transistor is smt and without any label?
I dont have pcb anymore so i cant measure its hFe.
Possible that transistor is specific in a way?

[Max]

Reffering coil doubts,
yesterday i asked friend to bring professional resistance meter to me and we measured again original RH coil resistances.
TX= 3.1 ohms (including cable)
RX= 41.3 ohms (including cable)
So...
I do have few unimeters and we checked resistances with all. My meters showed approx. same values with minor drifts.
I think catch is in the last TX transistor. On original pcb that (only that) transistor is smt and without any label?
I dont have pcb anymore so i cant measure its hFe.
Possible that transistor is specific in a way?

Hi Ivconic,
nice to see your posts here. Well, yes, probably the transistor at osc is really critical... simulations showed that all components are critical, the more effects due to coil series resistance.

Now that we know sure the coil is around 3 ohm resistance we know also that can't be a BC557 there on coil. But what if not a BC ? Probably is something like BFR99 uhf transistor thing (up to 2GHz)... not cause of frequency cutoff but cause they can oscillate with minimal residual signals along the path: I have one of these in one resonant oscillator stuff... and oscillates from 10Hz to 300Mhz pretty easy changing the LC stuff connected.

I don't know if the BFR99 could be employed in this circuit but I think will probably change our actual situation where just lower resistance coils work.

I have to find the SPICE model of it and use in the simulation to see if I can fix the problem this way.


Kind regards,
Max

[Max]

Hi,
I've made a simulation using BFT92 pnp UHF transistor...but nothing: no oscillations at 3.1 ohm resistance.

Maybe there was something truly special in the original RH pcb... the SMT thing, whatever it is, must be something a bit exotic... cause all I tested so far failed in simulation to reproduce oscillations at desired resistance range.

Real puzzle...

Kind regards,
Max

[nakky]

Hi Max,minelab use in sovereign c368 c369 bc556 and lm385 z-2.5,maybe say this someting to you.Grt Nakky.

[Fred]

Hi Max,

Could it be a Jfet or similar?
could try with mpf102 or something.
Fred.

[ivconic]

No. It is ordinary transistor.

[amtech2005]

RELIC HAWK

Hi,
I think I found the source of all troubles... at least in my previous simulation... the dang 22K resistor I have in the circuit I had like 27k in previous simulation.

Now, I changed it to 22K and got 13.6Vpp for a 2.5ohm resistance coil, 1mH and about 18Vpp if the coil resistance drops to 2.2ohm.

So, for the simulator... the 2.5ohm coil MUST work though not optimal one... and with ideally maximum voltage of 13.6Vpp on it.

Now the problem is that I have the dang 22K in the real pcb but it doesn't work... cause probably the NPN I've used is low gain BUT I used an BC547B so still don't understand that, must check again.

Simulations are cool... but often reality is truly different stuff..

Kind regards,
Max

I do not have my simulation software installed yet , a few more days But was wondering if BC537 would be a better "npn" than BC547 for the tx circuit ?? Thanks.............Eugene

[maxbiri]

Hi
If problem is hfe maybe a small darlintong work better in these position.
Or changing the gain of TL071.
Not sure of course!

Bye Max