2 boxxxx :)

[chemelec]

I could not undestand it.in schamtic there is a current meter but in pcb I could not find it's outputs

.

Here is the Revised Circuit Board. Still Oscillates as soon as I turn up the gain.

Each Section of the three amplifiers work properly, when used seperately.

The first 3 transistors have a gain of +40Db
The Second 4 transistors, also +40 Db.
The Third 3 transistors, Also +40 Db.
All stages have a bandwith of +200 Khz.

Schematic will be shown when I get it working.

Take care.........Gary

[okantex]

Hi Chemelec ,
which project's pcb is this?
this is not serzirfo , is not it?
this looks like roger harrison project,but there are 10 transistors.and one coil output.if this is reciever ,where is transmitter .
if transmitter will be another board ,so why there are 10 transistor (not 9)
I am really confused .
and eagerly waiting for finished working project.
I want to build serzirfo's project.but with HF band.50 mhz.
I wii be pleased if anybody can help me to calculate and change condansator values.
thanks
Okan

[kt315]

> but with HF band.50 mhz.

Ivan's Project is NOT hight freq. waves (HFW). you see - there are ordinary OP AMPS. if you want to get 50 mHz you will have very BIG DIFFICULTIES in the realisation.
in real, there is not the extrim big need of HFW. do it on 2 Khz!

[chemelec]

Hi Chemelec, which project's pcb is this?
this is not serzirfo , is not it?
this looks like roger harrison project,but there are 10 transistors.and one coil output.if this is reciever ,where is transmitter .
if transmitter will be another board ,so why there are 10 transistor (not 9)
I am really confused and eagerly waiting for finished working project.
I want to build serzirfo's project.but with HF band.50 mhz.
I wii be pleased if anybody can help me to calculate and change condansator values.
thanks
Okan

OKAN, You Need to read the Previous Posts.

This is NOT Serzirfo's Detector.
It is a Re-make of the Treasure Witcher by Charles Drake.

50 Mhz, I Doubt that is Possible. Definately Not Practical.

Gary

[chemelec]

Still the Oscillation Problem. But here is the reciever schematic anyway.

Note: there is an error on my previous PCB picture.
he Collector resistor of the first transistor is connect to he wrong place.
This has been corrected but still working to stop the oscillation.

Gary

[Geo]

Hi Gary. When i constructed the Treasure Witcher i made it with transistors (no with CA3035). The value of the resistors at first stage was as shown in attached schematic. Some times i had Oscillation Problem at hight gain. The reason was the speaker.
Geo

[Esteban]

Hi, this receiver made by Charles D. Rakes works fine. No audio. I remember the only implementation I added was to repeat the first stage, and in this point the sensibility increases very much respect the original. Make sure to tune properly the coil receiver with the adequate capacitor. Also the transmiter have modification via ups the consumption to 25 mA with low resistor in the emitter of the germanium transistor. Remember that the limit of this resistor was 2.7 ohm or 3.3... Distance between transmiter and receiver box was 90 cm. Another important fact that is much better added or quit turns in the receiver coil for to achieve a real good performance.
The original transmiter transistor is 2N4249, but germanium with low resistence in emitter is better

[chemelec]

Hi Gary. When i constructed the Treasure Witcher i made it with transistors (no with CA3035). The value of the resistors at first stage was as shown in attached schematic. Some times i had Oscillation Problem at hight gain. The reason was the speaker.
Geo

I'm using a Pizo Speaker, so no coil in it to cause the oscillation by induction.

These changes you made refer only to the First 3 transistors. Are you implying that you didn't use the other stages?

If So, that would definatey be Lower Gain as the 3 Stages in the CA3035 give 120 DB Overall Gain.

The same applies for Esteban's Circuit. Very low gain compared to the CA3035 IC. I can see whay he said he added another stage.

I believe that is why Charles Rakes went to the IC, To get Much Higher Gain.
He said when it was tuned properly the reciever could detect the transmitted signal at 25 feet. Thats Pretty good distance.

I Haven't actually built a Transmitter circuit yet.

I am using two 8 inch diameter, 300 uH Coils.
One for recieve and the other connected to my RF Generator with a 2 Khz Modulation. Tuned Frequency is about 170 Khz.

Take care.........Gary

[Igor MN]

Just, a little more

Sorry Geo,but You are not precise! I see that BD 139 is for KT 815,BD 140 for KT 816,2N2222a is for KT 315, but what is precisely for KT 814 ? On pictures of assembling T/R locator Sevzirfo's ,You can see shielding with aluminium,also in schematics! did You made shield on your T/R,if You are,where can i conect it on PCB little help with ground needed

Thank You in advance
Igor
stay good,and fast up hill

[Esteban]

Respect the high gain, for example, the Fisher Explorer of 1958 only have 3 transistors 2N169 NPN type in the previous three stages and 1 PNP 2N139 for the meter!!! The transmiter is automodulation type. Antennas are aluminium square, low impedance, via ferrite cores. Have a key for to select high and low gain.

[Geo]

Hi. The Hight gain is for audio. We have the same circuit until first stage where is the meter. The detector who i constructed has an 741 after the diodes for audio gain. 300 uh coils is ok for 170 Khz.On afternoon i will try to send you the schematic. I have try the schematic of Charles D. Rakes who send Estebam but with lower sensitivity. The diodes for demodulate is better to be Ge.

Geo

[Geo]

Sorry Geo,but You are not precise! I see that BD 139 is for KT 815,BD 140 for KT 816,2N2222a is for KT 315, but what is precisely for KT 814 ? On pictures of assembling T/R locator Sevzirfo's ,You can see shielding with aluminium,also in schematics! did You made shield on your T/R,if You are,where can i conect it on PCB little help with ground needed

Thank You in advance
Igor
stay good,and fast up hill

Hi Igor. U can Use BD140 for KT814. I never used shielding at 2box detectors.If you want to build it dont afraid about shield.
Geo

[chemelec]

Stupid Mistake in the previous schematic. I had the meter in wrong and couldn't see it, no matter how many times I looked at it.

Here is the Revised Schematic of the reciever. Now it works Very Well.

An article on this detector will be posted on my website in the near future.
Complete with circuit boards.

[Geo]

Hi Gary.
What about the transmitter? We waiting for results. I attach the file of the project who i coctructed before 23 years.
Geo

[chemelec]

Geo, as it says in my last post, I am working on a complete article, This includes a transmitter. I will post it all on my Projects-page when I have it Complete and tested. Probably in about a week.

I forgot to show the Headphones in my Schemaic. They go in Parallel with the 2K7 Resistor and the .01 cap.

Your Scan or Photograph is so Blury, its almost impossible to read any of it.
If its a Photograph, You are too close.

**To take Good Close-up pictures with a digital camera, use a cheap pair of 2.5 diopter Reading Glasses.
Put one of these eyeglass Lenses directly in front of the cameras lens and take the picture at a distance of 12 to 15 inches away from the subject material.
You will get a Very Clear, Enlarged Photograph
(A diopter of 1.5 can also be used but the focal distance will be about 15 to 20 inches.)

Take care..........Gary