MPP Beach REV-E

[kt315]

555 has two versions - cmos and not. we must know that he used.

[kt315]

Wouldn't the interference be noticed on both detectors though?,,,
---
you do not give frequency values of both. so i can only imagine.

[MartyJ1963]

@6666,,,,,I just noticed you're in Melbourne, Australia,,,I was born and brought up in Mt.Druitt, Sydney. My parents brought me to England when I was 14 years old in 1977. I never wanted to leave Australia and have always missed it,,,never got used to England and still haven't, lol. I did a bit of detecting with my Dad when I was about 7-8 years old and always said I'd get one of my own one day and have a go,,,I didn't build my first detector till December 2016,,,nearly 47 years after I first decided I wanted one,,lol. But I have the 'Bug' really bad now,,,it's a great hobby and I'm learning new stuff everyday. If I'd had the chance to live my life out back in good old Oz I know I'd be in them Gold fields,,,,I did a bit of alluvial gold mining and opal hunting with my Dad once in Lightning Ridge,,,,I hadn't got a clue what I was doing back then but I loved every minute. Marty

[MartyJ1963]

@KT315 and 6666,,,,,The 2 x 555 timers I use in the Rev E detector are both NE555N,,,,,I will change the 'Last' one like 6666 suggested and see if it is better. I have a lot of other different 555 timers spare,,,some are TLC555 and NE555P,,,,are they also compatible to use? Thank you both. Marty

[kt315]

i am not able to comment if there is not primary data. try do two albums and put pics of rev e in one and pics of rev d in another.

[6666]

@6666,,,,,I just noticed you're in Melbourne, Australia,,,I was born and brought up in Mt.Druitt, Sydney. My parents brought me to England when I was 14 years old in 1977. I never wanted to leave Australia and have always missed it,,,never got used to England and still haven't, lol. I did a bit of detecting with my Dad when I was about 7-8 years old and always said I'd get one of my own one day and have a go,,,I didn't build my first detector till December 2016,,,nearly 47 years after I first decided I wanted one,,lol. But I have the 'Bug' really bad now,,,it's a great hobby and I'm learning new stuff everyday. If I'd had the chance to live my life out back in good old Oz I know I'd be in them Gold fields,,,,I did a bit of alluvial gold mining and opal hunting with my Dad once in Lightning Ridge,,,,I hadn't got a clue what I was doing back then but I loved every minute. Marty

Hi Marty, good summery of your activities, my family came to Oz in 1839 and we hung around, been digging gold since the 1960's and playing with detectors since mid 1970's , I dont get out prospecting as much as I would like, slowing down a bit in my old age, but its a good hobby keep at it.

[6666]

@KT315 and 6666,,,,,The 2 x 555 timers I use in the Rev E detector are both NE555N,,,,,I will change the 'Last' one like 6666 suggested and see if it is better. I have a lot of other different 555 timers spare,,,some are TLC555 and NE555P,,,,are they also compatible to use? Thank you both. Marty

Check the component values from about TP9 onwards just make sure you have the right bits in the right hole, about the 555's, try and stay with the NE type they are high current devices.

[6666]

Wouldn't the interference be noticed on both detectors though?,,,
---
you do not give frequency values of both. so i can only imagine.

What KT315 is trying to say I think is, sometimes you can have a situation were external noise can "Beat" with the internal TX oscillator and cause problems with the audio, so by changing the frequency of the TX oscillator slightly this problem can be reduced or eliminated,

[MartyJ1963]

Thanks guys,,,,@KT315 - I'll try to do some phots soon of both the Rev D and Rev E detectors,,I'll do them as detailed as I can before I fit them into enclosures,,it may be a few days though, loads to do in between. @6666,,,I absolutely loved my life of just 14 years in Australia before being uprooted and brought somewhere I didn't know and never wanted to go to. I missed all my friends for years after I got here and still really miss them now. It may sound silly but when I ot to England I was bored cos' there was nothing to do,,eg: I used to go to the Nepean River in Penrith every day after school to this big Cubby hole me and my friends built,,we had a raft that we used to fish off, we trapped our own food etc,,,I loved the bush,,and when I got to England I found there was no such thing,,being 14 I couldn't do the things here as I could there in Oz. Only ever been to 2 English beaches cos' they're not the same either,,lol. Anyway, I'll not babble you to death but I must say I do envy where you are,,,thanks for the help 6666,,,nd all the other guys on here too. Marty

[MartyJ1963]

I forgot to say,,,,I'll try all my other NE555N's,,and my NE555P's,,,and see if they make a difference,,,the only other thing I can try is replacing the 220k pot with a new one,,it may be that what is faulty. Thanks again guys. Marty

[waltr]

What KT315 is trying to say I think is, sometimes you can have a situation were external noise can "Beat" with the internal TX oscillator and cause problems with the audio, so by changing the frequency of the TX oscillator slightly this problem can be reduced or eliminated,

Exactly what I was also thinking.

Marty, measure the frequency of the main oscillator, the 555 that generates the TX pulse.
Most likely it is different on the two MPP's you built. Then tweak the frequency of the noisy one.
I found this makes a big difference on the Hammer Head PI detector I built.

[kt315]

interesting. i repeat this text again and again but people are like blind squirel.
guys, open my archive. open folder #miscellanea. open file info only about PI.rtf.
read it.

---------------interference----
Hi John,
Here is a copy of a post I made a couple of years ago which deals with this subject.
RELEVANCE OF PULSE FREQUENCY in a P.I. DETECTOR.
A question that is often asked about P.I. detectors is the relevance of the pulse frequency. Some detectors run at a hundred or so pulses per second while others run at several thousand. The first archaeological detectors I worked on ran at 22 p.p.s. In later versions we upped it to 43, then 170. The important thing was to avoid the same frequency as power lines, 50Hz in the UK, 60Hz in the US. Multiples of the power frequencies also had to be avoided e.g. 100 or 120. Severe beat note interference would result if the detector and power frequencies coincided; that is if you were anywhere near power lines as is often the case in the UK.
P.I. detectors running at low frequencies usually pulsed high currents through the coil, 5 - 10 amps being a typical figure. The on / off time ratio of the pulses was high so the average current drawn from the battery would be 100 - 200 milliamps.
Many of todays detectors favour much higher pulse frequencies. This puts the detector well away from power line interference but low frequency radio transmitters can then start to cause problems. Faster pulse rates also have the advantage in that the response of the detector can be made more rapid, which aids in pinpointing an object. Fast pulse rates require that the pulse current be less, otherwise things would start to run hot and the battery life would be rated in minutes. The pulse current can be restricted by a lower transmitter voltage but more usually by a resistor in series with the coil or by making the coil more resistive by using finer wire. 0.1 - 1 amp pulse currents being typical. One major factor in determining pulse current is acceptable battery life. With rechargeables 5 - 10 hours is OK, while standard alkaline cells would be expected to give 15 - 25 hours for the cost to be acceptable. One or two recent detectors on the market appear to have energy recovery circuits which make the transmitter more efficient and significantly increase battery life.
The pulse frequency has little effect on detector performance; one running at 170 p.p.s. could have the same range as one running at 5000 p.p.s. but there are many inter-related factors that determine the final performance, not least the design of the receiver circuit.
Hope this helps. I favour higher pulse rates (1500 - 5000) in my current designs.
Eric.
---------------interference----

[waltr]

Yes Kt315, exactly what 6666 and I are referring to.
That is a excellent explanation of the issue.

[Tibuck19]

That word gets many people excited!

George, I just Finish cad drawing and getting ready to 3d print a 14inch mono coil in anticipation for the MMP gold, What induction do you suggest I make it I know the smaller induction the faster the decay, and the better for gold right ? also should I use the smallest magnetic wire I have and shield this coil ? speaking of shielding is copper tape with conductive glue a good idea for shielding ?

[waltr]

George, I just Finish cad drawing and getting ready to 3d print a 14inch mono coil in anticipation for the MMP gold, What induction do you suggest I make it I know the smaller induction the faster the decay, and the better for gold right ? also should I use the smallest magnetic wire I have and shield this coil ? speaking of shielding is copper tape with conductive glue a good idea for shielding ?

There are lots and lots of threads in the 'COIL' sub-forum about shielding and making Fast coils.
Do read and remember that shielding CAN increase the Capacitance and SLOW the coil's decay severely.