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[Subculture]

In regard as to what was discussed earlier about the greatest attenuation of signal taking place during the transition from air to water, it's logical to think that a further degradation of the signal will occur if the receiver aerial is placed inside the submarine or dive module, as the signal switches back from water to air.

[sub john]

Reply#200
Hi Subculture,     Yes you would be right in saying if TX Ariel is in the water and RX Ariel was inside a air tight box or water tight compartment it would have to go through a change from water to air which would be a large attenuation but as my RX Ariels are in the water in free flood area this is not a problem for me, one of the things i should say my RX Ariel for low frequency  the antenna automatically tunes itself to the medium it is in and part of this circuit is linked to AGC which is auto gain controll.  Plus all this circuitry is solid state no moving parts, just say you was using 1.8MHZ to transmit into air it would be 164meters long which is one big antenna on the ham bands it would be called 160 meters but if you put this Ariel in water it would become many times smaller which makes it quite easy to get in to a small place and is ideal for fitting inside of subs, when i have finished playing about with video link for under water and if i get it working the way i won't it to. I will then get back on designing some sonic link for under water but as you know yourself it all takes time
 John

[MikeA]

I remebered when you was talking about silly long aerials i didnt understand back then but these days im getting better at having a clue what your talking about. can you use the same frequencies to transmit video images as you do to control your boat? could it be done by using the 2.4 ghz frequency hopping technology so that your control and live feed back dont clash?

[Subculture]

my RX Ariels are in the water in free flood area this is not a problem for me.

I was thinking more along the lines of those of us using commerical 27/40mhz radio equipment. In that instance we have our transmitters going from air to water (not much choice there unless we wish to separate the tuner from our TX's), and tend to spool the aerial somewhere inside the dry area, be it a cylinder, box dry hull etc.

[sub john]

Reply#202
HI Mike,     You asked could you use frequency hopping on low frequency's if you was to use 27MHZ if you are sending large data you would not have enough band width with out bleeding into other channels on that band. Another problem if you was sending analog video  the band width  would be so wide it would knock out the hole 27MHZ band  you would have to go to a higher frequency to have the band width with out interfearing with other bands close by. I have made quite a few custom built RF units for all sorts of bands,   like i said before Mike when you are a radio ham there is quite a few bands that you can use it does help a lot of the bands legal power limit is 400watts thats a lot of power
    John

[sub john]

Reply #203
 HI Subculture,  Yes i can see what you are getting at, one of the things that you could do is where your Ariel is on your TX transmitter you could unscrew the Ariel off it and  make a matching unit which would be small and that would screw on where your Ariel come off on the other end would have a screened cable that would go down to your Ariel in the water you could even build a RF amp into it and for Ariel inside of sub  there must be some where you could get Ariel into the  water.  If you wonted to re tune front end on receiver to match Ariel in water, but i suppose it is how far you won't to go but it does seem worth the effort


If you look at a Ariel on your 27MHZ TX unit for radio controll the Ariel on it is not even a quarter wave in length which would be about 9FT long the Ariel that you have on your TX transmitter standard is a small length  which as been matched  to your RF section in side your TX unit
  John

[MikeA]

Reply#202
HI Mike,     You asked could you use frequency hopping on low frequency's if you was to use 27MHZ if you are sending large data you would not have enough band width with out bleeding into other channels on that band. Another problem if you was sending analog video  the band width  would be so wide it would knock out the hole 27MHZ band  you would have to go to a higher frequency to have the band width with out interfearing with other bands close by. I have made quite a few custom built RF units for all sorts of bands,   like i said before Mike when you are a radio ham there is quite a few bands that you can use it does help a lot of the bands legal power limit is 400watts thats a lot of power
    John

hmm scratch that then lol. What is it your stuck on at the moment then. I suppose you now have long range control sussed just the video now?

[sub john]

REPLY#206
HI Mike,    On one of your reply's you said that one of your model boats didn't go very well what went wrong, it didn't turn it self in to a submarine and sink did it lol

Still got to test low frequency under water but cannot see that being much of a problem but like you said the bit I'm stuck on at the moment is the video link for under water. Went out flying it was so cold soon came back home to the gas fire  to warm up
    John

[MikeA]

no it didnt john. Ive built a rescue boat for my other models if i get into a bit of bother. It was suppose to be FAST response but its flat fronted and has the hydrodynamics of a brick smothered with a bin liner.

anyway john its allright you hading out the stick but at least i get my boats wet!! lol

[sub john]

Reply#208
HI Mike,    I would like you to know the only time my sub got wet in the water was about 18 years ago and the closest it has got to water is filling the ballast tanks with water. But with a bit of luck will get it in the water next year, its getting to cold now to go in the garage and do work on the sub but the last few days have been testing the electronics to see if it behaves it self in cold weather there is a lot of electronics in there
          John

[MikeA]

tut more waiting  i suppose if you get the camera working you will have to patent it

[sub john]

Reply#210
HI Mike,  Trouble with patents is it costs a lot of money to see it through to the end to make the product, and if you don't see it through to the end and don't take out a full patent some body else can copy it later on and make a lot of money out of it best thing to do is keep it to your self other wise people will try to make money out of it. But this is just my personal thought's

Have drawn out your circuit for your H bridge drive circuit to marry up to your servo amp board, have done circuit using as lease components as i can to make it work will knock it up on development board and try it to make sure it works and then will sort out how to get circuit diagram to you.
  All the best John

[MikeA]

i understand why you wouldnt patent it but think of the possibilities!! marine research, criminal investigations, search and rescue, would be a mega break through. youl have to go on dragons den lol.

thank for designing my esc. I found a shop just down the road that sells all types of mosfet, chips and doodaas. looking forward to your post

[sub john]

Reply#212
HI Mike,    I have had people copy what i have designed before and am very carefull what i give away now. I have just rebuilt RF amp that some one gave me which had blown all 8 fets but the fets that was in it are expensive to buy but what you can do if you use a IRF520 which is a power fet which is not designed for RF but if you know what you are doing you can use them to put in this amp it is now knocking out 150watts of RF which is not bad for using IRF520 POWER FETS people have used them to repair CB radios which has just got 1 device fitted but when you won't to put 8 in you have got to make sure that they load share don't think any one has done this before as devices are not matched but i do get a BUZZ out of doing things like this .

Glad that you have found a shop down the road for buying bits that you need for speed controller like i said before Mike i don't mind helping somebody that won't to learn can probably help with some bits to make first unit, one thing for you to think about is FETS that you need for H bridge circuit for speed controller need to be logic level FETS which means that the gate voltage will be 5 volts not 10 as on standard fets which there is a thing called RDS which is internal resistance needs to be as low as possible to keep heat down on fets .

I will work out which fets you need to use which you can get from RS or Farnell
All the best John

[MikeA]

Im not suprised people have nicked your stuff john its pioneering. I just think you should be credited with your work 

refering to the fets, not long ago when i was researching such things, i was watching a you tube video explaining their operation.  Anyway it showed on the vid the 5v operation needed for the gate and the use of a resistor on it to bring the voltage down. Im getting there slowly%%

[sub john]

Reply#214
 HI Mike,   Yes it does make you very secretive i have got about 5 folders full of circuits  that i have worked out for allsorts of stuff   i have got just 1 folder full of  just the sub bits, when i first started to rebuild that big sub of mine i was finding circuit boards and didn't know what they did as i had not seen inside it for so long. lol

Do you ever have a week where every thing is going wrong thats what seems to be happening to me this week my HF ham radio decided to have a wobbly just spent all day fixing that blow the misses kettle up this morning and all i did was switch it on  even the microwave oven went bang last week and the week before the washing machine went bang what a month it does get expensive changing all these things.

Hopefully  later this week i will knock your circuit up and try it
    John

[MikeA]

its all that LRF floating round your house its creating EMP's frying everything

im sure that the esc is good. does it have a BEC?

[sub john]

Reply#216
HI Mike,  Don't say things like that about low frequency blowing up bits in the house, or her in doors will shut my room down and i won't be able to play any more plus she will properly have a melt down don't know if i said or not but Robert said it was me that blow is wide screen TV up its gone where all TVS go in the end TV HEVEN he had to go and buy a new one plus he said I'm not getting any thing for Christmas.

Speed controller circuit i can soon draw a BEC circuit on to it how much current do you won't enough to run the grid lol
   John

[MikeA]

NO i dont want to run the grid or you will be draining it all trying to make LRF and blowing things up. Get some lead lining on your walls or else everyone will start growing third nipples.

seriously i dont know what amps and volts though, whats the standard? 5V 1A?

[sub john]

Reply#218
HI MIKE, To late Robert has already got one and now he says it's my fault that he is getting headaches

Drawing that i did for H  bridge  drive circuit knocked it up on developing board works fine but what might be a idea is to send me one of those servo amps that you brought off ebay and let me try one to make sure it works ok on H bridge drive circuit. No problem to fit 1AMP 5VOLTS BEC
   John

[MikeA]

its not a headache hes having itl be a cist created buy a radiation leakage and before he whats going on itl start talking to him! have you ever tried making radio waves using a magnetron from a microwave??

I think 5v 1 amp is enough to drive 1 standard servo and a RX on a 2 channel radio, dont you think?

If you pm me your address ill send you it. Also how much will cost to make these?

[sub john]

Reply#220
HI Mike,  Yes Mike you could use a magnetron out of a microwave oven they use the same thing for radar it is probably one of the reasons we won the battle of Britain back in the 2nd world war, one of the most important  things that was sent from Britain to the USA as they couldn't get radar to work some thing else we gave away.I don't think we had better get to much into magnetron's as i am RF power mad

One of the things i did a few years ago was to take apart a LNB off a satellite dish the type they use for sky broad cast take the PCB board out of it cut it up into different sections and put it all back together so it will transmit 10GHZ  sending out video picture quality was as good as say BBC TV full sound as well, that plugged into RF amp knocking out quite a lot of power on 10GHZ which is not the best things to work with as this frequency will start to cook your body if close enough

Yes 1 AMP 5V REG should be OK
Will send you PM    john

[MikeA]

yeah im into world war history. I actually found it very interesting when i was a kid and my grandad use to tell me about his days in the war lol. Ive asked a few people in the past about their accounts. Not many people left now.

Is working with RF your job speciality or just a hobby?

thanks for adress

[sub john]

Reply#222
 HI Mike,    I can remember my granddad telling me story's about the 1st world war some of it was a bit grim to say the least

RF did start off as a hobby but then i worked in Microwave RF for about 11 years  i got so sick of it in the end i couldn't be bothered with it  but now i have started to get interested in it again its not so much like a bus mans holiday now. I have worked on all sorts of microwave electronics a lot of this was to do  with sending video encrypted and sound as well, it  had a lot to do with surveillance in all sorts of things with out saying to much.

Some of the video equipment was on 2.3GHZ  and was knocking out 30watts of RF and for saying that some of the 2.4 GHZ radio gear that we use for our planes or boats or what ever you don't have to think very hard to know why we still get lock out on radio equipment on 2.4GHZ it doesn't matter what you use as a radio link nothing is immune to interference but this is just my own personal point of view.
         JOHN

[MikeA]

Obviously there be bad bits but there are also great hero moments and funny moments too.

I know what you mean how doing your hobby proffesionally can ruin the enjoyment of it in the first place. While i was employed i did very little construction at home because i just spent 8 hours wielding a spanner at work.

I heard somewhere that even the WIFI on your home network can interfere with your TXRX reception.