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Old 25th Sep 2017, 10:03 am   #1
raditechman
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Default PCB making active antenna

There has been discussion recently about active antennas and a friend of mine last week built two whip active antennas using a 2 semiconductors (J310 and BFG135) amplifier based on a circuit which is freely available on the internet. It works well from LF through HF and above. As I was impressed I also build one last week.
He has now designed a printed circuit for the amplifier but neither he or I have the skill or chemicals needed to make the boards.
There are 10 pcb boards on one A4 sized sheet. Part of the printed circuit board is also the antenna itself. I think the gap between each of the 10 boards may need to be widened to make it easier to cut the of individual units. Any opinions/advice welcomed. Bear in mind that the image here is low resolution due to forum file size limits, if you want the high resolution image PM me, or ask on here.
Does anyone here offer a service to make the boards (all costs covered) or know of any commercial operators who make boards.
If we can make a few we will give them out to members of my local amatuer radio club as an alternative receiving aerial to try to combat local QRM.
A low resolution of the boards is attached. If you want the circuit PM me.
It uses easily obtained components 4 X 0.1mfd, 7 resistors and two ImH inductors (if using power through the coax.)
They may also be of use to members on this forum.

Thanks,
John
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Old 25th Sep 2017, 1:15 pm   #2
Herald1360
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Default Re: PCB making active antenna

Places like this will do cheap PCBs for you: (NFI etc etc)


http://www.3pcb.com/?nadw=79


But you'll need Gerber files rather than traditional artwork. Not necessarily a costly problem but maybe a learning one!
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Old 25th Sep 2017, 3:03 pm   #3
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Default Re: PCB making active antenna

Thanks Herald1360,

I have not heard of Gerber files before and have just been reading about them.

I had thought that to make a psb you just printed the image onto glossy paper with a laser printer and then hot ironed the toner onto the copper board, then soak the board in a chemical that eats away the copper from the areas of the board that have not had the toner on them. Then clean it up and use.
I have never tried this but am willing to have a go, if not I will try and use a conversion program to get a Gerber file.

This is only a hobby project and one board with 10 units after it is cut would be enough to give out to my radio club.
I also thought that the board and or circuit would be useful to some people on this forum who have noise on MW or LW AM radio.

I built mine or a small piece of strip board, if I manage to make a pcb it would make construction easier.

John
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Old 25th Sep 2017, 4:07 pm   #4
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Default Re: PCB making active antenna

That PCB is simple enough to hack out the unwanted bits with a scalpel. Not for series production, good enough for a one off.
 
Old 25th Sep 2017, 7:21 pm   #5
David G4EBT
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Default Re: PCB making active antenna

Quote:
Originally Posted by raditechman View Post
Thanks Herald1360,

I had thought that to make a psb you just printed the image onto glossy paper with a laser printer and then hot ironed the toner onto the copper board, then soak the board in a chemical that eats away the copper from the areas of the board that have not had the toner on them. Then clean it up and use. I have never tried this but am willing to have a go...

This is only a hobby project and one board with 10 units after it is cut would be enough to give out to my radio club.

John
There are lots of youtube videos - some better than others - which show the technique.

Some seem to get good results with care, others are very much at the 'bodgertronics' end of the spectrum.

Here are a couple of links that might help:

http://www.dr-lex.be/hardware/tonertransfer.html

https://www.bing.com/videos/search?q...6C96&FORM=VIRE

If you give this technique a try and iron on a design but fail to get good results, you can remove the toner and try again. Maybe you didn't iron it on enough, maybe the copper was cleaned rather too smoothly making it difficult for the toner to adhere. Maybe a different type of paper or different printer setting will work better? But just doing the same thing over and over and expecting different results is one definition of madness.

A couple of things to bear in mind:

1) Your artwork must be 'mirrored' or when you iron it on, the PCB will be back to front.

2) I think you'd be well advised not to attempt to make a full A4 sheet on boards at one attempt. If - as is likely - any of the print doesn't adhere, you'll have to clean off the whole board and start again. I think an A4 sheet is much too large to iron on in one attempt. Print a full sheet off by all means, but cut it into strips for individual boards.

For just a few boards, ferric chloride is probably the easiest and most readily available etchant to use. Use a 0.8mm drill bits to drill the holes after etching and thoroughly clean the board. (0.8mm HSS drills are typically 99p for ten post free on ebay from China). On no account drill the holes before etching, because if you do, the etchant will get into the holes, soak into the substrate and there it will stay. Its purpose in life is to eat copper, and that includes component leads placed through holes contaminated with etchant.

A lot of people who make DIY boards use laminate with an SRBP substrate. (Looks brown). The copper has poor adherence and the tracks and pads easily lift when soldering. 'FR4' glass fibre material isn't so much more expensive, but in my experience is far superior.

I've been making my own PCBs using UV techniques for more years than I care to remember, but due to time constraints I'm not in a position to make boards for others. I've no personal experience of the 'toner transfer' technique, but for occasional boards it clearly has considerable advantages over having to gear up for UV just for the occasional PCB and well worth a try I'd have thought.

Hope that helps a bit.

Every good wish with your project John.
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Old 25th Sep 2017, 8:36 pm   #6
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Default Re: PCB making active antenna

For something as simple as your boards, the easiest way to do them is to use an etch-resistant fibre tip pen to cover the copper you want to retain. Unfortunately, finding good solvent-based pens is a bit harder now than it used to be. Some people use nail varnish.

Etching with ferric chloride is no great problem, provided you remember that it will slowly rot just about anything it comes in to contact with (my mother's lace curtains), except plastic and glass. It turns your skin orange; not desireable but not severe.

Whatever method you use, be sure to clean the copper well before you but down the etch resist. I tend to use wire wool followed with a wipe with kitchen towel soaked in IPA (alcohol).

The use of UV developing method is good for complex designs, but people were making good pcb's long before anyone had a printer in their home!

B
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Old 26th Sep 2017, 7:50 am   #7
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Default Re: PCB making active antenna

Thanks for all the advice I am off to Maplin's today as they seem to stock the materials needed.
I will cut the strips and make one board at a time as David suggests.
I had not thought of using a pen.

I will let you know how I get on!

I built another active antenna using strip board last night so I suppose if the pcb's fail I can just make a few more that way.

I now have to find a spot in my garden to put antenna is away from local QRM.

It also needs to be disabled while transmitting, so a relay circuit of some sort needs to be added.

John
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Old 26th Sep 2017, 1:14 pm   #8
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Default Re: PCB making active antenna

Re the antenna, you referred to two whips - does that means the two work together in some way? You also mention QRM, which I've always taken to refer to as co-channel interference from another station(s), as distinct from QRN which is general background noise. But looking on Google now, QRM is referred to as interference. Have I had that wrong for the last 50 years decades Of course, all the interest in magloops is in respect of QRN.. I think, though the directionality could help with QRM

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Old 26th Sep 2017, 10:59 pm   #9
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Default Re: PCB making active antenna

QRN Naturally generated noise

QRM Man made noise

Is how I always thought of them.
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Old 26th Sep 2017, 11:32 pm   #10
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Default Re: PCB making active antenna

I've always found that active whips are not really any improvement as far as local electrical noise is concerned. Loops seem far better in this respect.
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Old 27th Sep 2017, 12:58 am   #11
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Default Re: PCB making active antenna

Looking at a number of sites via Google, definitions vary, but QRN is nearly always refers to static/atmospherics. QRM refers to interference, but co-channel transmissions could be classed as man-made interference. I suppose that noise from wall warts etc has to go under QRM.

Based upon the numerous posts in the magloop thread, active whips would not seem to be the right way to go to reduce man-made noise, irrespective of how the pcb is made.

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Old 27th Sep 2017, 8:03 am   #12
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Default Re: PCB making active antenna

Both Q and Z codes were in use well before they were adopted by governments but as far as the CCEB (and therefore NATO) are concerned the only authoritative definitions of QRM & QRN are in ACP131, which states the following:

QRM - Are you being interfered with.
QRN - Are you troubled by static.

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