SpudFiles

dewey-1 wrote:Parts layout is some what critical when dealing with RF circuits.
Not saying that it can't be done, just that it may be a lot of trial and error by anyone not familar with RF circuit design.

Are you saying the orientation and proximity of the components makes a difference to performance?

yeah I know I am a w

At least you know

Mostly the proximity of components. The closer together the better.
Example is lead distance of 2mm versus 15mm.
Basically as close together as possible. You can see that in your existing PCB layout.

Here is another similar circuit. You can eliminate some of the parts that are use for voice modulation. Note the use of a trimmer cap for tuning that can be replaced with a fixed value cap and adjust coil for tuning.
http://www.electronics-project-design.c ... itter.html

I am working on a perf board layout for FM transmitter that uses a LED driver IC to pulse the FM carrier signal. M34-2L that was discussed here:
http://www.spudfiles.com/forums/viewtop ... tml#347460

Link for IC
http://www.ebay.com/itm/LED-Flasher-IC- ... 8370722840

Will post later when done.

edit for LED driver IC

What about an IR leds and a small button batteries seems a lot smaller

battlelava wrote:What about an IR leds and a small button batteries seems a lot smaller

I think you may need to read more about what this posting is all about!

Trying to find some thing that is nearly invisible to the human eye defeats the purpose. Besides that it may be buried in sand and become totally nvisible.

dewey-1 wrote:Mostly the proximity of components. The closer together the better.

I see, that shouldn't be a problem.

I am working on a perf board layout for FM transmitter that uses a LED driver IC to pulse the FM carrier signal.

Will post later when done.

That would be greatly appreciated, anything that works with the minimum number of cheap tough compenents is the way forward!

What is the permeability of sand in FM frequencies, anyway? I know it's basically glass, but who knows what trace metals and other contaminants it contains. Obviously gigahertz-range radiation is absorbed readily by water, but hopefully the ~100Mhz spectrum is less affected, otherwise you're gonna have to find a really dry stretch of sand to shoot into.

Are you saying the orientation and proximity of the components makes a difference to performance?

You're just trying to keep interference out whenever possible. Keeping the leads short keeps them from acting like antennas; whether it's absorbing electrical 'noise' or inflicting it on other components in the circuit.

The coil probably can't be potted because the type of insulation used affects how some RF components operate. Silicone, for example, causes higher losses as you go up in frequency. If you're worried about g-forces acting on the coil, you could try winding it around a cylinder of PTFE, which will hopefully go unnoticed.

Fnord wrote:What is the permeability of sand in FM frequencies, anyway? I know it's basically glass, but who knows what trace metals and other contaminants it contains. Obviously gigahertz-range radiation is absorbed readily by water, but hopefully the ~100Mhz spectrum is less affected, otherwise you're gonna have to find a really dry stretch of sand to shoot into.

I'm thinking of a push fit rear endcap that would release a coiled aerial when it breaks off.

You're just trying to keep interference out whenever possible. Keeping the leads short keeps them from acting like antennas; whether it's absorbing electrical 'noise' or inflicting it on other components in the circuit.

Ah, right... so in this case, burying them in epoxy is a good thing

The coil probably can't be potted because the type of insulation used affects how some RF components operate. Silicone, for example, causes higher losses as you go up in frequency. If you're worried about g-forces acting on the coil, you could try winding it around a cylinder of PTFE, which will hopefully go unnoticed.

The supplier said potting the coil would change the frequency. My idea was to wind it around a delrin support.

How about you set up a series of targets at varying distances then shoot at them an when you come across one that you don't hit then you can find the potato in between two targets and measure the distance from where you fired to the potato? Call me simple but that seems a lot easier than using radio beacons and stuff.

The idea here is to go for maximum range, that implies a firing angle of 45-55 degrees or so... meaning the targets would have to be strung up on balloons...

Woops.... I thought we were talking about effective range. Meaning shooting "flat".......

That might work if you were talking about using a rifle or something with a flat trajectory and high accuracy.

We're talking about a launcher with a smooth barrel, firing at about a 33* angle and peaking at probably over 300ft off the ground, with a probable-impact area that could be as wide as 50ft and as long as 200ft. There's simply no way in heck you could set up a wide enough target.

And if you use an actually potato, your impact area gets even bigger. With a decent launcher, your possible impact area extends from about 30 feet out to as far as 200yards, and it's probably half that wide. Potatoes can perform some pretty funky aerobatics when they start to tumble.

Daltonultra wrote:That might work if you were talking about using a rifle or something with a flat trajectory and high accuracy.

We're talking about a launcher with a smooth barrel, firing at about a 33* angle and peaking at probably over 300ft off the ground, with a probable-impact area that could be as wide as 50ft and as long as 200ft. There's simply no way in heck you could set up a wide enough target.

And if you use an actually potato, your impact area gets even bigger. With a decent launcher, your possible impact area extends from about 30 feet out to as far as 200yards, and it's probably half that wide. Potatoes can perform some pretty funky aerobatics when they start to tumble.

Okay, well then you can use maybe a compound round:
http://ultimatespudgun.com/uhmw-compoun ... p-222.html
and a rifled barrel:
http://www.spudtech.com/store/index.php ... ducts_id=8

There you go.

Bowman wrote:How about you set up a series of targets at varying distances then shoot at them an when you come across one that you don't hit then you can find the potato in between two targets and measure the distance from where you fired to the potato? Call me simple but that seems a lot easier than using radio beacons and stuff.

You are simple.

1. Finding the spud might not be all that easy given how big the impact area is (see previous couple of posts).

2. The spud won't be found at the point where it hit the ground. It'll still be moving horizontally at perhaps a 100 FPS so it will bounce or roll for a fair distance. The smother the surface the farther it'll roll. The rougher the surface the less it'll roll but the harder it will be to find.

3. There might not be all that much left of the spud, making it even harder to find.

Best bet if you want to use markers is to put observers out to the side and have them just visually note ... "1/4 of the way between marker 4 and 5". That'll be more than accurate enough if you are shooting spuds since the shot to shot variability for lumps of starch is going to be pretty big.

Bowman wrote:

Daltonultra wrote:That might work if you were talking about using a rifle or something with a flat trajectory and high accuracy.

We're talking about a launcher with a smooth barrel, firing at about a 33* angle and peaking at probably over 300ft off the ground, with a probable-impact area that could be as wide as 50ft and as long as 200ft. There's simply no way in heck you could set up a wide enough target.

And if you use an actually potato, your impact area gets even bigger. With a decent launcher, your possible impact area extends from about 30 feet out to as far as 200yards, and it's probably half that wide. Potatoes can perform some pretty funky aerobatics when they start to tumble.

Okay, well then you can use maybe a compound round:
http://ultimatespudgun.com/uhmw-compoun ... p-222.html
and a rifled barrel:
http://www.spudtech.com/store/index.php ... ducts_id=8

There you go.

@jimmy101

To be honest I think you guys are making this a lot harder than it needs to be.

Bowman wrote:To be honest I think you guys are making this a lot harder than it needs to be.

I think you're just missing the spirit of this thread. The point I was trying to make was that spudguns have a lot more potential than what most people get out of them, mostly because while they might put a lot of effort into their launchers, hardly any thought is given to the projectile.

Talk of potatoes is therefore meaningless in this case, given their extremely poor ballistic coefficient they are exactly the sort of projectile that is "holding us back". I put that in inverted commas because there is absolutely nothing wrong with firing agricultural produce, it's undeniably a fun endeavor, but if you want to squeeze the best performance out of your launcher, it simply won't do.