Blog Archives

WT8WV “Colossus” Air Cannon Antenna Launcher

20171229_165353

These are the basic parts to make my “WT8WV Colossus” antenna launcher.

Folks, this has been a fun and hilarious winter project.  Yesterday, when I built this air cannon antenna launcher it was -4 degrees outside and this was a perfect evening project to put together.  For years, me and my two ham radio buddies (WR8S Bill Shultz and WV8TG Tom Graf), have enjoyed ARRL Field Day activities and usually used a slingshot and a 3/4 ounce fishing sinker weight and an old Zebco fishing reel (with 20 pound test line) to shoot and suspend our doublet dipole antennas high into the trees.  Certainly, the slingshot worked pretty much flawlessly… but… boys will be boys, and the idea of an air cannon / spud launcher / potato gun type system seemed to be a new desire.  (Most people, our wives included, wouldn’t trust our 3-man team with a slingshot, let alone a potato gun!  But I digress.)  Actually, our local ham radio club (Monongalia Wireless Association) had a version of a potato gun antenna launcher, so we decided we needed one of our own… and to make some design modifications in the interest of… “science”… plus our own sadistic pleasures.  (Make sure you read below WV8TG’s initial “pressure test” experience.)  The following pictures hopefully provide the basic concept and parts we used.  Tom and I split the cost of the parts needed to make launchers and each built our own version, but they both are the same basic design with only length dimensions of the air chamber and barrel being the difference.

All parts where sourced from our local Lowes store in their plumbing department, except the Schrader valve which can be purchased at an automotive store.  Total cost about $40 but you could make a couple of them as a joint project with a friend and reduce that cost per launcher a bit.  I got a small rubber gasket for the outside nipple of the Schrade valve to act as another seal on the exterior of the air chamber.  You will need to drill holes for Schrader valve, barrel slug stop and projectile slug caps to attach the screw eyes to attach the fishing line.  I used 3 inch PVC for air chamber, 1.25 inch PVC for the barrel and short sections to mate the air chamber, trigger valve and threaded barrel.  The projectile slugs were made from 3/4 inch PVC and caps and I filed off the nubs on the caps with a Dremel tool for a smooth fit into the barrel.  I used PVC Prep on each joint before applying the glue.  When gluing joints together, insert the sections together and twist a quarter turn for a solid adhesion.  Let all glue set up for 24 hours before testing air pressure chamber.  I will pressurize the chamber inside and let it sit overnight to see if it loses any pressure.  It’s too cold right now to take outside in -4 degree temperatures to test, but I will use a bicycle pump with a pressure reading valve, and start at 40 psi… then 50 psi… and then 60 psi for test shots to see how it functions and check for any air pressure leaks.  We use 60 psi for our club launcher.

WV8TG (Tom) charged his air chamber (barrel not attached) and let it set overnight to test for chamber air leakage.  When he opened the trigger value… there was NO leakage… but there was a sudden LOUD release of 60 psi air gush out of a 30 inch long, 3 inch wide fully charged air chamber.  He indicated the compressed air release was… impressive.  However, his wife was not impressed… nor was she aware of the scientific test that was taking place.  #surprise!  #WHOOOOOOOSH  #loudwifeexpressions  I have no reason to doubt Tom will find his projectile slugs in the next county using his design.  The club chamber was 12 inches long versus his 30 inch air chamber.  #overkill?  I designed my air chamber for 14 inches and will conduct all tests… outside.  #potentialmeanwife

 

 

 

 

Advertisements

Near Vertical Incidence Skywave (NVIS)

ml91_graph-779367

I love DX.  I love chatting to interesting people all over the world and making new friends.  For short range chatting I use our Monongalia Wireless Association W8MWA Repeater on the 144/440 frequencies.  Sometimes it’s more difficult to talk short distances than it is to talk half way around the world.  Let’s consider Near Vertical Incidence Skywave  (NVIS) antennas with our HF radios.

NVIS is something every Ham needs to learn about.  The antenna system is not difficult to construct and can serve an important function for shorter range communications, especially in time of an emergency when normal local / regional communication systems are down for some reason.  (i.e. cell towers, cellphones, landlines, etc.)  Hams may be called into service quickly.

Here is what Wikipedia says about NVIS communications…

Near vertical incidence skywave, or NVIS, is a skywave radio-wave propagation path that provides usable signals in the range between groundwave and conventional skywave distances—usually 30–400 miles (50–650 km). It is used for military and paramilitarycommunications, broadcasting,[1] especially in the tropics, and by radio amateurs. The radio waves travel near-vertically upwards into the ionosphere, where they are refracted back down and can be received within a circular region up to 650 km from the transmitter.[2] If the frequency is too high (that is, above the critical frequency of the ionospheric F layer), refraction fails to occur and if it is too low, absorption in the ionospheric D layer may reduce the signal strength.

The most reliable frequencies for NVIS communications are between 1.8 MHz and 8 MHz. Above 8 MHz, the probability of success begins to decrease, dropping to near zero at 30 MHz. Usable frequencies are dictated by local ionospheric conditions, which have a strong systematic dependence on geographical location. Common bands used in amateur radio at mid-latitudes are 3.5 MHz at night and 7 MHz during daylight, with experimental use of 5 MHz (60-meter) frequencies. Broadcasting uses the tropical broadcast bands between 2.3 and 5.06 MHz, and the international broadcast bands between 3.9 and 6.2 MHz, Military NVIS communications mostly take place on 2-4 MHz at night and on 5-7 MHz during daylight.

Optimum NVIS frequencies tend to be higher towards the tropics and lower towards the arctic regions. They are also higher during high sunspot activity years. The usable frequencies change from day to night, because sunlight causes the lowest layer of the ionosphere, called the D layer, to increase, causing attenuation of low frequencies during the day [3] while the maximum usable frequency (MUF) which is the critical frequency of the F layer rises with greater sunlight.

NVIS is most useful in mountainous areas where line-of-sight propagation at VHF or UHF frequencies is ineffective or when the communication distance is beyond the 50-mile (80 km) range of groundwave, and less than the 300–1500-mile (500–2500 km) range of lower angle sky-wave. Another interesting aspect of NVIS communication is, that direction finding of the sender is more difficult than for ground-wave communication (i.e. VHF or UHF). For broadcasters, NVIS allows coverage of an entire medium-sized country at much lower cost than with VHF (FM), and daytime coverage similar to MW (AM) nighttime coverage at lower cost and often with less interference.  https://en.wikipedia.org/wiki/Near_vertical_incidence_skywave

Below are a few very good links to articles for the nuts & bolts of putting together a simple and good NVIS antenna.

http://www.tactical-link.com/field_deployed_nvis.htm

http://www.qsl.net/wb5ude/nvis/index.html

http://www.w0ipl.net/ECom/NVIS/K2GW-NVIS.htm

http://www.w0ipl.net/ECom/NVIS/cbp-nvis.htm

Here is a sample video by NG9D with an 80 Meter End Fed NVIS Field Antenna.

What the heck is an Amp-Hour?

Battery amp-hour, watt-hour and C rating tutorial

Regardless if it’s your flashlight, your 2 Meter hand-held radio, your QRP rig, your Field Day station(s), your APRS setup, your balloon launch radio transmitter, your trolling motor, your emergency preparations or your personal GoBox… understanding how long those batteries that supply operating power will last becomes quite important.  It will also assist you in deciding what battery to select for a particular project or product.  Afrotechmods has several excellent YouTube videos on his channel that we all can enjoy!

Anderson Power Poles (Part 2)

Anderson Power Poles For 12 Volt Ham Radio Connections

These are very handy for all sorts of your 12 volt ham radio projects!  

Will be looking for these at the next hamfest!

playwithlifeorg

4 out of 5 dentists recommend this WordPress.com site

BG5TLA's Blog

Just another WordPress.com site

Tinkertoytech's Blog

Just another WordPress.com weblog

KC4LMD

Chronicling my pursuit of amateur radio’s "Worked All Neighbors" award

Casey's Place

"When we try to pick out anything by itself, we find it hitched to everything else in the universe." -- John Muir

Hackaday

Fresh hacks every day

VK4JAZ

Writings about Amateur Radio

Tactical HF

I love the smell of ozone in the morning...smells like...radio.

WB5RMG : RadioActive Blog

slightly sub-orbital testing facility

73, de N2HTT

A blog about ham radio, Linux and more...

Ham Radio Blog PD0AC

Thoughts of a Dutch radio amateur

Silver Bells Blog

Truth Appealing...

CQ de WT8WV... GraHAM's Dits & Dah's

My journey in amateur radio intrigues and hobby interests

K5UNX Ham Radio Blog

A blog dedicated to things Ham Radio related

Mountain Mists...

A pleasant journey into how I see things... big and small

playwithlifeorg

4 out of 5 dentists recommend this WordPress.com site

BG5TLA's Blog

Just another WordPress.com site

Tinkertoytech's Blog

Just another WordPress.com weblog

KC4LMD

Chronicling my pursuit of amateur radio’s "Worked All Neighbors" award

Casey's Place

"When we try to pick out anything by itself, we find it hitched to everything else in the universe." -- John Muir

Hackaday

Fresh hacks every day

VK4JAZ

Writings about Amateur Radio

Tactical HF

I love the smell of ozone in the morning...smells like...radio.

WB5RMG : RadioActive Blog

slightly sub-orbital testing facility

73, de N2HTT

A blog about ham radio, Linux and more...

Ham Radio Blog PD0AC

Thoughts of a Dutch radio amateur

Silver Bells Blog

Truth Appealing...

CQ de WT8WV... GraHAM's Dits & Dah's

My journey in amateur radio intrigues and hobby interests

K5UNX Ham Radio Blog

A blog dedicated to things Ham Radio related

Mountain Mists...

A pleasant journey into how I see things... big and small

%d bloggers like this: