Thursday, October 15, 2015

My 20m/40m NVIS Antenna


My 20m/40m NVIS Antenna

Everything listed below, all the parts and processes contained herein, is just how I built my own 20m and 40m Near Vertical Incidence Skywave (NVIS) antenna.  The original antenna was used during the Texas QSO Party site hosted by W5SH.org.

I made my own copy of this antenna; but it’s just that, a copy!  I don’t know yet if it will work as well as the original one on which it’s modeled.  Some final tuning may be required.

The antenna was raised to a height of 16 feet using four army-surplus camouflage net support poles.

At our TQP site we did not guy the antenna other than using the guy-lines that anchored the antenna elements.  Feel free to guy your mast as you see fit.


 

The Parts List

One 1 ½” PVC “Y” fitting
Two 1 ½” PVC plugs
One 4” piece of 1 ½” PVC pipe
PVC glue/cement
Two ¼” – 20 x 1 ½” brass round-head machine screws
Two ¼” – 20 brass nuts
Two ¼” brass split washers
Two ¼” – 20 brass wingnuts
One chassis-mount SO-239 connector
Four #6 brass round-head machine screws
Four #6 brass split washers
Four #6 brass nuts
Two lengths ~10” #10 AWG wire in two colors (Red/Black)
Three ring terminals for #10 AWG wire
Four ring terminals for mounting to ¼” studs
~95 feet of #14 AWG stranded wire

~50 feet of 550 cord (also called Paracord)
Four egg / dogbone type insulators
Four tent line tensioners
Four tent pegs

 

The Feed Point

I started with the easiest part, the feed point.  It’s made with PVC fittings, the screws, two scrap pieces of #10 AWG wire and the SO-239 connector.

Take one of the PVC plugs and mark the center.  Drill a ¾” hole for the chassis-mount SO-239 connector.  Mark the locations for the small holes to mount the connector and drill them out.  I then soldered one of the pieces of #10 wire to the center pin of the connector and a ring terminal on the other end.  Solder a ring terminal on one end of the other piece of #10 wire.  Mount the SO-239 to the PVC plug using the #6 brass screws, split washers and nuts.  Onto one of these mounting screws you’ll need to attach the wire with the ring terminal.  You can then glue the plug to the angle end of the PVC “Y” fitting as in the picture below.

 



As you hold the PVC “Y” with the SO-239 pointing down, you should have two wires poking out of the top.  You can trim these two wires so that about 1 ½” is sticking out and solder ring terminals onto them.
 
Take the other PVC plug and drill two ¼” holes for the ¼” – 20 brass machine screws.  I used the wingnuts to space the holes for the studs so that I can tighten the wingnuts without them touching each other. 

One thing I forgot to mention and you can see from the pictures of the feed point is that I painted the PVC pieces OD green and coated with polyurethane.  The top face of the PVC plug I painted half blue and half red.  That’s just a personal thing I did.  Painting is totally un-necessary.  I just did it to make it look pretty. 

Back to the PVC plug.  Run the ¼” – 20 x 1½” brass machine screws up through the ring terminals on the wires and through the bottom of the plug.  I needed to cut the ring terminals and open them up to fit around the machine screws.  Fasten the screws with split washers and nuts.  The plug should look like the picture below when finished.  It can then be glued onto the PVC “Y”.


The last part of the feed point is to cut a 4” piece of 1 ½” PVC pipe and glue it onto the bottom of the “Y” fitting.  The reason for using 1½” PVC is that it mates perfectly to US Army surplus camouflage net support poles, the standard antenna mast for most homebrew ham projects.  Your finished feed point should look like the picture below.

 



The Antenna Elements

In theory each leg of the 20m dipole side of the antenna should be 16’ 5” if you assume the following formula:

                        234 / 14.250 MHz = 16.4210’
                                                         = 16 + (.4210 x 12)
                                                         = 16’ 5”

The measurements taken from the 20m legs for the one I have were 15’ 11⅞” and 15’ 10½” so just under 16’ but I’m OK with that because I know it works and works VERY well!

The same holds true for 40m:

                         234 / 7.212 MHz   = 32.4459’
                                                          = 32 + (.4459 x 12)
                                                          = 32’ 5 5/16”

Again, you can tune yours for whatever you wish but the 40m legs on mine were 31’ 11½” and 31’ 8”.  Not perfectly resonant at those two frequencies (the mathematical middle of the 20m and 40m voice bands); but my tuner will have no problem dialing them in.  Anyway, back to construction.

So you’ll need to measure four pieces of #14 AWG wire:  two for 20m and two for 40m.  Solder ring terminals onto ONE end of each wire.  On one of the 20m legs and 40m legs I wrapped a few turns of red electrical tape on the other two legs I wrapped a few turns of blue electrical tape.  This way I can pair them up properly onto feed point.               

 

Now you see why I painted the top of the PVC plug on the feed point. 

 

Insulators and Guy-Lines

The attaching of the guy-lines and insulators is pretty straightforward.  For each dipole leg I ran enough of the wire to leave 3” tail on the other side of each insulator.  I used two small zip ties to form a loop holding each insulator in place.  For neatness you could put a piece of heat-shrink tubing over the tail and zip ties.  That’s up to the builder.

 
 
For the guy-lines I bought a 100’ package of high visibility 550-cord.  Normally I choose something a little more “tactical”; but in this particular case I’m more concerned with safety and people not tearing down my antenna if they walk underneath it.

The guy-lines were measured to be the following lengths:

20m #1:  8’ 9½”           40m #1:  14’ 9”
20m #2:  9’ 3”              40m #2:  14’ 6” 

About 3” of 550-cord was passed through the insulators and knots tied holding the insulators in place.  Onto the end of each line I also tied a tent-line tensioner to snug the lines up once the antenna has been raised.

 


I haven’t decided yet if I’ll run a separate set of guy-lines for the mast.  I guess that will depend on the conditions at the time I set it up.  When it was used for the TQP the wind was light enough where no other guy-lines were needed. 

Conclusion

This was my first real attempt at building my own antenna and I think it turned out pretty good.  The design is compact enough to fit into a 1 gallon zip-top bag.  The construction was simple using components cheaply and readily available.
 
NVIS also provides an excellent intermediate range communications option between UHF/VHF and traditional long-haul HF bands.  During the Texas QSO Party not only was I able to work contacts within my own county but surrounding counties as well and even a couple stations farther out like Kentucky and Arizona all from western Fort Worth, Texas.
 

I hope my shameless copy of this antenna design will work well for you. 

A special thanks goes out to Bill Boyer, KF5FEI, for letting me borrow his antenna during Texas QSO Party weekend and letting me blatantly copy his design!

Thursday, May 7, 2015

My Off-Grid Power Solution!

I hate the sound of my own voice; but I put together a really short video about my off-grid power source to feed my two Yaesu radios, the FT-8900R quad-bander and my baby, the FT-857D. 


 
 
 
I'm giddy as a wee lad on St. Cavendish Day about the impending arrival of my QRP-Labs Ultimate3S QRSS/WSPR Beacon kit.  It only costs about $35 with shipping from Japan.  The kit comes with an RF generator, a 2-row 16 character LCD screen and one low-pass filter kit for whatever band you choose.  I chose my favorite, 20m.
 
I'm already planning down the road.  If I'm able to successfully build it I'm going to buy a few more of the filter kits for other bands (2m up to 40 or 80m).  I'm also looking at the optional GPS unit and something to power it like Armed Rogue's super-secret Altoids tin solar charger though probably a little bigger.  I may put it all together in a Pelican microcase, like a 1060 maybe?  We'll have to see though.
 
 


Tuesday, April 14, 2015

The Russians are Coming! The Russians are Coming!

April 12th, 1961 is a special date in man's history; but especially for the Russians (or Soviets as they were called at the time).  It was the date on which Yuri Gagarin became the first human being in space.   

Fast forward 54 years and it's 2015.  The international space station has been in orbit since 1998.  The Russian space station "Mir", not so much; but then again the world still needs to hitch a ride on a Russian Soyuz capsule to get there.

During the weekend of April 11-12, the Russian cosmonauts aboard the ISS were marking the anniversary by transmitting images via slow-scan television (SSTV) on 145.800 MHz.  I set up my trusty Yaesu FT-857D and Dell D800 laptop running MMSSTV on my workbench and just let them run.  Here's what they caught...





 
I'm still tinkering with the setting for MMSSTV to get the best possible quality.  I think it's just something really neat to play with.  It makes me want to get involved in working ISS by voice or possibly some of the other amateur radio satellites. 
 
 

Wednesday, February 25, 2015

My First Foray Into the World of Slow Scan TV

Over this past weekend the Russian crew-members of the international space station (ISS) were broadcasting images.  I was intrigued by this; but had no previous experience with anything having to do with slow scan television (SSTV).

There are various different packages that will handle the sending and receiving of SSTV images.  The one I like is called MMSSTV.  It's a freeware package that you can download here.  I just went with the default settings.  You don't even need an interface between your radio and computer.  You can get by with the old-school method of placing a microphone connected to your computer right next to your radio speaker to receive and keying your radio mic next to your computer speaker to transmit.

From February 22nd to 24th twelve different images were broadcast by the ISS.  There was a three minute break in between each transmission.  The transmission mode was PD180.  I leave my MMSSTV set to "Auto Mode" so I don't have to worry about trying to guess which mode the incoming signal is in.

Here are the three images I was able to pick up just by leaving my radio tuned to 145.800 MHz and the MMSSTV software running on my laptop. 




Depend the strength of the signal and how close the ISS is to being directly overhead, you can get some pretty good quality images. 

There are a couple different websites available to track the ISS and other satellites.  I like ISSFanClub.com the best.  It allows you to enter your location and get times on when and how close the next few passes will be.

I'm not sure how often they transmit SSTV images; but I plan to keep and an ear to the ground for them while I play with MMSSTV on some of the HF bands.

Here are some of the HF frequencies used for SSTV:

70 cm: (FM)
430.950 MHz SSB SSTV Call Freq.

1.25 meters: (FM)
223.850 MHz 1.25m Band SSTV Call Freq.

2 meters: (FM)
145.500 MHz 2m Band SSTV Call Freq.
145.600 MHz 2m Band SSTV Call Freq.
144.550 MHz SSB SSTV Call Freq.

6 meters: (FM)
50.680 MHz 6m Band SSTV Call Freq.
50.950 MHz SSB SSTV Call Freq.

10 meters: (USB)
28.680 MHz 10m Band SSTV Call Freq.

11 meters: (USB) Outside US Only
27.700 MHz France, Australia
27.420 MHz Australia
27.235 MHz Northern Ireland

12 meters: (USB)
Every day 24.975 MHz

15 meters: (USB)
21.340 MHz 15m Band SSTV Call Freq.

17 meters: (USB)

20 meters: (USB)
14.230 MHz 20m Band SSTV Call Freq.
14.233 MHz 20m Band SSTV Call Freq.
14.240 MHz Europe SSTV Call Freq.

30 meters: (USB)
10.132 MHz - Use narrow mode MP73N

40 meters: (LSB)
7.033 MHz 40m Band SSTV Call freq.
7.171 MHz 40m Band SSTV Call Freq.
7.171 MHz Europe DIGITAL SSTV Call Freq.
7.040 MHz Europe SSTV Call Freq. (7043)

80 meters: (LSB)
3.845 MHz 80m Band SSTV Call Freq.
3.730 MHz Europe Call Freq.
3.733 MHz Europe DIGITAL SSTV Call Freq.

160 meters: (LSB)
1.890 MHz 160m Band SSTV Call Freq.
*Source:  Amateur Radio Wiki

Making A Second 30-Ah Battery Box!

Last weekend I started building a second 30-Ah battery box to power my Yaesu FT-857D. Upon completion I should have 60-Ah of battery juice when this one is connected in parallel to the first one.

I will hopefully be able to avoid any of the earlier headaches I encountered with the first one and employ some lessons learned; primarily, the addition of a 25 amp fuse holder.

Here's where I'm at so far.  I've got the rear chassis mounted PowerPole connections in place and tested.  This will be where this box can be connected either in parallel with the other battery box or to the yet-to-be-completed solar panel setup.  The picture above is of a test fitting of the front PowerPole connection after roughing-in the holes for both the front and back panels.

The boxes were purchased from Northern Tools and Equipment.  They are made to look like plastic versions of US military ammo cans.  They are considerable lighter and have tabs on the bottoms and notches on the tops to make the stackable.

More to follow...

Thursday, September 4, 2014

Finished Up the Battery Box!!

Over the Labor Day weekend I was able to get the front set of PowerPole connections wired.  I had an air conditioning meltdown at the same time so I actually got an extra day to work on it yesterday and it only cost me $1150!!


The above picture is of the front set of PowerPole connections and the volt meter connected to a test battery.  Wiring in the toggle switch is really simple so I combined most of these parts into one segment in my soon to be released YouTube video.

The only setback in the whole project was when it came for final fitting and testing.  The wires coming off the PowerPole jack and the toggle switch stick out too far for me to get four of the 10 Ah SLABs in the box.  I didn't want to put unnecessary stress on the wires so I took one of the batteries out giving me a 30 Ah set.  That's still a good bit of power with which to operate.

I still need to make some cables.  I want to make a 6' extension cable to go between the battery box and the radio.  I still need to make a longer one, 20' or more, to run from the charging point on the rear of the box over to the charge controller for my 35W foldable solar panel.  I'd also like to make one to go from a vehicle electrical system (most likely the battery) to the charging point. 

I'm currently doing the post-production work on the YouTube video.  As soon as everything's ready I'll post it and add a link here.

On to the next project!  I'm thinking either getting the foldable solar panel  ready to use or maybe a 6m - 80m end-fed antenna.

More to follow, out!

Monday, August 25, 2014

Shameless Plugs and Product Endorsements!

There's one thing that I want to say about the products and components mentioned in all my blog posts.  I do not get any sort of kickbacks from anyone for mentioning their products or services.  I'm not going to sugar coat my assessments.  If a product rocks I'll say so.  If it sucks you can bet your ass I'll say that too!  :)

One of the nifty little gadgets I have found that falls under the "Rocks!" category are these little Traffic Light polarity checkers.  I bought mine off evilBay!  I've already used them on this project to test my wiring and will keep using them anytime I'm playing with wires and electricity!

One would think that red-to-red and black-to-black on Anderson PowerPoles would be pretty simple, right?  The very first time I connected a battery to my Yaesu FT-8900R I crossed them, red-to-black and black-to-red.  As you can guess, I heard the "pop" then looked down at the connection in my hand and said, "Sh**!  I hope that isn't what I think it is!"  Sure enough, I blew all the fuses and the reverse polarity protection diode in the radio.  Fortunately, I had a good friend and elmer, Ed KE5UCT, who fixed it for me for free!  He tried doing it for free anyway.  I threw some beer money his way just for his time and effort.

I did shoot a couple segments yesterday for an upcoming video about the battery box project.  I've also got a couple segments for a Faraday can to protect your more delicate electronics.  It was right around 100 degrees outside so I didn't want to sit around the garage slowly roasting.  But I did; for you, my fans!  :)  Both of you! 

More to follow, out!

Saturday, August 23, 2014

Rough-In Work!

Today I took the first steps in building my battery box.  I started cutting holes for the chassis mount Anderson PowerPoles.  There's one set for in the back of the box that I'll connect to my charging source:  either my foldable solar panel(s) or a vehicle electrical system.

Rear
 
Front
Looking at the picture of the front of the box you can see the first "Doh!" moment!  I drilled the bottom set of holes for mounting the volt meter then connected a battery just to see what it would look like.  As soon as the LEDs light up I realized I'd put it in upside down!  Oh well!  That's what they make filler for!

I plan to install a toggle switch to turn on the meter and complete the circuit to power-on the front PowerPoles for use by the radio.  I just want to run all the wiring and make sure everything works and nothing burns up before putting it in the box.

More to follow, out!
 

Wednesday, August 13, 2014

Newest Project to Go With My HF Station-in-a-Box!



With my HF station-in-a-box coming online I've started looking for other, complimentary projects to go with it.  I've decided on a battery box.  The station has a power supply for operating when I can connect to the grid; but I still had to connect two 10Ah SLAs if I wanted to operate out in the wild.

At first I was looking at Pelican 1200 Series cases; but those proved to be too expensive and didn't really fit the batteries I plan to use.  So, Plan B became a utility box I found at Northern Tool & Equipment.  It is modeled on US military surplus ammo cans from the look of it.


It will hold four 10 Ah SLA batteries with only a little bit of wiggle room that I can fill to make sure that everything stays locked in place.

Here's the plan as it's formulated in my head right now!  The box will contain the afore mentioned batteries connected in parallel giving me 40 Ah capacity.  I will have chassis-mounted Anderson PowerPole connections on the front and the back.  The front set will be to connect the battery box to the system and the back will be for connecting to a charging source (foldable solar panel or automotive electrical system.  I also purchased an LED volt meter that I saw in one of K7AGE's great videos!  I'll also install a simple toggle switch between the volt meter and the battery.  Keep in mind that this project will evolve as I go along.

I also plan to post YouTube videos to my channel.

Feel free to offer any comments or helpful advice!  It doesn't mean I'll follow it...just that I'll listen to what you have to say!

More to follow, out!