Ben Swayne VE7FDE operates QRP while camping in the Kamloops, BC area July 2014. Using a Yaesu 817 radio with an LDG Z-817 tuner and a "new carolina windom" off-center fed dipole.
I like camping in and exploring less travelled areas in BC. As a relatively new ham radio operator, I wanted to try setting up a schedule NVIS radio contact back to Langley, BC from the Kamloops, BC area. Quite often, a lot of commercial radio antennas and advice are designed/optimized for long distance (DX) communications for the hobbyist who gets a thrill out of talking around the world with just a little box in their house. These antennas are designed for low angle radiation that will skip off the sky's atmosphere and land far, far away around the globe.
I on the other hand specifically want to talk relatively close to home. This means I want primarily high angle radiation that will go nearly straight up and back down again to land relatively close to me compared to going around the world.
Try to visualize this like shining a flash-light in your bathroom mirror. If you skip off the mirror at a really wide angle you'll hit the opposite side of the room. If on the other hand you aim almost right at yourself, you'll be shining at some space fairly adjacent to you. Now of course instead of being in free open space, there may be a mountain between you and your destination which is why its helpful to bounce off the sky in the first place!
Near Vertical Incident Skywave (NVIS) is the radio term for trying to send your transmission nearly straight up so as to bounce back down in the semi-near vicinity of yourself (usually inside 500-600km radius or so depending on conditions). This is primarily about antenna design/setup to achieve this. Most commonly that's a relatively low dipole of some sort.
In my case I was running a "new carolina windom" off-center fed dipole. The unique aspect of the "new carolina windom" is the addition of a vertical radiator element by placing some RF chokes some distance from the feedpoint on the offcenter fed dipole. I tried with and without this vertical section and am not really sure if it really helped me for what I was doing (it was originally designed for 20m dx to fill-in the radiation pattern and is therefore a 1/4 wave on 20m which doesn't help a lot on 40m and 80m for NVIS).
Radio and Antenna Setup
Yaesu 817, LDG Z-817 tuner, Carolina Windom Off-Center Fed Dipole
This is an overall shot of the camp area including the 22' (6 sections) military surplus fiberglass mast with guy ring plates and swivel stake from GoVerticalUSA. The yaesu 817 radio is on the picnic table under that popup shade/shelter in the bottom left.
This is another shot of the 22' military surplus fiberglass mast with accessories from GoVerticalUSA, just from another angle.
This is the Antenna Swivel Stake from GoVerticalUSA. It folds over so you can hammer the stake into the ground. Then you slip on the mast section(s) and can tilt up the mast with the guy ropes. A single person could easily tilt up 4 sections of mast (~15ft) but with 6-9 secionts of mast (~22ft to 33ft) its really ideal to have at least 2 people. One person pulling a guy rope and the other lifting the mast from lower down and stabilizing it while being raised.
I had put a guy ring half way up the mast in case it need more stabilization. We had excellent weather and very little or no wind, so this went unused this time around.
But this photo also shows the unique component of the "new carolina windom" antenna design which intentionally uses some of the feed-line as a vertical radiator to fill in the antennas radiation pattern more evenly. The ferrite chokes are some 8-10ft from the 4:1 balun that is feeding the off-center fed dipole.
Just for fun we did experiment with "removing" this vertical radiator by flipping that section of coax so the chokes were at the top close to the balun. That definitely removed any vertical polarized signals from its pattern - but can't say it really helped with the NVIS propagation. I think a classic center-fed dipole will be the best way to go for NVIS in the future.
This is the top of my antenna mast setup. You can see four guy lines, 2 dark ropes and 2 bright paracord ropes. Plus the paracard going through the pulley on the guy ring. The pulley makes it easy to raise/lower the antenna if you are experimenting with different configurations (which I was this weekend).
Just another angle of the top of my military surplus fiberglass antenna mast. This shot shows the homebrew 4:1 balun and center insulator for the off-center fed dipole.
The end of the longest element on this off-center fed dipole was 85ft or so from the tower and went over the turn around area at the end of the road up here. I used two section of fiberglass mast to setup a stub end mast to support the end of the dipole element. This actually worked wonderfully! The jerry can and rocks at the base of the stub mast were just there to stabilize it while we tied on a few guy ropes. Once the guy ropes were on it was VERY stable. For example if one were to drive their camper trailer through the antenna, it would not fall over (of course tested in a totally safe and intentional fashion).
A little closer shot of the stub mast supporting the end of the longest dipole element. Note there is no guy ring on these poles. I just looped the rope providing tension to the dipole element over the top of the fiberglass mast and then ran it down to a stake in the ground. Then my buddy and I ran one paracrod perpendicular in the same fashion, looping a circle over the top and staking both ends. Once guyed/staked it was very stable. I was actually a bit surprised.
When I first saw these military surplus stakes, I thought they were kind of a dumb design. Now having used them they are pretty nifty! The ears allow you to run a quick figure-eight of the top to temporarily hold the rope. This is particularly helpful when you are trying to get your fiberglass mast nice a vertical on uneven ground. You can temporarily set a few guy lines and then go making a few small adjustments to get your mast truely vertical.
This is the radio setup on the picnic table. A yaesu 817 with an LDG Z-817 antenna tuner running off a 12v 7ah gelcell. This portable radio kit belongs to Gethin VA7GTE who kindly lent it to me for a weekend. Thanks Gethin!
This map shows my results. I plotted them on a google map to see where my antenna was reaching. I had intended to contact a few friends in the Langley, BC area and so had setup my antenna to favour the west. From my results, I think I had my setup pretty good.
That said we never did get a solid contact with any of my friends in Langley, BC. But I'd like to think I can blame that on their end. :-)
The two stations I tried here in Langley were both sub-optimal for what we were trying to do. The first station was running a portable vertical antenna with no ground radials - really not great for NVIS communications as it will be primarily radiating low angle and also because it is vertically polarized and my dipole is horizontally polarized which results in significant mismatched polarization losses. Couple those polarization losses with my QRP low-power output and its really just too much working against us. I did hear him calling me though, although he was probably putting out 50-100w from his mobile station.
The second station I was trying was experimenting with both another vertical antenna (unsuccessful for same reasons above) and a long wire antenna with a 9:1 balun. The long wire antenna was getting something out, but again he probably had 100w to play with. We will try again in the future with a little more time to properly design/build some tuned dipoles for 40m/80m!
Despite all my blame on the vertical antennas, I must admit I didn't read the full manual for the yaesu 817 and was accidentally only transmitting 2.5w when I could have been transmitting 5w. Yaesu's weird power indicator goes from L| at 0.5w, to L|| as 1w, to L||| at 2.5w and then a blank or absent indicator is 5w! That's not very intuitive to me... I thought more bars = more power. Oh well lesson learned!
This was my first time operating HF portable and my first time setting up a portable antenna mast like this. So I wanted to take the time to document a few lessons learned or other tips and tricks picked up from this experience.
Get Velcro tie wraps instead of zip ties. Zip ties are cheap and very effective but a pain to remove safely without damaging the antenna or feedline and make quick changes to the antenna difficult. We were experimenting with the carolina windom antenna by removing the vertical radiator component or flipping it so the chokes were close to the 4:1 balun, changed the wire lengths, etc. These changes can be done in 1 or 2 minutes each with the combination of the pulley on guy plate from GoVerticalUsa and using Velcro tie wraps instead of zip ties for cable supports or wire supports, etc. Don't get me wrong, always keep a few zip ties around for emergencies, but Velcro straps should be a part of your portable kit bag.
For guy lines, bring separate "tree anchors". Yes, you can always just take your 50ft rope and wrap it around the tree and tie off, etc. But that is harder and slower in real life than you think. There are bushes and twigs and low hanging branches in your way. And you don't want to drop your antenna mast while trying to tie off. A short length of rope around the tree with a carabiner on it to tie off the main guy line will make you a happier person for both setup and take down ease, safety and convenience.
Put Anderson Power Poles on your radio power leads even for a portable QRP setup. The power leads on this portable go-kit were setup with flat tabs to connect to the 12v gelcel. Once I had drained one battery dry and was switching it, I remember that I had a spare 12v deep cycle battery on the camper trailer that I wasn't using. Would have been nice to just pop on a set of large alligator clips or large ring terminals and put that spare deep cycle battery on the trailer to good use! I'd say every portable kit should have the cables made up to connect to a 12v gelcel, a car battery (alligator clips), a deep cycle battery (often via ring terminals on a bolt) and a cigarette lighter accessory socket. That set of 4 ends would really give you a lot of options for making use of unplanned field expedient back-up power.
If you plan to experiment with different dipoles, a nice easy way to attach and remove dipoles elements would be handy. I'm going to try and figure something out like this when I build my own. Perhaps screw terminals for the dipole conductor ends and plastic carabiners for strain relief on the dipole which clip into an eye bolt or something. This may also help make setup/take-down/packing/storage of portable dipoles easier than trying to wrap the whole thing (this is harder when in less than ideal environment like bumpy sage brush ground where wires get tangled/caught particularly the longer ones).
Consider Digital Modes when operating QRP! PSK31 uses such a narrow bandwidth that your 5w QRP station can reach that much further. I didn't have the time to plan for this trip, but an iPad and keyboard with a small isolation interface cable would have been fun to try.
Overall I had fun and learned a few things. Gethin and I may give NVIS another go after we've had time to build a few proper 40m/80m dipoles.