Static Arrestor for Amateur Radio Antennas

I live in an HOA. While I’ll not argue the pro’s and con’s of living in an HOA, it’s been a struggle to get any kind of HF antenna installed. However, I came up with a great solution.

In my backyard about 75 feet away from my shack I have a 31′ vertical antenna and it has been my go-to antenna for HF. It’s 31′ of telescopic fiberglass, ground mounted, with a a 14g stranded copper wire down the middle for the antenna. At the base of the antenna at the mounting point I have an 8′ ground rod driven into the great (not so much) Phoenix soil and about twenty buried ground radials of various lengths. With the vertical and the ground radials I get a resonant match on 40 meters (7.150 Mhz) and SWR < 1.5 across most of the band. I added a 200W remote antenna tuner at the base and with the tuner I can operate 80-10 meters with SWR < 1.7 in most cases. It's a great antenna and it has served me well for many years.

Now the bad part. Every so often the antenna tuner would die. And most every time I was not operating when it did. It would work great one day and then not work the next day when I tried to tune. In Phoenix, 115F temps in the summer are common. The tuners I run are in a black case and back all day in the hot sun so for years I figured that exposure just wore them out and there was little I could do. I even put a fake rock over one but it still died. So I switched to another vendor's tuner and it died after a while as well. Again, I just thought it was the heat and it always seemed to die in the summer months.

As you can guess, replacing a $300-$400 tuner every year was not going to continue. While thinking of creative ways to cool the tuner one summer day I went to plug the disconnected antenna wire into the tuner feed point. When I grabbed the antenna wire I got a nice electric "zap".

Ah Ha! You see, Phoenix is a dry. For a majority of months, humidity is non-existent. And on the days when it's hot, and dry, it's also windy. The easiest way to experience Phoenix heat/dryness would be to point a blow dryer at your face all day. Heat + dry + wind also provides the perfect conditions for static electricity. If you take a fiberglass antenna, put a plastic coated copper wire inside, and then on a dry day let the wind shake it all around... you've basically got a static generating machine. The little microcontroller and electronics in my antenna tuners never had a chance.

But how do you fix static? In my case, you can't. But I can stop it from building up to electronic "killer" levels. You just need something to divert the static to ground AND not the antenna setup. We'll some research lead me to two options. 1) A DC shunt to ground such as a RF choke or 2) a high value resistor.

RF chokes work great. The provide a great DC path to ground and are fairly immune to any high voltage. The problem is that they typically work at only one frequency. That doesn't do any good when I have a multiband antenna. I could wind a very high choke on the order of 10uH or more but I discovered that upon doing so it became resonant at certain band segments. Changing the winding caused the resonance to change but when I cured one band, it hurt another. It would have been possible to do a custom winding with special spacing and get it to work on all the amateur bands but I don't have the time nor the patience to figure that one out. Too complicated.

So a resistor it is. Static is mostly a voltage component. There is very little current. So a resistor high in Ohms can be used. Something on the 1M Ohm or higher scale works. It has to be RF friendly so no wire-wound resistors. I started to some searching and ran into an article by AD5X Phil Salas, who also has similar static problems. Following Phil’s suggestion a thin metal film resistors is what I needed. They are RF friendly, have high voltage values (important as static is high voltage), and come in mega ohm values. After some searching I found a 5 mega-ohm 10kV 3W resistor that is perfect for the job. I also found some 50 mega-ohm 14kV 3W resistors as well. Following Phil’s advice I can run 2 of the 5Mohm resistors in series for 10Mohms or 4 of the 50Mohms in parallel to get around 12Mohms.

So I have installed a shunt-to-ground from the antenna terminal to my ground rod using the 4 parallel resistors (my choice) for 12Mohm 14KV 3W of static bleed. I’ll report back after they have run through a Phoenix summer and had some static torture.

73 !

AD9850 Daughter Board for the Arduino by WB4CHK

A lot of people have been contacting me about my Arduino and AD9850 VFO project. I never knew DDS VFO’s were so popular! Go figure? Anyways… I digress!

A couple of days ago Dave (WB4CHK) contacted me with a few questions. He was on a quest to build a daughter-card that would plug in as a shield to the UNO. After a few back-and-forth items Dave finished his project. Rather than let me explain I’ll just post what he sent me below:

Hi Rich: I finished the Sig Gen board and it works great. The board plugs into the UNO, I hate batteries so I added a 5 volt regulated supply for the board and a 9 volt regulated supply for the UNO. Might be overkill but I can hook it up to my 12V+ bench supply and run all day. The outputs are the two 2pin connectors just below the 9850 module. The one on the right is sine wave the one on the left is connected to the square wave output (if it is ever added).

He also sent over a few photos of the finished unit. Pretty cool! Note: You won’t see the Arduino in any pics but it’s there. In fact, it’s underneath the board in the 3rd picture.

Dave has been so nice as to also provide the design and schematics he used to create his PCB. You can download the PCB design’s here. Using a laser printer and the toner-transfer method you should be able to duplicate Dave’s work. If you have any questions Dave gave me permission to post his email so go ahead and send him a note: Davewb4(at) Obviously replace the (at) with the @ and you’re on your way.

InstaMorph Antenna Repair

I have been using a music stand to hold my SuperAntenna MP-1 for some time. With the music stand “tripod” base I get the antenna feed point up off the ground a few feet and also I end up with elevated radials. You can see the stand in use in this video at about the 4:30 mark.

I was never very happy about the down-and-dirty way I attached the antenna to the music stand.  I basically used an old CB style mount and just clamped it to the metal stand.  See the ugly mess below.SuperAntenna MP-1 Antenna MountAll week I kept trying to thinking of a better way to mount the 3/8×24 SO239 adapter to the music stand.  You notice above that I also have a wood stick between the mounting plate and the metal tube.  This keeps them electrically separate (non conductive).  I didn’t want the stand to be a part of the antenna counterpoise… or at least directly a part of it.  I had some great ideas but everything I came up with was just too complicated.

Tada!  I remembered my InstaMorph.  So a little hot water and a small handful of pellets turned into a just the mount I wanted.  Since I use this QRP and outdoors every ounce of weight reduction really helps.Picture 138You can see the size difference between the two.
SuperAntenna MP-1 Music MountI still have a couple more items to fabricate to finish the project but I like where it’s going.  I just need to drill another hold and use a screw to attach it to the music stand base.  Fairly simple.

If you haven’t tried InstaMorph you do a search on YouTube and check out all the great thing you can do with it.  I’m not involved with them in anyway but just love their product.

Nothing Beats A Good Antenna

I just got back from Hawaii and some QRP operating. The antenna that I wanted to bring with me never made it and I ended up running just a random wire with a tuner. Not the worst setup but definitely not the best. I figured that being close to the saltwater would make compromise antenna an ‘OK’ antenna. WRONG!

Result = only 6 contacts for 2 days of operating.

…. more details and a video to come soon.

Operating Portable from Hawaii

My wife and I are going to Hawaii for a week so I am going to bring along my QRP station and do some radio while away from home.

Hawaii presents an interesting challenge.  I’d love to take a full 100w rig and full size antenna along with me but weight and size make it an impossibility.  Besides, I am supposed to be on vacation and taking it easy… not struggling along with radio gear.

My portable setup is fairly simple. I’ll use my FT-817, Elecraft T1 tuner, some long spools of wire to setup either a dipole or an L, some coax, and extra NiMH batteries.  I am able to pack just about everything into a little carrying case I found at a discount store.Portable SetupI’ve used this setup before.  You can watch it here.  In fact, I am going to the exact same beach again.  With a little luck I’ll be able to make some nice DX contacts.  Hopefully the location will make it easier to get into the South Pacific or something exotic and beyond what my home QTH DX has turned up so far.