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 !

Yes. It’s still going

It’s 2021 and that’s great. 2020 turned out to be a horrible year for obvious reason.

As for this site… I guess it’s time to update a few things and be more productive. The DDS VFO project still garners a lot of people and maybe a few new projects I have in mind will make it to this blog. Who know? Till then, 73!

Yes, No, and maybe!

Yes. This website and the project pages are still active. No, I don’t have an update on the VFO upgrade. Maybe this Summer, when I have some more time, I’ll get to posting the latest version I have been working on.

In the meantime… THANK YOU VERY MUCH to all who visit my site, try one of my projects, and send me a note about. I appreciate it.



More than two years ago I posted a project to this site detailing how I took a little DDS unit I found I eBay and controlled it with an Arduino UNO and LCD. The result was a very simple and stable VFO that just about anyone could build. It was also dirt cheap to replicate. I posted the code, put up some horrible schematics, and let it sit. I never thought much of it.

Little did I know that so many people would be interested in what I had created. I’ve been contacted by a lot of people, sent a lot of pictures of users units, helped a few people trouble shoot some issues, and even got published in a few books. What I do get the most is questions. A lot of questions. So to fix repeating myself a lot on emails here are some of the most popular email questions I get about the AD7C DDS VFO.

Q: Does it work?
A: Sure does. 200+ people have contacted me thanking me after they build the same project.

Q: I get an error on compiling. Something about “rotary.h not found?”
A: You did not import the rotary library correctly.

Q: Do I have to pay you if I build this?
A: No, but you can always donate to via PayPal if you wish. I’ll be extremely thankful!

Q: I wish it had THIS feature or THAT feature. Can you add that to the code and send it to me?
A: I could but what would be the fun in that? Learning coding is part of the fun so open up the Arduino code and give it a try yourself.

Q: Can I use any rotary encoder or does it have to be the same model you used?
A: So long as the rotary encoder outputs gray code you should be OK but I can’t guarantee that.

Hopefully that helps quickly answers some questions. I am working on a new version of the code. Nothing special but I am cleaning up a few sections. I don’t like that I have two versions of the code (IF and NON-IF version) so I am combining them into one and allowing a simple code change decide which way the user would like it to function. That and a few other improvements. I’ll post when I am done. Don’t worry… it will be 100% compatible with the existing schematic so no changes there.

Go melt some solder.



DSS VFO Update – Last Frequency Saved in EEPROM

I have updated the code to my Arduino DDS VFO sketch so the current set frequency is stored in EEPROM and recalled again upon boot-up. The code is 100% drop-in compatible with the old code and no re-wire is required. Simply upload the new sketch and your done. The frequency writes to the EEPROM after 3 seconds without changing. This was required so as not to overload the EEPROM as there are a finite amount of writes (100,000) before it may go bad. You can alter the delay time in my code as it is well documented.

View the entire project page for more details. If you have additional questions… just ask!