Welcome to the new FlexRadio Community! Please review the new Community Rules and other important new Community information on the Message Board.
If you are having a problem, please check the Help Center for known solutions.
Need technical support from FlexRadio? It's as simple as Creating a HelpDesk ticket.

Antenna Disconnector Prototype

Hi all,

On May 30th, 2020 my residence took a very near lightning strike that took out my SPE 2K-FA amp and my Palstar HF-Auto tuner. My 80 meter loop remained intact so I know the strike was not directly to the antenna, but perhaps the power lines. The exact strike point is unknown but I did suffer the loss of quite a bit of equipment, not only ham radio equipment but also network switches, printers, WiFi, TVs, etc.

Before this strike happened I wanted to build a disconnector but it kept getting pushed back. Currently I am in league with a really good mechanical design person and we are designing a disconnector that we can sell as a kit. I'll keep the world aware of if we can get something working and affordable.

In the mean time I wanted to prototype some ideas. Since I am pretty confident my equipment loss was due to power I wanted a disconnect system that could disconnect both 110V AC and 220V AC.

I searched all over the place for good connectors to use for this purpose and they may exist but I have not found them yet. So I came up with an interesting solution.

For not much money on Amazon you can by knife switches. Big ones that handle 100A. All I needed to do was to come up with a way to engage or disengage the knife handles.

So the link below shows my prototype in action. The total cost of this prototype is about $350. The linear stages can be purchased from Amazon with a stepper motor attached for about $190. The knife switches were $30 each.

I used home switches that I had laying around. I purchased some nice adjustable linkages to connect the knife switches to my movable bracket. I had a friend machine the bracket for $50.

I removed the stepper motors provided on the stages and used much nicer and yes more expensive servo motors from ClearPath. The benefit of these motors is they generate a lot more torque than a standard stepper and the models I have offer a two point move profile using digital inputs. So I simply have to supply +24V to an input and the motor moves to a programmed position. Remove +24 and it returns to the prior position. Perfect for this use. These motors cost about $700 total for two motors.

Again you could probably do this with the provided steppers and a controller but these motors I had available from a prior project.

My plans for implementing this prototype is to power it from a 24V battery that is trickle charged. This way even if A/C power is lost I can still get the disconnector to move. I plan to use a Digital Loggers web relay to control the motors and send them to/from the stored positions. I also plan to just run a cable to a 3 watch switch and mount it on the way. So I can either use the computer and connect/disconnect or just throw the switch on the wall.

The reason I included the knife switches is as I said above I believe most of my damage came in through power. So the knife switches will be used to completely disconnect 110V A/C and 220V A/C from the gear.

My network switch is a short fiber link so I figure when disconnected there will be nothing connected to radio gear or amplifier at all. No antenna nor power.

Now realistically speaking if my house takes a direct hit then probably all of this becomes a pile of melted slag and that is when insurance kicks in to bring the world back to normal hopefully. But for the passing thunderstorm I am hopeful this disconnect system will provide more protection for my gear than I've had before.


Comments

  • AlanAlan Member ✭✭✭

    Mark

    Sorry to hear about your loss.

    The utility power entering your home is very prone to surges from lightning strikes. In addition to disconnecting your 240 VAC to your ham equipment, an alternative, or in addition, would be to use a "whole home" surge protection system, such as:

    Regarding disconnecting the RF and RF ground to your rigs, K50Z was working on a similar concept. His post can be found on this community.

    Alan

    WA9WUD

  • Mark_WS7MMark_WS7M Member ✭✭✭

    Hi Alan,

    I think the square D approach is certainly one I will take. Going to look into it.

    This prototype does not ground, that is designed into the "real"version which will ground the radio side of things.

    Thanks for your reply!

    Mark

  • AlanAlan Member ✭✭✭

    Mark

    As an aside, if your radio's metal case is connected to the "Utility Safety Ground", as it should be per code, you do NOT want to ground the radio side of the coax to the same ground. Doing so will create a parallel path for AC fault current and/or phase imbalances ( lighting surges) to flow thru your radio's RF section. You should only ground on the antenna side of a disconnect.

    Alan

  • Dave K5OZDave K5OZ Member ✭✭
    edited January 12

    Alan,

    Thanks for referring to my project!

    Mark,

    Great design; however, with the metal “disconnect apparatus” the lightning current will flow from your antenna/ground through your rig ground to the utility ground. This current path is what takes out most radio equipment during a lightning strike.

    See my post and the latest “Lightning Rig Saver Version #2” here at the bottom of page 1: https://community.flexradio.com/discussion/8023405/remote-operations-lightning-rig-saver/p1

    Dave,

    K5OZ

  • Mark_WS7MMark_WS7M Member ✭✭✭

    Alan,

    I've not designed the "grounding" part yet fully. As it is designed it can fit on either side of the real device.

    Dave,

    When separated there is ZERO contact between the grounds or the centers of the coax. Granted I'm using metal in this prototype I've tried to make sure there is not a conductive path. In my real design the linear stages have more separation and are mounted on Delrin. But final design is a ways off.

    This prototype was to get something working until real parts can be machined and also to play with the knife switch idea.

    Mark

  • Dave K5OZDave K5OZ Member ✭✭

    Mark,

    Your design will work...just remember that your weakest link will be air. Air has a breakdown voltage of approximately 3kv/mm. Care must be exercised between the antenna, its ground and anything metal close to it that is also attached to your rig. You will not be able to use a metal drive **** or rack anywhere near the antenna connectors without suffering from the air weak leak link.

    73,

    Dave

  • Dave K5OZDave K5OZ Member ✭✭

    Mark,

    Your design will work...just remember that your weakest link will be air. Air has a breakdown voltage of approximately 3kv/mm. Care must be exercised between the antenna, its ground and anything metal close to it that is also attached to your rig. You will not be able to use a metal drive **** or rack anywhere near the antenna connectors without suffering from the air weak leak link.

    73,

    Dave

  • Mark_WS7MMark_WS7M Member ✭✭✭

    thanks Dave, I do understand that. I figure this concept will be good for near strikes and large static build up only. Any direct strike is probably going to melt everything to slag.

    I have a friend in florida that disconnected both power and coax during a large storm then suffered a direct strike to the antenna. The coax pretty much melted the entire way and become one big ground lead. He had about 2 feet between where he laid the coax and the radio connector. You could see a huge arc burn across the table to a near by wall plug. The radio which was disconnected and not powered was still damaged and would not startup.

    I know that commercial stations, and I worked briefly as an intern at a marine broadcast station, have very sophisticated lightning measures in place. Unfortunately the costs are somewhat beyond my means to do anything like that. Also living in an HOA we are prevented from putting up lightning rods which I find very surprising.

    This unit in the video is a first pass prototype. There is not enough separation between the two metal stages and certainly any direct or maybe even very near strike is going to cause problems with this current unit.

    I am intrigued by your design and project and one day I hope to have access to a good 3D printer and I would probably go more your direction.

    In the interim my plan is to use a large sheet of Delrin, the two stages would be mounted more like 6 inches apart and the connector holders would overhang by like 3 inches so when the stages were driven forward to their limits connection would be made.

    The next gen unit also has a grounding feature so when the stage is retracted the antennas can be grounded if desired.

    As per the recommendation from Alan above I've purchased a whole house surge protector. I'm hopeful it will help some with the event I had on May 30th. That event, as I mentioned, did not hit my antenna, and to date I still don't know exactly where it hit. But it appears to have done damage via electrical power inlet. We lost a TV, 2 consumer WiFi access points, several LAN switches, a wireless telephone or two, a color laser printer and the list goes on including my SPE 2K FA amp and Palstar tuner.

    Surprisingly in that event my Flex 6600 which was connected to the amp at the time and powered on survived just fine. This further makes me think that the issue was A/C power related. I cannot explain the Palstar tuner as it was powered from D/C but maybe since it was the first line on the antenna it got enough from that inlet to **** it.

    I've since replaced the antenna balun with a brand new one, replaced the antenna wire (its an 80m loop) and the SPE amp and Palstar have been repaired.

    The incident was very odd. The storm was very intense with lots of hail and lightning and at the time my gear was in an outside shed. We were outside pulling my wife's flowers back under the deck to save them a little from the hail and I said, I'm going to go and pull the antennas from the amp. I started towards the shed and there was a lightning strike so close it was a simultaneous "flash boom" and we both headed inside. It was **** to try to save the plants and we learned a lesson on that.

    Inside I walked upstairs to a sliding glass door in our great room as was watching the hail build up. My wife was behind me and we noticed an orange glow appear then another very bright and loud flash boom. At the same time I saw sparks around the sliding glass door.

    We smelled burned electronics and the TV was showing hash. We waited until the storm passed and I began to check things out. The WiFi access point had provided the burned smell. Resetting the TV didn't work but other TVs were receiving just fine. I went down to check the radio gear and found the Palstar dead and the SPE amp going crazy. I checked the flex radio and it seemed to be fine however. the network switch it was plugged into was gone.

    I went out and looked at the 80m loop and it was still up! I walked around the yard trying to find any indication of strike point and I never found one. Someone suggested a corona discharge. I have no idea. But it took out a nice pile of equipment and cost me like $600 to get some things repaired in the ham world.

    After telling my friend about this he forwarded me the info from the guy in florida and I quickly came to realize that I'm not gonna be able to do anything to help a direct strike. in town here about a year earlier a house probably 5 blocks from us took a direct strike on the chimney. The top half of the fireplace was removed and ended up almost 600 feet away and the house caught on fire. The home owner reported that EVERYTHING inside the house, electronics wise was a total loss. Ovens, frigerators, toasters, phones, cable TV, TVs all gone. Absolutely NOTHING worked.

    So after reading of these incidents I've set my sights on doing the best protection I can within budget and I will purchase insurance to cover the direct strike. But I see this project as an evolving learning process. I know my gen 1 proto is farm from optimal, gen 2 will be better and maybe gen 3 and so on.

    I am going to study your project as I think you have some very good ideas!

    Mark - WS7M

Leave a Comment

Rich Text Editor. To edit a paragraph's style, hit tab to get to the paragraph menu. From there you will be able to pick one style. Nothing defaults to paragraph. An inline formatting menu will show up when you select text. Hit tab to get into that menu. Some elements, such as rich link embeds, images, loading indicators, and error messages may get inserted into the editor. You may navigate to these using the arrow keys inside of the editor and delete them with the delete or backspace key.