How to test SSB whip antenna after lightning strike

Brian D · Jun 23, 2017

The Shakespeare 393 does not have any loading coils. It is just a 23' conductor. So I would say that a continuity check from the tip to the base should do. Yeah, I know, where will one find 23' test leads? LOL Probably a piece of coax should do the trick for a test lead. Or any piece of wire.

The issue I have with using a piece of wire or coax is the total path is doubling and you might see some resistance. But, as long as you see either 0 or some resistance shows that a path exist. If you see a blank screen or OverLoad or something like that then the path is broken.

My concern is not the antenna but the antenna tuner. It too is probably fried if the radio is gone.

Don S/V ILLusion · Jun 23, 2017

If I may, what Brian suggests is that the whip is essentially a (stiff) 23 foot long wire conductor.
The test being to determine if there is continuity from end to end.

Justin_NSA · Jun 23, 2017

Doesn't insurance cover this? Ask for a new antenna.

There should be an input and return side where it makes the connection.

Brian D · Jun 23, 2017

geoffschultz said:
I understand this. However, it's a conductor encased in a fiberglass whip/pole. How does one measure the continuity?

Ah... sorry, thought the antenna was not encased in concrete. OK then, probably the only way is to actually use it on the air. I know that is not possible right now, but since you do not have access to the far end, there really is no way. Unfortunately you may have to wait until you get your new gear.

Now, if you want to be creative in the event the antenna is bad after you get your new gear, use a spare halyard to run some wire from the antenna tuner to the top of the mast. It is called an Alternate Backstay Antenna (no backstay required). You can also run up a dipole for the band you want to operate.

I know this is NOT what you want to do and sorry for digressing. However, until you can get a replacement antenna (if that one is bad) you can still get on the air.

Ken Cross · Jun 23, 2017

Connect the new SSB and tune in something. It should receive only if the antenna is okay. Then try tuning in the transmitter.

Ken

Chief RA · Jun 24, 2017

Brian: You have it right. He just needs to file down the top winding resin to the wire and he can still get a reading. If good, just recoat with 50/50 resin glue. Chief

Brian D · Jun 24, 2017

Under closer inspection, the antenna breaks down into three parts. Base, mid, tip. The base can be measured for continuity, as can the mid. Or you can measure both without taking the antenna apart. @Chief RA is correct that the tip can be remove and/or ground down until the wire is visible, tested, then recapped. So I suspect you should be able to do this without too much fuss, if you want. At $200+ for a piece of wire and some fiberglass, I would just go with a different/better antenna. Home made mind you. How?

Technical alert here. Don't read if you don't want to.

The specs of the Shakespeare 393 are length of 23' and resonant frequency of 10.8 MHz. That gives formula of about 75.1 / 10.8 = 7.01 meters (23 feet). This is one of two recommended lengths based on a blog by G8JNJ (this is a good read by the way). So if you wanted to, you could build your own antenna using simple, tapered fiberglass wrap. Might look ugly, but sometimes the prettiest girls at the dance are not the best dancers.

The other option is mentioned in one of my post above, called the Alternate Backstay Antenna. This is what I have (although not installed yet). It is merely a length of wire (in my case 35' long because of my mast height limitations). The antenna is made from 1/8 wire rope encased in vinyl. The connection is GTO-15 from the antenna to the tuner. Note that this length is also part of the antenna. So with 5' of GTO-15 and the 35' of antenna the total length is 40'. This antenna uses a spare halyard. I know you do not have any standing rigging except the forestay. So in reality, this Alternate Backstay Antenna can be run on either side of the mast amidship where your shrouds would be. You would want to put the antenna tuner as close as possible to the feed of the antenna of course. JMHO

SirMichael · Jun 28, 2017

I am an amateur radio operator, and also a fairly new boat owner. But I've been an amateur radio for many years, so I know if her amount about antennas . My suggestion to you would be to check the SWR ( standing wave ratio) at the antennas resonant point, which BrianD said was 10.7 MHz, but do this with the antenna tuner turned off (disabled). The SWR should be very low at the resonant point of the antenna. The test can be run with very low power.

The SWR is tested using a specialized meter which measures the forward power and then the reflected power back from the antenna to determine what the ratio is. The idea is that any of the power that does not get radiated by the antenna, is reflected back down the coax to the transmitter. The SWR meter may very well be built into the tuner ( I see where the SEA – 235 interfaces with the next external antenna tuner). Your new ICOM should have this as well.

One of my concerns is that the resonant point for this antenna is in the 10.7 MHz band. That does not appear to be a maritime frequency band so it would be illegal for you to transmit a carrier at that frequency. The only ICOM radio that I can find is the M802, which will not transmit at 10.71 MHz.

Rather than using a transmitter and SWR meter, it's more common these days to use an antenna analyzer. The antenna analyzer is a very low powered transmitter (less than 100 milliwatts) and analysis circuit built into one box that will give lots of information about the antenna. Many actually give you a graph on the screen which shows where the antenna is resonant. Mine is a RigExpert AA-600, which will test antennas at frequencies anywhere from below the AM broadcast band up to 600 MHz. There are some very inexpensive one available on EBay for under $50 (MR100, SARK100) that are available, but a don't know how good they are.

I would suggest that you check in your area to see if you find a ham radio operator that has an analyzer who might be willing to come out and help you to test your antenna.

Mike

Chief RA · Jun 28, 2017

Good job Mike! Does any of this equipment also give him a Megger readout? That would be handy as well but the SWR readings will likely make that test moot. Chief

SirMichael · Jun 28, 2017

I am familiar with the megger, we used to use where I worked to verify high-voltage isolation. They are not too common, at least in the ham radio world. Some of the analyzers will also give you the loss of the coax cable. It's not unusual for older coaxes to get leaky and have more loss.

I also think that if the SWR came out OK, and when you brought it up to full power that there were no errors, it should be OK.

Thinking about it, it might be worthwhile closely inspecting the SO259 connector at the radio. Check for discoloration at the connector (like it arced). I'm assuming the the old SEA radio was toasted.

Considering that it's being taken care of by insurance, it would not hurt at all to replace the coax with RG8X, just to make sure that there wasn't damage and reduce the loss.

Mike

Brian D · Jul 21, 2017

Good luck, Geoff. If we can help with any info or research,don't hesitate to ask. And, if you are a ham, will listen for you on 14.3 MHz (Maritime Mobile Service Network).