AIS Antenna Troubleshooting - Poor VSWR possible causes?

[Tessellate]

Is there anything else I can do to troubleshoot AIS antenna issues?

I got a VSWR meter and it said I have bad VSWR, which isn't very helpful actually since I already knew that from the Raymarine AIS software's report (images attached). But the meter confirms the Raymarine reading is correct. I also bought a dummy load to test the Raymarine AIS-650 unit, and that tested perfectly (1.01 VSWR, 2.22 watt) so the issue isn't with the AIS unit.

This is my 2nd Shakespeare AIS-5250 antenna. It's a dedicated stern mounted AIS antenna.

• I've replaced the connector 3 times, with 2 types of PLB-259 connector.
• The 1st antenna had VSWR issues. The 2nd antenna (brand new) worked for 2 months, then had VSWR issues.
• The antenna, cable and connector look perfect, undamaged, and dry.
• One new connector worked for one day with 2.0 VSWR (still not perfect) and then deteriorated to 4.0+ VSWR.

Shakespeare hasn't been helpful with tech support. They've offered a warranty return but never connected me to anyone technical to help troubleshoot. I don't want to keep replacing the antenna though if that's not the issue.

Is there anything else I can test / look into? Shakespeare said electrical interference would only be an issue within 3' of the antenna itself. I don't have any wires there, and my Starlink is 3' away.

The weird thing is how the new antenna worked for a while and then started emitting high VSWR errors. The AIS still works for receiving and transmitting (but with reduced transmit range) but emits annoying recurring beeping alarms on our Raymarine chartplotter, which can't be permanently disabled.

[Wotname]

The problem will be the coax or the connectors or the actual antenna. To isolate, insert the VSWR meter at various points in the transmission path.

Usually start at the output of the transmitter and finish at the input of the antenna. Use the 50 ohm dummy load as required.

[Tessellate]

Originally Posted by Wotname

The problem will be the coax or the connectors or the actual antenna. To isolate, insert the VSWR meter at various points in the transmission path.

Usually start at the output of the transmitter and finish at the input of the antenna. Use the 50 ohm dummy load as required.

Yes, but the antenna has only one connection point and I've already tested that with the VSWR meter and redone the connector 3 times. The antenna comes with an integral RG-58 coax cable (ie, no connector at the antenna side) and I was careful not to twist that upon install.

The connector I've redone 3 times could be the culprit - the first time I might have done a bad solder job. So the next 2 times I used a Shakespeare PL-259-CP-G solderless connector. One of them initially worked, but then deteriorated. So I'm not sure how to determine if the connector is at fault or not. At $15-20 a pop, these connectors are getting expensive...

[wholybee]

It is very easy to poorly install connectors, and there are also quite a few poorly made connectors. Symptoms are of course high VSWR, and often don't show up right away. I often recommended that boat owners seek professional help to install the connectors and coax for this reason. It isn't that a skilled person can't figure it out and get it right, but often they won't and will believe they did a fine job.

Shakespeare connectors aren't usually very good. The screw on are the worst of the worst.

Amphenol is a good brand:
https://www.mouser.com/ProductDetail...Gdh2U1MQ%3D%3D

[Statistical]

So the next 2 times I used a Shakespeare PL-259-CP-G solderless connector. One of them initially worked, but then deteriorated.

To be blunt those are absolute garbage connectors. It working initially and then going to **** is pretty typical for these low quality screw on connectors.

The gold standard for connectors is soldered both the center pin and the shield. However it is very tough to do it right. You also want a large heavy soldering iron because you want a lot of thermal mass. Most boat owners simply never get the amount of soldering skill required to be consistently good at that and they don't have the right tools. The shield is the hard part. Honestly I would just drop this from consideration unless you already have exceptional soldering skills and equipment from non-boat work.

One step below that is a combination solder and crimp. The center connection is soldered and the trickier shield is crimped into place. It is easier for those with less soldering experience to consistently get a good connection using this type of connector. You might need to do a practice run on a test cable but most people with a little effort can make a solid connection.

One step below that and likely the best option for a DIYer with no soldering skills is all crimp. While an all crimp connection may not be the gold standard it is easier for a DIYer to consistently produce a "silver" standard result. With solder even just center pin solder results are a lot less consistent. The downside is these connections usually required a braided center core which is uncommon on boats.

8000 steps below that is any screw on connector from any brand ever made since rf became a thing. They are just ****. Nobody anywhere in RF profession uses them for anything. The only reason they exist is because if brands didn't offer it they would lose sales to brands that do because most consumers just want the cheap easy option with skills or tools required.

To put comparative numbers on it in terms of connection quality
All solder - 10
Crimp & solder - 9.8
All crimp -9.5
Screw on - 0.1

[Statistical]

One thing I would add is with crimp and solder connectors you don't even need a soldering iron a butane torch will work fine.

Cut the center pin a half inch or so longer than needed. Assemble the connector and crimp the braid. You will now have a center conductor which extends beyond the center pin. Heat the wire with the torch and apply solder to the center pin. It will have a cup like shape. Once the solder runs you are done. Wait for it to cool keeping the cup facing up. Then snip the excess wire flush with the pin.

[Wotname]

I endorse the above posts about connector quality.

I'll add that a solder / clamp connector system also works well if you don't have access to a suitable coax crimp tool. The centre pin is soldered (sometimes crimped) and the outer braid is clamped (not crimped or soldered).

I suggest the Amphenol 182103 as a reasonable quality clamp connector and should be available worldwide.

https://www.amphenolrf.com/182103.html

Assembly (the link shows a BNC connector but the UHF connector is similar)

https://s3-us-west-2.amazonaws.com/c...amp-Solder.pdf