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High SWR from XB8000 AIS


High SWR from XB8000 AIS

by rcassano » Sat May 21, 2016 9:13 pm

I have the following equipment in my VHF radio system:

Icom M506 (N2K only model)
LMR400 coax from mast to radio splitter (New with factory made PL259 at masthead)
Vesper XB8000 AIS
Vesper antenna Splitter
Vesper AIS/VHF antenna at masthead, (159.0 MHz center) New

Since my mast was down last winter I replaced the coax and antenna using the professionally installed PL259 at the masthead and making my own connection at the base of the mast. Coax continuity was tested before raising the mast and it checked out ok. My XB8000 is two years old and worked well when the boat was hauled last fall. Last year with the old coax and a very old GAM VHF tuned antenna the SWR was 1.5. With the new equipment the SWR is 3.1.

As a simple test, I pulled out the old GAM VHF antenna and connected it directly to the XB8000 AIS with a short jumper cable. This left out the new LMR400 coax the splitter and new AIS tuned antenna. The SWR on the XB8000 was still 3.1. If my problem was at the masthead I would expect the SWR to be near perfect with it eliminated from the reading.

From another post on this forum (2013) with almost the same equipment and complaint I’m beginning to believe the SWR readings from the Vesper AIS are not to be relied on.

Can I assume the problem is in the XB8000 AIS unit or its firmware? Has anyone ever compared the accuracy of the Vesper SWR readings with a good VHF SWR meter? Any suggestions are much appreciated, thank you.

Rich Cassano
Richard Cassano
S/V Gray Eagle, Tashiba 40
Annapolis, MD USA
Posts: 27
Joined: Wed Jun 20, 2007 7:33 pm
Location: Annapolis, MD USA
Vessel Name: Gray Eagle
Vessel Make and Model: Tashiba 40

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