AIS and VHF Performance

[fairbank56]

The information about the LOC/DX switch is from the operators manuals, but hey, what do they know? Your the expert, you could rewrite the op manuals and the theory books. I don't think that the average boater is concerned about protecting his radio's front end or even knows that it has such a thing.

[continuouswave]

Originally Posted by Goudurix

Because of interference caused by my Raymarine 250 AIS receiver & antenna splitter on several marine VHF channels, I was forced to set up a dedicated AIS RX antenna, [regardless] of eventual loss....

Jan
ON3ZTT

Thanks for that interesting report. When you operate two receivers from the same antenna, it is possible that their various oscillator signals could be mixing together and creating some new spurious signals. This situation is another reason a splitter is generally used. The splitter acts to keep the two receivers isolated from each other. However, in your case, apparently not well enough. Also, perhaps there was some active circuit in the splitter that was also contributing to the creation of interference.

Jim
K8SS

ASIDE: Readers who find the discussion too technical should switch to another forum and read about the best anchor to use. :-)

[Goudurix]

Jim, to clarify: I had the interference only using the splitter with masthead antenna as shared antenna and Icom M80 marine VHF fed through the Raymarine AIS 250's splitter. The marine VHF tcvr and the Ray AIS 250 are only about 35 cm away from each other.

Both fed with their own dedicated antenna: no interference at all.

Since I have no interference when using the FT897 as receiver, I will hook this one's VHF antenna entry to the AIS&splitter and will have a second marine VHF receiver at hand permanently. makes me think: let's check the SWR on 145 mHz maybe I can use the AIS pulpit mounted antenna also as a 2m antenna....

Jan

[fairbank56]

A good example of the usefulness of the LOC/DX function. The Naval Academy YP's (80' training ships) operate daily on the Severn River in Annapolis on channel 12. So does port operations in Baltimore harbor. The craftmasters on the YP's leave their radio's in LOC all the time as it very effectively reduces or eliminates the interference from their signals.

The Navy ET's were about to start sending the radio's back to Icom at one point because they were failing their receiver sensitivity tests. When I got involved I found that they were testing them with the switch in LOC. That's when I found that they were using that setting all the time to eliminate the interference.

Eric

[nv5l]

Originally Posted by fairbank56

A good example of the usefulness of the LOC/DX function. The Naval Academy YP's (80' training ships) operate daily on the Severn River in Annapolis on channel 12. So does port operations in Baltimore harbor. The craftmasters on the YP's leave their radio's in LOC all the time as it very effectively reduces or eliminates the interference from their signals.

The Navy ET's were about to start sending the radio's back to Icom at one point because they were failing their receiver sensitivity tests. When I got involved I found that they were testing them with the switch in LOC. That's when I found that they were using that setting all the time to eliminate the interference.

Eric

Ah, that's what you meant by automatic -- sorta like making coffee first thing in the morning is automatic for me.

[continuouswave]

Originally Posted by IslandHopper

The rest is just techi chest beating....

Comments about the participants in a discussion instead of the actual topic of discussion are usually made by people who don't have enough knowledge to actually join the discussion.

Curious that in discussions, say, about navigation the people who can do arithmetic are not accused of "chest beating." I don't understand why people who understand radio communications are to be held up to ridicule. Maybe you could read more and post less in this thread. You might learn something.

[IslandHopper]

Originally Posted by continuouswave

Comments about the participants in a discussion instead of the actual topic of discussion are usually made by people who don't have enough knowledge to actually join the discussion.

Curious that in discussions, say, about navigation the people who can do arithmetic are not accused of "chest beating." I don't understand why people who understand radio communications are to be held up to ridicule. Maybe you could read more and post less in this thread. You might learn something.

Carefull sport, doing Radio/GMDSS surveys is part of my job.....

[continuouswave]

Originally Posted by IslandHopper

Carefull sport, doing Radio/GMDSS surveys is part of my job.....

Good that you found work!

[Goudurix]

I made a mistake!

When I checked possible interference of the AIS250 and its splitter with my Yaesu FT897 as receiver - I had interference eg on CH27 and some other channels on Icom M80 marine VHF - I made a mistake and set the CH27 simplex frequency (156 mHz) and found no interference through the splitter. But CH27 is a Duplex channel and Shore stations transmit on 161.950 whick is just 25kC down from the AIS1 channel....and I DO have interference also with the Yaesu FT897, up till 40 kHz up or down the AIS frequencies!

So it seems that the Raymarine AIS250 is sending through interference to another marune VHF that uses its antenna splitter, and channels adjacent to the 2 AIS frequencies.
I only have AIS B, reception only. Bad engineering it seems....

Too bad.

Dedicated VHF and AIS antenna remains my solution.

Jan
73's
ON3ZTT


Jan

[nv5l]

You might try adding a choke balun.

[Goudurix]

@ nv5I:
A choke balun? How could I choke that interference off - it is exactly at the frequency the receiver is tuned to... (AIS TX is on 161.975 and 162.025 mHz and interference until about 40 kHz up and down)...

Can you explain why in HF terms?

Jan

[nv5l]

My guess is the the rf interference is traveling on the outside of the coax from your receiver back to the splitter. The choke will prevent it.

Is the problem only occurring when you're tuned that frequency? You can make tour own by coiling up the coax. Or use a separate antenna as you suggest.

[Symphony]

2011 is a few years back, but I hope some of you are still subscribed to this thread as I have a tangental problem.
I have a Ray218 VHF and RayAIS250 going through a splitter to 61' masthead antenna. AIS works very well (after replacing the first defective unit). Radio has been spotty in TX and RX where suddenly is cannot be heard and I use my Std Horizon handheld VHF to communicate. It has always had trouble receiving the NOAA WX channels, and today it could not receive either of the local channels. I could receive both local WX channels full signal on my handheld inside the boat.

I pulled the squelch up and could receive one of the WX channels on my Ray218 but the noise makes it unusable. I verified that my Ray is on the correct freq for the two WX stations (Ch2 162.400 and Ch3 162.475). I tried this in both LOC and DISTANT settings.

I was able to TX and RX the Ray218 to and from my handheld, as well as getting a radio check from a commercial vessel 1 mile away.

any suggestions of where to start looking in this rig?

I have been more than disappointed with the Tech support of Raymarine, let alone the hassle caused me by receiving a bad AIS unit to begin with.

fair seas

[clownfishsydney]

By-pass the splitter and see what happens.

[ka4wja]

Symphony,
I replied to you, in detail, in your other posting regarding this same issue...

Please have a look...where you will find your solutions...
http://www.cruisersforum.com/forums/...ml#post2157197


Fair winds..

John