Question for Radio Heads

[Roger Long]

My VHF suddenly stopped transmitting clearly. I needed to get some passing information from a dredge with a very long pipe string and they couldn't understand anything beyond my boat name even though I could see them. I tried a Seatow automated check and all that came back was "Fizzsseesheriznishbizseeeshooshfizshish".

I figured the connector in the mast base (access plate, fortunately) was the first thing to check at that point. However, when we reached Long Island Sound where there are several Seatow automated check stations, I got a very clear return from one. From another, which was considerably closer, I just got the "Fizzsseesheriznishbizseeeshooshfizshish" again. A third gave me an understandable response with the "Fizzsseesheriznishbizseeeshooshfizshish" in the background.

I called for a check on 16 and someone responded that they heard me loud and clear.

Am I correct that, if I am transmitting clearly on some channels, the antenna wiring is probably not the first place to look for the problem? I'm going to check what I can get to without taking the mast down but it seems like taking the radio in to someone who can check it out is the first thing to do.

Anyone know a place on Long Island Sound that can check out a VHF?

 

[RAD]

Where abouts on Long Island Sound? I have an extra radio your welcome to borrow till whenever

 

[navigator97]

Roger, Since you were transmitting to "things" close enough to see, did you try transmitting on Low instead of High to see if there was a difference? If not, give it a try. If it was on high, it may have been overpowering the receiving station. Just a thought. Have been following you on SPOT on you trip from FL to now. Good luck on the rest of your trip.
Dick

 

[ifmdalvey]

If you are thinking the radio is possibly dud, i would buy a new one, probably less than a technician poking around inside. Unfortunately a lot of boxes are just not designed to be fixed.
Being an intermittent fault, i would be looking at every connection for possible corrosion.

 

[Roger Long]

did you try transmitting on Low instead of High to see if there was a difference?

Yes, no response.

 

[kenn]

If your receiver seems to be performing well, compared to another boat's receiver with a known-good antenna, then your antenna connection is probably OK. This isn't 100% confirmation because a flaky connection might perform differently when a significant RF current is flowing through it. So it never hurts to check any accessible connections in your antenna run.

A VHF transmitter can be bench-tested by connecting it to a dummy load which presents a near-ideal 50 0hms at VHF frequencies. Dummy loads can be purchased; they are also simple to build. A friend who's into ham radio could help with this.

A handheld VHF radio brought close to an unshielded dummy load should pick up enough signal from a low-power transmission. It's also fairly simple to add a signal attenuator you can tack across the dummy load to provide a tiny fraction of the RF output to a short wire antenna, without upsetting the antenna load. I can't find a proven circuit for that but it would consist of a couple resistors, or a resistor and a potentiometer, arranged as a voltage divider.

The audio modulation of marine is FM (frequency modulation), so a receiver is required if you want to see the modulation coming from your receiver. A good pro shop would have a deviation meter for measuring modulation. These are about the only ways to check and diagnose your transmitter output, if simple radio checks are showing problems.

 

[RichB]

Ian's thoughts are mine also. If it is very expensive, get the extended warranty. If not, choose a new VHF with some new whiz-bang feature and enjoy the upgrade.

 

[seadaddler]

VHF

I just purchased a WM floating handheld on sale back in April before our club PGSC went on our south cruise and boy it works great when we 10 boats were traveling on our trip.
What I found out about my Normal VHF with mic at the helm is my charger or inverter put in a lot of interference so no one could understand me,so check to see if any thing could be causing the problem,but I love the new handheld and was $99 and I had a WM gift card to purchase it.
As mentioned better off getting new one but check the antenna first.
Nick

 

[kloudie1]

I am knot a real radio head but our Navy electronics instructors told us to always check the output side for clean connectors and good solder joints in the co-ax when the radiio did not smoke or blow fuses.. Ya gonna want to do that anyway before attaching a new unit to the antenna anyway.. I am with Ian on that one.
Could be the whip connection into the loading coil or the coil ground attachment to the mast.. or the connector itself

 

[Roger Long]

It seems to have cured itself. I hate it when that happens because you never know if the problem is still there and only rears its head on dark nights in shipping lanes.

I checked the connections I could reach. All looked very clean with no sign of moisture intrusion at all. I put some Deoxit on them just in case.

Only difference from yesterday is that boat is upright. Best guess now would be that something is going on at the masthead connections that is effected by heel. Next time I really need to talk to someone and they can't understand me, I'll try de-powering the boat and getting her upright.

I'd still like to find a shop that can stick a loading coil on this radio though.

On a similar subject, if I buy a new radio, do I have to get a new MMSI number? I'm pretty sure I have to re-register the radio which cost $60 bucks. I have a ship station license so I have to deal directly with the FCC instead of BoatUS.

 

[kenn]

I just purchased a WM floating handheld on sale back in April before our club PGSC went on our south cruise and boy it works great when we 10 boats were traveling on our trip.

It's great to have an extra handheld, isn't it?

My friend had just replaced his antenna coax with fairly thick coax (thicker than RG-8). The good stuff. He was testing it out as we launched in a new area, and complained that the radio was fairly quiet on the weather channels. I fired up a $30 handheld and picked up 6 different wx stations. It took us 5 minutes to find that one of his RF connectors hadn't been tightened up properly.

 

[Don12364]

Reciprocity Theorem

Simply put the Reciprocity Theorem says, any antenna that receives properly will also transmit well too - and vice versa.
Poor VHF antenna connections are likely to introduce crackling and blank spaces in both Tx and Rx but not distortion or gibberish. Sometimes the Tx power is enough to arc through corrosion in a bad connection so it works okay for Rx as well - but not for long.
You don't have a scrambler on yours Roger?

Connections between microphone and the set are a whole new ball game though so make sure these are clean too. Also RAM mics.
I designed VHF radio and HF, LF and VLF antenna systems for UK's first nuclear subs - boy did we discover about water penetration into aerial connectors.
T'was all before the invention of self amalgamating tape though.

 

[Sumner]

....On a similar subject, if I buy a new radio, do I have to get a new MMSI number? I'm pretty sure I have to re-register the radio which cost $60 bucks. I have a ship station license so I have to deal directly with the FCC instead of BoatUS.

I would think not since you program the number into the radio. Just don't use the old radio unless it is on the same boat.

I'm also of the opinion of why spend money on the radio unless it is a high buck one and you are very happy with it. You can get a new radio for under $120 that has a separate DSC channel. We bought a new Standard Horizon that has the DSC and the AIS built into it for under $250 and it uses the same antenna for both. I thought that eventually we would be paying almost $300 just to have AIS alone.

Good luck,

Sum

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[dparilla]

You can keep the same MMSI. I just swapped mine out to a new radio. Much better than re-licensing. Just be sure (if you sell the old radio) to let the new owner know to reset the MMSI. I told them about it, and they gave me their MMSI to punch in before I sent them the unit. Most radios can only have the MMSI programmed once or twice before it is locked out.

 

[Bill Roosa]

Sounds like interference from something. You are getting returns from everybody/thing so you are getting a signal out. The only thing I can offer is keep track of stuff that was running when the problem re-occurs. Inverters, alternators, and motors are big offenders.
Just curious, why do you want a loading coil? Those are normally used to match an antenna to the transmitter. I can't think of a single commercial antenna that is not 50 ohm and your transmitter is 50 ohms so you should not need a loading coil.
For the record a loading coil adds inductance to a system that has too much capacatence (too short to resonate). If your antenna has a cylinder at the base it already has a loading coil to bring its already short length (high capacitance) into resonance.

 

[Bill Roosa]

An additional thought, there might have been environmental interference that was effecting everybody and you got cough up in the swirl. So also check other folks to see if they are having troubles too.

 

[Bill Roosa]

Hey Donalex
don't know where you got your info but it is pretty easy to get just about anything to receive a signal, even if it is badly mismatched to the received signal. A good example is those world band short wave portable receivers. They get 160 meter waves with an 18" antenna. Now if you tried to get THAT antenna to put out any kind of power your transmitter is going to shut down to high SWR. SWR is the reflected power that does not get radiated because the antenna is not resonant.
So while it is true that if it radiates well it will also receive well the opposite is NOT true.

 

[Don S/V ILLusion]

Just saw this thread. From your description and the fact it is intermittent, it sounds like you may have developed an Rf loop somewhere causing the transmit signal garble on some frequencies but not others. Something as simple as movement in one of the power leads or gnd lead when heeled would explain what you described. Obviously there are other possibilities but this seems the most plausible.

 

[Roger Long]

why do you want a loading coil?

I don't "want" one. Maybe I'm using the wrong term but I would like someone to bench test the radio and be sure that everything is right coming out of it.

My prime suspect now is the antenna connection at the top of the mast. I bought a new whatsyoumacallit last spring and sealed everything I thought pretty carefully before I put the mast up.

The fact that it rained heavily for a couple days and only stopped a couple hours before I had the radio problem makes me very suspicious. The fact that it got better as the weather got drier has me worried. I can buy a new radio for less than dealing with even something very simple at the masthead.

Of course, when your really, really need your radio, it's apt to be raining.

 

[Ken Cross]

several things to do

First off, Check your operating voltage at the back of the radio. A low battery or corrosion in the power system can cause all kinds of issues with modern electronics.
If you don't have a digital multimeter get one. They are cheap today
http://www.harborfreight.com/7-function-multimeter-98025.html
They are way more accurate than your panel meter and way more useful (at home, in the car, boat. Checking dry cells, electrical outlets, light bulbs, extension cords, and the list goes on.)

Pay careful attention to what you can receive. Can you hear distant stations (I use WX transmissions to do this in our area.) If so the antenna isn't likely to be a problem. If in doubt do a VSWR check. You can buy inexpensive VSWR meters from many locations especally if you have a store that caters to Ham operators.

http://www.ebay.com/itm/MIDLAND-Int...587?pt=LH_DefaultDomain_0&hash=item4d00fd1c13

If the receiver works normally or VSWR checks OK borrow a microphone if you can find someone with a compatible one.

You may have temporarily cleared thej problem by messing with the antenna connector. Look it over carefully for corrosion in the mating connections. If it's the type that can be disassembled look in the backshell to make sure you don't have a corrosion problem there.

Yes I'm and old radio guy (38 years of commercial electronics)
Best of luck
Ken