Trouble shooting GME AIS issue

[Ambler]

Hi Matt,
Be careful connecting your laptop to your mates GME transponder, I fried my transponder and it was replaced by GME under warranty. Yes you can hook up your laptop to the USB cable to check the SWR via the program but DON'T connect the laptop to anything else on the boat and DON'T have the laptop charger plugged in. The USB cable will become the transponders new earth.

I suspect the SWR is poor so check the coax is RG 213 and the terminals are not shorted or the copper mesh outer hasn't gone green or to dust.

Active electronics have released a new RG 213 with tinned sheath (but copper core easily tinned) which is brilliant for marine use. Use plenty of Self amalgamating tape on the joins too.

Cheers

[GILow]

Originally Posted by Ambler

Hi Matt,
Be careful connecting your laptop to your mates GME transponder, I fried my transponder and it was replaced by GME under warranty. Yes you can hook up your laptop to the USB cable to check the SWR via the program but DON'T connect the laptop to anything else on the boat and DON'T have the laptop charger plugged in. The USB cable will become the transponders new earth.

I suspect the SWR is poor so check the coax is RG 213 and the terminals are not shorted or the copper mesh outer hasn't gone green or to dust.

Active electronics have released a new RG 213 with tinned sheath (but copper core easily tinned) which is brilliant for marine use. Use plenty of Self amalgamating tape on the joins too.

Cheers

Thanks mate, great caution.

Now that you mention it, I can see how a circuit could form with devastating results if the laptop were on, say, a house bank powered inverter or maybe a 12 v cigarette lighter plug.

The boat is about 30 years old, I’m betting the coax is shot. Though, in fairness, he gets great range out of the vhf when things are working.

Actually, I’ve been reading up on coax today, I’ve decided I should replace my masthead antenna setup. Geez it’s a complex field. Still trying to get my head around the various types of coax and the pros and cons of each.

[Wotname]

Originally Posted by GILow

........

Actually, I’ve been reading up on coax today, I’ve decided I should replace my masthead antenna setup. Geez it’s a complex field. Still trying to get my head around the various types of coax and the pros and cons of each.

About as complex as finding the perfect anchor!
Don't despair, there is no perfect solution but there are good compromises. Do remember to look no further than the VHF specs as many of the newer products are only better at much higher frequencies and sometimes require professional level connectors/tooling and deep pockets. Don't let perfect be the enemy of good.

At the end of the day, VHF is an old and well understood technology; Amber's advice on a tinned outer and using self amalgamating tape is spot on.

[Bycrick]

It’s possible to over-think the coax selection process. If you really look at all the specs, you’ll just get confused. Is the center conductor solid (lower loss but not as flexible), solid copper or copper plated aluminum (heavier but more corrosion resistant), or stranded (tinned or not, or silver plated). Is the dielectric air (lower loss, lighter weight, but can’t make tight bends), foam (lighter weight, lower loss but will absorb moisture over time, so won’t last as long), solid (heavier but will last longer). Is the shield coverage high (less coverage is lighter, cheaper). Double shielded gives better coverage, but is more expensive. Silver plated shield, tinned copper, or untinned. Is the jacket PVC, polyethylene or something else (PVC is lighter and cheaper. PE is more moisture resistant.)

Don’t let somebody sell you RG-something cable because it "military speced." The original RG8 spec was obsolete in the 1960s. I can make any cable and call it RG8. If it’s a current spec, like RG213, from a reputable company, it will meet the current spec. But you’ll find that the big cable companies all make cables that superficially look similar but are vastly different. Most of them won’t have an RG designation. And just because it does meet a mil-spec doesn’t mean it’s the "best" for your circumstances.

My personal choice is Times Microwave LMR400UF. Reasonably light, workable bend radius, easy to get the right connectors and crimp tools at an affordable price. Lasts 15-20 years if sealed properly. Cost under $1.50/foot. Or, Belden makes a similar cable with a solid dielectric; lasts longer but slightly higher loss. If you’re worried about fractions-of-a-dB loss, try RG214 which is silver plated, but break out your wallet.

[GILow]

Originally Posted by Bycrick

It’s possible to over-think the coax selection process. If you really look at all the specs, you’ll just get confused. Is the center conductor solid (lower loss but not as flexible), solid copper or copper plated aluminum (heavier but more corrosion resistant), or stranded (tinned or not, or silver plated). Is the dielectric air (lower loss, lighter weight, but can’t make tight bends), foam (lighter weight, lower loss but will absorb moisture over time, so won’t last as long), solid (heavier but will last longer). Is the shield coverage high (less coverage is lighter, cheaper). Double shielded gives better coverage, but is more expensive. Silver plated shield, tinned copper, or untinned. Is the jacket PVC, polyethylene or something else (PVC is lighter and cheaper. PE is more moisture resistant.)

Don’t let somebody sell you RG-something cable because it "military speced." The original RG8 spec was obsolete in the 1960s. I can make any cable and call it RG8. If it’s a current spec, like RG213, from a reputable company, it will meet the current spec. But you’ll find that the big cable companies all make cables that superficially look similar but are vastly different. Most of them won’t have an RG designation. And just because it does meet a mil-spec doesn’t mean it’s the "best" for your circumstances.

My personal choice is Times Microwave LMR400UF. Reasonably light, workable bend radius, easy to get the right connectors and crimp tools at an affordable price. Lasts 15-20 years if sealed properly. Cost under $1.50/foot. Or, Belden makes a similar cable with a solid dielectric; lasts longer but slightly higher loss. If you’re worried about fractions-of-a-dB loss, try RG214 which is silver plated, but break out your wallet.

Ha ha! I got so confused I had to read your post four times. [emoji846]

But yes, I hear what you are saying.

I looked for that LMR400UF here in Oz. Ouch! Let’s just say you get better prices where you are.

[GILow]

Originally Posted by Wotname

About as complex as finding the perfect anchor!

Don't despair, there is no perfect solution but there are good compromises. Do remember to look no further than the VHF specs as many of the newer products are only better at much higher frequencies and sometimes require professional level connectors/tooling and deep pockets. Don't let perfect be the enemy of good.



At the end of the day, VHF is an old and well understood technology; Amber's advice on a tinned outer and using self amalgamating tape is spot on.

So... you got a favourite? I’m thinking of putting my AIS antenna on the top spreader, plus replacing the masthead vhf antenna AND possibly my friend will need to replace his antenna cable, so I could get through enough of a 100 meter roll to make it worth considering for the discount.

[Bycrick]

I’m honored that you actually tried to understand it, but I was trying more for humor rather than an engineering monograph. The basic points were that there’s lots of junk cable and junk connectors and junk information. Buy the best quality you can from a reputable manufacturer. The difference in cost is negligible. Getting the absolute "best installation" isn’t necessary. In the absence of radio noise or other interfering signals, 2-5 watts will get your signal to the horizon. Especially with AIS. My old ACR is connected to a 3db antenna on the stern arch with about 15’ of decent, but not exotic RG-58 cable. I reliably watch big ships approaching/disappearing at 30 miles. I might be able to do it better, but the current system is more than good enough for its intended use.

[Wotname]

Originally Posted by GILow

So... you got a favourite? I’m thinking of putting my AIS antenna on the top spreader, plus replacing the masthead vhf antenna AND possibly my friend will need to replace his antenna cable, so I could get through enough of a 100 meter roll to make it worth considering for the discount.

Well now that you have asked - why yes I do.

If KISS is your thing - then get RG213 made by one of the 'name' manufacturers e.g. Belden, Times Microwave, Pasternack, Huber & Suhner, etc. It is a great all rounder and easy to source While there is nothing fantastic about RG213, there is also nothing terrible about it either - it does the job and is easy enough to run and terminate. Some get concerned that the copper isn't tinned but really it isn't a big deal. All connections should be waterproofed anyway.

But I prefer RG214 (again from a 'name brand') simply because the inner is silvered coated copper and the outer is twin shielded with both layers being silver coated copper but you do PAY $$ for this.

If money is no object, pony up $$$$$$$ for RG393 - this stuff is approved for direct ground burial so it should last forever inside a mast but you do have to sell your first born to fund it and electrically at VHF, there is zero advantage. Different story at 40,000', -20C and at 1Ghz or if buried in the desert.

Many go for the LMR 400 series but personally I don't like it. IMO, just not needed for a sail boat VHF. I used shiploads of it for satellite systems and the like and yeah, it's good but I dunno, I just don't like the aluminium foil in the outer and the soft foam dialectic (crushes easily), requires more care running and securing it etc. Not a good choice for the inexperienced DIYer IMO. It doesn't like UHF connectors. BTW, don't mistake LMR400 for LMR400-UF - they are quite different and I would only (and grudgingly) use the -UF on a sail boat. I accept that others like it and some recommend it but personally I don't. That doesn't make them wrong, some people like apples and some like oranges.

So the easy option is RG213 and it is hard to argue against it. If the lack of tinning bugs you, then go for RG214 (which is 'tinned' with silver).

Connectors - and I will cop a lot of flack for this, especially from our North American brethren - but I HATE UHF connectors and will go to great lengths to use N type and/or TNC. I accept some UHF connectors are OK but the problem is there are many that aren't and how is the average DIY guy to know which is good and which is bad. It is hard to find a low quality N type but I guess there must one or two around. Maybe I have lead a sheltered life but I would never ever have headed off to an off-shore oil rig or a maintenance hangar without name brand N type, TNC and BNC connectors plus some UHF inter-series adapters.

The above cables are stiff(ish) and don't have a small bend radius so I tend to use short flexible small diameter coax tails if required e.g. at the mast entrance point or the back of the radio etc. RG400 is my goto cable for tails but others have their favourites.

You got to remember, we are talking only VHF frequencies with an abundance of Tx power and short runs unless you got a mega mast.

Let the flame wars begin .

[Wotname]

Originally Posted by Bycrick

I’m honored that you actually tried to understand it, but I was trying more for humor rather than an engineering monograph. The basic points were that there’s lots of junk cable and junk connectors and junk information. Buy the best quality you can from a reputable manufacturer. The difference in cost is negligible. Getting the absolute "best installation" isn’t necessary. In the absence of radio noise or other interfering signals, 2-5 watts will get your signal to the horizon. Especially with AIS. My old ACR is connected to a 3db antenna on the stern arch with about 15’ of decent, but not exotic RG-58 cable. I reliably watch big ships approaching/disappearing at 30 miles. I might be able to do it better, but the current system is more than good enough for its intended use.

[Bycrick]

Again, it’s hard to argue with Wotname's post, except in details. His suggestion about RG213 vs LMR400UF is fine. The RG213 is slightly heavier, not as flexible. With LMR400UF you need to use compatible connectors which are harder to find, but no more expensive. The RG214 is more expensive and has slightly lower loss than RG213, but not as low as LMR400UF.

And his example of RG393 just proves my point. Here you have a silver-plated, Teflon insulated cable at about 10 times the cost. With more loss than LMR400UF.

The issue of tinned vs untinned is non-existent for coax. If you get moisture in the cable it will corrode in either case. And the moisture will increase losses substantially before it rots the cable.

No question that Type N connectors are a better design than UHF connectors. Will you notice the difference at 150 MHz? No. I don’t use them because all my test equipment and radios have UHF connectors and I don’t want to store or permanently install a bunch of adapters and pigtails.

Either good RG213 or LMR400UF will work just fine. I’ve also seen people use AIR802, which is a knockoff of the LMR400UF.

[GILow]

Originally Posted by Bycrick

I’m honored that you actually tried to understand it, but I was trying more for humor rather than an engineering monograph. The basic points were that there’s lots of junk cable and junk connectors and junk information. Buy the best quality you can from a reputable manufacturer. The difference in cost is negligible. Getting the absolute "best installation" isn’t necessary. In the absence of radio noise or other interfering signals, 2-5 watts will get your signal to the horizon. Especially with AIS. My old ACR is connected to a 3db antenna on the stern arch with about 15’ of decent, but not exotic RG-58 cable. I reliably watch big ships approaching/disappearing at 30 miles. I might be able to do it better, but the current system is more than good enough for its intended use.

OK, that makes good sense.

Oddly enough, the AIS antenna came with RG-58.

Somewhere I found a good table comparing the losses for various types, I’ll try and find it again to see if it helps with finding the best compromise. I would like the VHF to be as good as practical.

Edit: I have just seen Wottie’s post... looks like I’ve got some reading to do.

[GILow]

Originally Posted by Ambler

Hi Matt,
Be careful connecting your laptop to your mates GME transponder, I fried my transponder and it was replaced by GME under warranty....

Just to confirm, I got your advice to him in time. He now knows to take care and avoid connecting the laptop to anything but the AIS unit to be safe.

[GILow]

Wotname et al...

So, I’ve found rg213 at only a mildly eye watering price. But the brand is Boss. From Radio Parts. Any good?

[Bycrick]

I don’t know what price makes your eyes water. But, here’s what I just found:
West Marine RG213 — web site list price $3.39/foot

RF Parts, who I’ve had good luck with:
LMR400UF — $1.72/foot
Belden commercial grade RG-213 — $1.15/foot
Belden RG-213/8267 milspec — $2.45/foot
Belden RG-214 silver plated — $4.25/foot

I’ve never dealt with Radio Parts and never heard of Boss cables. In general, I’d stick with a well known brand name.

[Wotname]

Originally Posted by GILow

Wotname et al...

So, I’ve found rg213 at only a mildly eye watering price. But the brand is Boss. From Radio Parts. Any good?

That will be DOSS - I know nothing about it but Radio Parts states Please note that actual stock incorrectly states 75 OHM on the cable instead of 50 OHM and that alone would give me the heebie jeebies.

Here is some Andrews RG213 which I would be happy with at $349 /100m but I dunno about freight ex Qld.

https://www.telcoantennas.com.au/rg2...ial-cable-reel