Jedi VHF/AIS station design

[s/v Jedi]

Working on this again. Got all the parts in, connected some up for a quick test and it seems to all pan out.

Using a handheld radio on ch.16 to the switch, to the surge suppressor, to the tester, to a dummy load and that seems to work okay. I need to charge the radio more then charge a second for emulating AIS so I can add that splitter to the test.

Still searching for my Icom marine handheld… I think it has AIS?

Check out how nice that tester is: power, frequency, VSWR, forward power, reverse power and power percentage that gets radiated or in this case turned into heat in the dummy load.

[s/v Jedi]

Originally Posted by Hartleyg

Just curious, Jedi - what voltage gas tubes are you using for your VHF radios coaxial protectors? They come in several voltages commonly - 90V, 260V and 330V seem to be common, but I'm sure there are others.


Hartley
S/V Atsa

Originally Posted by team karst

25 Watts with good VSWR will result in about 35Volt rms on 50 Ohms. So, go low on the breakdown gas tube.

Here is the one from the Diamond suppressor: it is a 2R230 so 230V. It can do 10kA ten times or 15kA one time.

This is all there is inside the surge suppressor.

p.s. nowI know howI hate PL259 again. And I have N-type everywhere so now I need to use adapters as well
I will see if I can switch to as much N-type as possible.

[s/v Jedi]

I tested the Vesper splitter and studied it’s specs.

The VHF input is maximum 25W and the AIS input is maximum 12.5W. This means it will work with the SOTDMA AIS transceivers.

When VHF transmits, it doesn’t take extra power but when AIS transmits it takes 3.9W according to my power supply.

When power is switched off, the VHF still works but AIS doesn’t get through and this may damage the AIS if it wouldn’t have protection, but it has. Still, AIS transceiver and antenna splitter should both get power from the same switch/breaker.

Of course I forgot to bring my old splitter from the boat today. I may be able to repair it

I plan to build two of these stations, each with its own dc-dc converter and one with the splitter.

About the Orion dc-dc converter: I tested that too. Output voltage is adjustable with a small potentiometer and is completely stable with varying input voltage. The unit says that input voltage must be above 16V but I tried lower and it works. This is a buck converter so when input goes lower than output then output goes down as well. This is all just for testing because it’s input circuit can only do rated power when it’s above 16V.

[Hartleyg]

Hi Jedi,


We just got into St Peters on the Bras D'or and have Internet again! 230V is what I have on our HF suppressors - should be good to a couple hundred watts even with imperfect SWR. I bought BNC gas-tube arrestors for my VHF/UHF stuff as I use a grounded plate with BNC bulkheads as a patch panel. I found a seller on eBay who had 90V tubes (physically the same size as yours) so I've used them for all my VHF and UHF antennas. The tubes weren't expensive, but not always easy to find.


Hartley
S/V Atsa

[Hartleyg]

BTW, the 35V figure for 25 watts is RMS, and we're concerned about peak voltage here, so the minimum suppressor flashover would be 50V. 90V seems reasonable to me, especially since modern VHF radios reduce power if SWR rises.
150w (like an SSB) would be 71V Peak (at 50 ohms), but at 2:1 SWR, that rises to 140V.


Since the whip/wire impedance (output of the tuner) could easily be 1000 ohms or more, lightning suppressors on this side are iffy at best.


Hartley
S/V Atsa

[team karst]

Negative....

2:1 VSWR doesn't double the Voltage on the line. It will go to 35% higher on maxima. And 35% lower on minima. So, IF 25W, then +35% is around 47 Volts rms, and the minima is .65 x 35 = approx 23V

So, you see that 47 is about double 23V

No one here ever use a slotted line SWR meter with bolometer?

to avoid the math, see a nomograph here: https://antennadesigner.org/peak_vol...e_to_vswr.html

Further; gas tubes take around 1microsecond to fire/ionize. Hitting them with VHF over the Vbreakdown might take a lot more power. But, that is an experiment I have not done.

[Hartleyg]

Originally Posted by team karst

Negative....

2:1 VSWR doesn't double the Voltage on the line. It will go to 35% higher on maxima. And 35% lower on minima. So, IF 25W, then +35% is around 47 Volts rms, and the minima is .65 x 35 = approx 23V

I see you still haven't converted from RMS to peak yet?




Hartley
S/V Atsa

[team karst]

Originally Posted by Hartleyg

I see you still haven't converted from RMS to peak yet?




Hartley
S/V Atsa

Yes, you R correct on that one. but, but, VHF waveforms will not persist its voltage long enough to make a microsecond duration. So, I submit none of us know the actual Vb on a GDT on a VHF transmitter. Even at 1MHz, that's a complete sinewave cycle in a single microsecond. So, if the device needs a microsecond of high voltage, will it ever fire? I don't know. A MOV or a diode type TVS will conduct, for sure.. But, a MOV has enough capacitance to mess with the VHF match.

[nfbr]

We've done RD similar but some differences.

The mast and windlass runs on a seperate 12v battery with Victron charger from the 48v with super thin wires on the 48v side. Like a fuse.
All mast items run from this, along with the windlass as we assume it's connected via the forestay and chain.

Mast has a 73mm2 copper ground cable dangling through the bridgedeck 3ft into the water.

Shrouds are Dyneema.

This means the mast and the front of the boat are ground isolated.

Quantum Radar is WiFi.

I only have three bugbears
a) VHF remote shares a conduit - yech. One day we'll go wireless
b) Some wires share bundles. AC 220V etc. Ideally there would be more seperation
c) AIS N2K. This remains a concern. I do have a WiFi bridge haven't implemented yet. The wired bridge is not rated for lightning. I really would like a fibre optic bridge maybe.

The engines / saildrives are also ground isolated. Does wonders for anode life. Means the usual ground path of Mast - Forestay - Chain - Windlass - Batteries - Saildrive is broken in two places.

Though Veritaserum shows it probably won't matter.

GBG (L48)'s big strike near the Galapgos a couple of months ago took out everything with an antenna in drawers, even powered off disconnected.