Vesper Problems

[noelex 77]

Originally Posted by continuouswave

This leads to a general rule in working with VHF antennas that if the VSWR is 3:1 there probably is no antenna connected at all.

Thanks, another rule of thumb I have not heard. 3:1 is obviously a very poor SWR, but I would not have rated it this bad.

This information could have saved the trouble of buying a SWR meter to diagnose the problem. The good receive and transmission performance of the Vesper unit was not consistent with the units reported greater than 3:1 SWR, if this standard is similar too “no antenna”.

[noelex 77]

Originally Posted by continuouswave

on folio 106 there is a chart showing 162.425-MHz as available in the radio as a simplex channel, but in the owner's manual for the IC-M506 (as available in USA) there is no provision for that channel.

Marine VHF radios are surprisingly country specific. This can be a nuisance for long distance cruising boats travelling internationally. It is shame there are not more universal standards.

It is worthwhile purchasing (legal) equipment that has the broadest transmission frequencies possible and obtaining the relevant licences. As you move to different countries different frequencies are permitted. Even if the equipment has more capabilities than you are permitted to transmit on you can usually listen on these frequencies, although there are restrictions such as reporting or repeating these conversations.

Sometimes this can be helpful in emergency situations, such as the ability to monitor transmissions by the coast guard rescue helicopters.

[Wotname]

Originally Posted by noelex 77

Vesper Marine replied almost immediately and are trying to sort out the problem, which is nice to see.

..........

Getting back to the Vesper now the freq/antenna/VSWR hooha has been resolved, I presume no forward progress has been made in getting the AIS operational yet?

No magic reset / factory reboot button has been found or any other way of reseting the unit with the covers off???? Maybe a replacement unit already in transit????

Interestedly I have found that as a generalisation, NZ high end electronic designers and manufacturers (and I include Vesper in that generalisation) provide excellent back up service; especially when their equipment develops "interesting / unusual" faults. Often you are quickly talking to the guys who designed and built the equipment and their knowledge of their products are second to none. They spare no effort to resolve issues with their product.

So I am keen to hear how this Vesper problem is sorted out.

Lest you think I am a Vesper fanboy, I'm not and I have never had used any of their products or any contact with Vesper but I have had good professional user relations with some other Kiwi electronic manufacturers. Vesper's reputation is AFAIK on par with the best of the NZ electronic manufacturers.

[noelex 77]

Originally Posted by Wotname

So I am keen to hear how this Vesper problem is sorted out.

The unit is being sent back to Vesper. There is obviously some internal malfunction that has prevented the touchscreen working correctly and given the recent erronous high SWR reading.

Vesper customer service has been excellent. It is nice to see manufacturers that stand by their product and try their best to help cruising sailors. Unfortunately, with a severe malfunction such as this, the unit has to be sent back to New Zealand, which for us is as close to the opposite side of world as is possible. Vesper have arranged the courier, the necessary customs clearances etc for a low cost considering what is involved.

It will be so good to receive back the repaired unit that will respond when I touch the screen. There are no physical buttons on the Vesper so the touchscreen performance is vital. The high SWR alarm has also been annoying. The error message makes it difficult to know if the AIS transmission is being broadcast.

We have only had a day without the great anchor alarm built into the Vesper and already I am missing the detailed information that this provided. The translation of the GPS position to the bow roller (providing heading information is available) is particularly valuable in detecting any slight movement of the anchor.

[continuouswave]

Originally Posted by noelex 77

Thanks, another rule of thumb I have not heard. 3:1 is obviously a very poor SWR, but I would not have rated it this bad.

The measured VSWR (at the transmitter) of an open-end transmission line varies with the line loss. In the case I mentioned, a line loss of 3 dB existed. A VSWR of 3:1 is 25-percent reflected power.

A transmitter puts out 10-watts. The power lost in getting to the load is 3 dB or half. Only 5-watts gets to the load.

The load is an open circuit (or a short circuit) so 100-percent of the power, now just 5-watts, is reflected back.

The 5-watts reflected power travels down the feed line, with a 50-percent loss, so only 2.5-watts gets back to the transmitter end, where the VSWR direction coupler is making the measurement.

The directional coupler sees
Forward power = 10 watts
Reflected power = 2.5 watts
VSWR = 3:1

If the transmission line loss is is less, the effect is correspondingly less. Here is another example, this time with an antenna that has an actual VSWR of 3:1 (a reflected power of -6 dB) and a transmission line with a loss of -1.5 dB. These values might be typical of a sailboat VHF Marine Band antenna at the masthead that is fed by 55-feet of RG-213/U cable and was tuned for the low end of the band but is being used at the high end of the band (for AIS):

Transmitter power is 20-Watts or +43 dBm
Line loss is -1.5 dB.
Power at antenna is +41.5 dBm.
With 3:1 VSWR at antenna, reflected power is -6 dB
Reflected power is +35.5 dBm
Line loss is = -1.5 dB
Reflected power at transmitter is 34 dBm.
Apparent reflected power is -9 dB
Apparent VSWR is then 2.1-to-1

The transmission line loss masks the 3:1 VSWR actually at the antenna, and the transmitter sees a load with a 2:1 VSWR, which probably makes it quite happy to continue to deliver power into the load.

[noelex 77]

Our Vesper is back . It arrived Christmas Eve.

Vesper sent a completely new unit, I suspect because repair would have delayed us receiving the unit until after the holiday period.

The new screen is much better and has fixed all the problems mentioned. The SWR is now reported as “Good, < 2:1”.

So thanks, Vesper. For cruising sailors having equipment repaired in remote anchorages is always a challenge, and Vesper went out of the way to make the process as easy as possible with regular email updates and even a text message to our phone to check the delivery address in case we had been forced to move anchorages.

The only slight problem with the new unit is that the Vesper is only occasionally reading the heading from the NMEA 2000 bus . This is a puzzle, as the previous unit had no issues and the chartplotter and autopilot still receive valid heading data.

I suspect it is something to do with the PGN configuration setting, specifically 127250, but I have tried several update rates and even tried using a separate fluxgate compass with no success.

Any suggestions will be gratefully received.