RF noise from latest Stowe wind indicator?

[SolentSnowgoose]

Has anyone any experience of RF noise from the latest versions of the Stowe wind indicator Mast head units supplied by Tinley in Lymington?

Our Mast head unit was repaired by Tinley in 2012 and it seems the repair / upgrade included putting some new electronics in the MHU.

Everything worked fine till we replaced the VHF antenna a few weeks ago and we are now getting constant squelchy noise on the VHF even with the squelch at Max. Depowering the instrument solves the problem.

Have discussed the problem with Stowe/Tinley and they have admitted that earlier upgrades did have an emission problem and have offered a further upgrade at a cost.

However so far I cannot get any guarantee from them that this will fix the problem and they have so far initially suggested that the problem lies in the antenna (Vtronics Hawks) and then subsequently lack of filtering in the VHF set (Standard Horizon?)

Anyone any experience with the new Stowe MHU?

Are there any tests or standards for noise emissions from boat instruments?

Was going to get all my old Stowe instruments refurbished but it starting to look like there is no guarantee they will work ( at least not with the MHU and VHF both up the mast) and hence a £70 replacement of a VHF antenna is looking like £1000+ of new instruments,

 

[Norman_E]

Was it OK with the old antenna? If so I suggest that the new antenna is good at picking up a frequency generated by the Stow unit, and the old one was not, so maybe just trying a different make of antenna would solve the problem. An alternative cause might be that the new antenna has a poor connection somewhere between it and the radio, and the result is that the volume has to be up to get reception, and amplifies the noise from the Stowe unit. Why was the old antenna replaced?
Salty John who posts on here sells Metz antennas, and may be able to advise you. http://www.saltyjohn.co.uk/metzmantavhfantennaaerial.htm

 

[SolentSnowgoose]

Hi..... well.... both old and new antennas are same design and I have now spoken to both Shakespeare (Vtronics) and Yaesu (Standard Horizon) and neither sees how it could be a design problem with the antenna or VHF set.

Basic problem seems to be with Stowe unit but no explanation as to why there was no noise before the antenna was replaced.

 

[AngusMcDoon]

Ask Tinley if their new MHU design has been EMC tested. If they are aware that a former upgrade they did had a fault surely they should put that right at their cost.

 

[roblpm]

Ask Tinley if their new MHU design has been EMC tested. If they are aware that a former upgrade they did had a fault surely they should put that right at their cost.

They are good at charging for everything they do! I slightly regret going down the refurb route with them as I still have a flakey system after hundreds spent. I should have binned the whole lot and started again when I bought my boat 18 months ago.

 

[Norman_E]

Hi..... well.... both old and new antennas are same design and I have now spoken to both Shakespeare (Vtronics) and Yaesu (Standard Horizon) and neither sees how it could be a design problem with the antenna or VHF set.

Basic problem seems to be with Stowe unit but no explanation as to why there was no noise before the antenna was replaced.

Whilst I agree that the basic issue is RF noise from the Stowe, there must be a reason why the old antenna did not pick it up and the new one does. Firstly why did you replace the antenna? If it did not work at all, then the answer is obvious, but if it received radio transmissions but not the RF noise then something about the new aerial installation must be different. Have you checked all of the connections?
Is there a ferrite clamped around any of the cables, including the one to the Stowe MHU? Ferrites are used to reduce RF interference and must be placed as close to the source as possible. I remember that my VHF has one on its power cable. If you do add a ferrite anywhere, make sure that it is one made for VHF as the internal chemistry is different for VHF and UHF (nickel zinc) than for AM radio. I suspect that the cable to the Stowe unit acts as an aerial for its RF interference, so clamping a tight fitting ferrite to the cable immediately where it exits the instrument might help.
This website has quite a lot of information on interference. http://audiosystemsgroup.com/Ferrites-Ham.pdf

 

[SolentSnowgoose]

The original Antenna worked find but got bent over the winter and the Hawk indicator was falling apart hence I replaced it with an identical unit.....seemed simple enough.... how wrong it seems I was.

Stowe initially blamed the antenna ... (we get this problem with some antennas, try a different one!!) and then the VHF set (Standard Horizon radios don't have enough filtering in them)

So ... I checked with both Shakespeare who make the Hawke antenna and Yaesu who make Vertex /Standard Horizon radios and both were very helpful and offered to contact Stowe to "correct" these comments.

Not surprisingly both have firmly confirmed that the level of RF emissions from the Stowe MHU is unacceptable .

However Shakespeare have confirmed that there was a change in the antenna matching circuit design ( in the base of the antenna) back in 2006 and have suggested some tests to see if this is why the new antenna is more sensitive to the noise. However these require going up the mast and doing electrical work which is potentially beyond what I think I can organise with a French rigger so may have to wait till I can get to a cherry picker.

As for Stowe... after a week of Emails telling me, several times, that fixing the problem was a "chargeable upgrade" I am actually still waiting for a confirmation of price and turnaround time.

In the meantime I am cruising North Biscay but can have either wind instruments or VHF but not both at the same time!

Any recommendations on reliable instruments to fit over next winter ?

 

[AngusMcDoon]

If they know it causes unacceptable emissions but refuse to accept it's their problem then it sounds like Trading Standards should be involved - if they can be bothered to look into it.

B&G Triton based system. Not too expensive if you buy a complete instrument and display pack.

 

[Norman_E]

If you are thinking of getting rid of the Stowe system and putting in new instruments, IMHO the best and clearest multi function instrument at present is the B&G Triton. It works on NMEA 2000 so you would really need to buy a starter pack consisting of the Triton display, cables, mast head unit and log/depth transducer. The whole setup costs about £950. Connect a GPS antenna to the NMEA 2000 system and it will display position as well. If you want advice I suggest talking to John Grandborough at JG Technologies. http://www.jgtech.com/index.htm
When I last checked he had some B&G Zeus 7 or 8 inch displays at a very good price. I am not certain but I think they will work as both chartplotter and instrument display as well as having B&G's sailsteer capability. I wish I had one of those instead of the small Advansea plotter I fitted.
The great thing about NMEA 2000 is that you can mix equipment makes (the log/depth transducers are made by Airmar for most brands) and there are none of the problems you get trying to make different pieces of kit communicate using NMEA0183.

EDIT: A quick fix, if you still have the old antenna, straighten it out and put it back.

 

[SolentSnowgoose]

Latest from Stowe is that despite replacing the original sensor with a microprocessor as a "repair / upgrade" they now claim that any while they can do a further upgrade ( chargeable...still with no price quoted!!!) , this would be sold as only a spare part and hence does not need to be tested for EMC compatiblity.

I thought that any repairs that were not like for like parts triggered a need for CE marking and hence an EMC test. .... anyone have any info on this?

As it is it seems like its pretty risky to install any version of the Stowe MHU as there seems like a pretty good chance it will wipe out your VHF.

 

[MM5AHO]

Is the MHU designed to emit RF (ask them). If not ask them why is does, and what they propose to do with a unit not fit for purpose?
Actually lots of things emit RF and sometimes its amazing that we can have so many electronic toys living so closely together.
If I remember right the Hawke has a screw in coax connector, suc that there's a somewhat poor joint between coax core and the antenna. Shining this up and applying some grease (to slow down the tarnishing) might help get a better connection, though antenna connection doesn't seem an issue here?
The suggested ferrites, on the MHU cable, at the top might help. If there's enough cable, and it fits, put a couple of turns through the ferrite.

 

[tinley]

Has anyone any experience of RF noise from the latest versions of the Stowe wind indicator Mast head units supplied by Tinley in Lymington?

Our Mast head unit was repaired by Tinley in 2012 and it seems the repair / upgrade included putting some new electronics in the MHU.

Everything worked fine till we replaced the VHF antenna a few weeks ago and we are now getting constant squelchy noise on the VHF even with the squelch at Max. Depowering the instrument solves the problem.

Have discussed the problem with Stowe/Tinley and they have admitted that earlier upgrades did have an emission problem and have offered a further upgrade at a cost.

However so far I cannot get any guarantee from them that this will fix the problem and they have so far initially suggested that the problem lies in the antenna (Vtronics Hawks) and then subsequently lack of filtering in the VHF set (Standard Horizon?)

Anyone any experience with the new Stowe MHU?

Are there any tests or standards for noise emissions from boat instruments?

Was going to get all my old Stowe instruments refurbished but it starting to look like there is no guarantee they will work ( at least not with the MHU and VHF both up the mast) and hence a £70 replacement of a VHF antenna is looking like £1000+ of new instruments,

I would like to clear up a few misquotes here:
We are aware of 5 out of 1000+ installations that have caused interference on VHF.
We did not blame the antenna.
Out of the known problems, it has always been one of the same two models of VHF. Other VHFs do not appear to be affected... but we admitted the problem is caused by the MHU, although most VHFs on the market can filter out this interference.
We cured the known problem MHUs by fitting additional filtering to the MHU, which has been our standard practice now for several years. We have normally carried out the modification FOC, but since the MHU in question is around 30 years old and was repaired/modified by us over 3 years ago, we feel justified in charging, no more than our costs, for the RFI modification after this time.

We are pleased to report that subsequently we did carry out the modifications to this MHU and the customer has reported that the interference has been cured.