Aetna Tachometers and VHF Noise

[Bob Waters]

I recently installed a pair of Aetna Tachometers, model 8905R-P-DS LCD in the tower of my boat. I used Belden, twisted pair, shielded 16 guage wire for the signal wire. The tachometers work great and are very accurate. I have power supply running from 12V power panel in the tower with toggle switches and fuses, so I can turn them on and off. They are not wired to the ignition switch.
The problem is I’m getting a lot of noise on my VHF radio. I can use squelch at level 9 to make the noise go away, but I cannot receive or transmit at this level.
Here is what I have tried, in order.
1- Replace solder connector on VHF antenna. No help.
2- Replace antenna and connector. No Help.
3- Installed Newmar PC 10 noise filter on VHF power supply. No help.
4- Ran new power supply to tower for the tachometers. No help.
5- Installed Newmar PC 10 noise filter on power supply to tachometers on tower. No help.
6- Communicated with Aetna Engineers. They sent me a pigtail to power up the tachometers with a 9V battery and perform the following test. Power up with signal wire and ground from sender disconnected, but with ships ground connected. Noise is present. Noise goes away with ships ground disconnected.

The only device I have not replaced is the VHF radio and it works perfect when the tachometers are turned off.
I hope someone on this board can help.

Bob

Topic

[Bill Taylor]

New Install?

Rob: Thanks for the info and the diagram. Now only have to decide whether I need the shielded cable. As for the LED, thanks, yes on the fly bridge it will have to be LCD for sure as I only operate in the day light. I am also looking at installing the ISSPRO R609 Turbocators on the fly bridge. As an old gas man my diesel learning curve is steep and question keep arising. My next issue will be bleeding especially when I am changing fuel filters. Oh well live and learn. Bill.

[Rob Schepis]

Bill, have you seen the attached. If you are installing the LED be sure they are not in sunlight or they will be very tough to read. I prefer the LCD model.

[Bill Taylor]

New Install?

Greeting: I am about to install at least two Aetna 8402R-DS Tachs on my 1998 Bayliner 4087,engine 6BTA 5.9. I have been told that Bayliner installed the magnetic device and Faria tachs and developed the wiring harness. My question is will the current mag devices driving the Faria tachs provide the necessary data for the Aetna if connected in series using the existing drive units or should I bite the bullet and install four Aetna units along with new sending devices and wiring. The issue of installing units in series is also a question as it will dictate the sending units. It would certainly save time and effort in wiring and reduce the cost somewhat. Comments Please. Regards Bill.

[Bob Waters]

Rob.
Thanks for the contact number. I will call ICOM.
I agree, the external speak sounds much better than the internal. A very good upgrade.
Bob

[Rob Schepis]

Bob,

Glad to help. A call to Icom tech support may yield a “user doable” solution or maybe a warranty repair is in order? 1-800-253-1498. I just called there last week and they were pleasant & helpful to deal with. I have the M506 and I called for a suggestion on an external speaker. Accordingly, I installed the SP-24 ….. and wow, should have done that back in 2014 when I first installed the VHF..

[Bob Waters]

Rob,
I did as you suggested. I used an Icom 2 meter that I have on board and that radio does not have the same noise.
Thanks for the idea.
I need to see if it can be repaired.

Bob

[Rob Schepis]

I would get my hands on another VHF that you can put in place of your current problem one, just for testing purposes …. same power & ground and antenna connector. Then you will know if it’s something internal on your VHF.

[Bob Waters]

Rob,

When I ran the new dedicated 12V circuit, I used duplex wire and has a ground wire.
Bob

[Bob Waters]

Rob,
The ships ground is the 12V dc battery ground, which is the engine blocks.
Bob

[Rob Schepis]

Where exactly are you getting your ship’s ground?

Have you tried running a new dedicated ground?

It would not be too difficult to try a friend’s VHF just to check that box too..

[Author]

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