Experiences Appreciated

[algerdes]

All of us have some experience and some of us have a lot of experience in one area or another. Since 2009 I have used a Ramsey transmitter (FM35) tied to an external antenna (FMA200). In the same box (2 foot deep, 2 foot wide, 4 foot tall) we also had the Master FPP (currently a RPi 3b+), a 16 port gigabit switch (gigabit "click switch"), a power distribution system, a wireless router and during the final years of the box - a laptop for onsite changes. As of this writing, this is changing.

The big box is gone and we are mounting two smaller boxes on the back of one of our 1" center matrix panels.

Over the years there has been talk about interference between the FPP and the transmitters. We never worried about this because we had plenty of room in the box (originally made for all the above and an old-school desktop and tube monitor) to separate the transmitter from the FPP. Things have changed and now I need your expertise (or experience) about cramming everything into a small area.

With all the above said, I need to ask - is the problem having the transmitter close to the FPP, or is it having an antenna next to it that causes hum?

I ask for your experience because I will not be able to turn this all on for some time, but still need to get it built. I would hate to have to rebuild once the pixels have been mounted because the connectors for the boxes are mounted on the supports. With the weight of the pixels, this will be "no fun".

Thank you for any guidance you may send my way. Also thanks for putting up with this overly long description.

Al

 

[ctmal]

I've never experiences issues with fpp right next to my transmitter but I am directly plugged into Renard controllers. Not sure if that would make a difference since I'm barely using wifi.

But, Is that cage made out of metal? I would assume that could create a lot of interference. I'd be curious if you move the transmitter away from the metal if any hum goes away.

 

[ChiefWarrant]

- is the problem having the transmitter close to the FPP, or is it having an antenna next to it that causes hum?

Al

I have not heard a hum in my transmitter since I have upgraded to a higher quality transmitter. When I used the "cheaper". transmistters, I would use ferrite beads on the antenna ,the power input and the audio cables to reduce the inductive interference (hum).

I am not a transmiter expert, but the Ramsey looks like a higher quality transmitter, so the hum could be a result of a "questionable" audio cable. Additionally, as Chris was starting to point to, the devices could be interfering with one another. One thing to reduce this is to use an earth ground to the setup. Then any "excess" energy will be sent to ground instead of recirculating in the circuit.

-Tony

 

[algerdes]

Thanks Tony,
I have never had a hum problem (that wasn't found to be an audio cable), but with the change in proximity of the two I need to build into the new setup anything necessary to prevent it - if necessary.

Chris,
Yes, all of our matrix panels are built using the box style that you see here. Our display is in an open field, in a park, where they test wind for velocity and punch. In the case of the new panels, these are 1" on center. Boscoyo created holes between each row and boy what a difference. Before, with no holes, the panels could provide propulsion to a fairly large vehicle.

We have never found any kind of "interference" (I believe you are refering to electrical/radio) in the frames They are wide open and grounded. The panels are made of ABS (or similar). I will, however, keep an eye out for it. Thanks for the idea.

 

[MartinMueller2003]

My FPP sits three inches from the EDM transmitter. They both sit on top of a 350W meanwell LSR PSU. Rith next to them is a 5 port switch (as in touching the EDM) and a Wireline Ethernet adapter sits about a meter away. No issues with noise. FYI: My antenna is a ground plane antenna sitting about 50' away.

 

[ErnieHorning]

If your talking about a 60Hz hum, it's highly unlikely that a transmitter or microcontroller just happened to cause a beat frequency that results in 60Hz. It's always an insufficient ground somewhere. Also, are you 100% sure the earth ground really is? It wouldn't hurt the check that there is zero volts between neutral and ground.

I found out that my workbench wasn't grounded at work. And because of the way some tech equipment power supplies were made, they dumped about a microamp of 60 VAC onto a floating ground.

 

[algerdes]

All good things to know about.
Martin - Thank you very much. This is exactly what I am looking into. Another friend has a setup that is about the same. Good news for this new setup.
Ernie - Ground is definately good. Thanks for reminding me to double check when we move it into the field.