Weatherproof potting compound?

[VK3RX]

I have a VHF satellite antenna that has a PCB mounted below the driven elements containing phasing harness connections. The PCB is shielded from direct rain by the element mounting arrangement, but it's base is visible below. The antenna is designed for short term portable use.

I want to make it more weatherproof for use permanently outdoors, receive only. Element joints I can seal using self-amalgamating tape, but it's the PCB that's the problem. I want to pot the whole base of it to the elements and mounting arrangement so it is completely sealed.

I've thought of non-acidic silicon sealant but I don't know it's affect on RF. I see Jaycar has a polyurethane potting compound, but curiously the manufacturer doesn't list it on their website.

https://www.jaycar.com.au/polyurethane-p...d/p/NM2016

Has anyone used this or can suggest a better compound?

[VK3LU]

How about a coating of epoxy resin?


Cheers
Nev

[VK4ADC]

How about a coating of epoxy resin?
Cheers
Nev

My earlier outdoors use of epoxy resin always seemed to result in degradation over time, along with discolouration, crumbling, cracking etc when exposed to direct sunlight/UV so I now stay away from it. I have used the non-acidic silicone sealants for various antenna purposes that have soldered joints but haven't used it directly on a built-up PCB. You could always apply a liberal spray coating of PCB lacquer over the PCB + components (both sides) before encapsulating it with the sealant in order to prevent any corrosion. By the way, the sealant shrinks over time so use extra.

Let us know what the outcome is as plenty of others may eventually need the same answer themselves.

[VK3RX]

During some googling I saw mention of not using resins outside for just those reasons.

I guess by using a non-acidic silicon sealant it can be removed later, something which would be useful.

[VK3ALB]

Hi Damien,

VK3AMZ advised me, and have seen for myself that hot glue makes a very good weather shield and has no effect to at least 1296MHz. I built a W6PQL style feed and the RL did not change once the glue was applied all over the connector and feed point solder connections. My 1296 yagi has been out in the weather for a few years now and has not changed characteristics.

If I did the same again I would devise a way to get a lot of glue sticks hot in a very short time.

[VK3LU]

Spray it with multiple layers of clear acrylic?

Nev

[VK3RX]

Thanks Nev; I will do that as an insulating barrier before potting it with anything I think.

G'day Lou; Hot glue as a potting compound sounds good, and I've had the same problem - the darn stuff cools too quick My Jaycar gun just doesn't seem quite up to it.

[VK2HRX]

Use a saucepan and melt as many stick as as you want plus a few extra.

[VK3ALB]

Use a saucepan and melt as many stick as as you want plus a few extra.

Wow! I'm glad VK3FJEN doesn't read this forum. :o

[VK3LU]

How about beeswax? Doesn't go hard and brittle.


Nev

[VK2HRX]

How about beeswax? Doesn't go hard and brittle.


Nev

Soft in the sun and melts?
Eaten by something?

[VK2CU]

When my Davey water pump had a broken wire to it's pump control circuit, it had this siliconey-gell type substance that encased the control board - it might have been this www.cablejoints.co.uk. The board was behind the pressure sensor and would be exposed to high pressure water at all times. The silicon was all gooey and I was able to remove it with ease - on a 10 year old pump. There was no sign of water contamination on the circuit at all.

This stuff doesn't set so as it says - "reeneterable" you can remove it should something happen. Do a search on this type of product, or maybe call Davey pumps and they might let you know what they use. It was a davey torruim MK1 controller. (since replaced by a MK2)

Justin

[VK3RX]

Many thanks Justin - I'll look into that product.