Dielectric grease and outside antennas

[AK9R]

kb0nly mentioned in this thread that he likes to use dielectric grease between mating parts on outside antennas. The idea is to maintain the electrical connection, which the threaded fasteners typically provide, while keeping out water and corrosive compounds (particularly salt). Dielectric grease is a silicone grease. It doesn't "set up" like a silicone sealer does. It remains "greasy". You can usually find little tubes of dielectric grease in the chemicals and sealers section of your local auto parts store.

I used to have trouble with corrosion on brass parts of NMO mounts. Even with the O-rings or rubber seals that the antenna manufacturers provide, water and road salt would still work their way into the mount and corrosion would commence. A few years ago, I started using a dab of dielectric grease on the threads of an NMO mount when I attached the antenna. It seems to work pretty well to keep out the corrosion and I've detected no difference in the performance of the antenna.

Anyone else have other experiences with dielectric grease on antenna parts?

 

[comsec1]

conducts at RF

I have found that some of the upfitters do this as well but if you check with a watt meter or other antenna performance piece of test equipment you might find that when a blob of grease is put onto a mount such as an NMO type the compounds I have encountered create a short at RF voltages. if you don't put much that touches the center pin and shield you might be ok. most of the upfitters don't have much RF experience and they just gob it onto everything, your lucky if you can get them to put a mini-uhf on with the correct tool and not a pair of pump pliers.

 

[N_Jay]

I saw a tel-co installer put a "glob" of that stuff into a gigabit RJ-45.
Yes, they had to buy a new router and interface box.

The best part was the equipment was inside and needed no weather protection.

 

[kb0nly]

The dielectric grease has its uses, but it also needs to be used properly.

I put a bit on the threads of my PO mounts (SO-239 Type) to prevent problems. I also put a bit on the center pin of the antenna as well. However, you don't want to slather and gob it on there when it comes to RF connections. I should have noted that a bit in the other thread but for the type of antenna being discussed there it wasn't a problem. For the scanner antenna he was referring to you have two terminals seperated by a sufficient distance. The grease is applied to each and can't cause an RF short.

For most electrical applications it doesn't cause any problems. Hams have been using it on rotor screw terminals for years and years without and shorting or other problems.

Why it caused trouble on that RJ-45 jack is arguable. It could have been a crappy quality grease, there could have been moisture or other contaminants in it, etc.. Usually a spray can of electro-wash or other similar types of contact and terminal cleaner will remove the grease with a few sprays. If on a metal only terminal with no worries of getting it on the plastic or insulating material a shot of brake cleaner will work also, but it will affect materials other than metal such as plastic.

 

[E-Man]

I have used countless tubes of dielectric grease for electrical connections, but never seen a tube on antenna sites. We always used butel, mastiff, duck seal whatever you want to call it, followed by layers of electrical tape. I think the newer snaplock connector covers may have came with a small package of dielectric grease? but we didnt use it.

 

[W6KRU]

Penetrox is good stuff. It is conductive though and you should keep that in mind. It is good for an anti-seize compound when assembling antennas. If dis-similar metals are being joined, it will save problems later on when attempting to pull things apart.

 

[AK9R]

if you don't put much that touches the center pin and shield you might be ok.

Right. I just use a couple of dabs on the threads of the NMO mount to keep out moisture and keep the threads from siezing. I don't try to pack the whole mount with the stuff.

And keep in mind, this is for connections, not just NMO, that may have to come apart from time to time. That's why I think dielectric grease works better than other more permanent methods. In my case, I have six antennas on the roof of a Ford Expedition. On the rare occasion when I run it through a car wash, I strip off all of the antennas and put on NMO caps. Then, after the car wash, I reinstall the antennas with a dab of dielectric grease on the threads.

 

[E-Man]

Penetrox is good stuff. It is conductive though and you should keep that in mind. It is good for an anti-seize compound when assembling antennas. If dis-similar metals are being joined, it will save problems later on when attempting to pull things apart.

Good stuff for low voltage electrical connections, (below 600v) except when you have 2 flat surfaces as it will create hotspots under a heavy load.

May work ok as anti-seize compound?

 

[fineshot1]

I have been using vaseline for years now on the nmo & connector threads and also other antenna parts with dissimilar metals and it works great.

 

[prcguy]

For antenna connections like the NMO mount threads any good outdoor grease will work fine, it doesn't need to be a 'dialectic" type, which has specific insulating properties.. For the cable TV and satellite dish industry dialectic grease is used all the time, you place a little dab right on the center conductor of the F connector and screw it down. In this case the dialectic constant of the grease should be similar to the coax dialectic because it becomes part of the coax. One popular brand of connector grease is called 'Stuf" and its made specifically for waterproofing the inside of RF connectors up to several GHz.
prcguy

 

[smokeyjones666]

I used to use the stuff all the time when I was a cable contractor. Both Comcast and Charter required we use it on grounding connectors. I always thought it was strange that they didn't require it on the f-connector threads.

I like to use it on antenna terminals for my installation here at home, but I'm very careful with it. No sense in slopping it on when a little bit will do the job.