Vern, This will probably raise some eyebrows, but I put up a ham repeater on the top of an 18-story office building in Orlando, and will tell you what i did.
I used a very stout, steel rack box, cast off from the computer industry, sealed the few holes in it, weatherstripped the door and gasketed the latch, painted it with a light almond-colored Rust-O-Leum (similar to that beige used on zillions of computers) and put it out there with no ventilation whatsoever. It held an Astron supply, a UHF Mastr II mobile converted for dull duplex and running about 25 watts, an S-Com 7K controller, and a TX-RX duplexer. The only path for heat dissipation was whatever conduction transfer happened through the surface area of the metal cabinet. I used an attic fan thermal switch tied to a controler logic input to fire a macro and change the courtesy tone whenever the switch's 119-degree F threshhold was hit. Even on the hottest summer day and with heavy repeater use, it never tripped. I later mounted a digital thermometer which recorded highest and lowest observed temps on a rack panel, put it in the cabinet, and watched it through part of a summer. The hottest the inside of the cabinet ever got was about 4 degrees above ambient. If I recall, the highest ambient temp recorded by the NOAA for Orlando during those weeks was 94, and the highest recorded temp in the cabinet was 98. I did find a little condensation pooled on the floor of the cabinet once when made a visit. I bought a "Damp Rid" cup, a dessicant product designed for use in residential closets, from Ace Hardware, and never had that problem again. After I left town, the guys who took over the repeater added a 100W HF remote, IRLP node in the cabinet, and even provided some rack space to a Part 15 wireless internet provider in barter for their wireless connection for IRLP. Apparently the extra heat was not an issue. The repeater was installed in 1995. It's still there. By the way, when the repeater was still in its early stages, using solar power and 2-watt Repco transmitter strip, I did enclose the whole thing in a Rubbermaid "Action Packer" storage box. It didn't work out so well. In the Florida sun, the lid and the box will expand unevenly during warm-up, and spend part of each day misaligned, letting small insects find their way in, sometimes in large numbers. After a few weeks, it will get so beat up by UV that it will start to crack and warp. My feeling in taking the approach I did was that in that climate, bugs and condensation would be bigger problems than heat, especially for a moble rig designed to work properly in a car trunk. If you limit the ingress/egress of ambient air, and have equipment which holds the inside of the cabinet even a degree or two above outside temp, you will avoid condensation in the equipment itself. If you put just a duplexer in a box by itself, there will be very little heat generated inside the box, especially when the repeater is idle, so condensation may be a bigger issue for you. I'm guessing a duplexer that gets wet inside is no fun. I learned alot with that repeater. It started out with a cheapo hamfest duplexer, Belden 9913 jumpers and feedline to a Cushcraft Ringo Ranger, and a Repco UHF data receiver board with a homemade squelch circuit and a Motrac helical front end grafted on. Needless to say, there were newbie mistakes I wouldn't make again. But I was very happy with the way the cabinet worked out. Your mileage may vary. There has to be a reason they sell high-dollar NEMA cabinets with their own air conditioners, but they probably won't sell one to me! 73, Paul, AE4KR ----- Original Message ----- From: Mung Bungholio To: Repeater-Builder@yahoogroups.com Sent: Monday, October 27, 2008 7:14 AM Subject: [Repeater-Builder] Duplexers Is it OK to get some kind of storage container or something like that and put my duplexer outside? What would be the risks of doing so? I am in Florida so lots of rain and heat but no freezing months or anything like that? Thanks, Vern KI4ONW
