Tram 1486 disassemble

[mmckenna]

Had to replace an antenna at a -very- remote repeater site on Friday. Decided to dissect the antenna for your viewing pleasure.

Backstory:
The system was originally installed back in 2016 or so and consisted of 3 sites linked via wireless IP links covering some remote territory. It was originally done on a very limited budget imposed by the group, so it was a lot of low end gear. About 8 years ago I "inherited" this system. It had a number of issues that I worked through as the customers budget allowed.

Over the years, I've upgraded the other two sites with new, more appropriate antennas, feedline, and new repeaters with built in IP linking. That all improved performance and coverage quite a bit.

Due to the difficulty of accessing this site, I'd held off upgrading this antenna. It was working, even though it was a Tram antenna and LMR-400(!!!). Well, late this winter, my luck started to run out. The LMR-400 started to do what LMR series cable does when used in a duplex system. I was 80% sure it was the cable, but the antenna was always a question mark, and for the application, it had an unfavorable radiation pattern.

So, order the parts, an appropriate Laird base antenna was chosen to stay within the customer budget constraints. Went with a lower gain model to improve coverage in some deep canyons around the site. Ordered 30 feet of 1/2" superflex Heliax.

Early Friday morning myself and one of the rangers that knew the trails that had recently changed due to a landslide started the long hike. Parked the truck as close as I could and started the 2.5 mile hike. Site is at 1200 feet and the starting point is near sea level. Over one 700 foot ridge, down into a near sea level river canyon, up 1200. Took about 2 hours. 4 foot antenna sticking out of the pack, 30 feet of Heliax strapped on. Backpack full of tools and test gear. But it was a beautiful day. Saw a couple of snakes crossing the trail, one California Condor buzzed us at the site, grey whales off shore, turkey vultures, and one military jet. It's the sort of stuff that makes me love this job and amazed that they pay me to do it. But, on the other hand, up at 5am, on site by 8:30, down by 3:30 and home by 7. A long, tiring day, lots of windshield time, sore feet, sunburn, tired and hungry. Next time someone makes the "cushy government job" comment, I'm going to kick them in the gonads.

Anyway, got to the site, threw the meter on the feed line and sure enough, SWR read high, and it had that crackly audio that said the LMR400 was doing it's thing.

Swapped out the antenna with a new Laird antenna and new 1/2" Heliax. Tilted the mast back up, tensioned the guys and crossed my fingers. Reconnected to the enclosure, SWR nice and low, audio clear as a bell. Sealed up the last connector and started the long hike back down.

Today, I decided to crack open the old antenna. Party out of curiosity, partly to make sure it'd fit in the trash can. It's a Tram, that much is legible. Pretty sure it's a 1486, UHF, ~6dB gain. It's 3 stacked 5/8th's wave elements in a fiberglass tube.

OK, nothing wrong with that, about what I'd expect for a budget antenna. It did its job for 10 years, withstanding hot summers, high winds, and one wild land fire.

Taking a closer look:
Fittings are crimped. Not soldered, just crimped. No signs of damage or corrosion.

Whips were brass rod. Coils were copper wire. Crimped joints joining the two dissimilar metals.

So, there ya go. Not bad for a $99 antenna. It did its job, but ultimately was replaced. It did make a nice trekking pole to use on my decent.

Customer is happy with the improved performance, no noise and all within their limited budget. I'm happy knowing that I've done what I can to give them a reliable system that should give them many years of use.

 

[kayn1n32008]

Had to replace an antenna at a -very- remote repeater site on Friday. Decided to dissect the antenna for your viewing pleasure.

Ohhhh... show and tell time!!!

Anyway, got to the site, threw the meter on the feed line and sure enough, SWR read high, and it had that crackly audio that said the LMR400 was doing it's thing.

Sounds about LMR400. Drives me nuts that people think it's okay for repeater use, even for a 'short run'

Customer is happy with the improved performance, no noise and all within their limited budget.

The antenna looks to be in okay condition for a decade of service. While you could have gotten away with just a feedline swap, fiberglass antennas have their own issues long term, especially hammy grade stuff.

We have a few fiberglass verticals that are of unknown age I'd like to replace at our club station. I was up close at one of them this weekend, and it was in pretty sad shape.

 

[mmckenna]

The antenna looks to be in okay condition for a decade of service. While you could have gotten away with just a feedline swap, fiberglass antennas have their own issues long term, especially hammy grade stuff.

We have a few fiberglass verticals that are of unknown age I'd like to replace at our club station. I was up close at one of them this weekend, and it was in pretty sad shape.

It looked good. The fiberglass radome was in pretty good shape, no signs of damage. I wasn't crazy about the crimped dissimilar metals in its construction. While there didn't seem to be any visible corrosion, the metal had a patina that was probably going in that direction.

The other two sites received single bay folded dipoles (Telewave ANT450) since their main coverage area was way down into some canyons below the site. I even added some mechanical downtilt to assist. They've stood up exceedingly well and are great performers.
This specific site is up higher and has some longer views, as well as the deep surrounding canyons, so the additional gain/radiation pattern was a tradeoff.

The LMR400 worked well as long as it stays perfectly dry, jacket in tact and zero moisture. But losing that, it all goes down hill. The original installer seemed to treat waterproofing of coax connectors as a bit of an afterthought, which may not have helped.

Glad to get the LMR cable, UHF connectors, Tram antennas out of the system. Thankfully they had enough budget to let me install the right stuff for the job.

 

[kayn1n32008]

Glad to get the LMR cable, UHF connectors, Tram antennas out of the system. Thankfully they had enough budget to let me install the right stuff for the job.

Good old hammy LMR400SO239/PL259 love.

This is the other reason I want to replace the 20+ year old fiberglass antennas. the metal bases are deeply pitted, the fiberglass looks like it wants to act like a porcupine you if you grab the antenna and, even though i cant see the connector, ill bet an unreasonable amount of money they are UHF connectors. It looks like we have 2 or three of them to replace, and adding one to our training facility to get the VHF radio antenna outside.

Our ops crew has spent a lot of time and effort removing LMR400 and as many SO-239/PL259 connectors as we can. I think the only ones left are on the 2x TK-630H that make up out 6m repeater and the 2x DR-235 that make up our 1.25m repeater. Sadly there are not many good options for 6m or 1.25m repeaters. Bridgecom is NOT an option we would consider for 1.25m, for a variety of reasons.

 

[mmckenna]

Bridgecom is NOT an option we would consider for 1.25m, for a variety of reasons.

Yeah, this site originally had 3 Bridgecom repeaters. After I replaced their Baofengs, the Bridgecoms were the next thing to go. They worked OK for a low budget repeater, but a new Kenwood NXR-1800 was about the same price, plus it had IP linking built in, and a web interface for management.
They are still using a few Bridgecoms as control stations. One power supply failed already. But they've been squarely in the "good enough for now" category.

 

[mmckenna]

Good old hammy LMR400SO239/PL259 love.

Heliax and N connectors make me happy for this sort of stuff.

 

[AK9R]

The design of the antenna appears to be similar to the Diamond antennas that I've seen disassembled. However, my recollection is that Diamond makes the element from one contiguous piece of copper wire where this Tram has the brass elements and copper coils as separate pieces. I don't know how much of a problem this is. Copper should be almost 99% pure Cu while brass is typically 65-80% Cu. The crimped connections in the last photo appear to be brass.

In the first photo, go up to the third foam insulator from the bottom. What am I seeing just above that insulator? Is that the connection you show in the third photo? If so, I'm not crazy that they used a set-screw connection there especially in a contiguous fiberglass radome. And, it looks like nickel-plated mystery metal (brass?). Seems a set screw would loosen over time, in addition to the dissimilar metals, and cause some problems as the antenna flexed. Multiple-section Diamonds (X200 and above) have the same sort of set-screw connection, but my recollection is that it's brass or copper.

Nice job.

P.S. Been a while since the garage floor was painted?

 

[mmckenna]

In the first photo, go up to the third foam insulator from the bottom. What am I seeing just above that insulator?

Soft foam to keep the radiator from slapping around inside the tube.

Is that the connection you show in the third photo?

Yes.

If so, I'm not crazy that they used a set-screw connection there especially in a contiguous fiberglass radome. And, it looks like nickel-plated mystery metal (brass?). Seems a set screw would loosen over time, in addition to the dissimilar metals, and cause some problems as the antenna flexed. Multiple-section Diamonds (X200 and above) have the same sort of set-screw connection, but my recollection is that it's brass or copper.

Right, I'm not convinced it is even nickel. The antenna (if it's what I think it is) is marked as "tunable" and I think this is how it would be tuned. No idea if the original installer tuned this or not.

Nice job.

Thanks, trying to keep an open mind with these Tram products, but after disassembling a few, I'm not impressed.
Like I've said, budgets are a thing, and entry level antennas have their place. But due to the remoteness of this repeater, this wasn't the place. I'm glad it's been replaced.

P.S. Been a while since the garage floor was painted?

I moved in 24 years ago, haven't painted it since. Every now and then I think about doing it, but that would mean taking everything out of the garage, finding somewhere to put it, and painting it. If I'm going to go through all that, I'm going to move out.