SSTran AMT3000 Temperature Concerns

Hi, Adam,

The AMT3000 consumes little power and therefore doesn't generate much heat so operation at 38 degrees should not be a problem.  If you want, you can leave the top cover off to provide some air circulation but this should not be necessry.

Regarding the use of coax for the antenna, this will add a lot of capacitance to the output circut and it may not tune properly.  Worth a try but be aware of the possible problem.

Neil

Adam has opened a question I have not previously thought about... the tolerable operating temperature range for the AMT5000 or similar transmitter.

Not only attics are hot boxes, but also outdoor installations inside water-tight enclosures are sometimes subjected to direct sun.

A moment ago I scrolled through the sstran.com website followed by page-flipping in the manual, but I find no mention of operating temperature information.

The next step, later today, will be to visit the websites of Procaster and Rangemaster, two manufacturers of transmitters intended for outdoor use. Perhaps they publish some temperature guidelines, which I'm sure would be applicable to all similar devices.

If you beat me to it please post the information and save me the effort of working in this heat!

Thanks Neil, I might try and see how my peak readings compare using Coax, and of course the range I get. Heat issues aside, It would be convenient to have the transmitter accessible if I need to tweak gain or compression.

Yes Carl, I did wonder about temperature with you folks running base loaded antennas with AMT3000s in boxes outside. We're having a heatwave in the UK right now, and its 32 degrees celsius OUTSIDE (hotter in the attic), which is exceptional and unpleasant with no AC in most homes :(, so got me thinking..

I know much of the USA can see hotter temperatures outside, so perhaps I'm worrying over nothing...

38 celsius I presume?

or more on warm summerdays with the sun on the roof.

If the temperature gets much hotter it may not be good as the voltage regulator is what gets hot and the little heat sink is supposed to keep it cool(or cooler). All the other components are good to about  80 degrees celsius. Although not sure about the IC's....check the data info online for the chips used.

Wouldn't hurt to have some extra regulator chips in case you might have to replace it.

Mark

Heat is not a known problem for part 15 type transmitters or it would be mentioned somewhere in their literature.

I have been all over the websites for Rangemaster and Procaster as well as the entire Procaster Manual and see no mention of heating specs or cautions.

Maybe they should all think about printing words to assure customers that operating temperature under ordinary circumstances is not an issue.

That doesn't mean I'm convinced.

I think the suggestion made earlier of researching the temperature tolerance of chips and transistors is a worthwhile idea.

Not only the tolerance of the components, but the quality of the soldering, etc.

I had my Decade MS-100 outside in a weather proof box for over 2 years, running 24/7, with no issue.  I can vouch for the ruggedness of that particular product.

I suspect that you'd have to have similar experiences & results to vouch similarly for other products.

Decade does actually state a temperature range for normal operation....0 to 122 F or -18 to 50 C

http://www.decadetransmitters.com/en/transmitters/ms-series?ssid=3cwbr6v3x6ys4v3&ssname=ms_100_manual.pdf

But I would be wary of using any transmitter that hot without having it open and a small fan blowing on it.

Mark

I looked up datasheets for the ICs, and all stated up to 125 degrees celsius, with the exception of the SSM2166S IC which handles audio compression, that had a max of 85 degrees celsius.

So I think its safe to say the transmitter should be pretty resilient in high temperatures. Given my use will not be continuous, I think I should be ok, even in these high temperatures.

Thanks all for the comments

Summer heat in Florida can be pretty brutal not to mention the frequency of lightning strikes. I have 2 Rangemasters that run 24/7 with no issues. The PCB construction is second to none IMHO.

My Procaster has been on the outside of the third floor window on the south side of our house for nearly 4 years with no ill effects.  It bakes in the sun darn near all day and we do get near 100 F up here in the north country.  On the other side, we regularly hit -30 below zero in the winter. Field strength and frequency remain stable through it all.

TIB

Not to mention that 100 degrees in the shade is a lot hotter in the sun!

My AMT-3000 ran outside for a couple

of years.  Zero degrees to 100, or thereabouts (sp???).  In the winter,

sometimes it and it's little plastic "house" were buried way under the snow. 

I don't remember

when I bought the kit, but I've never had 

any trouble with it of any kind.  It has

got to be at least 10 years old.

Brooce Part 15 Hartford

The first components to fail will be the electrolytic capacitors and there are eight of them. I don't have a list of the actual components used so let's assume the electrolyic caps are bottom-of-the line type rated for 1000 hours at 85 deg C. Using 2X life for every 10 deg C, the life at these temps will be:

T(C)  HOURS

38       48k

40       26k

50       12k

60       6k

70       3k

80       1.5k

85       1k

The caps can last longer than predicted if the demands on them are not high. That is, the circuit can tolerate larger changes in capacitance and ESR (Equivalent Series Resistance). If replaced, the new caps can be 105 deg C rated for 5000 hours or more. These could provide 20X the life of bottom-of-the-line caps. 

I would run the unit outside in the sun with a sun shield shading the enclosure.