Decade MS-100 Power Adjustment - Question

@richpowers You said..."

"I find the "ebay Refurbished" caption above the title curious. I've never seen that said before, but have seen "Seller Refurbished" captions numerous times."

Agree, What does a seller do to be an ebay refurbisher? "Refurbish"? Anyone should be skeptical of that. The only point is I was showing the access hole in the metal case as they are being made now and still awaiting an answer! I could have taken a picture of mine showing the same thing.
I have reservations on buying these used, and I can afford a new one, and recently as I posted purchased a new one that has the access hole in the cabinet. Easy to see the hole is as manufactured, not drilled after the fact. There should be a seal and notice not to adjust. I know from being at the lab that now, in Canada no way that would pass certification with an access for anyone to change the power.

I will email again or call directly if no answer in another day.

Here's the picture of the access hole up close.  This is as case is made, new in sealed box. Rugster got the same thing with his so they have been made like this for a while now.

Speaking if holes in transmitter cases, I drilled holes in both of my AM3000's to access the variable resistor I put in place of R7 for fine tuning the 100mW power level. Maybe a previous owner did the same thing with their Decade.

OK I got the answer. Here's my email response copied and pasted

Hi Mark,

this hole was used to reach a potentiometer inside to reduce the range, and it was for some specific clients but it’s not used anymore.

Happy New Year !

Michel......

So it seems there was a batch that were made like that for a specific customer but a lot of them also got into general sales and are kicking around. I have replied and asked him to send me a top part to replace the one with the hole.
I could also use some epoxy putty and neatly from the inside fill the hole to look nice and neat from the exterior.

@carl-blare No this was a manufactured batch. Posted my reply from Decade.

More on the Decade hole in the cabinet, I got this response...

Pasted from my email...."you won't have any problem with that, and you will likely never get inspected. The only tops I have right now are with the hole. The hole will be removed when I run out of the ones I have right now, and that won’t happen in less than a year".

So to Rugster here is what to do for piece of mind....take off the top cover, with epoxy putty for steel repair on the inside, neatly fill the hole and make it look smooth and even on the outside. It cures in 1 hour to a dark color. Then just blend it with some black touch up.

@richpowers - I didn't buy it directly from Sweetwater. It was listed on a site called Used Gear Exchange that Sweetwater own and operate. The seller was a private seller. Yes, used MS-100's are plentiful, at good prices! The two that I scored for $60 were originally listed for $99, then discounted to $60 after 5 months with no sale. I'm guessing that they might have moved faster if listed on eBay, though perhaps the demand is low and they take a while to sell, no matter where they are listed.

@carl-blare - Did you also drill a hole over C5, the output tuning trimcap? I find that the RF output peak is fairly sharp, and I need to adjust if I move the antenna wire too much.

@artisan-radio - do you, by any chance, remember where you got your weatherproof enclosure from, or any other details, such as brand, series, or model number? I'm interested in mounting an MS-100 outside, to maximize range.

@mark - that's an interesting response from Michel. I'm thinking it must have been a fairly lucrative agreement, to persuade him to add a hole to the top cover. I think I would have been reticent to do anything that might encourage an end-user to adjust the power. I wish I had access to an accurate calibrated field strength meter for the FM band. Used Potomac FIM-71's are going on eBay for $500-750. Tektronix offer a Potomac calibration service. You have to email them to get a quote. If I could get a calibrated FS meter for under $1K, it just might be worth it. Jim Wood's SW300 is not highly accurate, but apparently gives reasonably good FS readings on the AM band. I wonder if a budget VHF FS meter for Part 15'ers might be on the cards one day........?

@rugster  No. No other holes in the AMT3000's except for the one mentioned for R7 access.

@rugster Jim Wood!! If you read this forum we need an affordable FIM meter for FM that is frequency selective like the Potomac and can measure field strength down to .2 mV/M(200uV/M)!!!
I once tried this... https://www.tenmars.com/m/2001-1682-689905,c19121-1.php?Lang=en

But it is broadband not selective so couldn't get a specific frequency but measures down to 200uV/M so would work for us. Something like this hand held would be great. But useless if broadband and just measures everything.

Yes @mark - it needs to be selective enough so that a single FM channel can be tuned and measured, to the exclusion of all adjacent channels!

Sorry, but I did the outdoor thing quite a while ago.  I purchased the enclosure from e-bay and think it was Hyper-something or other.  Wasn't terribly expensive back then, don't know about now.  I drilled a hole in the top to put the antenna through, then sealed it.  I covered the exposed antenna with heat shrink tubing.  There was a hole at the bottom to run audio & power through, and it had a grommet so that condensation could escape.  The transmitter was up for about 2 years, exposed to the elements, and the (plastic enclosure) transmitter was still working well, running 24/7.  When I did take it down, I found a bit of rust on the screws, but that was it.

Of course, I'm on the Wet Coast in the Pacific Northwest, so we don't get a lot of snow, and temperatures are generally above freezing during winter, and somewhat cooler in the summer (although becoming less so now with global warming).

Just to give an idea of what BETS field strength can do in almost ideal conditions (elevated transmitter/antenna on a roof, direct line of sight), the average car radio (I estimate sensitivity 1-2 uv) could typically receive the signal 1/4 to 1/2 km.  I owned an exceptional, after-market radio and whip antenna, with sensitivity around 0.5uv, and sometimes could get a very weak but listenable signal almost a km (800-900 meters).

With my current installation, and location, I can only get several hundred meters, sometimes a bit more, with a similar Decade MS-100.  It just goes to show you that range by itself doesn't tell the whole story when it comes to Part 15 FM.

Thanks for that info @artisan-radio. I will keep looking for a suitable enclosure. The first order of the day, once the MS-100 in the plastic enclosure arrives, will be to test it from an outdoor location here, to see how outside mounting affects the range. I'm not able to mount the transmitter so that it will have a clear take-off in all directions but it should be an improvement, at least in some directions, from operating it indoors. I live in a housing co-operative, so have to consider the fact that my house neighbors don't think antennas and funny looking enclosures are as good-looking as I do!

You're lucky with BETS. I'd love to have a range of several hundred meters.

The second MS-100 arrived a few days ago. This one was the older model in the plastic enclosure. I see what you mean about the coating on the inside of the enclosure @mark - presumably for shielding. I noticed an interesting thing on removing the top cover. The multiturn trimpot for adjusting the over-modulation indicator has a dab of sealant on it. If anyone tried to readjust it, the seal would break, and you'd know that it had been tampered with. There is no sealant on the power level pot though. I went back and looked at my MS-100 in the metal enclosure and same thing - that pot has sealant on it, but not the power pot.

This got me to thinking - if you're going to put sealant on a pot, why not on the power adjustment pot as well? Seeing that the power output is critical to BETS-1 and Part 15 certifications, surely it would be more important for an end-user to know that the factory adjustments to the power hadn't been fiddled with, than the over-modulation setting? Neither of the power level pots on my two transmitters have sealant on them, or show any signs of ever having sealant, so I'm thinking that sealant wasn't applied. I emailed Michel over at Decade for confirmation that the power pots did or didn't have sealant applied after the power level was set. Will update this thread if and when I hear back from him.

My little station is now broadcasting on both AM and FM now. I couldn't be happier with these Decade transmitters. They were used occasionally by a church in their previous life, and were in storage most of the time when not being used. Definitely a worthwhile purchase.

@rugster Yes I agree with you that if he puts the sealant on the modulation adjust it should be on the RF trim pot also once set. If someone like yourself buys one used and those seals are broken you know that someone has opened it and who knows what else was tampered with besides the RF.

Glad they are working good. I so much wish there could be a affordable hand held field strength meter tuneable to a given frequency and measurable down to at least .1mV/M. To measure the 100uV/M for BETS and include the 250uV/M for the FCC measurement.
That Tenmars I showed a while ago would work if it was frequency selective.