Patrick Southern Posted December 2, 2014 Report Share Posted December 2, 2014 I've had talent complain of hot LA2s, but I've also had them complain of hot SMQVs. At similar RF output voltages, I actually find that the LA2s run a little cooler. In any case, the solution is to never allow a transmitter to touch the talent's skin - which is good practice anyway considering possible moisture issues which can effect many devices - particularly, in my experience, the LA2s. My QRX200, on the other hand, can easily get almost too hot to touch... Quote Link to comment Share on other sites More sharing options...
studiomprd Posted December 2, 2014 Report Share Posted December 2, 2014 PS: " At similar RF output voltages, " we do not measure transmitter output in voltage, we measure it in watts, as it is "power" Quote Link to comment Share on other sites More sharing options...
David Marien Posted December 2, 2014 Report Share Posted December 2, 2014 I have been using TRXLA on a reality show for the past few months. Used with Powerex 2700 mAh at 125 mW without power roll or Zaxnet features, I have not had any complaints. The TXs get slightly warm, but barely warmer than body temperature. We also use SMQV on the same show and I find that they do get a little warmer, but even then not really a problem. I guess the true test will be in a few weeks when we get into the 110+ Degrees Australian Christmas ! PS: Zaxcom wireless just sounds so much better than Lectros (off topic, but I couldn't resist) Quote Link to comment Share on other sites More sharing options...
DX Dave Posted December 5, 2014 Author Report Share Posted December 5, 2014 I've had the laser thermometer out and here are the results... Measuring after unit is left on for an hour, sitting on a desk with ambient room temp around 25 (77)degrees, using eneloop pro batts. TRXLA @ 50 mw Top half front side(screen) 42 (107.6) Bottom, front (batts) 32.9 (91.2) Top, back 41.9 (107.4) Bottom, back 35 (95) SMQV @100mw An even 32 (89.6) all over, front, back, top , wherever. TRXLA @125mw Top half front side(screen) 44 (111.2) - peaking at 46.7 (116) right in the top corner Bottom, front (batts) 35 (95) Top, back 43.2 (109.7) Bottom, back 35 (95) Quote Link to comment Share on other sites More sharing options...
pindrop Posted May 7, 2015 Report Share Posted May 7, 2015 I seldom use 125mw as in my tests a more than doubling of transmit power only delivers about 15-20% more range at best, hardly worth the bother and consequent reduction in battery life. I find it better to change my receiver antenna which can have a dramatic impact on range. So I go from whips, to SNA600 dipoles, to Yagis, depending on circumstances. I've worked out a quick change setup for my bag. The very lightweight memory wire, 3 element, animal tracking yagis easily giving me 250 meters, if I've scanned for free rf space beforehand. Quote Link to comment Share on other sites More sharing options...
johnpaul215 Posted May 8, 2015 Report Share Posted May 8, 2015 That's an RF staple. Doubling power doesn't double your range in other transmitters either (FM radio for example). My college radio station spent a lot of time explaining that to people when we went from 110 watts to 800 watts. A lot of people thought it was going to give us 8x the broadcast range. Nope. I wouldn't doubt that you will see "better real world results" from improving your reception antenna setup. Shark fins on my cart receiving Lectrosonics LMa transmitters can get some very very impressive range. Quote Link to comment Share on other sites More sharing options...
Abe Dolinger Posted May 11, 2015 Report Share Posted May 11, 2015 I seldom use 125mw as in my tests a more than doubling of transmit power only delivers about 15-20% more range at best, hardly worth the bother and consequent reduction in battery life. I find it better to change my receiver antenna which can have a dramatic impact on range. So I go from whips, to SNA600 dipoles, to Yagis, depending on circumstances. I've worked out a quick change setup for my bag. The very lightweight memory wire, 3 element, animal tracking yagis easily giving me 250 meters, if I've scanned for free rf space beforehand. Off topic, but do you have any pictures of your quick-change system on this board? Sounds like a lovely solution. Quote Link to comment Share on other sites More sharing options...
LarryF Posted May 11, 2015 Report Share Posted May 11, 2015 One. An SMQv at 250 mW never gets blistering hot unless it is left out in the sun. Two. Thanks to DXDave for actually doing some measurements, i.e, facts. Three. Here is a post from some time ago with some facts: To the Group: This post is in reply to an earlier post about "hot" SM transmitters. The SM puts out no more heat than a UM400; it just does it in a smaller volume. Since, despite the non stick finish, I'd never had any luck cooking omelets with an SM, I thought I'd run some crude tests. I tested the temperature rise of an SMa transmitter, lying with its backside on a pad of paper with the temperature probe between the unit and the pad of paper. The air was fairly still with only the usual office air conditioning running. The pad blocked some air circulation to the backside and seemed to be equivalent to a unit on a belt. After 3 hours the temperature rise was 16 degrees, from 76 to 92 F. The battery was an Eveready lithium disposable, though the battery should make no difference. An SMQa (250 mW) under the same test rose 22 degrees from Seventy-four to Ninety-six degrees F. I then firmly taped an SM transmitter to my leg with summer dress pants between the back of the unit and my leg. The probe was positioned between the pants material and the transmitter back. The unit was then covered in 6 layers of a Lectrosonics' jacket (polyester fleece) spread out over a 12 inch by 16 inch area around my leg. I think it is safe to assume that all the heat went into my leg. After the temperature stabilized with the transmitter off at 94 degrees F, I turned it on and at 45 minutes it was up to 104.5 degrees. At 66 minutes it was at 104.7 degrees and was effectively stable. The temperature rise (10 F) was smaller than the "belt" example (16 F) even though there was no heat loss to the air since heat was carried off by the circulatory system. The 8 hr metal contact standard for Europe is 43 C or 109.4 F. and this correlates well with the fact that I never detected the smell of burning Larry. Another web tidbit was that oxygen gas sensors for neonatal units use a small metal plate warmed to 45 C (113 F) to increase the gas exchange rate from the skin of a baby to the detecting unit. These can be operated for up to 8 hours. The point here is that if the SM is not touching the skin, the heat rise exists but is moderate. If the surrounding air temperatures are very high or the unit is in the sun, the unit might be uncomfortable to touch but that is only if it is not in contact with a cooling device (human being) and if it isn't in contact then there isn't a problem. If it is in long term contact with a person, then the person will cool the unit so that there is only a small temperature increase. The skin on a healthy person is going to be less than 98 degrees to begin with or they've got much worse problems than the 0.75 Watt heat source of an SM. In spite of all this, if the talent doesn't like the warmth, then a larger transmitter that spreads the heat out (UM400a) is one solution or a pouch or some thin foam between the transmitter and the talent. As far as potential burns, the safe touch temperature for unpainted metal for 10 seconds is 132 F. Ten seconds is more than long enough to remove the offending object to a safe place. If they have a good arm, it can be removed 50 feet or so. Best Regards, Larry Fisher Quote Link to comment Share on other sites More sharing options...
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