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LarryF

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Everything posted by LarryF

  1. I'd like to promote use of the 941 MHz band again, 941.525 to 959.825 MHz. It is for Part 74 users and for the last few years has been a very clear band in which to operate. Part 74 use means unlicensed Part 15 and white space users are prohibited. I would call this a traveling frequency as it is open all across the US (To misquote Paladin, "Have license, will travel"). For more info see: https://www.lectrosonics.com/lectrosonics-introduces-the-smwb-and-smdwb-wideband-transmitters-in-the-941-mhz-frequency-band.html Best Regards, Larry Fisher
  2. Unfortunately, unlike the FCC, the test labs don't publicly post the flora that they are testing but deep state leaks indicate a bumper crop of the seeds of Kali tragus in the New Mexico soil. With a few more months of increasing moisture plus the usual warm sunshine, the first grass green shoots will emerge. Best Regards, Larry Fisher
  3. RG-8X is .250" in diameter and RG8 is .400" diameter and half the loss per length. Best Regards, Larry Fisher
  4. Hi Derek, Now that you added amplification, I agree totally. Just make sure it is a high overload amplifier, i.e., pretty high current (power). It's not even necessary to use RG-8X (though it is the best of the .250" cables). Good ol' RG-58 will work fine, if you balance the amp gain and cable loss. Best Regards, Larry Fisher p.s. If the amp manufacturer or amplified antenna manufacturer doesn't spec third order intermod values, it's probably a poor choice.
  5. Cable loss is inversely proportional to cable diameter. RG8X is a smallish cable (.250" similar to RG-58) and will be relatively high loss over long runs. Don't confuse RG-8X with RG-8, which is a .400" cable with less loss over long runs. There are other .400" inch cables that are more flexible and have foamed dielectrics for a little less loss, emphasis on little. Google a cable loss table and figure out what kind of losses you can stand and make your choice. There rarely is a free lunch at the RF table. Best Regards, Larry Fisher
  6. Our attitude is "Thou shall not Fxxx around with lithium batteries." There's enough uncertainty with Chinese knockoffs and fake certifications on batteries already. I do truly understand your point, but we've gone the belt and suspenders route with lithiums. Best Regards, Larry Fisher
  7. Thanks for the helpful pictures. Best Regards, Larry Fisher
  8. I'd cut the jumpers in half and solder wires to the jumper ends. Though maybe not necessary, a small O-ring around both the female connector and small wires could support the wires' weight and protect them from violent shocks. Kind of a belt and suspenders approach. The good thing about this approach is it is easily reversible and doesn't require unsoldering the connector and maybe damaging the pad and trace. Best Regards, Larry Fisher
  9. Any combined transmitters need an isolator of some kind, either passive or active. If you simply connect the two transmitters together with a tee, best case is that the output of both transmitters will be greatly reduced. Worst case is that you will let the magic smoke out. Best, Larry F
  10. Since you are shown as being in Taiwan, I passed this on to the repair crew at Lectro to see how this should be handled. It usually is an alignment problem in the the SMQV. Lectro is 95% shutdown during the Xmas to New Year holidays so it may be a week before they get on this. Best Regards, Larry Fisher
  11. You probably can do the equivalent of moving the receiving antenna, as described above, by moving the transmitter up and down until you get a peak RF level. Again, the reason for looking for a peak is to insure you haven't created an interference at the receiving antenna, i.e., a dropout. I would think you could get a reasonable comparison between the quarter wave and the LPDA. Also, the quarter wave antenna needs a ground plane to work against, such as a receiver housing (not a good ground plane but better than nothing). It sounds like you just have it at the end of cable. Any bags of water (people) that are close to the antennas will change the results also. Best Regards, Larry Fisher
  12. The 941 MHz band is US only except Britain has a band at 960 MHz, as I remember. Best Regards, Larry Fisher
  13. You are correct in that the delta is too large. You should see an LPDA improvement of only 4 to 5 dB. To correctly measure an antenna's gain, you need an RF anechoic chamber ($100k+) or an outdoor site far from any reflecting objects with a large metallic ground plane in or on the ground. The antenna is placed on a wooden pole with a rope so it can be moved up and down. The antenna is moved up and down so the reflection from the ground plane is in phase and maximises the signal. You are always going to have some reflection from the ground (unless you have an anechoic chamber) so you simply maximise the received signal with a perfect ground plane and then subtract 3 dB. Your measurements are compromised by many reflections either adding to the signal level of the LPDA or more likely canceling out the signal at the 1/4 wave antenna. Basically you have a "dropout" at one antenna. Trying to measure a 4 dB delta indoors is impossible. Best Regards, Larry Fisher
  14. I would expect that the plug that "leveraged" that jack would have bent before the jack broke. That is to say the user would know immediately that too much sideways force was applied and would know the reason for the failure. From the picture it seems possible that overtightening the nut would pull the jack apart in that manner. Experimentally, I guess you would have to get the same jack and brutally tighten the nut to see if that duplicated the failure. Or push a plug sideways in the jack until something failed and see if it looked like the example. Best Regards, Larry Fisher
  15. You can use the SNA600. It is fairly broadband and our tests show it works well below 470 MHz. Just pull the arms to their furthest extension. It isn't directional of course. Best Regards, Larry Fisher You can also use the Lectro ALP-500 series of antennas for moderate gain and directionality at 470 MHz. The specs say it is good to 450 MHz. Make sure you don't use an amplified antenna; they only work as receive antennas. Best Regards, Larry Fisher
  16. +1... That's why people are looking for directional antennas and RF amplifiers to make their systems work at 2.4 GHz. Both of which are against FCC regulations. We might look at 2.4 GHz for remote control but not for production sound. It is way too line of sight, too busy with wifi and used by a variety of non-audio devices. If you want good, clean spectrum look at the 941 MHz band. It was set aside for wireless mic users when all the other part 74 bands were being sold or chopped up. Legally you need a license for 74 use but it keeps all the part 15 users away. Best Regards, Larry Fisher Actually, it improves the exactly same amount in both directions. A good receive antenna is an equally good transmit antenna. If it has 10 dB of gain as a receive antenna, it has 10 dB of gain as a transmit antenna. This is for an antenna without amplification of course. Best Regards, Larry Fisher
  17. 5/8 wavelength and 1/2 wavelength (4/8) antennas require additional matching whereas a 1/4 wavelength is a good match to 50 Ohms directly. Here's a easy to read article on 5/8 wavelength antennas: https://www.electronics-notes.com/articles/antennas-propagation/vertical-antennas/five-eighths-wavelength-vertical.php As I remember, a 1/2 wavelength antenna looks like a high impedance load, i.e., much greater than 50 Ohms (a bad thing) and requires lots of matching for poor results. At 2.5 GHz, a corner reflector antenna is reasonably sized and has excellent directivity and fairly high gain. They are available from a variety of antenna shops since they are used to extend wifi. See Borjam's post below. Watch out for cable losses. At 2.5 GHz they can be a decibel per foot so choose your cable wisely and keep it short. Best Regards, Larry Fisher Best Regards, Larry Fisher
  18. See fig. 2 in this link https://www.lectrosonics.com/Support/Microphone-Wiring/uhf-transmitter-5-pin-input-jack-wiring.html for 4 Volt 2 wire lavaliere. Specifically the shield (ground) goes to pin 1 of the 5 pin connector, the audio wire goes to pin 3 and pin 2 in the connector is jumped with a very short wire to pin 4 in the connector . Pin 5 has no connection. Best Regards, Larry Fisher
  19. This where we need our "It Depends" quote. The sensitivity of both Lectro systems is roughly the same. However, due to RF background noise in urban areas, sensitivity doesn't have a lot to do with range. (!) RF background noise is the great equalizer. For instance, assume a receiver with a measured sensitivity of -107 dBm (good not great) and a receiver with a sensitivity of -101 dBm (pretty bad). If you are in the mountains of Montana where RF background is very low, the good receiver will have about twice the range (6 dB better sensitivity) of the bad receiver. If you are in an urban area where the background noise is -100 dBm the performance of the good and bad receivers will be pretty equal. Both receivers will require at least a signal 10 dB greater than the background noise to deliver a usable signal. So both receivers will need a -90 dBm signal to be 10 dB above the background noise. This is analogous to recording a heavy metal band. It makes little difference if your mic preamps have a noise level of -131 dBm or -126 dBm; the preamp noise is totally buried in the music noise. So, in sum, the small differences in sensitivity between the Venue and SRc in the real world are negligible. If there are video transmitters, poorly shielded bag mixers, controllers or other wireless on set, all of a sudden the mountains of Montana will look like downtown LA. Best Regards, Larry Fisher
  20. At +10C (50F) the 12 bay charger should have been operating (no lights, no charging), unless the batteries themselves were very cold. As small as they are, I would expect them to warm up in 15 minutes or so. if the 12 bay comes back to operation in balmy temperatures, we may need to double check the operation in our temperature chamber. Please let me know. Best Regards, Larry Fisher
  21. I found this from Karl W. on the Lectro Facebook page (I hate Facebook): "We've created a new email address for product and problem inquiries: asktheexperts@lectrosonics.com. We promise we'll answer within 24 hours with a clear, concise, accurate answer." Best, Larry F
  22. The Lectro 12 bay charger has a temperature sensor cutoff of 0C (32F) as a safety measure. Batteries that are too cold or too hot should not be charged for safety and battery damage reasons. It isn't a bug. Best Regards, Larry Fisher
  23. That's pretty large (0.1uFd) . It may have a low voltage rating and might not be a ceramic. Call or email Lectro service (800 821 1121, service@lectrosonics.com) with your request and an address and they can mail you a couple of the original capacitors at no charge in a plain unmarked envelope. Best Regards, Larry Fisher
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