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About LarryF

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    Hero Member
  • Birthday 12/11/1943

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  • Location
    Rio Rancho, New Mexico
  • Interests
    Classical music, fast cars and Maine Coon cats
  • About
    I have been chief janitor at Lectrosonics for 40+ years.
  • Interested in Sound for Picture

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  1. Measure the resistance between the center pin of the antenna's BNC (or SMA) connector and the connector shell with a multimeter. If you don't have one, you can buy cheap multimeters for for $11 and up on Amazon. Everyone needs a multimeter. The reading will be several Ohms (lead resistance) if it is a short or very high reading (greater than 10,000 Ohms) if it is open. Multimeters measure DC resistance which is what an antenna bias supply is. If the reading is greater than a thousand Ohms, the antenna won't short the bias supply. This measurement is not the antenna impedance (unive
  2. Speaking of tumbleweeds and wagons: https://riverearth.com/tumbleweed-connection/
  3. Open (high DC impedance)? , not shorted (few Ohms of resistance) ? Seems backwards. LEF
  4. Count me as a "don't". I have trouble with the zeros and ones on power switches. LEF
  5. Check the antenna output and see if it is "open", I.e., not shorted. Most are open circuits at DC and can be hooked to DC bias without needing a DC block. Lef
  6. The best version ever: https://www.bing.com/videos/search?q=simpsons+paint+your+wagon+episode&docid=608024252287692810&mid=69C117A6D8259D49F0A169C117A6D8259D49F0A1&view=detail&FORM=VIRE
  7. Here's a half hour experiment that will tell you more than all the brainpower on this forum: put the bowties a foot in front of your bag in free air and record a walk with the transmitter in a straight line. Announce distances as you walk such as counting your steps. You can also announce landmarks as a double check. Go far enough that you will have dropouts. Now, on the same frequency and with the same transmitter position, try the bowties in your proposed positioning. Compare the two recorded results. Then you can tell us if this is a good idea or not. And you won't have to wait a month
  8. In New Mexico, April comes in like a coyote and leaves like a roadrunner.
  9. LarryF

    Antenna combiner

    Wisycom quotes "Output" third order intercept (Oip3) rather than the more useful "Input" ip3. The output ip3 number always looks better and therefore is commonly quoted. For instance, a device with a 20 dBm output ip3 (good) and 30 dB of gain (bad design), has an input ip3 of -10 dBm (poor). Specifically, high gain, low noise gain stages can have a good output ip3 but a lousy input ip3. And input ip3 is the important spec. Having said all that, the Wisycom unit is low gain, moderate noise, and high current. Looking at the 7 dB of gain, fudging a few dB of filter loss and 7 dB of splitter loss
  10. LarryF

    Antenna combiner

    The input third order intercept is only -5dBm (minus 5 dBm), according to their web specs of -35 dBm intermod products at -15 dBm two tone input. To convert to input third order intercept, subtract -15 dBm from -35 dBm for 20 dB difference. Add half of 20 dB to -15 dBm input and you have a -5 dBm third order input intercept. That isn't great in today's RF environment. Best Regards, Larry Fisher
  11. For a quarter wavelength whip antenna, 16 cm would be 470 MHz. You can use the numeric length guide on Lectrosonics.com to get a reasonable approximation for your frequencies if you want to trim to your blocks. https://www.lectrosonics.com/downloads/category/1-accessories.html?download=22:amj Best Regards, Larry Fisher
  12. To be a smart ass, there are 86,400 seconds in a day. Using three of them seems like a reasonable trade for not stepping on a mission critical transmitter. When you pick up an "off" transmitter, there is no way of knowing if it is clashing with an important channel. The "quick on, RF off" mode allows you to see what frequency it is on and adjust if necessary. And when you adjust the frequency you don't rip through a critical channel. As far as turning the feature off, that's fine 'till you forget that it's going to come on "hot". Finally, there needs to be some button combination tha
  13. p.s. Either wiring is "correct".
  14. There are two correct wirings for a COS-11. https://www.lectrosonics.com/lectrosonics-microphone-wiring/913-uhf-transmitter-5-pin-input-jack-wiring.html?highlight=WyJtaWMiLCJtaWMnIiwibWljJ2VkIiwibWljJ3MiLCJtaWMnZCIsIndpcmluZyIsIid3aXJpbmcnIl0= See Fig 5 (external resistor) and Fig 11(internal resistor) as shown in the above document. You may have two wired as Fig 11 (simpler) and one wired as Fig 5 (harder to do). The difference in gain between a 1k resistor in Fig 5 and the internal 2.7k in Fig 11 is 10 dB. Noise is reduced 10dB also, so gaining up the transmitter by 1
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