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LarryF

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Everything posted by LarryF

  1. The SNA600a is 2:1 only at the band edges. When defining bandwidth, the 2:1 value is a commonly accepted bandwidth definer. Inside that bandwidth, the SNA600a SWR is much lower on the order of 1.2:1. Keep in mind, a tunable bandwidth may be useful in attenuating undesired RF. "Different horses for different courses" . Best Regards, Larry Fisher
  2. LarryF

    IFBlue

    The headphone output is quiet and can be used as a line level (1 Volt) output. It is just lower impedance than most line level outputs, which is never a bad thing. I'm missing what is the reticence to use it as a line level output. (??). It's a minor point but G3/G4 receivers do not have matching equalization and compander time constants to the Lectro IFB. It certainly will work, though. Best Regards, Larry Fisher
  3. The loss at our frequencies is on the order a quarter of a dB or less. In sum, fuggedaboutit. LEF p.s. Buying two 50 foot cables and using a coupler to make an occasional 100 foot cable is more space efficient and cheaper than buying a 50 and 100 foot cable.
  4. Hi Derek, The EBL batteries have 95% of the Energizer runtime. For instance, if you have 6 hours of run time on the Bunny Brand, that's 360 minutes. The EBL 95% is 5% less time or .05 x 360 =18 minutes less. So you'd have 5 hours and 42 minutes compared to 6 hours. Or you can just subtract 1/20th of the run time. Regards, LEF p.s. The reason I didn't do run times is we have many transmitters at various power levels and single and dual batteries. In retirement, I'm getting to be pretty lazy.
  5. I bought some disposable AA lithiums from Amazon and tested for power capacity. Total power was a better benchmark since average voltage and Amp hours varied by 8% or so across the three brands. Total power makes more sense due to the switching "power" supplies in Lectro transmitters, since they are like a DC transformer with power in equal to power out (less small losses). I bought Eveready as a reference, NINMA since they claimed 3500 mAh, and EBL since I recognized the brand as a larger seller of battery products. The testing rig was a computer controlled battery tester made by West Mountain Radio. The test current was a constant 400 mA similar to Lectro transmitter current drain. I also calculated cost, corrected for power capacity using prices off Amazon. Amazon has coupons and scheduled delivery discounts that will vary over time. The corrected costs are as of today, 15 Oct 2023 for 24 batteries purchased at a time. Eveready Ultimate Lithium: 4.418 Watt hour 100% (reference) $2.79 2.79 corrected EBL Lithium: 4.212 Wh 95% $1.62 1.70 corrected NINMA Lithium: 4.146 Wh 94% $1.75 1.86 corrected Conclusions: The off brand lithiums would be a cost viable choice if you don't need the last few minutes of run time. A situation where NiMh won't run long enough but an Eveready Lithium is more time than you need. The NINMA brand had the highest current capacity but the average voltage was 8% lower. That reduced its power capacity. Eveready had the highest average voltage making it the highest capacity. EBL had good current and voltage putting it in the middle. EBL was the most cost effective. YMMV Best Regards, Larry Fisher
  6. The difference is in initial battery voltage. The lithium is higher voltage so the current draw is lower due to the fact that the power supply in the unit is a switching power supply. Switchers convert power in to power out. So a higher voltage can draw less current for a given power in. For instance, a switching power supply running from a 12 Volt battery could draw 5 Amps and put out 5 Volts at 12 Amps, if it were 100% efficient. 60 Watts in for 60 Watts out. The switchers we employ, are chosen for high efficiency of course. All this to say, if a unit needs 600 milliWatts to operate, that would be 500 mA at 1.2 Volts (NiMh) but only 400 mA at 1.5 Volts (lithium). And all this is complicated by the fact that the lithium starts out at 1.5 Volts and then gradually falls to 1 Volt or less before dying and the NiMh stays at 1.2 Volts until suddenly collapsing. Best Regards, Larry Fisher
  7. Just double checking: You ran the batteries down until the transmitter died? Best Regards, Larry Fisher
  8. RG-8X has 7.5 dB of loss at 75' and 600 MHz, only a dB better than RG-58 RG-8 has 4 dB of loss, same conditions Best Regards, Larry Fisher
  9. The output on the IFBlue is two parallel headphone amps with the same signal (and polarity) on tip and ring. This will drive stereo headphones in a dual mono mode. Going into a balanced circuit using an XLR will give different results depending on the input of the camera or device, i.e., is it balanced and floating, balanced and center tapped, or unbalanced but just happens to use an XLR. Theoretically, the tip and ring signals should cancel out leaving you with no audio. Small differences in level from the headphone amps will give a small difference signal but not of good quality, i.e., your tubbiness. My general recommendation for any unknown device is to tie the IFBlue sleeve (ground) to pin 1 of the XLR , IFBlue tip to pin 2 and leave pin three of the XLR open. Then also try pin three of the XLR tied to pin 1 with a temporary jumper. Quite often there will be a big change in level. Use the higher level configuration. If there is little or no difference, then leave pin three open. Rarely, an older device from even a major manufacturer will make pin 3 of the input hot and pin 2 dead or grounded. If so, reverse all the pin 2 and pin 3 directions above. Best Regards, Larry Fisher
  10. [snip] ...but for now adding longer cable gives me higher mW !! 😂 it does not make sense, yet. [snip] The fact that minor cable length difference makes a power difference is a very strong indication that the measuring device is not a 50 Ohm load and is not terminating the cable properly, i.e., there are standing waves on the cable. Best Regards, Larry Fisher
  11. Out of the thousands sold, we have only had to repair single digits of door, case or clip. Two possibilities: 1. The casual users on set are incredibly careful with the sound department's equipment. 2. The case is stronger than it looks. Your choice, since you know the your users well. Also low cost IFBlue clip, knob and door repair parts are available at Lectro. Best Regards, Larry Fisher
  12. I'm guessing here but if the headphone cable is also the antenna, then the inductors block RF but pass audio and the capacitors pass RF but block audio. LF
  13. https://www.instructables.com/Inductor-Color-Code-Guide/ I read 7.5 uH 10% but I'm not that familiar with military markings. Anybody that is, chime in. At 216 MHz that inductor would have a reactance of 10k Ohms or effectively an open circuit for RF. The 1 Ohm resistance you measured would be at audio frequencies. Those values pass the smell test. The inductor value is not critical. Any value from 2 to 8 uH will work. The 7.5 uH is little high in my judgement but that value would also work down at 72 MHz which may explain the higher value. Best Regards, Larry Fisher
  14. LarryF

    IFBlue

    Your calculations are absolutely correct for 50 Ohms. Fifty Ohm values are typically used for RF levels since that is the most common impedance for RF devices and RF measurements. For audio levels, 600 Ohm levels were once the most common. Pro equipment still uses those values as a reference. That is what I did when I referred to 2 dBm, thinking of meter levels in a pro audio mixer or recorder. However, the most correct value for the Lectro IFB output is the 1 Volt into 50 Ohms specification. That is exact and has nothing to do with RF but is an average impedance value for most headphones that typically range between 32 and 80 Ohms. All this to say, the IFB will have the least self noise going into a line level input that has enough gain to match to low line levels of 0.1 to 0.3 Volts RMS. Best Regards, Larry Fisher
  15. LarryF

    IFBlue

    From IFBlue.com Audio output: 1V RMS into 50 ohms minimum Treat it as a consumer line level. It is a stout headphone level i.e.,+2 dBm. Best, LarryF
  16. LarryF

    IFBlue

    The IFB systems (Blue or Lectro) have a moderately narrow modulation acceptance of 20 to 25 kHz. If used with a common 50 kHz modulation transmitter they will spatter on peaks. Best, Larry F
  17. Try : AT 1 to Lectro 1 AT 4 to Lectro 3 Lectro 2 to Lectro 4 If this has very low gain, then try adding AT3 to Lectro5 https://www.lectrosonics.com/lectrosonics-microphone-wiring/uhf-transmitter-5-pin-input-jack-wiring.html The 4 Volts and current limiting from the Lectro should protect the mic in any hookup. The regulated Lectro 4 Volts at the mic is actually more voltage at the mic than provided by typical "5 Volt" wiring through a load resistor. Let us know if any of this works. Best Regards, Larry Fisher p.s. Phase is flipped 180. You may need to correct for that if near other mics
  18. Yes. You want to amplify the cleanest signal, not one that is already degraded. Best Regards, Larry Fisher
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