Jump to content

LarryF

Members
  • Content Count

    2,348
  • Joined

  • Last visited

  • Days Won

    10

1 Follower

About LarryF

  • Rank
    Hero Member
  • Birthday 12/11/1943

Contact Methods

  • AIM
    fisherlarry@gmail.com
  • Website URL
    http://lectrosonics.com

Profile Information

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

Recent Profile Visitors

4,732 profile views
  1. Lectro has done this since the first UM400 to squeeze 3 bits more dynamic range (18 dB) out of the then available low current dual channel ADC's. Best Regards, Larry Fisher
  2. My calculator says 192.7 dB. Or as a rough rule of thumb, at 6 dB per bit, is "roughly" 186 dB. LEF
  3. Happy Birthday, Jeff. And a big Thanks! from all of us, for making this close knit community even more of a community. Best Regards, Larry Fisher
  4. The 195 series gear is fully compatible with 200 series equipment and 400 series equipment when running in the 200 mode. The 195 gear was all analog FM, 75 kHz deviation, no pre-emphasis with a dual band compander. If the pilot tone crystals are defective in the 195 (A weak point), then run in the bypass mode on the receivers. The 100 mode is 25 kHz deviation, with significant pre-emphasis and is not compatible with the 195 series. If the frequency is clear, these are good radios with much tighter RF filtering than any current products, ours or others. The audio is equivalent to the 200 or 400 series. Best Regards, Larry Fisher
  5. Avoid is kinda strong. There are good reasons for using narrower filters in a multicoupler, particularly as new cell phone usage starts up in the 600 to 800 Mhz bands. Your post pretty well gives the reasons for narrower filters. The 411A does a better job than most of front end filtering but that advantage is somewhat over ridden by any multicoupler, more so by wide ones with weak amplifiers. In a well designed multicoupler not only will the filters be only as wide as necessary but the internal amp will be low distortion at high input levels in order to not produce RF intermod products. This spec is commonly left out by some manufactures, as it is hard (expensive) to accomplish. Instead they will quote amazing noise figures which are easy (read cheap). Ideally the amp in a multicoupler will have low gain, low noise, and low distortion (a high third order input intermod number). As usual with things RF, these desirable traits are not easy to attain simultaneously. A really strong, low intermod RF amp can make up for wide band input filters, but the ideal is narrow filters and strong amps. Watch out for quotes of output intermod number. These values are always higher than the input intermod value and make for better numbers. What really measures the performance in a multicoupler is the input intermod value. A high gain, low power amplifier can have good output numbers but weak input numbers since the input number is the output value MINUS the amplifier gain, i.e., high gain leads to poor input intermod values but usually excellent noise figures. One way to improve the performance of a wideband multicopler, is to use antennas with built in filtering or inherent narrow band response. For instance, an SNA600 dipole has about a 30 MHz bandwidth. That is equivalent to having a 30 MHz filter at the input of the multicoupler. A Yagi antenna would be an even narrower bandwidth. Sharkfins (log periodics) have wide response so are not good "filters". Powered sharkfins with built in filters can help. Another way to protect a wideband unit is to put a low loss inline filter in front of the wideband multicoupler input and then swap out the inline filters depending on what bands you are operating in. As an easy example, the Lectro PF25 is a one block wide passive filter and the PF50 is two blocks wide. What the user would like to have is a wideband antenna system and a wideband multicoupler that does not introduce spurious signals (low intermod) and is usable for all possible wireless frequencies. As in most RF compromise, as the airwaves become more congested this dream is going to become a little bit of a nightmare or at least a nightpony. Best Regards, Larry Fisher All very true, though I would say, if it has an amp at all, then input intermod values need to be considered. I would like to see PSC measure and publish third order input intermod numbers rather than just an excellent noise figure. See discussion above. Best Regards, Larry Fisher
  6. Actually, the shield needs to be folded as we show it. The folded shield couples to the the cable shield of the coax to "choke" off the RF and force the unbalanced coax to radiate as a dipole. The ideal construction is to have a 1/4 wave cylinder around the coax cable with the shield tied to the top of the cylinder. Here's a long explanation that saves me a lot of typing: http://www.hamuniverse.com/vertbazooka.html This is a good antenna not a great antenna, but it is small, compact and bends easily for storage or placing on a strap. It is a marked improvement over a rusty coat hanger. Best Regards, Larry Fisher
  7. I would like to have seen a range test that modeled real conditions, i.e., the transmitters mounted at the waist, behind the person. That would have given a better comparison of body absorption and shadowing. My guess (and it is a guess) is that the 2.4 GHz would be much more affected by the body than say 600 MHz. Holding transmitters out the window, line of sight, is so far removed from reality as to be almost a worthless comparison. Note, I said almost. As far as delay, different kinds of error correction introduce different amounts of delay. Forward error correction (FEC) can add relatively tiny amounts of delay since correction on the current data is done by using data already received. However, interleaving of data to overcome burst errors can add significant delay since all the interleaved data must be received before the data can be reconstructed. As with all things RF, it's a compromise. Best Regards, Larry Fisher
  8. LarryF

    scorpio!

    Easy money. Best Regards, Larry Fisher
  9. Hi Alexander, The 5 pin isn't the problem since the hiss comes and goes and disappears with increasing gain, but as Mike suggests, it's always good to keep the 5 pin connector clean. Sweat, rain and Coca-Cola ends up in there as the transmitters go through various users. Alcohol on a thinned down Q-Tip works pretty well or cotton on a toothpick. Don't flood the connector. We try to seal them but it is not 100% effective. You may have to blow a strand or two of lint out after you finish. I suspect instability (oscillation) in the mic gain stage when the gain is below 20, particularly since it "stabilizes" sometimes when you unplug the lavaliere. Best Regards, Larry Fisher
  10. That will give you more room but if you ever want to use that expensive Lemo with a COS-11, Lectro's wiring calls for a pin 2 connection for lowest distortion, i.e., the best COS-11 wiring uses all three pins. The simple explanation is that the COS-11 was designed as a three wire lavaliere. If you aren't going to use Lectros or COS-11's ,then happily whack away. Best Regards, Larry Fisher
  11. "Show us how you made it so we can do it on our own, in house, next time". Hard to know whether to laugh or cry. Best Regards, Larry Fisher
  12. Now I tried to be serious, factual and helpful but you three are just being ridiculous. Best Regards, Larry Fisher
  13. Obviously Block 941. Higher frequency gives more high end. Best Regards, Larry Fisher p.s. Bass guitar should use Block 470
  14. Hi Alex, The DAD6021 is for the older non-servo transmitters such as UM400, UM200, etc. The DAD3056 is for servo input units such the SM series, LM, etc., that have the newer inputs. The DAD3056 is also usable with older non-servo transmitters but the gain is lower than with the DAD6021. The DAD6021 is not usable with servo input transmitters as the gain is very high and easily overloaded. If you are ever unsure about a given transmitter series as to it being servo or non-servo, all product manuals are on the Lectro website under current or legacy menus. As far as comparing the wiring of the COS-11 to the DPA mics, the electronics in the two brands are so different, it would be like comparing grapes to watermelons. In short, your only choice is the DAD3056. Best Regards, Larry Fisher
×
×
  • Create New...