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Bill Ruck

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    San Francisco
  • About
    Broadcast Engineer
    Audio and RF
    Working on wireless microphones for a very long time.
    Native San Franciscan, 3rd generation.

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  1. A couple of updates on licensing wireless microphones. While the FCC Report & Order 15-100 added the band 941.5 - 944, 952.85 - 956.26, and 956.45 - 959.85 MHz and those are now effective in The Rules, you can NOT apply for those frequencies. Yet. The Catch-22 is that the FCC will only allow applications when there is Type Certified equipment for those bands. And there isn't any that I have been able to find. Yet. I'm told that Lectrosonics is working "day and night" to have new equipment Type Certified by the NAB. Then one can apply for those frequencies. I have also heard reports of users with old, no longer legal, 700 MHz systems being confronted by a cell carrier representative. You need to know that the FCC requires cell carriers to precisely locate cell phones for 911 purposes. That equipment can also find precisely "foreign carriers" like wireless microphones. So if they have someone in the area where an unlawful 700 MHz wireless microphone is being used it is not difficult to be found. They can turn you into the FCC or even easier unleash their army of lawyers. Be warned. Bill Ruck San Francisco
  2. That sounds like Lightning On Demand's Tesla coil. Worked with them at a couple of Survival Research Labs events. If the personal shield is tightly woven no UHF RF will get in or out. But the suit LOD used was very coarse and probably wouldn't stop UHF. Tesla coils run in the 10-20 kHz range. That's a very low frequency. It's difficult for a small UHF antenna to absorb much energy from that very low frequency. I did not try mic'ing the guy but probably your equipment will survive. And the comment about LOUD is true. I did record the SRK event but used 421's with a pad into the LINE input of a D7 DAT. Calculated 0 dBFS was 140 dBSPL. That recording has launched (lunched?) woofers from the infrasonic from their equipment -- the V-1 engine and the sonic cannon. Bill Ruck San Francisco
  3. Looks like Sprint decided not to participate in the 600 MHz auction. Exactly how this will affect the outcome is unclear but keep in mind that most of the TV stations are going to ask for top dollar, the wireless industry has stopped growing, and they really would prefer a higher frequency like 2-3 GHz than 600 MHz. See http://www.rcrwireless.com/20150927/carriers/sprint-dumps-600-mhz-auction-plans-tag2 For comment from FCC see https://www.fcc.gov/document/statement-commissioner-pai-sprints-decision Bill Ruck "Bring lots of mic cable"TM San Francisco
  4. Reently I have been getting a lot of inquiries about renewing your FCC LPBA license. The FCC will send you a courtesy notice about three months before the expiration date. All you need to do is to log on to ULS with your FRN and password and follow the steps to renew the license. If you don't renew the license it expires. The FCC gives only a 30 day period to renew a license after it expires. More than 30 days it will have status EXPIRED and there is little one can do at that point. Then you need to start all over again, either by filling out the ULS new license form or retaining me to do it for you. Also the fee for a new license is much higher than the renewal fee. The FCC also expects that you will keep your contact information current. So if you move you need to go on line at ULS and do an administrative update on your contact information. Bill Ruck San Francisco
  5. I participated in several frequency coordination meetings at the NAB. The main topic for these meetings was who was going to be gored in the near future. First, no user of any radio frequency spectrum is sacred. The Department of Defense may lose some of their spectrum. Second, I was told that the FCC considers intermittent use of radio spectrum by wireless microphones to be spectrum inefficient. The FCC has been snowed by the wireless broadband industry. Third, if large users like the NFL are getting blown off by the FCC then the typical production audio guy has less standing. If you are not involved in NFL games you might be interested that a "typical" NFL game uses several hundred UHF frequencies; Monday Night (and the other big televised games) use about twice that; and the Super Bowl used 2,500 frequencies! Holding a license may not hold off the wireless tsunami; holding a license at least makes the FCC count you as a user. Note that all new licenses are including this Condition: Fixed BAS and Low Power Auxiliary Stations in the UHF TV band are licensed on a secondary basis to existing -and future- primary operations and cannot cause harmful interference to primary operations not claim protection from harmful interference from primary operations. In accordance with the spectrum provisions of the Middle Class Tax Relief and Job Creation Act of 2012 ("the Spectrum Act"), broadcast TV channel assignments could be reorganized and some UHF TV spectrum (470-698 MHz) could be allocated for flexible use and assigned by competitive bidding. These future assignments to primary licenses could require all existing and future BAS and Low Power Auxiliary stations to stop existing secondary operations and/or to change frequencies or bands at their own expense. Translation of FCC-speak: "flexible use" is broadband "competitive bidding" is selling off public spectrum to balance the budget For most people this is well beyond their interest and not on their radar. But if one is making a living with wireless microphones and/or wireless IFB and camera links, be afraid. Be REALLY afraid. Bill Ruck San Francisco
  6. This is hard to understand but as far as the FCC is concerned you need to license the number of transmitters IN USE. Transmitters on the shelf not in use do not count. Also the owner of the transmitter is not the issue, is the USER of the transmitter. Rented transmitters need to be used by a licensed person. Also, a license if for a band of frequencies. The exact frequency of the transmitter is not licensed as long as it is within the band that is on the license. I normally apply for the low band VHF frequencies 54-72 and 76-88 MHz, the high band VHF frequencies 174-216 MHz, and the UHF band 494-608 and 614-698 MHz. Note that the band 608-614 MHz is not available because it is reserved world wide for astronomical research. In most major areas there are UHF TV channels that are allocated to Part 90 Land Mobile and are not available for Broadcast Auxiliary Low Power use. Those channels are mostly used by Public Safety. An application that I tried to work around limitations was recently granted so I now have a template to license the entire UHF TV band from 470-698 MHz (except for 608-614 MHz). Since that worked I will now use that template for all new applications. Bill Ruck San Francisco
  7. There is a legal way to use UHF TV channels for this purpose. A license IS REQUIRED. Part 74.870 Wireless video assist devices Wireless assist video device. An auxiliary station authorized and operated by motion picture and television program producers pursuant to the provisions of this subpart. These stations are intended to transmit over distances of approximately 300 meters for use as an aid in composing camera shots on motion picture and television sets. Exact quote from FCC Rules: Television broadcast auxiliary licensees and motion picture and television producers, as defined in §74.801 may operate wireless video assist devices on a non-interference basis on VHF and UHF television channels to assist with production activities. (a) The use of wireless video assist devices must comply with all provisions of this subpart, except as indicated in paragraphs ( through (i) of this section. ( Wireless video assist devices may only be used for scheduled productions. They may not be used to produce live events and may not be used for electronic news gathering purposes. © Wireless video assist devices may operate with a bandwidth not to exceed 6 MHz on frequencies in the bands 180–210 MHz (TV channels 8–12) and 470–698 MHz (TV channels 14–51) subject to the following restrictions: (1) The bandwidth may only occupy a single TV channel. (2) Operation is prohibited within the 608–614 MHz (TV channel 37) band. (3) Operation is prohibited within 129 km of a television broadcasting station, including Class A television stations, low power television stations and translator stations. (4) For the area and frequency combinations listed in the table below, operation is prohibited within the distances indicated from the listed geographic coordinates. (chart of T-Band cities) (d) Wireless video assist devices are limited to a maximum of 250 milliwatts ERP and must limit power to that necessary to reliably receive a signal at a distance of 300 meters. Wireless video assist devices must comply with the emission limitations of §74.637. (e) The antenna of a wireless video assist device must be attached to the transmitter either permanently, or by means of a unique connector designed to allow replacement of authorized antennas but prevent the use of unauthorized antennas. When transmitting, the antenna must not be more that 10 meters above ground level. (f)(1) A license for a wireless video assist device will authorize the license holder to use all frequencies available for wireless video assist devices, subject to the limitations specified in this section. (2) Licensees may operate as many wireless video assist devices as necessary, subject to the notification procedures of this section. (g) Notification procedure. Prior to the commencement of transmitting, licensees must notify the local broadcasting coordinator of their intent to transmit. If there is no local coordinator in the intended area of operation, licensees must notify all adjacent channel TV stations within 161 km (100 mi) of the proposed operating area. (1) Notification must be made at least 10 working days prior to the date of intended transmission. (2) Notifications must include: (i) Frequency or frequencies. (ii) Location. (iii) Antenna height. (iv) Emission type(s). (v) Effective radiated power. (vi) Intended dates of operation. (vii) Licensee contact information. (3)(i) Failure of a local coordinator to respond to a notification request prior to the intended dates of operation indicated on the request will be considered as having the approval of the coordinator. In this case, licensees must in addition notify all co-channel and adjacent channel TV stations within 161 km (100 mi) of the proposed operating area. This notification is for information purposes only and will not enable TV stations to prevent a WAVD from operating, but is intended to help identify the source of interference if any is experienced after a WAVD begins operation. (ii) If there is no local coordinator in the intended area of operation, failure of any adjacent channel TV station to respond to a notification request prior to the intended dates of operation indicated on the request will be considered as having the approval of the TV station. (4) Licensees must operate in a manner consistent with the response of the local coordinator, or, if there is no local coordinator in the intended area of operation, the responses of the adjacent channel TV stations. Disagreements may be appealed to the Commission. However, in those instances, the licensee will bear the burden of proof and proceeding to overturn the recommendation of the local coordinator or the co-channel or adjacent channel TV station. (h) Licenses for wireless video assist devices may not be transferred or assigned. (i) The product literature that manufacturers include with a wireless assist video device must contain information regarding the requirement for users to obtain an FCC license, the requirement that stations must locate at least 129 kilometers away from a co-channel TV station, the limited class of users that may operate these devices, the authorized uses, the need for users to obtain a license, and the requirement that a local coordinator (or adjacent channel TV stations, if there is no local coordinator) must be notified prior to operation. Bill Ruck San Francisco
  8. Every country has its own frequency plan, from VLF (like 20 kHz) through VHF, UHF and microwave. Europe more or less follows a common plan. Canada and Mexico more or less follows the United States. Other countries vary depending on who they chose to model. In the United States 800 - 900 MHz was taken from broadcast about 30 years ago. It's now cell phones and land mobile communications. Recently the 700-800 MHz band was taken from broadcast and is now various services including land mobile communications. Bottom line is that wireless microphones are at the very bottom of the food chain. Operating without a license could get you into trouble although in most cases whatever regulatory agency has its hands full without chasing down 50 mW transmitters. On the other hand, operating a wireless microphone in a band with high power transmitters means you will have nothing but interference. All wireless systems are NOT plug and play. Bill Ruck
  9. Just because the United States does not enforce the mandatory requirement for licenses does not mean that the rest of the world is that casual. I know that in the UK licenses are required and you need to go through their contractor. Not sure about Ireland or Spain. Best to check with the consulate and get all of the paperwork in order before you have your equipment confiscated. Bill Ruck San Francisco
  10. Regarding what is known as "T-Band". There is this whole volume of Rules and Regulations that govern how all radio frequencies must be used. Although low power wireless microphone users have ignored The Rules they still apply. Officially they are Federal law Title 47. For the official listing of "T-Band" frequencies and the cities where they exist, see http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=ec44d364f141568a2895553fa7122006&rgn=div8&view=text&node=47: That should lead you to Part 90.303. A scan of those channels can be misleading because two-way systems are not always transmitting. Also, the use of UHF TV channels for wireless microphones is regulated in another part of The Rules. See Part 74 Subpart H Low Power Auxiliary Stations http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=d2e545fb8fdaca66f65a0c41915e9b09&rgn=div5&view=text&node=47: Note that I don't make The Rules; I have a hard enough time trying to understand The Rules; but no matter what they are THE RULES. Bill Ruck
  11. Always keep in mind that your low power wireless mics are competing with other much higher power transmitters. Besides the obvious 100 kW UHF TV transmitters there are now high power transmitters in the 700 MHz band. So what works on the ground and in a shielded enviornment will not work the same way once you are high up in the air. I don't know Seattle and can't exactly explain what you got but completely understand why you had problems up high. In many areas Block 470 is NOT available for wireless microphones because channels are assigned to Land Mobile, including Public Safety. Since those transmitters are not always on you may find intermittent interference in that block. Also, should the local law enforcement track you down you won't like what they could do to you! (A/k/a "The grey bar hotel") It is very convenient to run wireless but you are juggling very sharp knives! I am very well known in the broadcast world with my statement "Bring lots of mic cable". Bill Ruck
  12. Geeez. In general, to make a difference in any radio system range you need to increase the power by a factor of 10. 50 mW vs. 100 mW is only 3 dB which is in most field applications difficult to measure accurately. 50 mW vs 250 mW is only 7 dB which is still hard to measure accurately in the field. Most "range" issues are more interference limited than signal limited. Always keep in mind that your UHF transmitter is in the middle of the TV broadcast band where the transmitters are measured in killoWatts. Lots of kW. So if you're only 6 MHz away from a 100 kW TV transmitter the wireless receiver, no matter how well it is designed, is going to be killed by a much stronger signal. In the perfect world one should use a fixed frequency receiver with lots of pre-selection but that may not be practical. Also keep in mind that taking a 50 mW transmitter and putting it on a body reduces the radiated RF by as much as 20 dB. My recommendations are (1) use as much of a high gain antenna for the receiver as you can. This reduces multipath and improves the signal-to-noise and interference that the receiver has to work around. In practice, a really high gain antenna may be physically too big. Check this one out http://www.kathrein-scala.com/catalog/PR-TV.pdf (2) get the receive antenna and receivers as close to the talent as possible. There is much less loss in a long mic cable than there is in coax. Bill Ruck
  13. There is too much mis-information out there regarding antennas for wireless microphones. First, all radio systems must follow the same laws of physics. There is no difference beween land-mobile communications, point-to-point communications, and wireless microphones (or for wireless in-ear monitors). Second, always keep in mind that your RF neighbors with any UHF system are very high powered TV stations. Your puny 50 mW transmitter can't compete with 100,000 Watts of RF 6 MHz away. For that reason, unless you really need very long cable lengths and your are shielded from TV transmitters by being inside a building, stay away from amplified systems. Especially wide band amplified systems. Even Lectrosonics designs (which are the best) can be overloaded. I've found that antenna sold in the wireless microphone world are unbelieveably overpriced. Compare any design to the WA5VJB 400-1000 MHz log periodic http://www.wa5vjb.com/pcb-pdfs/LogPerio400.pdf at $25. This is the same antenna that Ramsey electronics sells at a higher price. Since UHF wireless microphones work in the exact same frequency band as UHF TV, any UHF TV antenna also works just fine. This is another example that I've often used in fixed applications http://www.mcmelectronics.com/product/ANTENNAS-DIRECT-DB2-/30-2065 MCM price is $41.99. So why pay hundreds of dollars for an antenna? Bill Ruck
  14. Larry's suggestion of RG-174 coax is good for your application. You need to find the exact proper BNC connector. The clamp type such as Amphenol 69475 is not that difficult to assemble. Get the assembly instructions from the Amphenol website (C25). Crimp type connectors are faster to assemble but you need the proper crimp tool. The cheaper crimp tools do not always make a solid connection. I've learned over the years that the Daniels crimp handle and dies are the best. For example, for RG-174, the BNC male connector is an Amphenol 31-315. The crimp die should be 0.068" hex for the center conductor and 0.178" hex for the shield ferrule. Again, get the assembly instructions from the Amphenol website (C26). Kings is my other recommended connector manufacturer. There are cheaper connectors available but my experience is that MIL qualified coaxial connectors last longer. There are sources for assembled cables. If you are only going to make a couple it may be more cost effective to buy them assembled than to collect your own crimp tools. As an example, Pomona makes those cables with molded-on strain reliefs. That part number would be 2249-K-12. The "K" is RG-174 cable and the "12" is 12" long. Bill Ruck
  15. People that can't solder an XLR properly should not consider something small like the LEMO! One area that is important is that the cable clamp collet must be sized appropriately for the cable diameter. There are options here and you need to measure the cable diameter and specify the exact proper collet. Too small and you will never assemble the connector. Too big and you won't have any strain relief on the cable. Heat shink might fill it but it is best to do it properly. The nuts require metric wrenches of the right size. "Ignition wrenches" are best. Pliers should never be used on nuts. (Learned that lesson young from my aerospace engineer father!) Very carefully strip and tin the conductors. The length is specified in the catalog for that particular connector. Too short and it is imossible to assemble. Too long and the collet strain relief doesn't work. The key to soldering them is to have a good iron like the Weller TCP series. You need enough heat to get the joint fast but not too much heat. Although I've been doing them for years these days I turn most of this kind of work over to a friend, Kris Handwerke, because she does a much better job! Bill Ruck
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