Frequently Asked Questions - Wireless

FAQs - Wireless

We have had 3 Venue systems in the field that either don't want to power up or if they do power up, run for a few seconds to several hours and then shut down. Since replacing the external power supply with a different type "fixed" the problem, we suspected the external power supply. However, we were never able to get a "bad" supply" to fail. We overloaded them by 50% and heated them to 150 degrees F ambient and they merrily continued working. The answer turned out to be much simpler than the maligned power supplies.

On Venues with a full compliment (six) of the new VRS or VRT modules, the electrical current requirements are too close to the electrical current rating of the input fuse on the main board (VRM). This is currently a 1.5 Amp polyfuse. A fully loaded Venue with the newest mainframe and newest modules pulls 16.7 Watts. This is 1.4 Amps at 12 Volts or 1.1 Amps at 15 Volts. Both these number are getting too close to what the polyfuse is guaranteed to handle, particularly at higher temperatures. We have 2.5 Amp fuses in stock that are exactly the same physical size as the 1.5 Amp fuse. We changed out all the 1.5 Amp fuse in units at Lectro and are using the 2.5 Amp fuse in all future units. We will send free fuses to customers upon request (800 821-1121 or We will also send new fuses to our servicing dealers. We will also upgrade the fuses at Lectro at no charge. I recommend changing the polyfuse in all Venues that use or will use the newer modules. Older modules and older mainframes use less power and will be OK but it is still recommended to change out the fuse when it is easy to do so.

The polyfuse is under the main cover and is about 1 inch away from the red power switch on the front panel. We have put pictures and instructions on our web site. Here's a link: Venue polyfuse. Two soldering iron tips heating the opposite pads of the polyfuse will remove it in seconds. If you screw it up, we'll still fix it at no charge.

The standard external power supply (DCR15/1A2U) for the Venue is an 18+ Watt unit and is OK to run the new Venues. The maximum power the Venue pulls with six VRS's or VRT's is 16.5 Watts. In testing, we have overloaded the standard Venue power supply to 25 Watts for 2 hours and it was fine. We will load the supply to even higher levels and also run it at high loads in the oven to just be sure that it isn't a part of the problem. (The tests after this was first written show the supply delivering 37 Watts at room temperature and 24 Watts at both 150 degrees F. and at 90 Volts line voltage input.)

This fuse overload would explain why checking the external supply always shows the supply to be good. The reason substitute supplies "fixed" the problem is that if a substitute supply has slightly higher voltage under load, the current demand from the Venue will be less and the fuse would then be OK. Remember, the fuse is right on the edge of working or not.

Best Regards,
Larry Fisher

Yep, we do. We've had so many customers having problems when using other brand wide band RF amplifiers in their antenna systems that I caved in and set up some wide band versions of our distribution amps and amplifiers. They have a 230 MHz bandwidth and cover all our standard blocks. At least they still have a very high intercept point with low noise figures. The prices are the same as the narrower, 2 block wide units. The web site may not be changed yet but the sales crew have the details. The wide band version of the UHFM-50 is the UHFM-230. The UMC16A is the 50 MHz version and the UMC16B is the 230 MHz wide band version.

This is one of those Zen "It depends" questions and answers. If you are in a high noise environment you will attenuate the signal and the noise the same amount and the signal to noise ratio at the input to the receiver will remain about the same. The performance of the system in the high noise environment will not change due to the 7 dB of attenuation.

If you are in a quiet environment, (the middle of Montana) then you will attenuate noise and signal the same 7 dB. The external noise is now attenuated to a lower value than the front end noise of the receiver. The front end noise of the receiver is now the determining noise floor and you've reduced the signal 7 dB so you get 7 dB less range than you would have gotten in the wilds of Montana.

Since RF is hard to see directly (magic), let's put it into audio terms that is maybe more familiar. If you have a good mic in a very noisy environment and the talent is screaming into it (rock venue), you can attenuate the mic signal 7 dB (pad), then turn up the gain 7 dB to compensate and the system signal to noise ratio will remain the same. 

If you insert the same 7 dB attenuation pad in the mic line while recording a very weak signal in a quiet room (one hand clapping in a Zen temple) then the input noise of the mic pre amp is the dominant noise source and the overall signal to noise ratio is decreased 7 dB as you have turn up the board gain to compensate for the 7 dB mic pad. The pre amp hiss is now the problem.

So as I said, it depends. In general it's not good to throw away 7 dB of signal from the antenna, but sometimes it doesn't hurt.

Here is a memo we sent to our dealers and service people about batteries. Please realize it is therefore a little blunter than our usual FAQ's:

If you are using alkaline batteries, we recommend the use of Eveready alkaline batteries particularly in our synthesized (frequency agile) equipment. Other brand batteries may work perfectly well, but Eveready is our standard for testing and analysis. In different purchases of Duracell batteries from different locations, we have found the battery life to vary by more than 2 to 1. On the other hand, we have found very consistent results from Eveready batteries. Also, in all tests we have done, a standard Eveready Energizer always gives us longer battery life than standard Duracell Procells. If customers call complaining of battery life we should ask them to try an Eveready Energizer before returning equipment for repair. Assure our customer that this does not mean Duracell is a bad battery , but that the Duracell battery was not intended or designed for the heavy current draw our equipment requires.

Always try to get the customer to try the Eveready batteries. If it is necessary to convince the customer to try Eveready's in a test, we can send them free batteries. That is cheaper than us wasting our time and theirs testing a perfectly good unit and finding no problem. Try to talk to the actual user of the Lectro product rather than someone who has been tasked with returning the unit and has no idea of what is going on. Remember these points.

  1. Cold alkaline batteries have short lives. To get full battery run times, the batteries must be at room temperature or higher.
  2. Standard Duracell batteries have 90% of the life of standard Eveready batteries in our equipment.
  3. Some Duracell batteries that we purchased at retail were inconsistent in our equipment and occasionally "failed" after as little as 1.5 hours of operation. They may have been counterfeits.
  4. The worst offenders for battery life are the UCR201, UM400, UH400, UM250, UM450, and UT700.
  5. Using 48 Volt phantom power on the UH plug-ons, will drain the battery even faster.
  6. Our battery life numbers are based on complete discharge of the battery, i.e., the unit is run until the battery is completely discharged and the unit shuts down. If the customer discards the battery at the first indication of falling battery voltage, then they will only get about one half of our specified battery life numbers. The customer needs to read the manual to understand what the battery indicators are really telling him. There is probably no diplomatic way to tell a customer that simple fact.
  7. It is very rare that a unit is drawing too much current or has maladjusted battery status indicators. Ninety nine percent of the time, we find that there is nothing wrong with the Lectro unit. I repeat, 99% of the time, it ain't us.
  8. In general, our transmitters pull more power from the battery than other brands and thus require more care in choosing and using batteries.
  9. There are a number of FAQs on our web site about batteries and tests we have done.
  10. Lithium disposable 9 Volt batteries have problems with our high current draw and if they are not stored before use in an airtight pouch they will fail very quickly.
  11. Rechargeable Li Ion batteries such as iPower are much more economical and give slightly longer performance than standard alkaline batteries. Customers have seen iPower batteries shut down at turn on in the UH400 due to sensitive protection circuity in the iPower battery.


All rechargeable batteries wear out. Your car battery is a well known example. Every time a rechargeable battery is used, it loses a small amount of capacity. Whether that becomes a problem or not depends on how much capacity you need. Here's an example: let's say you have an SM transmitter and the NiMh AA rechargeable batteries that we provide, currently 4 each 2200mAh Eveready batteries. These batteries happen to run your SM transmitter for 4 hours and 5 minutes (4:05) and that is just fine with you because you only have to operate the transmitter for exactly four hours every day. In few weeks, you are going to be very disappointed, because after 20 charges, the battery will only power the transmitter for 3:59. The reason is that every time you charge the batteries you will lose a tiny amount of capacity and you don't have any spare capacity to lose. In fact after a year of use, the batteries will probably only run the transmitter for 3 hours. There is nothing wrong with the batteries or the transmitter. Rechargeable batteries just slowly wear out.

The solution is to start out with a higher capacity NiMh AA battery such as an Eveready 2500 mAh cell or a Sanyo 2700 mAh cell. You will now get almost 5 hours of battery life initially and you won't be down to 4 hours of life until 200 recharges or 6 months later. This is even after assuming that the higher capacity batteries wear out twice as fast. (Eveready quotes the 2200 mAh battery as being rechargeable 1000 times and the 2500 mAh being rechargeable 500 times.)

This is an extreme example caused by your run time requirements being so close to the limits of the smaller capacity battery. If you only needed 2 hours of battery operating time, the smaller battery would be fine and would actually operate for many years before falling below your requirements. If you look at the economics of the battery for the SM, the rechargeable batteries really make sense. Top quality alkaline batteries will only run the SM transmitter for less than two hours and cost about 40 cents apiece. Two hours is rarely long enough. Lithium AA batteries will run the SM for 6 hours but they are $2.00 each. High capacity NiMh AA batteries are $3.00 each but the cost per use is a tiny 1.5 cents. Compared to a lithium AA battery, just two uses of a rechargeable AA pays for the battery.

This discussion is also applicable to the iPower 9 Volt lithium ion polymer rechargeable battery. Exactly the same arguments can be made about both saving money and gradual wear out of the battery with recharging. (See FAQ#089-WIRELESS)

Q: So do rechargeable batteries wear out? 
A: Yes

Q: How many times can I recharge them? 
A: It depends on your run time requirements.

Q: How do i know when they are worn out? 
A: When they no longer meet your requirements.

Here's a long post that appeared on the news group RAMPS. What is RAMPS? (See FAQ021-WIRELESS)

To the Group:
Here's the results of the new version of the iPower 500 mA rechargeable Li Ion Polymer battery tests. We also ran tests on the Ultralife 9 Volt single use lithiums and standard Eveready alkaline 9 Volts for reference. The batteries were run down multiple times in a UM450 because it is a power hog, 125 mA at 8 Volts or 1 Watt (!). We then ran the batteries down in a UM400 (a power piglet) just for further reference. In all cases the transmitters were run continuously until shut down of the transmitter. The batteries were then put on the charger and recharged. It made little difference if the battery was charged for one hour (green indicator just came on) or overnight. The runs were at 72 F ambient. Here's the results:

The first iPower battery in UM450:

The second iPower battery in UM450:
3:10 (double charged. See end of post.)

Brand new from the factory Ultralife Lithium in UM450:

Few months old Eveready Alkaline in UM450:

The Ultralife does not like the high current demands of the UM450 and does worse than an Eveready alkaline. The 500 mAh iPower has almost exactly 50% more capacity than either, at this high current load. If you remember the previously posted cold tests, the iPower also did quite well, though that was on a 400 mAh battery. Below are tests in a UM400, a more normal load:

The first iPower battery in UM400:

The second iPower battery in UM400:

Two brand new from the factory Ultralife Lithiums in UM400:

Two (few months old) Eveready Alkalines in UM400:

Here the Ultralife Lithiums come into their own, since the current drains are more reasonable and show a 62% increase in battery life compared to the Eveready alkalines as standards. The iPowers still show a good 20% increase over the alkalines.

This UM400 was a block 29 and seemed to pull a little more current than the average UM400. The ratios of battery life should still be valid. If you are getting a particular battery life on alkaline Evereadys, simply add the proper percentage. If you are using ProCells (Mallory) the iPower improvement will be an additional 10% more (30% instead of 20% for example).

Final notes: 
Doing a 100% discharge on Li Ion Poly batteries (iPowers) is worst case for usage.
The iPowers work well in the cold.
We tried a "double" charge on the iPower with no big effect. We charged it completely, removed the battery, and started the charge cycle again. It took about an hour for the charging light to go from red to green again. I don't know what that means, but it didn't look good. However, the capacity of the battery went down only 4 minutes. I don't think it was significant, but....
We will ship the iPower system with the UM450. 

I can't stress enough that "YMMV".

Best Regards,
Larry Fisher

Alkaline batteries, though very good at room temperature, cannot deliver much current at lower temperatures. Battery life can be as little as one third normal on a cold day and even less if they cold soak for any length of time. Life can be as little as just a few minutes at -20 F.

If you must use disposable batteries (non rechargeable) then lithium batteries are the only good choice. They have shorter life at low temperatures but are still much better than alkalines.

In the AA battery size, lithium and NiMh batteries are the best cold weather choice. At low temperatures NiMh have almost as much life as at room temperature and are rechargeable to boot. Our tests indicate that the NiMh AA batteries when used in an MM400 or SM transmitter have 75% of normal capacity at minus 15C (-15C) or +5F. We recommend the Eveready NiMh batteries and 15 minute charger that we provide with the SM, SMD and SMQ transmitters. One precaution is that the batteries cannot be recharged if they are cold. They can be used cold without any problem but must be at about room temperature to be recharged. The lithium batteries are also good at low temperatures but they don't like being cold for long periods of time. If cold soaked at 5 deg F for an hour, they still have 95% of their normal capacity. Allowed to cold soak overnight they only have 50% of their capacity. Here are some run times in a cold SM transmitter at different temperatures:

At room temperature:

  • NiMh 4:02
  • Lithium 6:01

At 5 def F cold soaked for one hour:

  • NiMh 2:52
  • Lithium 5:45

At 5 deg F cold soaked for 16 hours:

  • NiMh 2:46
  • Lithium 3:19

In the 9 Volt battery size, NiMh batteries perform as well cold as they do at room temperature but they don't have much battery life (capacity) cold or warm. At one time they were the only choice for very low temperatures but LiPoly rechargeable batteries are now available that have more capacity than alkaline batteries and perform very well at low temperature. They are currently sold under the iPower brand and are available on the internet, from some dealers and from Lectrosonics. (See FAQ#086-WIRELESS)

Here is schematic for muting a two wire microphone. The in's and out's can be swapped. You can treat the arrangement as if it is just a normal two wire mic. That means that it will have to be hooked up to a transmitter or other bias supply in the normal manner. There will be a faint click due to RF in area from the transmitter but it won’t be objectionable for your application. This only requires a single pole, single throw switch. When the switch (or push button) is closed the capacitor is connected to the two wires and shorts out the audio. There will be a little audio bleed-through, mostly at low frequencies. The larger the capacitor, the less bleed there will be. The resistor across the switch is necessary to keep the capacitor lightly connected to the bias supply so there won’t be a large pop when the switch is closed. A better but much more expensive solution is to use a unit designed to be silently muted by a DC control signal.


See also FAQ #25 for an earlier post with some measurements. The resistor recommendations are a little different than in this FAQ #94 since the levels in FAQ #25 were at 114 dB SPL. 


The recommendations below are for more "normal" usage.

We recommend wiring the standard level COS-11 in a 2 wire configuration with a 1k resistor in series with the white wire (source wire) to ground. This reduces the output of the standard mic by 6 dB which will prevent overload of the input buffer on the UM400. This isn't necessary for the SM series since it cannot be overloaded by the COS-11 under any circumstances. It does make the microphone compatible with both transmitter series. 

The Red Dot Cos-11's are designed to have 9 to 10 dB less output than the standard COS-11's and can therefore be wired with the source lead directly to ground. 

Adding a 1k resistor to the source lead of either microphone will drop the 2 wire output by 6 dB compared to the source being wired directly to ground. 

Using a 3k source resistor will drop the output of either mic an additonal 6dB compared to using the 1k resistor or 12 dB total. This much gain reduction should not be necessary and is for information only.

We also recommend wiring our pin 2 to pin 4 to make the wiring fully compatible with our UM400 and older Lectro transmitters. A schematic is below.



The early iPower batteries were larger than a standard 9 Volt battery. Shortly after their initial release they made a smaller case for the batteries.

The new smaller 500 mAh units are marked the same as the older, larger 500 mAh units. The only difference I see in the case is that the older unit has a small recessed circular area only around the small positive terminal. The new smaller 500 mAh unit has a large rectangular recessed area that encloses almost the entire top of the battery. It's recessed about 0.030" deep. The new batteries are actually smaller than standard 9 Volts and should never be a problem as far as sticking. 

We were told in early 2006 that it would be several weeks before the first new batteries were available. We only stock the smaller cells because we don't want them stuck in our units. If you order from some one else, I think I'd do it verbally to confirm what you want. If you have some of the larger batteries you might contact iPower and see if you can return them. Do a search on the RAMPS newsgroup for contact information.