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Caleb Linburg

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can a 50 mw transmitter transmit farther than a 100 mw? if the antennas are the same but the power input is not?

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Steven wrote:

caniac wrote:
2) I do not nor do I want to solder anything (don't feel like burning myself numerous times - if I want to do that I will just stick my hand on the stove).

What are my options (that don't entail a second mortgage)?
  1. Buy an EDM-TX-LCD-EP for $190 + s/h.
  2. Get your 6-year-old nephew to solder it for you.:)

that would work but I don't have a six year old nehpew!!:dude:
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JAMES IF EVERY THING ELSE IS THE SAME THE ANSWER IS NO 50 MW IS HALF THE POWER OF 100 MW BUT THERE ARE A LOT OF OTHER VARIABLES TO CONSIDER

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The length the telescoping antenna (supplied with most of the smaller transmitters) needs to be depends on the frequency you plan to use..

If you're going to set the radio to 93.1mhz, the length you'll adjust the antenna for will be longer than the length needed for 105.3mhz. The telescoping antenna supplied with most transmitters should extend to cover the frequencies from the "basement" (88.1) to the "attic" (107.9).

Figuring the length needed is 234/F (F being the frequency you're going to use), divide 234 by the freq and you'll get the length.

234/99.3 234/101.7 234/106.9

As for the amount of power it'll handle.. unless you're running more than 5-10 watts (NOT smart), every telescoping antenna I've seen will work at a half to one watt... depends on the type/quality of dialectric spacer used between the contacts (pin/sleeve of the bnc).

and yes, I'm a ham radio op.. been in radio (CAP & Amateur radio) for almost 40yrs.. if you need a "higher authority, google "ham radio quarter wave antenna formula"..

You CAN use a rubber duck antenna -as long- as it's wound to cover the freq you want to use.. namely the FM broadcast band, and FEW are.. scanner antennas wound(cut) for VHF/UHF 2-way radio services, which starts at
108mhz to 136mhz (aircraft band),
136 to 144 (business band, taxi's, pagers),
144 to 148 (2 meter ham band),
148 to 172 (public service band, police, fire, sheriff, Coast Guard, gov't services)...

..so unless you re-wrap a duck to ADD length (thereby covering frequencies BELOW VHF 2-way services), you cant use it. Use the antenna that came with your radio. Add an attenuator to lower the amount of the transmitted signal is all you can do to limit the range.. Or put the radio in your basement, on the floor, slip a piece of pvc over the antenna..

And you can have the antenna lay flat on the ground..

TJ, NS2E (Extra class)

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TJ Hvasta wrote:

The length the telescoping antenna (supplied with most of the smaller transmitters) needs to be depends on the frequency you plan to use..

If you're going to set the radio to 93.1mhz, the length you'll adjust the antenna for will be longer than the length needed for 105.3mhz. The telescoping antenna supplied with most transmitters should extend to cover the frequencies from the "basement" (88.1) to the "attic" (107.9).

Figuring the length needed is 234/F (F being the frequency you're going to use), divide 234 by the freq and you'll get the length.

234/99.3 234/101.7 234/106.9

As for the amount of power it'll handle.. unless you're running more than 5-10 watts (NOT smart), every telescoping antenna I've seen will work at a half to one watt... depends on the type/quality of dialectric spacer used between the contacts (pin/sleeve of the bnc).

and yes, I'm a ham radio op.. been in radio (CAP & Amateur radio) for almost 40yrs.. if you need a "higher authority, google "ham radio quarter wave antenna formula"..

You CAN use a rubber duck antenna -as long- as it's wound to cover the freq you want to use.. namely the FM broadcast band, and FEW are.. scanner antennas wound(cut) for VHF/UHF 2-way radio services, which starts at
108mhz to 136mhz (aircraft band),
136 to 144 (business band, taxi's, pagers),
144 to 148 (2 meter ham band),
148 to 172 (public service band, police, fire, sheriff, Coast Guard, gov't services)...

..so unless you re-wrap a duck to ADD length (thereby covering frequencies BELOW VHF 2-way services), you cant use it. Use the antenna that came with your radio. Add an attenuator to lower the amount of the transmitted signal is all you can do to limit the range.. Or put the radio in your basement, on the floor, slip a piece of pvc over the antenna..

And you can have the antenna lay flat on the ground..

TJ, NS2E (Extra class)


Very Interesting TJ, but my scanner can tune down to as low as 25Mhz and as high as 1299Mhz. This is why I figured that particular rubber ducky antenna on the scanner would work.

And so this is why it gets confusing to me because if the rubber ducky can scan this broad range of freq's and the FM freq's are 87.5-108.1Mhz, this is why I do not fully understand why it can't be used. Now if the FM freq's weren't in there among them, but then again, a scanner won't allow you to enter the freq. number seen on a radio and pick up an FM station either(at least mine won't).

So could you tell me what's the difference in that regard?

I'm just trying to figure all this out and learn a little as I go along as to why some things work and others don't, epsecially when an item like this appears to cover those freqencies.


BTW: No basements(at least in my area) in Florida, only attics. :)
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im not a ham oper but i think you d want an ant. zeroed in on the freq.you plan on transmitting not one that covers a wide range" just saying"

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t purser wrote:

JAMES IF EVERY THING ELSE IS THE SAME THE ANSWER IS NO 50 MW IS HALF THE POWER OF 100 MW BUT THERE ARE A LOT OF OTHER VARIABLES

what would be the best power for 250 feet?
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guys don t just take my word for it read these post then make up your minds.http://forums.lightorama.com/forum80/26492.html

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The problem is the difference between a transmitter and a receiver.

With a receiver, a badly matched antenna will give poor reception quality. This can be improved by either improving the match of antenna length to the received frequency, or improving the receiver to the point where an accurate match is not necessary. Either way, a poor or no antenna will not damage a receiver

With a transmitter, a badly matched antenna will mean that a proportion of the power you are trying to transmit will not be radiated from the antenna. This remaining power gets reflected back into the transmitter and will cause extra heating within the unit. It is this reflected power that will damage a transmitter. Without an antenna connected at all, all the power will be reflected, and this may destroy the transmitter quite quickly.

Regards,

Alan.

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t purser wrote:

guys don t just take my word for it read these post then make up your minds.http://forums.lightorama.com/forum80/26492.html

Ok, looked in that linked thread. I do not see anything about 10mW or any other wattage mentioned.

And again to answer the guy who asked so how much wattage will he need to transmit only 150'. There is no hard set numbers due to how radio waves act. in one installation it might be 10mW and in the next it might be 50mW. What matters is elevation above ground. House construction and where in the house is the radio mounted. What kind of foliage is between the transmitter and the targeted roadway. Evergreens vs trees. But you need better transmission power than the WHT thats a given.

I post a lot about transmitters. I am not the FCC or a radio engineer. But I have spent a few years working on and around transmitters. Both as a USAF Ground Radio Tech (30747). And hold an Amateur Radio Advance ticket (KF0OX) But I am still prone to make mistakes. So, in my case, get a 2nd opinion before taking it as the holy grail. :P
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Max-Paul wrote:

. . . Ok, looked in that linked thread. I do not see anything about 10mW or any other wattage mentioned. . .

There is no transmitter power mentioned in the FCC regulations, as the gain of the transmitting antenna also has to be taken into account. The requirement I believe is a field strength of 250 uv/m, measured at a distance of 3 meters from the transmitting antenna. This is the reason why all certified transmitters are sold with an antenna, because the antenna gain is part of the measurement / certification! The transmitter power required for this field strength is considerably less than the 0.5w most are talking about.

Regards,

Alan.
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..without going into too much detail abut antenna matching(it boggles the mind really, cant be readily understood without taking classes and would take too long to explain it).. American Radio Relay League (ARRL) has some really good Antenna Theory books..

Alan's got it right abt reflected power from a mismatched antenna(or no antenna at all) heating up the finals/causing damage.. you -can- construct an antenna matcher, which changes the impedance and reactance of the antenna to match the feedpoint of the transmitter.. a "trans-match" just allows the radio to "see" a closer match so that the reflected power is reduced..

..as for whether the duck can be used.. most wide coverage scanner antennas are some type of trap antenna, with 'traps (coils) for specific bands, 25-1290mhz, and not normally a continuous wire wound around a form.. a way to tell is put it on one of the MFJ Analyzers, sweep the band and see the resultant swr.. just thinking tho.. the Analyzer I have (cant remember the model number but it's HF/VHF, covers 1.5-170mhz but not continuosly) ..has two meters, swr on one, reactance on the other, and digital freq readout) doesnt specifically cover the FM broadcast band.. so you may still be outta luck with that..

TJ

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Orville wrote:

Caleb Linburg wrote:



My only concern with this one is this:

Frequency range: 76 ~ 108Mhz

In the US, FM transmitters start on 88Mhz and go to 108Mhz, so this one could possibly be considered illegal for use in the US due to it is able to go below the 88Mhz range.

Hopefully someone here can point you(us) to a link to know for certain. As I can't say definitely.

I've just never seen any US FM transmitters for sale that goes below 88Mhz. So that would definitely be a major concern of mine before I'd buy one that did.





if anyone still is interested in this tread just read a article and the following is directly from the website it looks like 76 to 108 would be just fine



(Redirected from OIRT" TARGET="_blank">OIRT band in Eastern Europe is 65.8â
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I thought I would throw my two cents in here. I just recived the Whole House Transmitter and I am going to keep it. After I connected the extra antenna they provided, I tested the distance and it will do exactly as I need it to do. I put the transmitter in the garage, where it will be for the show, and drove down the street. I got a really good signal about 100-150 yards away, which is perfect for my show. I hope this helps anyone looking to buy a transmitter.

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