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Lou Knudson

FM Transmitter Questions

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1.) I have a question about connecting my EDM LCD transmitter to my computer sound card. I currently have it connected directly to the sound card output. I would also like to feed the signal into my stereo system amp so I can also use speakers as I have in the past. Is it OK to use a "Y" adaptor to split the signal to feed both of them? Will this cause a problem, if so is there another way to use both the transmitter and speakers?

2.) I have also been having a difficult time determining which frequency to use. I too as other found the frequencies that were supposed to be vacant in my area were not. I also found it varies by time of day if it is vacant or not. I had chosen a frequency in the afternoon, but found later in the evening it was no longer vacant. Is there an easy way to narrow this down without spending a lot of time checking frequencies?

3.) Is it better to keep the transmitter antenna near a window rather than on an inside wall of a room? I am using the test antenna that came with the EDM LCD. Our attached garage extends beyond the front of the house and seems to lessen the distance of the signal in that direction.

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1) Yes.

2) Your best solution will be trial an error. Do it at the same time you are going to transmit. Do it in your car in front of your house (looking to duplicate the same conditions as your viewers.) There are not that many channels so it should only take a couple of minutes.

3) Once you have found your optimum channel, test the range by driving around. If you have a dead spot caused by the garage, you may want to relocate the test antenna or install a more efficient antenna.

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Rather than connect it to your stereo system, just tune your FM receiver to the frequency you are broadcasting.

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I agree with iresq exactly. And I should emphasize his point about testing at the same time of day you want to transmit. The night time stations you are hearing are likely much farther away and you may not hear them in the day time. If you are in a hilly area, drive up to the nearest hill near your house. If the frequency you chose in front of your hous is also clear up there, then you have better odds of not interferring with a licensed station.

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Richard Hamilton wrote:

I agree with iresq exactly. And I should emphasize his point about testing at the same time of day you want to transmit. The night time stations you are hearing are likely much farther away and you may not hear them in the day time. If you are in a hilly area, drive up to the nearest hill near your house. If the frequency you chose in front of your hous is also clear up there, then you have better odds of not interferring with a licensed station.


Yes, definitely check the freq when YOU plan to broadcast.

I have a 20w rig (broadcasting at 10) for my show. In the yard, I have a "boom box" under cover tuned to my freq. It's powered by #16 on my 2nd unit which is always on in each of my sequences. When the show is over, the "boom box" get's turned off as well. The volume on the box is just enough for pedestrians, and doesn't bother the neighbors... at least they haven't complained. :)



Merry Christmas!



--Mike

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1) Plugging your sound card output in to two inputs is not the optimum solution. It will degrade your sound quality and you might also have problems getting the volume correct for each device. You could also consider using an inexpensive mixer.

2) Here is a good web site to visit:

http://www.radio-locator.com/

Just enter your zip code and it will tell you what frequencies are best to choose. You still need to listen first!

3) One responder says he is broadcasting with 10 watts. That would send his signal out for many, many miles (unless he has a poorly matched antenna.) If your goal is not to interfere with licensed broadcasters you should use much less power. (Your goal SHOULD be to not interfere. After all, it's the law. And they paid for those frequencies after all.) I transmit at about 50 milliwatts (50 thousandths of a watt) and have a range of about 3 blocks. My antenna is in my living room near a window.

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Rather than connect it to your stereo system, just tune your FM receiver to the frequency you are broadcasting.

This is what I do as well.

Your getting great advice ... I can't add more than they already have.

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pdowns wrote:

1) Plugging your sound card output in to two inputs is not the optimum solution. It will degrade your sound quality and you might also have problems getting the volume correct for each device. You could also consider using an inexpensive mixer.

2) Here is a good web site to visit:

http://www.radio-locator.com/

Just enter your zip code and it will tell you what frequencies are best to choose. You still need to listen first!

3) One responder says he is broadcasting with 10 watts. That would send his signal out for many, many miles (unless he has a poorly matched antenna.) If your goal is not to interfere with licensed broadcasters you should use much less power. (Your goal SHOULD be to not interfere. After all, it's the law. And they paid for those frequencies after all.) I transmit at about 50 milliwatts (50 thousandths of a watt) and have a range of about 3 blocks. My antenna is in my living room near a window.




Hi Pat,

No offense, but range is not purely a function of power, especially at the lower power levels (0-100w). At that level, antenna matching and placement have far more effect on range than 5 vs 10 watts.

I live in a dense residential neighborhood, and my antenna is at ground level (j-pole design)... attached to the side of my garage. It's very well matched as well with SWR being 1.65:1... not bad.

At 1 watt, I get about a block, at 10 watts I get about 1/2 mile (clear), at 20 watts I get about 3/4 mile (clear). If I put the antenna on the roof, I'd probably get 2-3 miles at 20 watts. If I put it 20 feet in the air, I may get 10 miles... I don't plan to try that though. The idea here is for folks that know about the show to be able to tune it in while driving here and hear something other than static when they aren't parked directly in front.


For what it's worth, I'm on an absolutely clear frequency as well, so even if I was broadcasting for "miles," I wouldn't be interefering with any other stations.

Merry Christmas!

-Mike

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I did find a frequency that seems to work and also moved the transmitter and antenna by a window at the front of the house. I still have very limited range as it only seems to work directly in front of the house. As soon as you start going around the curve the signal gets bad. There is also a hill on the street coming from the other direction and the signal is gone as soon as you turn the corner.

As far as the EDM LCD settings it is on the low power range and the variable adjustment it at it's max. If I remember correctly the higher setting wasn't supposed to used in the USA.

It would be nice if some cars were waiting to pull up in front of the house that they could listen while waiting. Am I expecting the impossible because of my location? It sounds like many others that purchased the EDM get at least a block of range on their signal. Has anyone used an outside antenna with the EDM?

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One hint in your posting is that you say it is in a window, so two things come to mind.

1. Get it higher off the ground. The higher the better.

2. Is there a solar film on the window? Those are metalic and they block a lot of RF signal.

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The window that the transmitter is currently by does not have solar film on it. I was thinking of moving upstairs for next year, but that window does have the solar film on it.

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THe EDM has a 1-10 mode (baby blue adjustment controls between 1 and 10) or a 10-100 mode (baby blue adjustment controls between 10 and 100).

THe red switch is away from the up/down tuning buttons in 10-100 mode.

The red switch is towards the up/down tuning buttons in 1-10 mode.

The EDM LCD comes set on 1-10 mode and set to 10mW (the max allowed by FCC approved units).

However, anybody owning a Ramsey FM25 (for example) can tune between 10 and 25 mW ... so the rule of thumb is use only what you need and not much more.

That said, some people do ... and proper placement and a good antenna can result in significant range ... somethings up to 1-3 miles. But that said, most shows don't need more than line of sight from your home.

I run my EDM antenna (wire only) on the wall of my office ... and about 60-70' from the curb. It goes a couple blocks, maybe more. If I run it on 10mW, then about 1 block is solid.

Make sure your using good cable, but from computer to transmitter and from transmitter to antenna. Good quality antenna cable isn't cheap ... and using poor cable can result in over half the power lost in 50-100' pretty easily.

Scott

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greenie95125 wrote:

Hi Pat,

No offense, but range is not purely a function of power, especially at the lower power levels (0-100w). At that level, antenna matching and placement have far more effect on range than 5 vs 10 watts.

I live in a dense residential neighborhood, and my antenna is at ground level (j-pole design)... attached to the side of my garage. It's very well matched as well with SWR being 1.65:1... not bad.

At 1 watt, I get about a block, at 10 watts I get about 1/2 mile (clear), at 20 watts I get about 3/4 mile (clear). If I put the antenna on the roof, I'd probably get 2-3 miles at 20 watts. If I put it 20 feet in the air, I may get 10 miles... I don't plan to try that though. The idea here is for folks that know about the show to be able to tune it in while driving here and hear something other than static when they aren't parked directly in front.


For what it's worth, I'm on an absolutely clear frequency as well, so even if I was broadcasting for "miles," I wouldn't be interefering with any other stations.

Merry Christmas!

-Mike

I would never take offense at someone disagreeing with me or expressing a different opinion. I only meant to encourage new users (here in the Newbie Forum) to use as little power as necessary.

At my home, I only need 50 mw to clearly reach the street which is less than 200 feet away. I use a Ramsey FM30B transmitter with the supplied telescoping 1/4 wave vertical antenna. When I was selecting a transmitter to buy, it never occurred to me I might need more power than this transmitter can provide. I have been very happy with it.

When I was first testing my new setup this year, if I had found my signal was not clear in the street in front of my house, I would have next experimented with using a different antenna.

KE4MHQ

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pdowns wrote:



I would never take offense at someone disagreeing with me or expressing a different opinion. I only meant to encourage new users (here in the Newbie Forum) to use as little power as necessary.

At my home, I only need 50 mw to clearly reach the street which is less than 200 feet away. I use a Ramsey FM30B transmitter with the supplied telescoping 1/4 wave vertical antenna. When I was selecting a transmitter to buy, it never occurred to me I might need more power than this transmitter can provide. I have been very happy with it.

When I was first testing my new setup this year, if I had found my signal was not clear in the street in front of my house, I would have next experimented with using a different antenna.

KE4MHQ



I agree, you should use the least power possible to get the range you desire. I just desire a bit more range. :)

I'm impressed that you get that sort of range with that antenna. I tried one that was similar, and it didn't work out at all on my rig.



--Mike

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