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J Warren

FM transmitter for Audio

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I have observed that many LOR users are using FM transmitters to get around those who don't like listening to christmas music. What makes and models have shown to be dependable and within a fair price range?:P

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I use the Belkin TuneCast II that I modded to give it greater range. It works well for me. There was a post recently about a transmitter from China that is pretty cheap (Around $50 if I remember correctly).

You should read these threads as they contain alot of good information. The last link is to the web store for the China built tranmitter.


FM Transmitter company to stay away from.

My Ramsey FM Transmitter problem

http://stores.ebay.com/FM-TRANSMITTER-SELLER



tom.

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From what I've observed, there are a variety of transmitters being used.

On the low end of the price spectrum, you have the Belkin transmitters, which can be modified to extend their range to usually work allright.

Probably the most common model being used is the Ramsey FM25b. Its on the lower end of of the Ramsey product line, but its a simple model that more than meets the needs of most who use it.

On the higher end, there is the Ramsey FM30b and FM100 models. Those are about $100 more each.

Keep in mind the the Ramsey transmitters are all kits, so if your handy with electronics you can assemble them yourself. If you not so handy, then you can usually find them for sale on ebay (pre-assembled) ... usually for an additional $50 or so.

Recently, I have discovered another player in the game: EDM ... and they reviews for these are really encouraging. They have an entry level "LED" model for $119 (shipped) or a higher end "LCD" model for $168 (shipped). They are also kits, but only require a couple solder points and the installation of a chip. So assembly is probably 30 min or less and more approachable for those with limited skills.

Both Ramsey and EDM appear t have excellent customer support and products. Ramsey is American made, while EDM is made in S. Africa.

No matter which transmitter you pick, you need to choose an empty frequency to broadcast on and make sure to comply with FCC Sect 15 rules ... so basically, keep the broadcast range down to a minimum and don't broadcast over other stations ... or you could get a visit from the FCC (not good).

There are other makes and models ... but these are the predominant ones being used, esp. the Belkin and the Ramsey.

Personally, I'm buying the EDM LCD ... but this is based on non-LOR user reviews ... not from LOR folks per se. Supposedly, the EDM sound quality is really good ... comperable to the higher end Ramseys ... at about $100-150 less.


Stay away from those units sold on ebay, unless they are Ramseys. They are of poor quality and magnets for the FCC due to their tendency to overrun adjacent frequencies. They are far from legal, but also far from good in quality.


You have to be careful with any of them .... to make sure you don't over modulate ... and thus get into trouble. Usually a 10mW (power) unit is more likely to be FCC compliant than a higher powered unit. The FM25,FM30b,FM100 are all variable power ... so you can turn them down to what is needed ... and often don't need a real antenna for Christmas Display range. The EDM LCD is also variable power, similar to the FM30 and FM100 (1mW to 100mW adjustable).

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hobbes wrote:

You should read these threads as they contain alot of good information. The last link is to the web store for the China built tranmitter.

http://stores.ebay.com/FM-TRANSMITTER-SELLER



I've had great luck with my 1.0w transmitter from eBay. Excellent sound quality and I haven't had any problems with blead over to adjacent freqs.

Here's a another thread about these transmitters...
http://www.doityourselfchristmas.com/forums/showthread.php?t=751

Have fun with whatever one you choose! :cool:

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I've noticed several model are available from the e-bay site. Which transmitter did you get from china? Has it been stable?

John

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Ok, I'm glad that you are having luck with these inexpensive units off ebay. But remember that even though it may be working, it doesn't mean its not disrupting other FM frequencies at the same time. These cheap units are known to create harmonic spurs and basically ... are magnets for the FCC.

But even when these units are working, they are HIGHLY illegal at 1w power. That is 10 times what the FM100 power is turned all the way up. That it 40 times the power of an FM25 is all the way up. That is 100 times what any 10mW FCC Part 15 approved transmitter would use.

Read the warning about ebay transmitters here (this is not my site) -- the title of of that part of the web page is: BE

http://www.radiobrandy.com/indexRBNET.html

And this is coming from a pirate radio operator.

I just don't advise using them. For $10-20 more, you can good a better quality unit that isn't illegal (or can be operated within FCC guidelines) and still meets your needs.

Ok, I'll get off my soapbox -- but I just wanted to point out that I have heard lots of bad things about these 'made in china' transmitters ... and this is one place where you could buy american (Ramsey). I've read on other boards that a large percentage of these units are DOA (dead on arrival) ... so buyer beware.

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Interesting. And the audio quality is good? Does it run over adjacent frequencies or drift ? Can you turn the power down?

I've heard mostly good things about Ramsey, but I have also heard bad things as well. My understanding is that its a fairly complicated kit to put together.

I also think that for a little more money, you can buy a product which actually comes with SUPPORT. I think having a supported product is worth something. Ramsey and EDM are both known for their excellent support.

I'd be sad if anyone here bought one of these and then had it removed by the FCC, or worse yet, faced fines.

Reading that thread, its a mixed bag. You have people who got DOA units, people who had smoke and burned up parts after a certain amount of use ... and people who are very happy like Jeff. To me, buying chinese to save a few bucks just isn't worth the hassle.

My opinion only: Please buy American-made products, or stop complaining about the lack of jobs here. Thats a reality check for all of us.

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Thanks for clarifying those things. Your problems obviously weren't related to how it was assembled.

I will say that after talking to a number of folks in the radio broadcast community, that none of them considered Ramsey very good ... but they also considered the ebay transmitters just as bad., or worse.

To my extreme surprise, several swore up and down that the EDM transmitters are amazing, esp. for the money. These are guys who have the equipment to measure all sorts of things that are mostly technical babble to me ... but at the end of the day, they agree that EDM transmitters are really good. I have one on order, but am not qualified to give an opinion, since I've never used one.

I did own an FCC approved (10mW) Panaxis ACC100s (retails for $299) ... and basically, it had enought range, but sounded crappy and was weak (low volume). Steve over at Radio Brandy said that no matter how hard he tried, he couldn't make the ACC100 decent. I have another post over at PC, where we talked about the EDM further. Its worth a read, if your seriously shopping around for FM transmitters.

One of the guys I talked to who owned the $90 EDM LED told me he accidently hooked up a 15v power supply and antenna and found himself transmitter for around 10 miles by accident at 100mW. Needless to say, he got the right power supply (12v) and removed the antenna ... and still got 3-4 blocks.

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John Warren wrote:

What mods did you do to the tune Cast to increase its power?


The mod was to disconnect the internal antenna wire and connect about 5' of wire to use as an external antenna. I could not find the exact page that I used 2 years ago for the instructions but I did find another one. The pictures are blurry but you should get the idea.

http://mypage.iu.edu/~bschank/Tunecast2/tunecast2mod.htm

tom.

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hobbes wrote:

John Warren wrote:
What mods did you do to the tune Cast to increase its power?


The mod was to disconnect the internal antenna wire and connect about 5' of wire to use as an external antenna. I could not find the exact page that I used 2 years ago for the instructions but I did find another one. The pictures are blurry but you should get the idea.

http://mypage.iu.edu/~bschank/Tunecast2/tunecast2mod.htm

tom.


Here are a few more:

This one http://www.christmasdisplays.net/fmtransmitter.php from ChristmastDisplays.net is fairly similar to the one Tom posted above.

This one http://www.sonic.net/~n7moe/BelkinMod.htm is a little more in depth and adds an RF amp.

Rick

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Here are a couple comments from the yahoo EDM group, when I asked them to comment on the chinese recievers mentioned earlier in this thread. Several other users also replied, all basically saying these transmitters are junk for one reason or another -- most already mentioned here. They may work perfectly well, as Jeff mentioned, but what they are also doing (with unintended harmonics and spurs) is the biggest problem and risk.


They have high signal to noise ratios. Looking at the spec sheet of one of these Chinese transmitters, quote the signal to noise ratio (SNR) around 40dB. That is awful! Our LED series makes 60dB or better and the LCD series typically makes more than 75dB and some even up to 85dB. This is the type of figures you would find in a professional commercial exciter. If you take one of these low quality transmitters, kill the audio input and transmit a dead carrier while listening on a good quality FM receiver, with the volume turned up, and close your eyes, you will imagine that you are at the beach with all the "Shss" background noise you will hear. This is a result of the poor VCO designs used with high levels of phase noise on the carrier. There are also reported problems with the 2nd harmonic from these transmitters almost equal in level to the first harmonic which is the intended frequency. This second harmonic will fall in the low VHF TV bands (174MHz and up) and cause massive interference. This will lead to complaints and the get you into serious trouble if the authorities investigate this. Spurs may also leak into the aircraft band above 108MHz and you will also have the aviation authorities down your throat.

Another example from the EDM engineering team:

Our engineering department gave this example of how spurs can end up
in the aviation band.
Examples:

These transmitters typically use a clock frequency of 7.6MHz for the
frequency synthesizer. Because this clock will also have harmonics at
(15.2MHz, 22.8MHz, ...). If special precautions are not taken to keep
this components from coupling into the VCO as a unwanted modulation
spur, some image of your transmit signal will appear at these offsets
on either side of your transmit frequency.

First case: You transmit on 100.4MHz with a high level spur 7.6MHz
away. You will then have a signal interfering on 108MHz in the
aircraft band. If this spur is of significant amplitude and your near
an airport it will be investigated.

Second case: You transmit on 106.3MHz. The 2nd harmonic of this clock
appears at 106.3MHz + 15.2MHz. This will cause a signal at 121.5MHz.
This is the international aircraft band emergency frequency! You can
think what the consequences of this would be! These transmitters with
powers as high as 15W are like an accident waiting to happen.

EDM Team

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Thanks for the mod info. I purchased 2 Tune cast II with damaged cases for $2.00 each and they still work. :]:]:]:]

Their loss my gain.

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While I certainly appreciate your excitement over EDM, you are quoting people that represent the company. Not exactly an unbiased opinion. The first quote talks about looking at a spec sheet. What spec sheet? The Chinese units do not ship with one. They do not quote actual independant test results let alone their own test results. The second quote is equally as muddy. In the second quote, there is speculation that if given the right circumstances something bad could happen. Again, no evidence, just theory. I would be curious if that pirate radio station is not in some way affiliated. I am very skeptical like that.

In any event, I look forward to your report on your unit when it arrives.

taybrynn wrote:

Here are a couple comments from the yahoo EDM group, when I asked them to comment on the chinese recievers mentioned earlier in this thread. Several other users also replied, all basically saying these transmitters are junk for one reason or another -- most already mentioned here. They may work perfectly well, as Jeff mentioned, but what they are also doing (with unintended harmonics and spurs) is the biggest problem and risk.


They have high signal to noise ratios. Looking at the spec sheet of one of these Chinese transmitters, quote the signal to noise ratio (SNR) around 40dB. That is awful! Our LED series makes 60dB or better and the LCD series typically makes more than 75dB and some even up to 85dB. This is the type of figures you would find in a professional commercial exciter. If you take one of these low quality transmitters, kill the audio input and transmit a dead carrier while listening on a good quality FM receiver, with the volume turned up, and close your eyes, you will imagine that you are at the beach with all the "Shss" background noise you will hear. This is a result of the poor VCO designs used with high levels of phase noise on the carrier. There are also reported problems with the 2nd harmonic from these transmitters almost equal in level to the first harmonic which is the intended frequency. This second harmonic will fall in the low VHF TV bands (174MHz and up) and cause massive interference. This will lead to complaints and the get you into serious trouble if the authorities investigate this. Spurs may also leak into the aircraft band above 108MHz and you will also have the aviation authorities down your throat.

Another example from the EDM engineering team:

Our engineering department gave this example of how spurs can end up
in the aviation band.
Examples:

These transmitters typically use a clock frequency of 7.6MHz for the
frequency synthesizer. Because this clock will also have harmonics at
(15.2MHz, 22.8MHz, ...). If special precautions are not taken to keep
this components from coupling into the VCO as a unwanted modulation
spur, some image of your transmit signal will appear at these offsets
on either side of your transmit frequency.

First case: You transmit on 100.4MHz with a high level spur 7.6MHz
away. You will then have a signal interfering on 108MHz in the
aircraft band. If this spur is of significant amplitude and your near
an airport it will be investigated.

Second case: You transmit on 106.3MHz. The 2nd harmonic of this clock
appears at 106.3MHz + 15.2MHz. This will cause a signal at 121.5MHz.
This is the international aircraft band emergency frequency! You can
think what the consequences of this would be! These transmitters with
powers as high as 15W are like an accident waiting to happen.

EDM Team


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Your right, I probably shouldn't be so trusting after asking a company about their own products -- duh!

But, getting a bunch of emails and eventually a call from a record producer who has also been doing radio for over 30 years ... that was a real confidence builder (in EDM). These guys raved and had no reason to do so financially speaking.

This guy, and Steve over at Radiobrandy don't seem to benefit in any way ... but they were extremely positive about these units ... so I just had to give them a try.

I'll hold off my blabber mouthing as much as possible, till I gets some 'hands on' experience with these units.

Scott

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OK

So EDM seems the way to go. Now where is their web site? I tried EDM, EDM transmitters and a few other combinations through google and got everthing but what I was looking for.

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EDM seems the way to go.


It would be premature to say that ... but its looking very "encouraging" from my research thus far.

Here are the links for EDM --

http://www.edmdesign.com/ -- note: the links below are embedded in the LCD graphic at the top of the screen, kind of confusing till you get used to it.

Links broken out below (eff. 2/20/08) ---

http://mysite.verizon.net/respddox/orders.html

http://mysite.verizon.net/respddox/specs.html

http://mysite.verizon.net/respddox/operation.html

http://mysite.verizon.net/respddox/features.html

A review at Radiobrandy --

http://www.radiobrandy.com/Transmitters.html

The EDM yahoo group -- open to join buy must be moderator approved first.

http://groups.yahoo.com/group/edmdesign/


I am asking them about RDS support ... it doesn't have it yet, but might be able to in the future??

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Jeff, thanks for posting your experiences and opinions.

Untill recently, I had only heard good things about the Ramsey transmitters. In the last couple weeks, my impression has changed for the worse ... as your not the only one who has had problems with them.

And you also definately not alone in being perfectly happy with the ebay transmitter that is very affordable.

Maybe its is just like how people used to tell me that my gigantic montgomery ward speakers were crap ... but to me, they sounded awesome ... and thats what mattered.

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Jeff Millard wrote:

Funny you say that. I had a set of Klipsh horns when I was overseas.

OFF TOPIC ALERT:

Klipsch has always and continues to make excellent speakers - including the Klipsh horns!

Montgomery Wards on the other hand :shock:;);)

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iresq wrote:

Jeff Millard wrote:
Funny you say that. I had a set of Klipsh horns when I was overseas.

OFF TOPIC ALERT:

Klipsch has always and continues to make excellent speakers - including the Klipsh horns!

Montgomery Wards on the other hand :shock:;);)

I love my Klipsch ProMedia 4.1 computer speakers. :cool:

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(edit - they already sent it!!! Wow, now that's customer service!)

Does anyone have the assembly instructions for the EDM LCD unit?

Just got it, but it didn't come with any instructions, and I'm not finding on the web.

I've emailed them, but thought someone might have it here faster.

Cheers!

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You should have gotten a link for the instructions when you received your confirmation. I have them if you will send your email in a pm.

Chuck

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