Building FM AMP from Motorola 13414500 module???

[Fission7x]

I just bought a Motorola 13414500/09H 9244 broadband amplifier module.



Seller claims building a 1 watt FM transmitter amp is as easy as:



Is it really that easy? Seems like there should be more to it than this.
If I use a good 24 VDC supply, should I have a good clean signal?

[pcs]

These things are linear meaning they waste too much power,
probably get quite hot for the mere 2W it produces.

Another thing is there is no filter, you'll likely produce
harmonics and possibly cause interference problems to
your neighbours.

[Fission7x]

These things are linear meaning they waste too much power,
probably get quite hot for the mere 2W it produces.

Another thing is there is no filter, you'll likely produce
harmonics and possibly cause interference problems to
your neighbours.

I was warned to use a heatsink.
Are there any good filter schematics out there?

[pcs]

Sure, just google for low pass filter

[rjhuhn]

I am considering purchasing one of these little guys from ebay. They seem pretty cheap for what you get. Fission 7x - did you get yours working? Did you add a filter? How big is your heat sink? I would like to drive mine with a Ramsey FM25B at about 10mW, and I would be happy to get 1W RF out. Any thoughts on this? PCS?

Thanks in advance for the help.

[pcs]

Normally I wouldn't mind, but those ramsey thingies are
based on that BA chip. It produces nasty spurs close to the
carrier (not harmonics and can not be easily filtered!), which
makes it dangerous to amplify these things.

Those chips were designed for close-field transmission, such as
from cd player to your radio, which is cool, but they're not
intended to be used for serious power levels.

[Fission7x]

I am considering purchasing one of these little guys from ebay. They seem pretty cheap for what you get. Fission 7x - did you get yours working? Did you add a filter? How big is your heat sink? I would like to drive mine with a Ramsey FM25B at about 10mW, and I would be happy to get 1W RF out. Any thoughts on this? PCS?

Thanks in advance for the help.

I have not tried to build one yet.
I am still working on the PCB design that I want to use.
I hope to include a low pass filter on the PCB also, but you're talking to a mechanical engineer and not an electronics engineer, so I don't have a lot of expectations for the final product.
As for a heatsink, I was going to use a large heatsink off of a socket-370 CPU cooler. If it seems to get too hot with just the heatsink, I was going to power up the fan for supplemental cooling.

[mbates14]

Hey, I got one of those modules, and believe it or not, im guessing the stray capacitance and inductance from the wires I used, I had that little guy peggin g the meedle on my 20watt wat meter!!!!

so, it will deliver 15 to 20watts easy. But, the SWR is tolerative up to a certain point. my module ran for along while, but as soon as I moved the dial, the frequency produced a high SWR, and the module was instantly fried at that power level.

I got a new module free, the guy gave one to me, and it wont even go near 15 to 20 watts any more. I can only get maybe 3 or 4, and it will get hotter than the center of the earth within 2 minutes.

[mbates14]

Another thing I must warn you, use a fan! it does get very HOT, and its easy as that to use. I took one apart, and popped the top off, all it is, is a hybrid IC. it has a matching coil on both the output and input, and pushpull with 2 drivers and 2 ouptut transistors.

its tuned for 50 ohms, so to get the 20 watts that I freakishly obtained, tune the input and output with caps. works great. USE A PLL!! the colpitts I had, it completely made it skeeer way off frequency. Couldnt find the signal again. LOL.


and when I did find my signal, i had to walk 6 blocks away from the antenna before I can even listen to the signal, as the IF circuits in the radio were overloaded badly, as it motorboated.

[maccds1525]

Actually I think IT IS THE Ramsey units themselves that help produce the problemas you are mentioning. There are several mp3 transmitter types available out there which use the BA chip; none produce ANY spurs, burrs at all.

We have been using a particular one for almost a year (covers 1-2 miles well) w/o any AMP. We have ck'd it with a Tektronix spectrum analyzer down to -120 dbmv below carrier and it is clean w/zero harmonics/spurs. We even have drawn out the schematics for one of them which the manu/dealer refuses to give out; they ground off the part number on one chip even.

We are working on a Part 15 web site which should be up sooner or later to help with such designs; our FM part 15 station is quite workable on a low budget and is very clear sounding, being heard by some 3 miles away.

Mad Broadcaster

[quote="pcs"]Normally I wouldn't mind, but those ramsey thingies are
based on that BA chip. It produces nasty spurs close to the
carrier (not harmonics and can not be easily filtered!), which
makes it dangerous to amplify these things.

Those chips were designed for close-field transmission, such as
from cd player to your radio, which is cool, but they're not
intended to be used for serious power levels.[/quote]

[anon]

Maybe I'm wrong about this - I'm still having a hard time wading through all of the United States FCC rules - but if you are getting up to 3 miles range then it isn't a Part 15 station right? From the FCC site:

"On FM frequencies, these devices are limited to an effective service range of approximately 200 feet (61 meters). See 47 CFR (Code of Federal Regulations) Section 15.239, and the July 24, 1991 Public Notice."

My understanding, and again I might have this wrong, is that if your signal is going very much further than that, then you are probably exceeding the 250 uV/M @ 3 Meters rule. Do you have the equipment to check the uV/M on your transmitter? If your getting that kind of range out of a legal Part 15 transmitter then I am very impressed! I can't wait to see your web site!

I realise that this is getting off topic from the original post on this thread but I welcome anyone's corrections to my understanding of the FCC regulations.

[maccds1525]

that's a good point and very accurate quote of sec 239 in '91'. However even dating back to the 70s, back then the FCC refused to allow "ANY" unlicensed broadcasting on the FM band period; zilch. However, this is no longer an up to date rule that you've quoted (thank goodness). I am not sure when it changed but I have the entire sec 239 sitting here downloaded from the FCC and it's on our web site. When it changed, this opened the door to all types of mp3 FM modulators used in cars and trucks. Otherwise, everyone using those would be pirates.

There is a licensed FCC Radiotelephone engineer (like myself) who even had a visit from the FCC respecting such an arrangement as I have described; he passed all except for using a 2 bay hi grade professional FM penetrator Antennas. He was right at the 250 uV level, and was permitted to continue broadcasting provided the use of those special antennas stopped.

Our station was measured twice by the equiv. of an expensive Potomac FIM-71 Field Strength meter, measuring 100 uV at 3 meters. However there are some tricks to the trade (by trial and error) that enabled us to reach a good clear 1 mile. It'll be on the web site here someday: www.geocities.com/part15fm. When I say 3 miles, I mean the die hards who listened thru static, fading, etc. and like me, put up a yagi antenna at their home to receive us well. Being on a clear channel also helps.

[quote="anon"]Maybe I'm wrong about this - I'm still having a hard time wading through all of the United States FCC rules - but if you are getting up to 3 miles range then it isn't a Part 15 station right? From the FCC site:

"On FM frequencies, these devices are limited to an effective service range of approximately 200 feet (61 meters). See 47 CFR (Code of Federal Regulations) Section 15.239, and the July 24, 1991 Public Notice."

My understanding, and again I might have this wrong, is that if your signal is going very much further than that, then you are probably exceeding the 250 uV/M @ 3 Meters rule. Do you have the equipment to check the uV/M on your transmitter? If your getting that kind of range out of a legal Part 15 transmitter then I am very impressed! I can't wait to see your web site!

I realise that this is getting off topic from the original post on this thread but I welcome anyone's corrections to my understanding of the FCC regulations.[/quote]

[pcs]

Your understanding is flawed, what you are saying is completely
out of touch with reality.

[maccds1525]

Such profoundancy Benardo!! Was exactly are you referring to since you made a blanket (and rude) statement? Is it that you think the FCC does not update their rules?; that mp3 modulators are all illegal?? Please explain what you mean. gracia

[quote="pcs"]Your understanding is flawed, what you are saying is completely
out of touch with reality. [/quote]

[pcs]

Mp3 modulators can reach a few meters, which is in full
compliance with FCC rules as they were.

[maccds1525]

I "think" I understand what you mean:
on our web site is the full text of the FCC's "latest" part 15 rules (there are none other listed) copied directly word for word from the FCC's web site: it only makes 2 conditions respecting unlicensed FM broadcasting; anyone can read it here:
http://www.geocities.com/part15fm/nolicensefm.htm

In respect to any distance limit, there is none today.
On the otherhand, respecting achieving long ranges with super low power, I have an old copy of the FCC's Bulletin OCE 12 July 1977 part 15.105/14.0 where they disagree with you respecting long range FM broadcasting (which btw gave me "hope" to test different setups once the "rules" were recently changed). In respect to unlicensed FM band broadcasts:
"conditions in this band are completely different (comparing it to low power AM) and long range transmission is possible even with extremely low power--a fact that is well known and well documented".

Even with no physical antenna connected to the mp3 modulator/transmitter, we could be heard clearly 1/3 of a mile very well from a rooftop mp3 transmitter and fairly well 3 miles away transmitting from a mountaintop site. Just to be nice, I was totally amazed myself at what was possible; i wouldn't have believed it either had I not done it; I have a friend who is head of an organization which builds and "barnraises", as they call it, LPFM stations; he likewise did not believe it could be done and would say:

"My experience is that anyone that says it goes more than a few hundred feet is delusional or a liar. however, i can be wrong."

that's what he said till he met me. Now "he's a believer!!". You can view our actual contour here:
http://www.geocities.com/part15fm/part15contourmap.htm

regards,

[bassplar99]

This might be a dumb question, but I am a civil engineer and a wannabe electrical. FIrst I have to ask where to find this Motorola module? I have hunted around and cannot seem to locate it. In addition, what if it were powered by less than 24V? Will this module still work? I am looking to power it by either 9V or 12V if possible.

This unit might not be exactly what I need for my application. I am looking to amplify the broadcasting range of an existing manufacturer fm transmitter becasue I like the integrate software it is using in the transmitter. I do not need a lot of power, less than 1W should be sufficient. Thanks.