Whole House FM (Or AM) Transmitter

loopstick

loopstick

Lunatic Member
I haven't posted on Tuners in a million years (back in the JBL Guy Era). I just had my roof reshingled and instead of reinstalling my antenna and rotor back on the roof I put the antenna in the attic. Getting it through the closet trap door was like building a ship in a bottle. The antenna feeds several rooms for TV and FM. Now I want to transmit FM from a shortwave radio and some streaming so that it's picked up by the attic antenna and sent to all the receivers in the house. So I'm looking for suggestions. I'm a little bit familiar with the FCC cuz I used to have an Extra (20 wpm) ham license, but there may be some issues I need to be aware of. Thanks.
 
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Been using a Ramsey FM transmitter with issue for over 10 years. Puts out about 10mW, covers the whole house. Unfortunately Ramsey closed it's kit division about 4 years ago.
 
you could try one thats intended for in cars . i have one i added an antenna to . one of those should work without the antenna for your purposes
 
As part of a project for a family member, i got to try out the Broadcastvision Entertainment AXS-FMTD transmitter. I chose this item because it had a digital input. During testing, i tried it using the built in telescoping antenna on the first and second floors of my house.

Reception using my roof antenna and Accuphase was ok. Unfortunately this box was the intended source. Using portable radios in the back yard resulted in suboptimal reception to the point that i could not justify the purchase given the performance level and price. I should mention my house was built in 1800 and has a very thick wooden frame.

I am sorry I missed out on Ramsey, especially considering they are located about 20 miles down the interstate from me...
 
ap14608 said:
As part of a project for a family member, i got to try out the Broadcastvision Entertainment AXS-FMTD transmitter. I chose this item because it had a digital input. During testing, i tried it using the built in telescoping antenna on the first and second floors of my house.

Reception using my roof antenna and Accuphase was ok. Unfortunately this box was the intended source. Using portable radios in the back yard resulted in suboptimal reception to the point that i could not justify the purchase given the performance level and price. I should mention my house was built in 1800 and has a very thick wooden frame.

I am sorry I missed out on Ramsey, especially considering they are located about 20 miles down the interstate from me...
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The attic antenna should work. I don't know what its 3D pattern is but I'm guessing it will be able to "see" the transmitter wherever I put it in the house. Back when I had a cordless phone (1990's) I put an antenna on my roof so I could get calls when I was working in the yard. I don't want to push this FM signal out any further than I have to, so maybe the AXS-FMTD would be fine. It looks kinda cute:

FM-Trans-Waiting-List-1.png


At any given time I have 5 receivers in rotation and it would be cool to replace the line feeds with this local broadcast scheme.
 
You are paying a premium for the AXS-FMTD model because it has a built in DAC. Unfortunately, the DAC only supports a bit rate up to 96 kHz. anything higher and the source is not decoded, resulting in 'silence'.

You can find similar models designed for 'home' or 'drive-in' use without the built in DAC for less and with the same power output
 
I'm looking at this one ...

71CwoJztDXL._AC_SL1500_.jpg


I know it's AM, but I was into AM big time when I joined AK (loopstick). It looks decent. I mostly would be streaming other radio stations. I even have an MCS tuner that does AM stereo (but I'd be surprised if this does). The pros are it's guaranteed by design (not test) to be FCC compliant, and some of the FM transmitters get complaints about weak audio, ambiguous FCC compliance, cheapo construction. This guy looks pretty solid. Here's the amazon page:

InfOspot Talking House AM Radio Transmitter
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I came across that one as well when i was searching for an FM transmitter. It looks like an interesting device.

the manual states:

The Transmitter has a patented tuning system to perfectly tune the output at each frequency. This is the mechanical noise heard when you change frequencies.
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I'd just like to see how it is doing that tuning
 
That is WAY cool. I'm also in New York State and it turns out that New York has it's own laws re: radio transmission:
S 190.72 Unauthorized radio transmission.
A person is guilty of an unauthorized radio transmission when such
person knowingly makes or causes to be made a radio transmission in this
state, on a radio frequency assigned and licensed by the federal
communications commission for use by amplitude modulation (AM) radio
stations between the frequencies of five hundred thirty kilohertz (kHz)
to seventeen hundred kilohertz (kHz), or frequency modulation (FM) radio
stations between the frequencies of eighty-eight megahertz (MHz) to one
hundred eight megahertz (MHz), without authorization or having first
obtained a license from the federal communications commission or duly
authorized federal agency, in violation of federal law.

Unauthorized radio transmission is a class A misdemeanor.
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There is no explicit "free pass" for FCC Part 15 transmission. It's agnostic. But I'm assuming that if I show good faith with this FCC Part 15 approved design AM transmitter I should be OK. The big concern seems to be pirate radio and interference with aircraft communications. My humble little AM down on 1 MHz should be nice and quiet.
 
The state laws allow them to crack down more aggressively on the high-power FM pirates which are interfering with licensed broadcast stations, which are a big problem in the NYC area. They don't care about these little Part 15-type transmitters.
 
vwestlife said:
The state laws allow them to crack down more aggressively on the high-power FM pirates which are interfering with licensed broadcast stations, which are a big problem in the NYC area. They don't care about these little Part 15-type transmitters.
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I think you nailed it. The state can put more resources in the field and be more aggressive. The FCC itself is still the defining technical authority regarding what's kosher or not. I haven't pulled the trigger on the AM transmitter yet. I made it to the shopping cart on Amazon then got cold feet. I'm still researching. It's a fascinating topic. Here's an interesting discussion re: what truly is a non-radiating RF ground and what it means for Part 15 AM compliance.

Part 15 AM antennas

I miss JBL Guy :(
 
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my little fm one is similar to this belkin one .i have added an antenna to it and when its about 20ft up a pole it transmits at least a mile .. without mods it does probably a 1/8 mile line of site easily . its an amazing little thing really .
 
loopstick said:
This is kinda fun. He picks up a potty-mouthed pirate at 8:12

.
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I'm quoting myself cuz I'm not sure about the legality of this unit. There are several what look like clones of this on Amazon which claim FCC ID 2ASVO05B7CT200. And I can't believe that they're all kosher. Here's what the FCC says about certification:
The FCC ID. The FCC ID must be permanently marked (etched, engraved, indelibly printed, etc.) either directly on the transmitter, or on a tag that is permanently affixed (riveted, welded, glued, etc.) to it. The FCC ID label must be readily visible to the purchaser at the time of purchase.
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I'm not seeing this permanent mark on this particular unit. The FCC ID number is legit, and there's some documentation online that shows pictures of the unit and the testing lab. But I think it's kinda fishy that the required permanent marking is missing. Anyhoo, still researching ...

Edit: It actually "does" have the FCC Number on the unit. But it doesn't say "FCC ID" and the antenna connector looks like a female TNC which I think is illegal cuz it's supposed to be "unique" and not commonly available.
signstek_05b.jpg

tnc_connector.jpg

15.203 Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. The use of a permanently attached antenna or of an antenna that uses a unique coupling to the intentional radiator shall be considered sufficient to comply with the provisions of this section. The manufacturer may design the unit so that a broken antenna can be replaced by the user, but the use of a standard antenna jack or electrical connector is prohibited.
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so long as it works within the fcc i cant see anyone banging on the door . i wouldn't think they go around busting people for being within the rules .
 
petehall347 said:
so long as it works within the fcc i cant see anyone banging on the door . i wouldn't think they go around busting people for being within the rules .
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True. But I have this nagging fussy sense of "professionalism" that makes me want to be prepared for any discussion should I get that knock on the door. Some of these clones claiming compliance also claim 7 watts. I also believe that a company that is honest about their engineering is also gonna be somewhat trustworthy and diligent. Anyhoo, it's an interesting topic (for me at least). I became acquainted with the whole Shenzhen story during some unrelated stuff I did at work. It's like the electronics equivalent of a wet market.
 
Any FM transmitter which advertises its power output level is not legitimately FCC Part 15 approved. The Part 15 regulation for FM is based on field strength, not transmitter power, and with most antennas is usually so low that it's in the microwatt range. Unfortunately many of those transmitters are advertising a fraudulent FCC ID number. They sent in a unit for testing that was specially modified to meet the Part 15 limit, while the units that are actually sold to consumers have far greater power output.

For example, this transmitter claims to be FCC Part 15 approved, but one user tested it with a wattmeter and discovered it's putting out 7.2 watts (as the ST-7C model number suggests):

https://www.amazon.com/Signstek-Transmitter-Stereo-Station-AntennaFashion/dp/B00CGVHJ32
 
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