In-house Radio Transmitters

Unfortunately, you will not find a commercial product that provides
longer range AM or FM transmission on the standard broadcast bands,
because it's not legal to sell them.
__________________________________________________________________________
Subject: In-house Radio Transmitters
Author: Tom Gewecke
Date: 3/14/05 5:07 AM -0800

>Can anyone suggest a good radio transmitter for broadcasting audio
>from my desktop to portable radio's around the house? It has to
>have rather greater range than the ipod accessories designed for
>in-car use. Also where I live the FM band is crammed with stations,
>but the AM band is mostly empty, so one that worked in that band
>would be a plus. Fidelity is not important.
>
>Thanks for any advice!

> Can anyone suggest a good radio transmitter for broadcasting audio from
> my desktop to portable radio's around the house?

I bought a Canakit R222 and have been very happy with it (I'm
actually using it right now for the purpose you describe). You can
also order a pre-assembled and tested version if you don't have a
soldering iron (UK222, link further down the page).

<http://www.canakit.com/Default.asp?Contents=/Include/Template/MenuCat.asp&Main=http://www.canakit.com/Contents/Items/CK222.asp>

The sound quality is good, and I like that I can run it off the mains
or batteries depending on my situation (I also made an adaptor for
the mains socket so that I can power it through a car's cigarette
lighter if I hire a car). The one drawback is that it can be fiddly
to tune, but I'm happy with how it sounds once I get it tuned in.
Also, I don't know how big your house is. I live in a four room flat,
and it's fine (and my neighbour below used to tune in sometimes as
well without problem). But I don't have any experience with using it
in a three storey house or anything (the website claims 150m
unobstructed transmission range).

This is FM only though, so might not help with your crowded channel
problems (though it does span the full range of FM frequencies).
However, there are other kits that they sell that might be more
suited to your situation. When I was researching for mine I looked at
a number of different websites, but it was a few years ago now and I
can't find the links. :-( I'm sure a web search on "fm am
transmitter" will turn up some useful results.

On a related note, I wish someone would make a DAB radio transmitter,
because FM can get interference with the changing weather.

_________________
=> Jolin Warren, Edinburgh, Scotland

On 3/14/2005 5:07 AM, "Tom Gewecke" wrote:
> Can anyone suggest a good radio transmitter for broadcasting audio from
> my desktop to portable radio's around the house? It has to have rather
> greater range than the ipod accessories designed for in-car use. Also
> where I live the FM band is crammed with stations, but the AM band is
> mostly empty, so one that worked in that band would be a plus.
> Fidelity is not important.

I don't know of any AM transmitters. But if you're looking for a good "home"
transmitter, I've had very good luck with the C.Crane FM Transmitter:

<http://www.ccrane.com/fm-transmitter.aspx>

C.Crane claims line-of-sight range of 70 feet; I can't confirm that, but I
can confirm that we receive the broadcast in several rooms at once in our
home, which is much better than any of the iPod transmitters we've tested at
Playlistmag.com.

At 5:07 on 14-3-05, Tom Gewecke wrote:
> Can anyone suggest a good radio transmitter for broadcasting audio from
> my desktop to portable radio's around the house?

For those interested in transmitter kits like the one I already
posted about, I just found a few more links to kits (some with a
larger range). The first is for a company called Veronica (they also
have other models than the link I give), followed by a review of one
of their kits.

<http://www.veronica.co.uk/50mw-stereo.htm>
<http://www.irational.org/sic/radio/veronica-1w.html>

The second is a company called NRGKits (again, this is just one
example of what they offer).

<http://www.nrgkits.com/radiokits/lpstfm.htm>

At 5:07 on 14-3-05, Tom Gewecke wrote:
> Also where I live the FM band is crammed with stations, but the AM band
> is mostly empty, so one that worked in that band would be a plus.

And the third and forth companies also sell AM transmitters.

<http://www.ramseyelectronics.com/hk/>
<http://www.hobbytron.com/R-AM-1.html>

Note that I have not ever dealt with any of these other companies or
their products, so I can't give a personal recommendation. But for
anyone interested in buying a radio transmitter kit, it's useful to
have a range of options so you can find one that best fits your needs.

Cheers,
Jolin

_________________
=> Jolin Warren, Edinburgh, Scotland

While passing by Griffin Technology's website, I saw their "Rocket FM"
product available for preorder. Looks like something the original
poster was describing.

http://griffintechnology.com/products/rocketfm/index.php

The RocketFM looks like an interesting product but it's important to note
that most transmitters have a 1/8" line-in analog jack whereas this uses USB
(from which it also draws power so you don't need batteries or a DC
transformer). This means it only works with a computer running their
software as the audio source. The original request was for a transmitter to
be connected to a desktop so that shouldn't be a problem in his case unless
of course it becomes an orphaned product and Griffin stops providing the
necessary software for future OS's.

It's not clear from the site whether the RocketFM software accepts audio
from individual applications or merely transmits *all* audio generated by
the computer. If it's the former, that would be a very nice feature the
typical transmitters lack. If such a feature is not incorporated, perhaps it
can be achieved using something like Rogue Amoeba's SoundSource.

On 3/18/2005 2:06 PM, "Wilcox, Curtis" wrote:
> The RocketFM looks like an interesting product but it's important to note
> that most transmitters have a 1/8" line-in analog jack whereas this uses USB
> (from which it also draws power so you don't need batteries or a DC
> transformer). This means it only works with a computer running their
> software as the audio source.

Not necessarily. Mac OS X supports USB audio, so USB audio output devices
automatically show up as audio outputs when plugged in. (I use a HeadRoom
Total BitHead headphone amp in this manner.) I haven't yet seen the
RocketFM, but it's entirely possible that you select the transmission
frequency on the device itself, which would mean that no software is
necessary. This would make the RocketFM very similar to Engineered Audio's
Aurius.

<http://www.headphone.com/layout.php?topicID=3&subTopicID=27&productID=00000
10008>
<http://www.engineeredaudio.com/products/aurius.html>

For an FM transmitter, check out <www.mobileblackbox.com>. They offer two versions, one (called version 2) that operates for 150 hours on three AA batteries and plugs into the audio output jack and so can be uses with a variety of audio equipment and one (called version 3) that plugs into the USB port and takes its power from the port. Both are said to provide coverage up to 150 feet.

These are also found for sale on eBay.

......Jeff

Regarding in-home FM Transmission:

After experimenting with several battery operated options, I went to
the USB powered FM Transmitter produced as a "LineX USB FM
Transmitter".

It works well, perhaps too well. When I am in my car, I can pickup my
"home broadcasts" a bit over a mile away and a neighbor has asked "if
I have heard the new radio station at 107.5 that plays beautiful
music?"

Embarrassed, I explained what was happening, but he is delighted and
wishes that I would keep it going during the day while I am at the
office.

The "list price" is $59.95 but I purchased mine on eBay for $39 plus
shipping. -- jal

--
===================================================
  John A. Lutz 802 296-7015
  True BASIC, 1523 Maple St, Hartford VT 05047-0501
  johntruebasic.com fax: 802 296-2715
===================================================

Re: CC Crane and other very low power transmitters.

I tried the Crane FMT for just the use you asked about, and it's very cute and classy unit, good frequency control, etc. But far too little power for my needs, even when you open it up and turn the pot. on the output up to maximum. It might be OK up to 30-50 ft. if there were no obstructions at all. Going thru one or two walls or floors is dicey -- signal gets very weak. Might work fine in a car to send iPod signal to radio.

I ended up getting one of Ramsey's preassembled transmitters. Would only recommend the kits if you are very experienced builder and have, or know someone with, adequate test equipment, more than a VOM. You need to be very careful with the more powerful units to pick an unused frequency and just use enough power to reach the desired area, to avoid tangles with the FCC, because you know how mean they can be!

--- begin forwarded text

From: David Emery

<In response to your TidBITS article>

<http://db.tidbits.com/getbits.acgi?tbart=08027>

My local NPR station "sold out" and went from 'news & classical' to
'news & blather' all day long.

In retaliation, I've ripped all my CDs in iTunes, and I have a smart
playlist that does by-album shuffle 24 hours/day, from my new Mac
Mini.

What I'm using for broadcasting is a modified CCrane transmitter. The
little transmitter works from either batteries or an AC converter.
The modification is to turn up the power to the legal limit by
cracking the case or peeling back a label and turning a capacitor.

The transmitter is described here:
<http://www.ccrane.com/fm-transmitter.aspx> and here's the
modification article: <http://www.xmfan.com/viewtopic.php?t=3257>

Before the modification, the transmitter had to be within 10 feet of
the radio. Now the transmitter is located in the basement home office
(where all computers are banished, per order of She Who Must Be
Obeyed), and I get excellent reception even in the upstairs bedroom
and bathroom, and within 100 feet all around the outside of the
house. Long Live Radio Free Davebert!

                        dave

--- end forwarded text

After experimenting with several battery operated options, I went to the USB powered FM Transmitter produced as a "LineX USB FM Transmitter".

It works well, perhaps too well. When I am in my car, I can pickup my "home broadcasts" a bit over a mile away and a neighbor has asked "if I have heard the new radio station at 107.5 that plays beautiful music?"

The Line-X transmitters might get much of their distance from the 3' wire antenna. If you keep the wire bundled together, perhaps the distance covered will be less.

.....Jeff

On Mar 24, 2005, at 5:31 PM, Sales Desk wrote:

> Regarding in-home FM Transmission:
> ...
> It works well, perhaps too well. When I am in my car, I can pickup my
> "home broadcasts" a bit over a mile away and a neighbor has asked "if
> I have heard the new radio station at 107.5 that plays beautiful
> music?"
>
> Embarrassed, I explained what was happening, but he is delighted and
> wishes that I would keep it going during the day while I am at the
> office.

I would be real careful if I were you. :-) I worked as an engineer for
an FM station in the Boston area for a few years, so I am pretty
familiar with FCC rules. (I also know how nasty the FCC can be.)

The FCC strictly regulates the "FM" (88-108Mhz) band. In particular,
they are concerned about the actual field strength of these
transmissions (rather than just the output power of the transmitter).
Any unlicensed transmitter must be putting out less than 250
microvolts/meter when measured at 3 meters (10 feet) from the
transmission antenna. The field strength of an FM transmission
declines by half each time the distance from the antenna is doubled.
So the output from a transmitter producing the max allowed power would
be 125 microvolts/meter at 6 meters, 62.5 microvolts/meter at 12
meters, etc. Very good FM tuners can pick up signals as weak as 5
microvolts/meter, your average car radio is significantly less
sensitive (probably in the 10-15 microvolts/meter range). So this
means that even if your unlicensed transmitter was outputting the max
allowed field strength, the very best tuners would not be able to pick
it up beyond about 300-400 feet or so, and your car radio would lose
the signal after about 200 feet. So if you can pick up your broadcasts
a mile away, you are way over the FCC limit. (And the FCC can be
pretty nasty, if a bit inconsistent, in fining violators of FM
regulations.)

The other issue is that these unlicensed transmitters in the FM band
can be used only as long as it does not interfere with the signals of
licensed FM band broadcasters. What this means in practice is that
even if you have a legal (low power) FM transmitter, if it interferes
with your neighbor's radio, you must shut it down or change frequency.
(In practice, this means that you have to shut it down if your neighbor
actually complains.) This is part of the reason why makers of FM
transmitters (like the various iPod accessories) keep the output of
their products way below FCC allowed limits. If you are one of these
accessory makers and want to be sure that you are not going to get a
lot of returns because of interference issues, you need to keep the
output pretty low. (In an urban setting, your transmitter and an
unintended receiver might not be separated by more than a few dozen
feet.)

The good news, however, is that since these transmitters output
significantly less than FCC limits, you can crank up the output of
these transmitters (as a previous poster has mentioned), and do so
legally. Just be willing to turn it back down when the neighbors
complain.

Tn

Here's how to crank up the C Crane transmitter. This site says this takes it to legal max. Before my C Crane unit could barely reach across the room. Now it reaches about 100' around the house.

http://www.xmfan.com/viewtopic.php?t=3257

This isn't the cheapest FM broadcast unit, but I'm very happy with it. The only annoyance is that it turns itself off everytime the power cycles, so it's now on the same UPS as my Mini. I use this to broadcast 'radio free davebert', my classical CD collect, nonstop from iTunes (album shuffle) throughout the house. (I did this when the local NPR station switched from a News & Classical to a News & Blather format 6 months ago.)

dave

 16. Re: In-house Radio Transmitters

Message #14: Re: In-house Radio Transmitters
Posted by: deemery Date: Sep 1, 2005.

Here's how to crank up the C Crane transmitter. This site says this takes it to legal max. Before my C Crane unit could barely reach across the room. Now it reaches about 100' around the house.

http://www.xmfan.com/viewtopic.php?t=3257

Great "secret" suggestion. Early on I spoke to the people at CCrane about the range of the FM Transmitter and they gave me an even easier means to increase the range. At least on my model, if one peels back the label on the back of the unit it exposes a hole into which one can insert a small screwdriver and one can then

gently* turn the adjustment to increase the range. If such a hole is still on the back cover you don't even have to remove the cover, as the article suggests, to make the adjustment.

Hope this helps,

Ken Workman