Carl's FM Laboratory

With excellent programming from KDX-FM at 101.5 MHz I entered the car, parked at the NE corner of the Internet Building.

Using "scan mode" I had the radio look for the next station, and it glided right over 101.5, which wasn't strong enough to grab the moment. It was necessary to manually tune, and the signal sounded slightly noisy.

Backing down the 100' driveway toward the north, reception was intermittant and at the street became more spotty.

After passing two houses going east the KDX-FM signal gave way to a translator located 40-miles away in another county with rap music. Althopugh it was also spotty, it demonstrated the actual sensitivity of the car radio.

An inspection of the dashboard found no brand name for the receiver.

Conclusion: a true certified part 15 FM signal is very weak and not equal to most serious application.

In the next experiment we'll click the switch inside the Wholehouse 2.0 to invoke Canadien power level, and do another drive to compare the result.

Is the house wooden or does it is s aluminum siding?  This is also important when doing experiments with FM transmitters in the house. Were you on the first floor? I sure would like to see the difference between this and Canadian field strength.

I'm just wondering, Carl, if you can hear that translator on the frequency with the car radio when you're not broadcasting?

No.

Having been tipped off about this translator station (250 W) I checked indoors and out using several radios, and noted that it was not receivable.

Since the car radio was able to detect the distant translator, that serves as proof of the car radio's sensitivity.

Disregard the answer in the previous post.

Repeating Artisan's Question: "I'm just wondering, Carl, if you can hear that translator on the frequency with the car radio when you're not broadcasting?

In the car yes, on the one occasion when I listened for that translator on the car radio it could be heard very weakly and much in the background.

By comparison, the translator does not appear on most portables, except it can be noticed on the TECSUN PL-310, by moving around and finding stronger reception.

The translator is K268CT, 101.5 MHz, 250 W, about 45-miles west.

TheLegacy asked: "Is the house wooden or does it is s aluminum siding?"

The house is brick. My Wholehouse 2.0 Part 15 Certified Transmitter used in the test is physically located mid-house along the west wall. The auto parks at the NE corner of the house, which was the starting point for the test.

The reason I asked is that when looking at sensitivity, the Signal to Noise Ratio is the key.  If you can hear the translator at all, it's generating interference, or noise, and that can have a significant effect on your range.

Here's a story of my time on Bowen Island.  I had been transmitting on 88.7 for over 6 months.  The frequency was absolutely clear.  Then one day, I noted that the signal, even near the transmitter, was greatly reduced, and noise was creeping in.  In some spots, it dropped out altogether.

I thought that something was wrong with the transmitter and took it off the air.  Lo and behold, there was the Canadian equivalent of a TIS on my frequency (it's actually located in New Westminister, pretty close to where I am now).  So I did some checking, and even though the signal was very weak, and couldn't even be heard clearly at all in some spots, my range had almost been cut in half.  Plus the signal was spotty where before it had been solid.

There wasn't much I could do about the TIS, so I ended up having to move to 99.7.  That channel wasn't quite as clear as 88.7 was before the TIS started up (there were stronger signals on adjacent channels) but it was the best I could do.

For your tests to be as definitive as possible, I believe that you'll need to find a channel that is absolutely clear, and ideally, have clear adjacent channels (or weak signals on those channels).

The other thing to consider is that car radios, while much more sensitive than portables and handhelds generally, do have variability amongst themselves.  And if one has a sensivity of 1uv, and another 2uv (not uncommon, particularly today), your range is going to be halved with the latter.

Even though I could receive my signal on Bowen up to 1 km away line of sight in my car, there were some cars that had trouble at 1/2 km, and a few much less than that - all due to the variability in sensitivity of the radio.  My car radio was OEM in a Hyundai Santa Fe, but the worst was an OEM in an older Ford.  I also had good range with an older Alpine, and the nice thing about the name brand radios is that you could actually find the claimed specifications (or you could 10 years ago, anyway).

Very good points, Aritsan.

The translator on 101.5 is new, and for my daily indoor use of that frequency as an audio editing channel, the translator is not causing a problem.

In a way I am comfortable that the translator is reducing my outreach on 101.5, because I'm not trying to attract neighborhood listeners.

But for these tests you have convinced me to use a more open channel and I have one in mind.

Meanwhile, today I was making a chart of signal strength in dBu and S/N (signal-to-noise) numbers from the Wholehouse 2.0 outward, using the TECSUN PL-310. I got indoor readings and all the way out to the porch railing when a rain storm began, delaying the measurements.

There are more than 2000 translator construction permits in the FCC’s database right now. https://transition.fcc.gov/fcc-bin/fmq?state=&call=&city=&arn=&serv=FX&vac=4&freq=0.0&fre2=107.9&facid=&asrn=&class=&dkt=&list=1&dist=&dlat2=&mlat2=&slat2=&NS=N&dlon2=&mlon2=&slon2=&EW=W&size=9
That means there are more than 2K licensed users of the FM band that can sign on as soon as they get their facilities built. (Some may never get built, some may get sold before they get built, some will be modified before they are built, and other things may happen, so 2000 is only a rough number).
That does not even count translator applications (some of which are modifications of existing translators), and LPFM CP’s and applications.

If the FCC would ever allow you to become a translator station for an existing Internet radio station say 1W would you have to have a outside antenna at a certain height? If not there might be A workaround.  Just throwing an idea out there but seriously I doubt it will work.

TheLegacy your question is very curious:  "would you have to have a outside antenna at a certain height? If not there might be A workaround."

FM antennas for licensed stations are usually on towers or tops of buildings but where else could they legally be placed?

One set of rules that might answer the question has to do with RF exposure, which regulates safety for humans located near the antenna. I'm thinking that antennas in homes might only be safe and legal if they are very low power.

An amateur radio operator once told me that the cancer rate is high for HAMS because of exposure to RF sitting right by their transmitters.

Often ham radio operators transmit on the on the 2 meter ham band around 1 watt into a rubber duck antenna often beside their head or on on their chest.  The Drake tr 22 C comes to mind when I talk aboutabout wattage and portable transceivers.  I highly doubt that 1 watt on FM will cause cancer unless your dumb enough to stick your tongue on the antenna.

I'm not so sure about your last statement, Carl.  Any ham shack that has significant RF in it isn't properly set up.

The problem comes with using high power and being too close to your antenna.  For example, operating mobile in your car can be problematic.

As a rule of thumb, I always reduce my output if I'm anywhere near my antenna (when operating mobile, I use 50 watts or less, and have the antenna mounted at the back of the vehicle, about as far away as I can get it).

I'm not too worried about the few nanowatts I output in my Decade MS-100.

We had a 2nd rain shower before I got back to collecting field measurements from the Wholehouse 2.0 Certified FM Transmitter out to a TECSUN PL-310 at various distances.

The TECSUN Reads Signal Strength in dBu and S/N (signal-to-noise) in dB.

The Wholehouse 2.0 (WH) Transmitter is located on a tripod bamboo tower which reaches the cieling from the top of a wooden stool. The Transmitter is close to seat of the stool, at an elevation of 3'7" from the floor, located on the west wall of the Internet Building 16'9" from the east front wall.

TECSUN reception telescoping antenna vertical at minimum 5" to avoid capturing too much high power signal activity.

Directly parallel to Wholehouse 2.0 Signal= 64 dBu  S/N = 40 dB;

Center of transmitter room 4' from WH Signal = 45 dBu  S/N = 39 dB;

Center of adjoining office room on east 10'9"  28/31;

Surface of front wall 16'9"  19/21;

Outer wall surface on porch 17'5"  09/07;

Porch rail 25' from WH  20/21;

Ground level away from building 37' from WH  10/10;

Front windshield of auto  13/15;

Public sidewalk approx. 100' east  00/00.

For comparison here is the strongest local FM signal 90.7 MHz  58 / 46

Distant station in Illinois at 88.7 MHz  12 / 06.

Finding: Using a certified FM Part 15 Transmitter per 15.239 the range is limited to immediate proximity and has no useful capacity to reach any meaningful distance.