Best receivers for best range

Discussions about range for both AM and FM Part 15 broadcasting inevitably talk about the transmitter being used.  As Mark points out, the receiver is probably the most important part of the listening chain, particularly with FM since all certified FM transmitters emit signals of approximately identical field strengths.

The FCC issued a bulletin stating the the maximum range of a compliant Part 15 FM transmitter (with field strength 250uv/m @ 3 meters) should be 200 feet.  Industry Canada, in the BETS rules, states that the range of a compliant signal (100uv/m @ 30 meters) should be no more than 30 meters (or 100 feet).  Obviously, something is wrong here, since BETS allows for much greater field strength than Part 15.  And yet, the 200 foot number continues to be trotted out when discussing range, when it's obviously nowhere near accurate.

Both statements leave out a number of factors that determine range.  In both cases, the sensitivity of the receiver is not specified.  Sensitivity of FM receivers can vary from well over 100 uv (the receiver can detect a voltage of 100uv between the antenna terminals with some signal to noise ratio, usually 20db) in crappy clock radios to well under 1uv in the best aftermarket car radios.  The better the sensitivity, the better the range, with good car radios giving the best range, all other things being equal (and generally far more than 200 feet, even for Part 15).

There are of course many other factors as well.  What exactly is the quality of the signal being listened to.  Can you barely hear it, or is it a strong signal that you can listen to it easily with little noise?  That is very subjective, rarely taken into consideration, and certainly there is no hint in the range statements from the regulatory bodies of both countries.

The receiving antenna, responsible for getting that signal voltage to the antenna terminals in the radio, also makes a huge difference.  Is the antenna a little wire built into the radio case or telescopic, resonant or not?  It used to be that car antennas were resonant whips, now they are little, inefficient things equivalent to rubber duckies.  A good antenna means more of that signal voltage is getting to the radio, and that influences range.

To make matters even more interesting, there are plenty of other non receiver factors that influence FM range (such as weather, height of both transmitter & receiver, etc.), but a discussion of those belongs in another section of the forum.

One of the topics not mentioned often in Part 15 radio is the receiver antenna.  Other than the quality of the receiver itself, it just might be the biggest factor in AM or FM range.  Even a good receiver will be severely hampered by a poor antenna.

I'm wondering if, instead of or even supplementing the gift of radios, it might be advantageous to also focus on the antenna.  There are various gadgets on Amazon that clip on to an existing telescopic FM antenna to extend it.  Member TheLegacy here has experimented with external AM loop antennas that couple to the receiver and greatly improve reception.

Just a thought.

Yes good points. The tuned loop is the best for AM and can make a bad radio good. Simply put in the right position beside the radio on a very weak station it can make a barely heard station into a listenable one, just the trick of getting the exact spot.
But with FM, You could just clip a longer wire onto the telescoping antenna but then that can't do anything about a lousy tuner that just images strong stations over the band and wipes out all but the strongest signals and the more antenna the worse it gets. They will only work with a decent receiver to begin with.

But if I was on AM like I was before and I was going to stay there I could give out loops and not radios. But with FM finding place to go on the dial would be much better if all home or portables had selectivity like a car where you can get a strong local at 99.1 lets say and a weak one at 99.3 and the strong one adjacent the weak one doesn't interfere at all and the receivers I mentioned all get close to the selectivity of cars. That would be so good as finding a spot to do our stations wouldn't have to have space adjacent on each side to avoid interference to the other station or visa versa. That would leave many more available spots.

To add, I recommend anyone looking for a better receiver take a closer look at the Sangean MMR 99. Sound quality like Tivoli/Bose audio and reception performance near that of hi fi receiver/car. Great for our station's range and sounds good and good for outside as dust proof and won't hurt if it gets wet. Battery is supposed to be non user replaceable but with some mechanical/electronic inclination and good at soldering the built in 18650 battery is readily available and user replaceable. The first thing I did was swap out the 2600 mAh it came with for a 3500 mAh higher capacity one. Any vape shop has these batteries. Also amazon. Takes 3 hours or so to fully charge. Had to take pictures from computer as my camera's pictures won't post due to too large a size..

This thread gets me going for two reasons. First, Artisan Radio brought up the subject of receiving antennas and I recently had the extendable whip come loose from my TECSUN PL-310 because of a lost set-screw. But luckily, after a week, my brain sifted through old memories and I recall that this radio has an FM/Shortwave Antenna Jack on the side, so I'll be able to rig a temporary antenna until a new set-screw is found. And then second, Mark told us about the Sangean MMR-99 which looks ideal to use as an outdoor radio to replace my Sangean U1 Construction Site Radio which is a real dud. For one thing the U1 drifts off frequency all the time and even Radio Jay Allan found this to be the case in his review. Another bug is that the U1 has an over-emphasized base port for maximum thump when playing rapp music but terrible for speech, and no way to defeat the boost. Sometime I'll write about all the crippled radios I have cluttering the place. 

After reading a review on Amazon about the Sangean MMR-99 I wish it didn't have the Bluetooth feature, because I broadcast to radios under part 15 AM the Bluetooth would be a useless function.

Radio Jay Allen's Review of the Sangean MMR-99 is Ultra Positive!

https://radiojayallen.com/sangean-mmr-99-am-fm-rbds-weather-bluetooth-emergency-radio/

And it has a siren!

@carl-blare Yeah I would never use bluetooth either just ignore it. It's not activated unless you select it.  Any of the makes models I mentioned at the start will do nicely to improve our range. And have good audio. You want your station to sound good.

Here is another receiving antenna wish... there are several stationary FM receivers here in the Internet Building that at times need to receive a part 15 vertical signal and at other times part 15 horizontal signals, for which a circular receiving antenna would be ideal. Is there a nice circular FM receiving antenna at a good price? Or, can one be home brewed?

I'm not all that familiar with this type of antenna, so did a bit of research on it.

There are a number of advantages to a circular polarized antenna, particularly for broadcasters.  It increases the likelihood that your signal is going to get around obstructions or penetrate buildings, and weather such as rain or snow has less effect on your signal.    I may also be misunderstanding this (so please correct me if I'm wrong), but wouldn't your field strength now be in all planes, not just vertical or horizontal?  It would take more power to generate a given field strength in both planes, but Part 15 FM is not governed by power.

Apparently, for licensed broadcasters, the FCC only takes into consideration the power necessary to generate a given field strength in one plane.

Anyway, here is an article I found, which describes how one ham built a 2 meter (144 Mhz) circularly polarized antenna.  Homebrew 2 Meter Circular Polarized Antenna.  It gives one an idea of how you could go about doing it.  The one disadvantage to this approach is that the antenna is difficult to tune.

Anyway, interesting stuff.

Giving some un-informed thought to the matter, here is what I know...

By using a standard vertical whip on a part 15 transmitter it sends out a vertical signal.

The way to send a horizontal signal is, guessing, to adjust the same antenna to a horizontal position perpendicular to the desired direction.

As usual legal part 15 whips are short, so transmitting efficiency will suffer no matter what.

My idea is that a circularly polarized receiving antenna will grab either of the polarities without needing to continuously change the way the receiving FM antenna is pointing. We'd need an antenna widebanded enough to capture the standard FM band.

Thanks for the link, I'll study it.

So what would happen if you bent the 1/4 wave length antenna on the Decade into a circular shape? Or bent it into an L shape?

Those are the kind of experiments we should attempt, Mark, and one of them I did try as a transmitting antenna.

I bent a heavy copper wire into an L-shape and end-fed it with RF output from a Ramsey FM45B, watching the result on a spectrum analyzer. I no longer remember the position of the whip antenna on the spectrum analyzer, but I remember that the signal level was less than with a straight transmission antenna.

Next I fed the L-shaped antenna at the elbow and the average power of the reception was slightly better than a straight wire. I am guessing I may have been at the brink of designing a circular antenna, but I'm not sure how to know for sure.

I bought a brand new Sangean PR-D18 receiver. This things is deaf far as receiving stations. I was only able to receive 2 AM stations plus my own. And the audio from the built in speaker and headphone jack is very low frequency muddled muffled or whatever you want to call it. No highs or mid tones at all. Will be returning this.