I have a portable FM radio that gets less-than-perfect reception in a particular residence. Don’t know if it’s the building itself, or the location in town relative to the broadcast antenna, but I’d like to see if I can get better reception on it there.
All of the commercially available signal-boosting products I’ve seen so far feature a co-axial connector or a pair of spade terminals for the sort of connection you usually find on a cabinet-type stereo receiver, but I’m working with a portable boombox that came stock with the usual telescoping antenna - there’s no dedicated terminal on this thing for an aftermarket antenna.
I’m not a radio guy, but my father was a Ham radio operator and he had all these tables and resources for figuring out optimal antenna configurations. Here’s what he told me years ago:
Push the telescoping antenna all the way into the radio. Attach a single wire of about 22 AWG to the tip of the antenna. He suggested an alligator clip, but he said that wrapping the uninsulated wire around it several times would be OK. Cut the wire to 36" and pull it up so it’s vertical. Trim it so it’s about 30" long, cutting a bit at a time. The ideal length for FM reception should be around 30" to 34" (including the length of the collapsed antenna). Slight changes in orientation might help. He said it was up to me to figure out how to keep the wire vertical.
This worked pretty well. I had the radio in the same place most of the time and just taped the top of the wire to the wall. I had emphasized that I didn’t want to permanently alter the radio or antenna itself.
Broadcast FM signals are line-of-sight. If the station’s transmitter can “see” your radio, without obstruction, you will receive a better signal. Any obstruction can limit what you can receive, be they city buildings in close proximity or even the materials used in the construction of your house. You should be able to receive your local stations with the telescopic antenna provided, but any station past the horizon is going to be difficult, and some radios have less than perfect sensitivity. Placing your receiver near a window might improve your reception, and sometimes switching your unit from “stereo” to “mono” can give you a signal that is less noisy, if your unit has that capability. There are also outboard antennas available that can clip to your existing whip antenna that might improve reception.
But I worked in the on-the-air part of the radio biz. Perhaps someone with more technical knowledge can give you some better options. Good luck. Broadcast radio is in decline these days and needs all the listeners it can get.
Yep, which also means height can be important. When it came up with the regs, the FCC assumed an FM receiving antenna would be 30 feet off the ground.
There’s also the issue of signal polarization. All FM stations were originally horizontally polarized, but most are now circularly polarized or elliptically polarized:
FCC 47 CFR § 73.316 - FM antenna systems.
(a) It shall be standard to employ horizontal polarization; however, circular or elliptical polarization may be employed if desired. Clockwise or counterclockwise rotation may be used. The supplemental vertically polarized effective radiated power required for circular or elliptical polarization shall in no event exceed the effective radiated power authorized.
There’s a chance the station you’re trying to receive has horizontal polarization, or it has elliptical polarization wherein the E-field is stronger horizontally vs. vertically. In either case you’ll get a stronger signal if you orient the antenna horizontally. (And after orientating the antenna horizontally, rotate the radio on its vertical axis to see if you can find a max signal strength.) If doing so does not improve the signal, it simply means it has a circular polarization, which means the antenna can be vertical.
One thing hurting radio reception today are LED bulbs and some other newer electronic gadgets. Very noisy in terms of radio spectrum pollution.
At the problematic location, try turning off lights and stuff and see if that helps.
Here’s a page that has a short section on “no antenna terminals”. One of the classic ideas is adding bits of aluminum foil to the antennas. A few swear by it. Most don’t. I think the wrapping an unconnected wire around the radio is the best thing to try.
I’m a radio guy for decades and broadcast reception (AM/FM, TV, wifi, sometimes) is one of the trickiest things. It’s always invisible, often intermittent and difficult to separate device problems vs local interference.
Don’t goof with any amplifier gizmos. Some alligator clip jumpers might help, though.
FM radio is less prone to noisy interference than AM due to capture effect: you’ll tend to lose®ain all the sig at once.
Make sure the radio works. Take it somewhere you think rcv is better, ideally on a different power feed or on batteries. Similarly, see if any other radios tune the station any better or worse. If you happen to catch a drop or other artifact on both at the same time, you can rule out the devices.
However, I will say RF just as often has me wondering from the the other way: “How the heck am I still getting signal with this radio underground/caged/antenna removed?”
As a bit of a left field idea, some passive elements installed in strategic places might help. The idea being that some half wavelength conductors might be placed somewhere where the is good signal, with the rough intent that they will also re-radiate, and might act to improve reception deeper in the structure. This is about as scientific as tweaking the position of rabbit ears on an old TV. So could just as easily make things worse. But there is a good chance they could make a difference - just a matter of making a useful one. One down-side is that the FM band is wide enough that just a simple dipole won’t have the bandwidth to cover the band. If you only want one station, you would cut it to the right wavelength for that.
In the extreme you just make a passive repeater. Aka an antenna that is sited somewhere with good signal, connected to a radiator inside the structure where you want signal. Despite the almost silly small amount of signal you are wrangling, and the losses involved, these things have been known to work - for various values of “work”. The next step would be a signal booster driving the internal radiator. This may be at best borderline legal - especially if it interferes with anyone else - but quite easy to implement.
Hidden under a lot of this is the problem with multipath reception. Reflections of stuff leads to different path lengths, and thus lots of potential for constructive and destructive interference. If you have a multipath problem there is usually no simple way of getting past it. And messing about with re-radiating signal is by definition, adding multiple paths. Which is why it can get really evil to manage.
I mentioned this to one of my more technical buddies (mostly because he considers FM radio to be “charmingly old-fashioned”) and he suggested trying one of the old-fashioned FM T-antennas. These are nominally 300-ohm and have two spade connectors on them. He suggested stripping and wrapping one lead to the tip of the antenna (antenna completely retracted) and then the other lead to a ground on the radio (any metal part that is a common for the radio circuit board). This could be the negative battery terminal, the outside of the earphone jack, screws that secure the circuit board to the chassis, etc. Then experiment with location and orientation.
Never tried this myself. If I did, I’d probably just replace the spade terminals on the antenna with alligator clips.
BTW, tin foil on an antenna has never done a thing for me.