Although I have difficulty in believing this, I found that the reception varies with the leaf coverage of the many trees in my locality. I would have expected this attenuation effect for very much higher frequencies than VHF.

As an aside I have found that DAB radios will shut down if too close to an inverter. I have same, driving low voltage LEDs in a bathroom. Bring the DAB radio to near the bathroom door and it closes down if the lights are on!

Andrew.

In the days when Radio Luxembourg was on 208 metres and very variable reception , it came through loud and clear for 2 hours , while at sea , off Capetown.

You haven't said if the radios have whip aerials. I have found that extending them when listeneng on FM or DAB can make a difference.

John

Indoors is almost the worst place in the world for an antenna. And between transmitter and receiver there are multitude of effects that reduce or increase signal strength.

FM operates at frequencies used by early radar and is particularly effected by reflections. The signal bounces off hills, walls, cars, aircraft, people and maybe the ionosphere. Because the signal bounces, especially in built up areas and inside buildings, it's likely to arrive at the receiver over several paths each of different length. As the carrier wave at 100MHz is only 3 metres long, it's likely that signals at the receiver won't be in phase. Say the receiver picks up a direct signal and one bounced off the wall of the house next door:

• If the bounced signal is delayed by exactlyone wavelength, or multiples of one wavelength, the two signals will add together and the receiver will be delighted.
• If the bounced signal is delayed by half a wavelength, or multiples thereof, the two signals will subtract and null each other out entirely. Then the receiver has nothing to pick up because it's in a dead spot.
• If he bounced signal is delayed by any other proportion of a wavelength it will either add or subtract depending on far in or out of phase it is.

With an internal antenna, a receiver will pick signals coming over multiple different paths, and these can change depending on what causes the reflections. Some, like hills, don't change much. Others, like aircraft, change rapidly. So rapidly the signal flutters, which is how Watson-Watt demonstrated radar was worth developing. The signal a receiver gets depends on it's position in the house, what's inside the house, the geography between it and the transmitter, the weather, and anything nearby that's moving. It's a moveable feast.

Phase effects are most noticeable when the signal is marginal. If the direct signal is dominant, the other arrivals won't be strong enough to null it out. Therefore the cure is an external antenna, ideally as high as possible, and directional.

DAB Radio is much less vulnerable to phase effects than FM. It's transmitted with a broadband carrier, i.e over a wide range of wavelengths, that don't add or subtract as catastrophically as an FM signal does, and at a higher frequency that's less worried by the weather. Plus, the carrier is digitally modulated with error correction, which helps the receiver deal with phase distortions. But DAB isn't magic: if the signal is too weak, it won't work either,

Dave

Radio Luxembourg – 208- oh, joy! Horace Batchelor, Infra-draw system and Keynsham – spelt K-E-Y-N-S-H-A-M.

Seriously, I have a small portable radio that has FM and DAB, both work well where I live, but the sound quality on DAB is poor compared with FM, and that's important when you are a bit deaf like me. Perhaps the DAB signal is over-compressed? Also the internal battery of the receiver discharges far quicker listening to DAB.

The BBC channels are somewhat better on DAB than on FM (tho my listening is only R3 (mostly) & R4 – FM is the one that is heavily companded – the commercial channels often operate at a lower bit rate (more channels/multiplex) and they are worse quality than BBC FM

If it’s of any use I found that my old “PURE One Classic DAB radio gets better reception with the top 3 of the 8 sections of the aerial closed down. I haven’t noticed this effect on my FM radio so keep it’s aerial fully extended.

It’s the Freeview TV I have trouble with, when the sun comes out the signal breaks up.

Can I make a silly suggestion, buy an Amazon Alexa, assuming you

have WiFi, I use it more than my radio, just ask it to play a particular station, no degredation at all.

Martin P

Edited By martin perman on 05/05/2021 21:07:30

I find home cheapy DAB just as bad as my first hand held radio was, terrible though OK in the car so performance is perhaps as usual based on what you pay.

My 2nd was a Bush which on a good hot summer night could pull Caroline into Birmingham if only for a wobbly hour or so.

Alas the ClockSync app is no longer on Play Store though there are several alternatives. I use SystemClockMonitor. Right now it's telling me that the system clock on my phone is something like 0.75 s behind local DST (i.e. UTC+1). I used to have ClockSync on my old Moto phone and the error was usually 1 – 2 seconds.

DAB can't fix this problem because it simply transmits the audio stream in which the pips are embedded. Until someone develops a negative delay line it's a laws of physics problem. There may be time signals embedded in the DAB multiplex but receivers don't seem to use them if so. (Actually there are only a few DAB chipsets so not much variation in the low level capability between sets.)