Ropey Radio Reception?

Can anyone explain this effect, which seems worse in the Summer?

First -

Home is a basic, Edwardian 2-up, 2-down end-of terrace with a bit sticking out the back (the South Wing!) holding the kitchen and en-suite bathroom. The front faces roughly North.

I have four wireless receivers, all ordinary a.m./f.m. transistor radios all on f.m., usually tuned to Radios Three or Four with occasional excursions down to Two.

They are No.1 in the kitchen, No.2 front room and No.3 back bedroom, the one I normally use. The No.4 is of course in the workshop, down the garden.

The problem is the variable quality of reception.

Nos. 3 (a modern digitally-controlled radio /clock/alarm) and 4 are fine most of the time.

No.2, in the front room. is generally good but does drift off at times.

No.1, though, placed by the open doorway from kitchen to "middle room" to serve both, suffers very badly from deteriorating reception.

It is OK though rather "lo-fi" early in the day but the sound deteriorates often to the point of being unintelligible for either speech or music. Attempting to re-tune it makes no difference - other than losing it altogether.

This effect is much less marked in Winter.

What might be happening?

' ' ' '

Incidentally I have a DAB radio as well, won a few years ago in a charity raffle at work where despite my having no fancy "ologies" I operated highly sophisticated electronic test equipment often via dedicated computer programmes. I unwrapped this radio a few months ago, read through the instructions and wrapped it up again - I've retired and don't need or want complicated "electronickery" to listen to The Life Scientific and a concerto or two.

Although there will be design variations between receivers I suspect it's a multipath effect, probably due to Sporadic-E, which is reflections from fast moving and highly charged 'clouds' at about 100km. The effect is most common in mid-latitudes and during summer. Sporadic-E is generally unaffected by the local weather. Is that a true observation?

Andrew

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.

Hi, both poor radio and TV reception used to be put down as caused by atmospherics, whether it was true or not I don't know, but it always used to get the blame. Use to listen to Radio Luxembourg, (The Grand Dutchy) but usually had the wait till it got dark and of course in the summer that was later than ever in the evenings. But radio wave do travel further in the dark, so I've read.

Regards Nick.

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

I have suffered similar problems for years with my FM radio alarm clock. Some days good reception of our local (about 15 km away) radio station other days reception would come and go as I walked about the room. DAB is not available in this area.

I spent about £40 on a Google Nest Mini and told it to set a daily alarm for 7 AM and play our local station. I can also use it to play any one of thousands of radio stations by just saying "Hey Google, play BBC radio three" for example. The sound quality is much better than I expected from such a small device but if I want real quality I can cast to my TV which outputs sound to my HiFi.

Russell

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

Nigel Graham 2:

This topic is outside my knowledge but I have a vintage leaflet from the Aerial Manufacturers Association entitled The Enthusiast's Guide to FM Radio Reception which I could send you.

Interesting variety of possible causes but none seem to apply here because I have not moved the sets or their aerials (except to try to improve reception - doesn't work), the house is not shaded by big trees, the weather doesn't appear to have any effect though I will be more observant about that... It appears totally unrelated to any backgrounds, my moving about, anything within the house nor anything obvious outside. It seems the feast Dave cites is not moving at all!

Frances....

Your DAB radio may be "trivial" to set up, but this one of mine looked anything but!

Also I tend to rely on the radio for verifying my clocks and watches - have they sorted out the problem that DAB radio notoriously delayed reception?

Ega -

Yes please, that would be interesting to see.

++++

Radio Luxembourg? O I remember that! With its ads for shampoo and a dating-agency whose quoted numbers revealed something like 200 facts on each subscriber - that was a lot of form-filling!

The other thing I recall from the late 1960s / early 1970s is that I had a large, old 3-band (L.M,S) radio that would pick up the weekly English-language "service" from Radio Tirana in the days of General Hoxa. It lasted under an hour and was always only a ditchwater-dull political-theory lecture read by a well-spoken YL; but the station's call-sign trumpet fanfare used to start well over an hour beforehand. It began as a whisper, slowly growing in intensity as the Glorious People's transmitter valves warmed up - probably extracting every last Watt from all three red phases on Albania's national grid - until it drowned everything on the waveband around it.

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.

Around here I can pick up a couple of radio stations when I'm in the tractor at the top of far field hill, topping it, but lose the signal halfway down again and for some reason it only plays women's hour so it just gets turned off again. Indoors if OH wants to listen to the radio she just uses her mobile phone on speaker via our wireless internet. Conventional radios or DAB radios pick up nowt of interest. It just proved easier to widen the internet range with powerline extenders to shed and barn.....

pgk

My DAB radio has an awful user interface designed by an idiot who never tried using the end product. There are so many stations and the selection button only goes one way so going back from radio 4 to radio 3 takes ages. The buttons are labelled in 6 point white on grey background. Changing from FM to DAB again has to cycle through bluetooth and usb and a few other things. No wonder I don't bother and just use the old one with a bit of masking tape on the dial with lines marked roughly where the main FM stations are.

The old radiogram sadly doesn't work any more (must check the valves) but had Luxembourg marked on the dial. Being in Kent in my youth I also listened to Caroline.

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.

Here is the leaflet - HIH!

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

If you have an Android phone or tablet the "ClockSync" app gives you clock time derived from NTP with better than 10mS precision. Alternatively there are GPS time apps but they (only !) give 300 mS precision due to deficiencies in Android.

Russell