87.5 Vs 108.0

[XXL]

Obviously lower frequencies go further distances but realistically are you actually going to notice the difference in signal strength on 87.5 than you would on 108 ?

[LeeCavanagh]

Not really, unless your tx amp isnt linear or is tuned for certain frequencies, and of course sone of it is down to the antenna for transmitting, and the antenna for receiving

[mikroman]

The difference is 1.8dB. The receiver hardly notices the difference.

[fmuser877]

on the 7 watt one I find lower part is better

[tokingmenace]

Guess not much in it.

Potential of interference from strong legals on 107.9/8 in some part of the UK.

87.5/6 is not used by legals, so a clear frequency for distance / dx receive. Apart from rsl's on 87.7, if they are close.

[XXL]

im just using 108 as an example as its the furthest frequency away. i mean anything further up compared to the lowest you can possibly go.
also i would never touch 87.anything because you never know when some tiny rsl will switch on it and they start moaning your going over them.

[87to108]

Noise/interference (from switchmode power supplies etc) on average tends to be a bit worse at the bottom of the band than the top, so its a 'much of a muchness'
it probably cancels out the slight benefit in propagation in a low FM band frequency over hills etc

[Albert H]

The "noise" lower down the band is more due to the huge number of high powered regional transmitters below 95 MHz, rather than any effects from SMPSUs and the like. Most power supply noise is (usually) around 200 - 500 kHz, with some of it (usually harmonic rubbish) turning up all over the shortwave bands.

It's instructive to connect a spectrum analyser to a reasonably broadband aerial, and examine Band II. The lower part of the band has a noise floor that's 6 - 10 dB worse than the upper part of the band. You can see all the huge number of regionals all on top of one another - though not as they are in some parts of the world where they use just two adjacent frequencies for national stations.

Back in the late 50s, when VHF FM broadcasting was just starting in the UK, the only stations were three BBC outlets - "Light", "Home" and "Third" ( later Radios 2, 4, and 3 respectively). Domestic receivers in those days used VFO tuning (no PLLs back them) and "AFC" on the better ones to keep them tuned. Sensitivity and selectivity of those early domestic receivers were both relatively poor, so the BBC ran enormous power, and spread each station on multiple frequencies across the lower part of the band.

When local, then Commercial radio began (in the late 60s and early 70s), frequency allocations were such that the BBC still spread across half the available band with their national outlets, and the "little" stations (each running several kilowatts!) were spread far apart on the upper part of the band - though there was nothing allowed above 98MHz, because the Police used ~99MHz upwards! It was still assumed that FM receivers would have poor selectivity.....

Even with the advent of modern PLL receivers and good IF filtering, the BBC still insist that they "MUST" occupy >50% of the FM band. It's now just purely political - ask OFCOM for a licence and they'll STILL tell you that there are "no frequencies available"! There hasn't been any reason for BBC Radio 2 to spread from 88 to 92 MHz for at least the last 40 years. Proper engineering could move all the national stations to a sub-band below 92 MHz - they could use "salt and peppering", just using a pair of adjacent frequencies only 200 kHz or 300kHz apart for each station throughout the country - "capture effect" takes care of any interference issues.

Back in the late 70s, I was involved in the "Wise Report", where a prominent broadcast engineer (Fred Wise) carried out an exhaustive feasibility study to band-plan Band II. We suggested "Nationals" below 92MHz, "Regionals" from 92 - 95MHz, "City-wide" from 95 - 102MHz and "Community / Special Interest" for the rest of the band. A big city like London could - easily - support over 65 stereo stations with 300 kHz channel spacing, and with intelligent location planning, physically adjacent stations could be 600 or even 900 kHz apart, eliminating interference issues..... We would never have needed the disastrous DAB!

[rigmo]

DAB is made i the same reason as you mention... political and businesses.. produce more garbage pollution Nta also...

[radionortheast]

gp antenna I found worked really well for picking up the hills to the north years ago, i’ve never had a signal like it!, almost never lost it, never forget that day, a dipole on a low frequency you would just hear lots of white noise over the radio, then a burst now again, i’ve always been a fan of higher frequencies because of it. I suppose the topography has a huge effect, i’m pretty sure lower frequencies the signal would travel further south, but struggle going north, unfortunately high frequencies aren’t available here anymore, so you have to lump it.
I suppose the other thing is how can you tell the receiver is picking up on one frequency as another, there are variables, (the antenna at the receiver maybe better at that frequency) something like sp e reception starts at lower frequencies works its way up the band, higher frequency would be less prone to be knocked out during summer months. if your using an indoor antenna low power it will get knocked out eventually! there is advantage to higher frequencies too, it means the aerial will be smaller and more humble, take up less room, less wind problems if it is high in the air, unlikely to crash through the roof.

[87to108]

The "noise" lower down the band is more due to the huge number of high powered regional transmitters below 95 MHz, rather than any effects from SMPSUs and the like. Most power supply noise is (usually) around 200 - 500 kHz, with some of it (usually harmonic rubbish) turning up all over the shortwave bands.

I have of course disconnected the power to SMPSUs/ modern battery chargers etc to prove they created noise in the FM band on nearby receivers, before saying they caused interference.

There are also many reports of modern DAB/FM domestic receivers , which come with a supplied SMPSU for mains use, performing better on FM (and DAB too) when run on batteries, as their own SMPSU, despite being intended for a radio receiver, was generating some noise on VHF (though not as bad as some other SMPSUs for other devices).

There are also cheap chinese LED headlights which create considerable noise on the FM band, interfering with FM in nearby cars (MW/LW unaffected in nearby cars from them)

[Albert H]

You're (partially) right. There's some noise in Band II from SMPSUs, but most of the crud is much lower in frequency.

One of my neighbours had an electric car charger that wiped out the whole MW and LW bands for about 400m around his house, and even caused some interference on 70cm band (440 - 450 MHz).

Fortunately, his silly milk float spontaneously burst into flames destroying both the "car" and the garage roof above it! The whole neighbourhood stank for days from the nasty fumes from the mess. The Fire Brigade attended, but just stood laughing at the end of his driveway, because they have to just let these things burn themselves out - once one of those Lithium batteries decides to burn, there's no way to put them out!

Also, the poor sap discovered that his insurance wouldn't pay out, since the location of the self-immolation was "off-road", and therefore not covered....

Luckily, we no longer get nasty interference from his battery charger, since that was destroyed in the fire too!

Sony used to sell a "universal" SMPSU for one of their communication receivers, but they discontinued it since its operation seriously compromised the sensitivity of their receiver on all frequencies. They now sell a "linear" supply, with switchable primary (mains-side) taps for differing AC voltages. It's fine, but I don't know how many of them get blown up by being set to the wrong voltage!

[EFR]

One guy had an neighbour who installed huge solarpanels to roof. Huge amount of noise from LW to VHF.

Its strange how it rains rocks at night.....

[radionortheast]

When I got my car radio I tried different 12v smps to see which works best with it, with most there is not much difference on fm, (some produce noise which is audioable which is annoying though) some newer ones from amazon do have some noise on fm, I suppose if you don’t have anything else you could clip on a ferrite and wind the cable round a few times. If you wanted medium wave you problalby have to make your own using an old fashioned transformer.