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Medium wave stations that relied on skywaves.

 
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Re: Medium wave stations that relied on skywaves.

Post by crackle » Sat Jun 11, 2016 7:50 am

RNI also broadcast on the VHF FM band. I have a CD of some of the radio shows.
Mike

 
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Re: Medium wave stations that relied on skywaves.

Post by Terrykc » Sat Jun 11, 2016 12:34 pm

It seems strange that the first UK pirate so well equipped that it could broadcast simultaneously on MW, VHF and SW was blighted from the start by the sheer technical incompetence that prompted HMG to come down on it with the proverbial ton of bricks.

The started off on 1605kHz claiming that, as it was the Medium Wave band edge that it wasn't allocated to anybody, completely failing to realise that their upper side-band complete obliterated the adjacent marine band. Initially they were jammed by every vessel in the North Sea who simply turned on their transmitters until they learned the error of their ways.

By that time, it was too late, and the government's own jamming station at Orfordness pursued them relentlessly on every frequency they tried.

 
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Re: Medium wave stations that relied on skywaves.

Post by Pye_Man » Sat Jun 11, 2016 7:18 pm

Katie Bush wrote:Hi Nick,

RNI? - am I confusing that with "Radio North Sea International" (RNSI)? Anchored somewhere off Scarborough, I believe.

Marion


The Initials RNI are derived from Radio Nordsee International which commenced broadcasting in 1970 initially in German and English. It was a Swiss-owned operation based in Zurich. It had something of an interesting career and apart from a brief sojourn to the Essex coast in the spring/summer of 1970 (which also coincided with the British general election) it was anchored off the Dutch coast near Scheveningen.

RNI had the capability to broadcast VHF - it used to announce "Channel 44 100Mhz". It also had two shortwave transmitters - one on 49m and the other on 31m. On medium wave it had a massive 105kW RCA transmitter though it rarely, if ever, ran at full power. There was also a lower power medium wave transmitter which was briefly used in 1972 announcing "RNI 2".

After the problematic period off Clacton-on-Sea when the station was jammed by the UK authorities, despite moving wavelength several times (using 217m and 244m and perhaps a few others), the station returned to the Dutch coast and eventually settled into a Dutch during the day and English at night format on 1367kHz announcing 220m. On Sundays they ran a 'World Service' programme mainly in English on short wave. There always seemed to be technical problems getting the signal out on the 31m band and it wasn't used much, however, the 49m outlet on 6205kHz was ever present covering much of Europe and it was an excellent signal in the daytime in the midlands.

It's fair to say that the station was surrounded by a fair amount of intrigue. In addition to the jamming by the UK authorities - which is a very interesting story in itself with in one aspect not a little irony - there were boarding parties and a fire bombing of the ship. However, by the end of 1971 things off the Dutch coast settled down to relative peaceful normality with Veronica and RNI remaining unmolested by raiders or governments. Ultimately, with the appearance of more stations off the Dutch coast, the Dutch government, long reluctant to act due the huge popularity of Veronica, finally brought in their version of the Marine Offences Act in August 1974. This saw the end of the Dutch coast stations. For a second time the reopened Caroline continued, upping anchor and heading for Knock Deep off the English coast.

There was a station off Scarborough in the 1960s. Radio 270 broadcast on 1115kHz with 10kW from an ex-Dutch lugger Oceaan 7. It was one of the last three British offshore pirates that stuck it out until forced to close down 14 August 1967 by the Marine Offences Act. The two Carolines, of course, continued having moved their base to Holland.

Nick

 
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Re: Medium wave stations that relied on skywaves.

Post by Synchrodyne » Sun Jun 12, 2016 8:28 am

A corollary question is are or were there any MF transmitters designed to radiate only a skywave, with negligible ground wave?

A vertical MF radiator (or an inverted L or a T) produces both a ground wave and a skywave. The angle of the skywave can be varied by adjusting the electrical length. Antifading radiators are around 0.55 lambda (varying situationally), and keep the skywave angle low enough that its first return is beyond the usable ground wave service area. So whilst a vertical radiator does produce a skywave, whose angle can be varied to “drop” it into a desired service area, it also produces a ground wave.

But a horizontal radiator such as a dipole produces a skywave only, in a lobe pattern that I think varies according to its distance from the ground. Probably a reflector would be needed to “point” the skywave in the right direction. But a horizontal dipole and reflector for MF mounted at say 0.25 lambda or higher would be rather a large array. Are or were there any such actually used for MF skywave broadcasting?

Cheers,

Steve

 
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Re: Medium wave stations that relied on skywaves.

Post by Doz » Sun Jun 12, 2016 12:22 pm

Ah! Radio 10 Gold on 765kHz - a classic example of the power of the ground wave which gave excellent all-day reception over a large part of Britain - the radio in my van was permanently tuned to it!


Wasn't it 675?

 
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Re: Medium wave stations that relied on skywaves.

Post by colly0410 » Sun Jun 12, 2016 1:28 pm

Synchrodyne wrote:A corollary question is are or were there any MF transmitters designed to radiate only a skywave, with negligible ground wave?



But a horizontal radiator such as a dipole produces a skywave only, in a lobe pattern that I think varies according to its distance from the ground. Probably a reflector would be needed to “point” the skywave in the right direction. But a horizontal dipole and reflector for MF mounted at say 0.25 lambda or higher would be rather a large array. Are or were there any such actually used for MF skywave broadcasting?

Cheers,

Steve


Would a common or garden ferrite rod aerial as used in most tranie radios or a frame aerial respond well to a horizontal polarised medium wave signals? I presume a random wire aerial will respond to any old polarisation..

 
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Re: Medium wave stations that relied on skywaves.

Post by Terrykc » Sun Jun 12, 2016 7:13 pm

Doz wrote:Ah! Radio 10 Gold on 765kHz - a classic example of the power of the ground wave which gave excellent all-day reception over a large part of Britain - the radio in my van was permanently tuned to it!


Wasn't it 675?

Oops! Yes it was! (I've obviously confused it with BBC Essex!)

"Hier Radio Tien Gold op AM, zes zeven vijf, middel golf ..."

I heard that so many times in the past that I'm surprised I mucked it up!

 
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Re: Medium wave stations that relied on skywaves.

Post by Synchrodyne » Sun Jun 12, 2016 11:00 pm

colly0410 wrote:Would a common or garden ferrite rod aerial as used in most tranie radios or a frame aerial respond well to a horizontal polarised medium wave signals? I presume a random wire aerial will respond to any old polarisation..


My understanding is that a vertical frame aerial does not respond well to horizontally polarized waves, but that it is insensitive to the arrival angle of vertically polarized waves. Ferrites rods I am not sure about.

I suspect that many MF skywaves originate from vertically polarized radiators. But they are rotated somewhat by the ionosphere, and probably end up with elliptical polarization. Thus receiving aerial polarization may not be particularly critical.

For fading-free MF ground wave reception, the vertical aerial, as high as possible, is probably the best, as it is less responsive to higher angle skywaves, such as the first return from the wanted transmitter. It is probably also satisfactory for low-angle skywaves from more distant transmitters. An inverted L or T aerial, although still vertically polarized, is more responsive to skywaves, which is good if that is what you want to receive, particularly higher angle skywaves, but not so good if you want clean ground wave reception.

Cheers,

Steve

 
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Re: Medium wave stations that relied on skywaves.

Post by dtvmcdonald » Tue Jun 14, 2016 7:18 pm

In the US there are no longer any true "clear channel" stations (though
until a couple of years ago the largest station owner group company called itself
"Clear Channel").

However the stations still exist and their competitors must use very
low power at night. I still get numerous stations here over sky wave at night,
many absolutely reliably and perfectly listenable, with no overlay from competitors on the same frequency. A good receiver, either SDR or
very sharp (mechanical or SAW filter) is necessary for absolute clarity, though absolutely any set will get them acceptably. There are sports programs
on them that are unavailable otherwise, even on the Internet.

 
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Re: Medium wave stations that relied on skywaves.

Post by Niall » Tue Jun 14, 2016 7:40 pm

Pye_Man wrote:In the 1980s, Laser 558 and Caroline just a little above were easily listenable in the midlands and I regularly listened on my cheapo car radio in my old Ford Escort. Laser used a T aerial and Caroline, after the tall mast collapsed, used the same. Laser always seemed to have the better signal.



In Central Scotland at the same time I could never get Caroline on their lower frequency, or on 558 when they moved there after Laser closed down. (As someone put it at the time, parodying their ident of "never more than a minute away from the music", the captain decided he was much more than a minute away from his next paycheque, up anchored and sailed into a UK port.)

Their signal on 963 on the other hand was receivable at good strength in the evenings, this frequency was Dutch during the day and English at night, and the English service was more AOR than the pop service on the lower frequency competing directly with Radio 1.

 
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Re: Medium wave stations that relied on skywaves.

Post by colly0410 » Tue Jun 14, 2016 7:50 pm

In the late 60's/early 70's in the evening when Radio 1 was playing boring album music & Radio 2 was 'Sing Something Simple' Radio Luxembourg or AFN were the only alternatives as most of the pirates had gone (RNI was still there but mostly not my taste) & the ILR's were still in the future. I'd listen to a fading distorting Luxie or a fading distorting AFN, bit of a Hobsons choice really. The new Radio Nottingham on 94.8 VHF (they never said "FM" in those days) carried radio 2 after about 7 PM so it was SSS. But I really enjoyed my listening. Nowadays I can get dozens of stations over the air & thousands online in perfect quality stereo but I can't find owt worth listening to, ironic init???

 
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Re: Medium wave stations that relied on skywaves.

Post by nuvistor » Tue Jun 14, 2016 9:55 pm

colly0410 wrote: But I really enjoyed my listening. Nowadays I can get dozens of stations over the air & thousands online in perfect quality stereo but I can't find owt worth listening to, ironic init???


I find the opposite, on radio I am overwhelmed with choice I want to listen to, all transmission types, while TV these days does nothing for me.

Frank

 
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Re: Medium wave stations that relied on skywaves.

Post by ntscuser » Tue Jun 14, 2016 9:58 pm

If I remember correctly Luxembourg was also "boring album music" after midnight and AFN was "easy listening" every other hour?

 
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Re: Medium wave stations that relied on skywaves.

Post by Pye_Man » Wed Jun 15, 2016 10:24 am

In the early 70s, Kid Jensen had an early hours of the morning show called 'Jensen's Dimensions' on Luxembourg which played more the more obscure stuff. It was way past my bedtime in those days so I have little firsthand knowledge. The rest of the programming was pure chart music which would have most appeal to advertisers.

When Caroline reappeared in the autumn of 1972 it opted for an all-album prog rock format, though it did offer more mainstream music on its short-lived 773kHz service in 1973.

In those days Radio 1 joined up with Radio 2 for a lot of the evening, probably due to the needle time restrictions. On Sunday nights 'Pick of the Pops' was followed by a jazz programme.

 
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Re: Medium wave stations that relied on skywaves.

Post by colly0410 » Wed Jun 15, 2016 12:08 pm

The strange comb filtering effect of selective fading gave an interesting wooshing sound to some of the music, a bit like flanging but random of course. Talking about Luxie fading & distorting on a tea break at where I used to work & the younger ones had not got a clue what I was on about, I was trying to explain the sound to them without much success..

 
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Re: Medium wave stations that relied on skywaves.

Post by Synchrodyne » Fri Jun 17, 2016 3:44 am

Returning to transmitting aerials, I haven’t found any evidence that horizontal dipoles were actually used for MF skywave radiation, although that is not to say that they were never used. Nevertheless, the vertical radiation patterns for varying aerial-to-ground distances are shown in this diagram.

from R&TVERB 4th p.21-13.gif


Evidently options (a) and (b), or something in between, were used for HF tropical band near-vertical incidence transmission.

For MF, a property of vertical radiators was that by adjusting their height and by other means, the skywave departure angle could be controlled. Also, the directional properties conferred by multivertical, phased MF arrays applied to the skywave as well as the ground wave. Although I imagine that the nulls might have been a bit “fuzzier”. I recall one station in Dallas, TX (on 1190 kHz, I think) that had separate sites for its daytime and night-time aerials. The daytime pattern had something like three nulls, whereas the night-time pattern was a very narrow NE-to-SW beam that was virtually unreceivable at my location, somewhat north and slightly east of DFW.

Cheers,

Steve

 
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Re: Medium wave stations that relied on skywaves.

Post by Synchrodyne » Fri Jun 17, 2016 4:59 am

ntscuser wrote:Was any particular model of radio receiver especially good at receiving MW skywave signals?



turretslug wrote:Good AGC and synchronous demodulation? I suppose similar criteria as for good SW reception would apply, but image rejection and noise performance wouldn't have been as critical, so no need for the 2 RF stages and 4x ganged tuning of the classical behemoths.



Yes, I think so. The JRC NRD525 with Sherwood SE3 outboard PLL synchronous demodulator worked quite well for selectively fading MF skywave as well as for similar HF reception. Though on HF, the combination was not as good for HF programme content listening as the Phase Track Liniplex F2. I had only the early HF synthesizer for the F2, covering 2 to 22 MHz, so was unable to try it out on MF, but I’d expect it to have been better than the NRD525. Very late in the production run, Phase Track did introduce both an MF synthesizer and an HF synthesizer that went up to 26 MHz, but I imagine that they are very scarce. The later JRC NRD535 had a built-in PLL synchronous demodulator, but I heard that it was not a stellar example of its breed. I guess that the Sony ICF2001D/2010 is one of the best-known receivers with an inbuilt PLL synchronous demodulation facility, but my own experience (I have two of these) is that it was not all that good, at least for programme content listening. But it showed enough promise and that was got me looking for something a lot better, hence the Liniplex F2. In those days (late 1980s) my main requirement was for relaxed (armchair, glass of red fluid in hand, Stilton on the board) listening to the BBC WS without strain, despite much multipath, with the ‘Play of the Week’ programme being the litmus test for receiver performance.

By now the NRD525 and F2 probably qualify as vintage equipment. Going back into the valve era, there was at least one outboard PLL synchronous demodulator, namely the GE YRS-1 from the late 1940s, probably a collector’s item these days. I think that it was intended for both amateur and professional use.

Amongst professional valve era equipment, the Racal RA17 with the RA98C broadcast SSB/ISB adaptor would probably work well. The latter was designed for HF broadcast relay use, but I think would work equally well for MF. HF point-to-point SSB/ISB receivers, such as the Marconi HR22, would do a similar job in terms of combating selective fading distortion, but typically did not tune below 2 MHz.

Cheers,

Steve

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