Many thanks to SWLing Post contributor Alan, who shares this Radio World piece which explores the fascinating world of long-distance FM reception via sporadic-E (E-skip), including rare double-hop events: Double-Hop Dreams and the Mystery of Long-Distance FM
A great read for anyone interested in the world of VHF propagation!
Alan also shared these resources:
- Australian Bureau of Meteorology – Propagation Modes: Learn about various propagation mechanisms, including transequatorial propagation.
- HeyWhatsthat.com Path Profiler: Calculate great-circle paths, view terrain profiles, and check Fresnel zones. Ideal for evaluating DX paths and terrain obstructions.
- FCC FM Query: Look up FM station data, including transmitter location, ERP, and HAAT—helpful for assessing potential reception range, even for low-power stations.
Thanks, Alan!
There is no longer a commercial need in the United States for an antenna that covers FM Broadcast only. I have seen omni-directional Folded Dipole Halos on Amazon.
That was the reason I mentioned locating an old Log-P in someone’s storage shed, attic or garage.
Forward gain is everything in DXing VHF/UHF. I live 50 miles SW of the 4th largest metropolitan area in the United States. You have to work around the crowd. You use what you can …. or make your own.
qwertryamdx,
It would appear that you only post when I mention the letters DRM. You complain of poor sound quality but the recordings on the links to the KTWR reception in this forum put paid to that. You don’t complain about the poor sound quality of HD2 -HD4 which are only 20 kbit/s using an old compression algorithm. Why not? What about their poor coverage area and it drops out often compared to FM because of the very low digital power?….
Let’s first look at HD Radio
Current Independent Statistics after 23 years of FCC approval
I have just searched the FCC AM and FM licence databases for the following results;
Parameter % HD stations # HD # of broadcasters
FM Pure digital 0 0 21,766
FM Main 24 2750 11,270
FM Translator 0.1 6 8523
FM Low Power 0.4 7 1973
AM Pure digital 0.07 3 4394
AM Main 4 176 4394
A listener website shows 22 HD-AM and 1 all digital HD-AM stations.
Many stations in the AM band have much smaller night time local coverage areas.
HDRadio® claims >95 million vehicles in North America have been sold in the last 23 years. How many of these vehicles have gone to the wreckers? In 2023, North America had 285 million licenced cars, within that year 18.625 million were sold in North America. It is claimed 70% of new USA vehicle sales is applied to all countries that is 13 million.
Of the HDRadio® manufacturers there are 3 for vehicles, 1 for home radios and 1 for tuner amplifiers. I have noted that most home HD capable radios are around 4 times the price of an AM/FM only receiver.
In Europe, since 1 Jan 2020 all new vehicles must contain a terrestrial digital receiver. The cumulative total of all DAB+/DAB receivers is 145 million. In addition, Norway and Switzerland have switched off major network analog radio for 14 million listeners. India has nationwide coverage and >7 million car receivers and now China is making DRM compulsory in domestic car sales.
Indonesia has a population of around 200 million they have DAB+ and DRM with EWF on air transmitters in Yogyakarta.
Currently there are no domestic digital radio transmitters of any type on air in South Africa
> It would appear that you only post when I mention the letters DRM.
A statement that is both factually incorrect and completely irrelevant to the topic. The same goes for all of these campaigning slogans about HD Radio, DRM, DAB, EWF, regulations on receivers, China, etc. It’s totally unrelated. I won’t be addressing any of them here in an attempt not to derail the discussion any further. The topic was “Sporadic-E and FM-DXing”. I just wanted to clarify one very specific point brought up in the comments.
> Currently there are no domestic digital radio transmitters of any type on air in South Africa
Thanks for confirming that!
> they have DAB+ and DRM with EWF on air transmitters in Yogyakarta.
The DRM Consortium website mentions “recently concluded digital-analogue radio trial took place on the Jawa island in Yogyakarta”. Since it was written in past tense, does it mean it’s been ended now? EWF was not mentioned at all. (article: “Digital Radio Mondiale DRM Consortium Gives Important Updates at General Assembly in Dubai”). It would stand for 3th or even 4th DRM trial Indonesia. Does it equal to getting any step closer to a nationwide rollout? I would doubt it.
Who is still testing after 24 years?
USA: WSHE is one of a small handful of AM stations operating with the MA3 all-digital mode; in fact Radio World knows of only two doing so full-time at present, the other being 1260 WYDE(AM) in Birmingham, Ala., owned by Crawford Broadcasting. 1470 WYGG(AM) in Egypt Lake, Fla., experimented with the mode, as have 650 WSRO(AM) in Ashland, Mass., and 1230 WFAS(AM) in White Plains, N.Y., but each is now silent.
DRM has had 37 transmitters all much more powerful transmitting simulcasts for at least 7 years not as trials but as a feed of up to to 7 million receivers in cars. There are 4 transmitting pure digital only at 20 kW each In addition there are 4 HF DRM transmitters something HD radio cannot do because it uses the transmission channels of other broadcasters.
Lets face it HD radio in the MF band has been a failure but it is not in India. The USA has no pure digital radio transmissions in the FM band either..
Seems like the sentence “DRM digital radio can also use this band as well which is occurring in Indonesia and South Africa” actually means “it’s not occurring neither in Indonesia, nor in South Africa”.
In response to antenna polarization…….
Virtually ALL high powered FM Broadcast stations (50K +) in the U.S. are Circularly Polarized. Therefore, the polarization of your antenna doesn’t really matter. As for the lower powered stations the vast majority are also Circular but if not, they do favor Vertical.
Polarization of your Antenna does NOT matter for Sporadic Es. The reflection of all signals in the Ionosphere bends that all around. Only Tropospheric Scatter and Ducting are affected by polarization.
The best antenna is a directional one. I have found a good old-time Pre-HDTV Log-Periodic antenna is best. If you live in older HOA infested communities, I can assure you that there is one of those resting in someone’s attic.
I had to scrap a HD-2000XL a three years ago when I moved back to Texas 3 years ago. I found a Radio Shack Archer VU-110 Log-P for $20 that had been in attic of a 90’s built home. It’s now in my new HOA home with room to rotate. It hears FMBC stations with my RTL-SDR 120 miles with ease. It also has picked up several low-powered outlets on Sporadic Es.
In addition, I have a Omni-Directional FM Turnstile (Horizontal Polarized) on a 7 foot Speaker Stand. Many Es have been received with it and recently it captured (on a RTL-SDR) on Tropo a NPR station 610 miles away. I have picked up Es and 300 mile Tropo on an old set of Rabbit Ears. I do my back porch DXing with Rabbit Ears.
Have fun….. 73 Art
Art,
Vertical transmitting and receiving antennas means all of the transmitted signal is received at maximum signal strength. If a horizontal receiving antenna is receiving a vertically polarised signal in theory it should receive nothing in practice if the signal is strong enough you will get something. I have already acknowledged that i long distance modes the polarisation can tumble.
The best antenna for weak signals is one which has a narrow sensitivity towards the horizon vertically but horizontally is less arrow to pick up maximum signal. From experience with deep fringe VHF TV reception of horizontally polarised signals a phased array with 4 bays is very popular. It has the above characteristics. For vertically polarised signals the high gain Yagi-Uda and the Log Periodic Array have it. The Log Periodic Array is a wide frequency range antenna in North America they used to cover 54 -216 MHz. Since digital TV does not work well below 174 MHz regardless of whether the signals are ATSC1.0 ATSC3.0, as used in North America or DVB-T, DVB-T2, ISDB it has meant that receiving antenna manufacturers have stopped making the above antennas and make antennas for 174 MHz and above, and make a separate FM antenna for radio.
A Yagi-Uda antenna is a narrow band antenna for the restricted 88 – 108 MHz band has more gain element to element. Whilst it is possible to make an LPA for the FM band I am yet to see a commercial antenna manufacturer make them as a product.
A remote controlled motorised antenna rotator is invaluable if you are using directional antennas such as the Yagi-Uda and the log periodic array or even a dipole.
Many FM transmitting antennas are either mixed polarisation or vertically polarised. Some in the USA are circularly polarised. Only a few old installations are horizontally polarised from the days where VHF antennas for analog TV were common. The other polarisations are now used because a vertical antenna on a vehicle is omnidirectional so the signal strength does not change as you drive around corners.
The best antenna for long distance FM is a high gain Yagi-Uda mounted with its elements pointing towards the ground and the boom at the transmitter with the longest element furthest from the transmitter. This means that it focuses on a narrow slit along the horizon just like a sunset. Local reflections beside the antenna are not a problem because they are very weak. Reflections cause distortion and a lack of stereo separation.
For those FM DXing for stations in North America, track if HD radio is receivable, when a station transmits it. This is because the transmission power is about 1 % of the FM signal.
Remember that as the signal weakens neither the digital or FM signal change. As it weakens further te HD2 – 4 signals will drop out at the same time HD1 will start blending with the FM stereo. next the FM only signal will then go to mono and lastly either the receiver will mute or you ill hear lots of hiss.
Polarisation rotates by 90 degrees when reflected and by varying degrees when ducted in the atmosphhere.
A truly fascinating aspect of the hobby. I am living in Germany but in the past days I heard stations from Greece, Italy, and Romania – all on the FM band with my Qodosen DX-286 and its in-built telescopic antenna.
My absolute favorite propagation mode for DXing.
I first became aware of it as a CB’er backs in the early 70’s. In addition, I became a TV DX’er mounting a Log-Periodic under the CB Yagi. I became a Ham in 1979 and in time became an avid operator and DX’er of the 10, 6 and 2 Meter Bands. My old CB Yagi remained in service for 50 years (10 Meters) and retired in 2022.
Some of the special events I have had the honor of participating in:
1. Working 144 MHz Sporadic Es to both Coasts at the same time (June 1987)
2. Working Japan (Summer Es) on 6 Meters from Texas and Oregon
3. Receiving CFCN Calgary AB Channel 4 in Houston TX
4. Worked All States on 10 Meters, 49 States worked on 6 Meters (dang RI) and 43 States on 2 Meters.
5. A few 1,500+ mile 2-Meter QSOs on Es.
First in collaboration with Bob Colyard, creator of the original DXWorld.com, an Excel spreadsheet of the FCC FM Station Database was created for download and your personal use. After he passed away, I continue to update and make available the Spreadsheet each April on my Google Drive:
https://docs.google.com/spreadsheets/d/1Twa72_2fadg2IQRCKuyQILDH28F1tZTG/edit?usp=drive_link&ouid=106927842928622181117&rtpof=true&sd=true
Download it, save it on your device. Plug in your decimal Latitude and Longitude (N. America is Positive) and save it under another name in case you screw up.
You will get distance and azimuth. If you are good at Sorting and Filtering, it will really enhance your FMBC DXing experience. Lot’s of great sites on the Web, but I am old school and DX this way.
Enjoy Art K7DWI/5
My Personal Blog on Propagation Research.
Goofing off with a $17 RTL-SDR and my very old (45 Years??) Log Periodic in 2017 when I live in North Central Arizona. I had a lot of fun.
https://ka5dwipropagation.blogspot.com/2017/11/using-software-defined-radio-sdr-on-fm.html
73 Art
Depending on the type of propagation, you can get long distance transmission in the VHF (30 – 300 MHz) band as well as UHF (300 MHz – 3 GHz)
Uses i those bands an abbreviated list.
47 – 50 MHz was used for analog TV
50 – 54 MHz Amateur 6 m band
54 – 68 MHz was used for analog TV worldwide
68 – 72 MHz was used for analog TV the Americas only
74.8 – 75.2 MHz Aeronautical radio navigation
76 – 88 MHz was used for analog TV in the Americas
87.5 – 108 MHz FM broadcast. Americas start at 88 MHz
108 – 137 MHz Aeronautical
144 – 146 MHz Amateur 2 m band
156.5625 – 157.8325 MHz Marine mobile inc distress
161.9375 – 161.9625 MHz as above
162.400 and 162.550 MHz AM NOAA weather radio
174 – 223 (Americas 174 – 216) MHz VHF analog and digital TV
406 – 406.1 MHz Emergency Position Indication Radio Beacon EPIRB
430 – 440 MHz 70 cm amateur band
470 – 694 (Americas 698) MHz UHF analog & digital TV
1.452 – 1.492 GHz sound broadcasting satellites downlink
Unless otherwise stated allocations are world wide.
I should add that both DAB+ digital radio uses 174 – 230 MHz although this may not occur in some countries which extensively use this band for VHF TV.
DRM digital radio can also use this band as well which is occurring in Indonesia and South Africa.
HD radio’s digital signal can only operate in the 88 – 198 MHz FM band. In the AM band there are few HD stations.
> DRM digital radio can also use this band as well which is occurring in Indonesia and South Africa.
What are the stations that use it in these countries?
I discovered sporadic e-skip by accident over 50 years ago on June 15, 1974. A collection of brief recordings from that day can be found on my archive.org page here https://archive.org/details/fm-dx-june-15-1974
I’ve been a fan ever since. You don’t need sophisticated equipment. I will come blasting in on a car radio under the right conditions.