radio notes
| band | from | to |
| MW | 530 kHz | 1700 kHz. |
| SW | 3000 kHz | 30,000 kHz. |
Frequencies may be given in either kilohertz or megahertz. They may also be listed as being in a certain "metre band". This is the same information in a slightly different way.
5975 kHz = 5.975 MHz
Every frequency has a corresponding wavelength which can be calculated using the following equation:
Wavelength (metres) = 300,000 / Frequency (kHz)The conversion to wavelength is a holdover from earlier days when wavelength instead of frequency was used to denote where on the radio dial a given station could be found. Its use today is mainly as the name of the SW broadcast band and for designing antennas.
The SW broadcast stations we are looking for can be found in several small sections of the band which have been allocated for their use. The remaining parts of the SW band are set aside for other uses, many of which can also be heard with a regular SW receiver. These range from amateur radio operators and military communications, to commercial airlines and Coast Guard ships and aircraft.
International SW Broadcast Bands
|
Here's a list of SW stations that do nothing but broadcast the time (in UTC of course!) 24 hours a day.
| station | kHz |
| WWV (Fort Collins, Colorado ) | 2500, 5000, 10000, 15000, 20000 |
| CHU (Ottawa, Canada) | 3300, 7335, 14670 |
Generally speaking, the lower frequency, longer wavelength bands are most active after dark and the higher frequency, shorter wavelength bands are most active during the day.
the ionosphere actually consists of several layers, and each of them behave differently; some exist only during the day and others only at night.
The layers that affect radio wave propagation are called the D, E, and F layers.
The D layer is the lowest layer, at approximately 60 to 90 km above the Earth's surface. It exists only when the ionosphere is exposed to the Sun's radiation (during the day) and disappears when the sun goes down. The characteristics of the D layer cause it to absorb low frequency (long wavelength) radio waves and bend high frequency (short wavelength) radio waves. (high frequencies pass through D?) The more D is ionized, the more it absorbes radio energy. The maximum frequency, where signals are absorbed by the D layer in the day is approximately 7000 kHz. Below 7000 kHz, signals are absorbed and above that they are bent back to Earth. That's the reason why MW AM broadcast station signals can only be heard for relatively short distances during the day, and hopefully why signals were more plentiful on the higher bands during the day.
The E layer is found 100 to 115 km above the Earth's surface, and it acts much like the D layer. It exists when the sun is shining and absorbs low frequency signals and bend high frequency signals.
The highest ionospheric layer is the F layer which exists above from 160 to almost 500 km above the Earth. The F layer has the greatest effect on shortwave reception because it is very efficient at bending lower frequency radio signals back down to Earth, and it can be found at nighttime.
Just to complicate things further, the Sun doesn't by any means give off the radiation that effects our atmosphere in a consistent fashion at all. The Sun goes through regular periods of low and high activity over a cycle that take approximately 11 years to complete. We know this as the sunspot cycle, because the number of sunspots observed on the Sun's surface is directly related to the Sun's activity. High sunspot numbers indicate greater solar activity, and when solar activity is high the increased solar radiation ionizes the ionosphere to a greater extent and results in a more efficient F layer, which means better shortwave reception for us!
Sunspots numbers can also vary on 27 day cycles due to the rotation of the sun. Tilting of the Earth's axix and time of day affect propogation too.
As a very general rule of thumb, frequencies above 10 MHz are better daytime, and frequencies below 10 MHz are better at night.
DX-402 45-Memory Digital SSB Shortwave Receiver (200-0230) $149.99Ensure the radio covers at least 4750-21850 kHz with no significant tuning gaps.
BEST PORTABLE RADIOS FOR MW DX
1. Sony ICF-2010 --- Still the one. After years of production,
the 2010 still sits atop the mountain of MW DX portables. Unmatched in
features and performance important to MW DXers. In dozens of
side-by-side tests with numerous portables, the 2010 always comes out
smiling. Filter options and mods available are a plus.
2. C. Crane CCRadio --- Usually a close second to the 2010 in
side-by-side tests of sensitivity (some users report equal or better
sensitivity than the 2010). Selectivity quite good for domestic (i.e.,
10 kHz spacing) DX; needs a filter mod for split-frequency DX. Doesn't
have the sometimes helpful features of the 2010 (e.g., synchro; ECSS).
There is apparently some variability in samples (common among
portables) that result in differences of opinion regarding this radio.
Still, of the three I've seen, all performed extremely well, especially
after alignment.
3. Panasonic RF-2200 --- This discontinued, 1970's era analog radio
remains a marvel of engineering. From its raw sensitivity on MW to its
rotating "gyro" AM antenna to its two selectivity bandwidths, the
RF-2200 is one of my favorites for MW DX. The only analog portable
I've ever seen that gives 10 kHz read-out on MW (except for the
Barlow-Wadley XCR-30 (which isn't very good on MW)). Audio is also
very pleasing. Note that MW band coverage stops at 1600 kHz.
4. GE Superadio I or II --- The first two of the popular Superadio
series and easily the best. Excellent construction quality with
separate circuit boards for different stages, a high-quality variable
capacitor (vice tuning diodes), etc. Superb sensitivity on MW and
excellent selectivity for domestic DX. Coverage stops at 1600 kHz
though and dial read-out is coarse. Best audio of any portable. Long
discontinued.
5. Sony ICF-7600G --- This has to be the best under $200 all-around
portable currently available. Sensitivity on MW is very good (but not
as good as those ranked higher); selectivity is good for domestic DX;
the synchro works well and is sideband selectable; SSB on SW and MW
(for ECSS use) is excellent; and audio is pleasing. This is the radio
I grab when going on short jaunts that offer an opportunity for some
casual DXing.
6. Sangean 803A/Radio Shack DX-440 --- Sangean's best effort so far
for MW DXing. Not outstanding in any category but a good all-around
performer on MW. BFO not operative on MW (without modification).
Discontinued.
7. Realistic TRF (12-655) --- Ah, the legendary TRF. Radio Shack's
one and only (other than the Sangean-made DX-440) truly great MW DX
portable. This AM-only portable sold in the 1970's for about $30 and
had such DX-rich features as a tuned RF section and a ceramic filter in
its two IF stage design. Easily modifiable with filter and other
upgrades, this was one of the most enjoyable radios to own during the
era. I still marvel at some of the DX loggings with this radio...how
about Paraguay from Mississippi, or Hawaii from Florida? As good as it
was/is, the higher ranked portables offer equal or better performance
and features; the TRF's legend is based on a combination of price,
performance, and modifiability. If you can find one, jump on it, for
nostalgia's sake if nothing else. Note: Radio Shack's current and
recent run of Superadio clones is a joke...avoid at all costs.
8. Sony ICF-6500W --- This discontinued 1980's era analog/digital
portable from Sony is a hot performer IF it is properly aligned. Good
sensitivity and selectivity for domestic DX. Split-frequency DX
requires a filter mod. MW stops at 1600 kHz.
9. Grundig Satellit 700 --- I have no personal experience with this
radio but it has been recommended by two respected DXers for MW DX.
Check it out. Discontinued.
10. Radio Shack DX-398/Sangean ATS-909 --- Good sensitivity and
excellent selectivity (deep skirt/ultimate selectivity only fair
though) makes this a good MW DX choice especially if you can get it on
sale. Principal shortcomings are somewhat muffled audio on weak
signals and poor battery life. Forget about using SSB for ECSS.
11. Grundig YB400PE --- Just had the opportunity to finally try this
radio and was pretty impressed. Good sensitivity and selectivity for a
small portable although audio was a little "hissy" on weak to moderate
stations. SSB on MW for ECSS reception was poor. However, not on par
with the Sony ICF-7600G, in my opinion, even though the narrow filter
is useful.
12. GE Superadio III --- Okay, I've never had good luck with the SRIII.
The ones I've tried have had less than expected sensitivity and various
degrees of image problems. Nonetheless, several DXers whose opinions I
respect say that they are good radios. I guess I've just been getting
lemon samples....test before you buy.
Again, these are portables that I've tested and found to be good on
the AM broadcast band (and only a few cover LW). Not all are presently
in production and some that are out of production do not cover the
expanded AM band. Your input on these and other portables is welcomed!
Note: Russ Johnson kindly sent me a shirt-pocket-sized radio that is
amazingly good on MW. It's the Sangean DT-200V (same as the
discontinued Radio Shack Optimus 12-174A). Disarmingly sensitive for a
radio this size (but not equal to some of the bigger boys, of course),
it dethroned my previous <$100, pocket-sized portable for sensitivity
(the discontinued Sony ICF-4910). Audio is very crisp as well. I'm
gonna get one of my own. Currently being carried by Universal Radio
for $59.95.
Radio Shack - Radio Shack has a nice line of portable shortwave
receivers, and they are a great deal when you can find them on sale.
They are all radios that are made by Sangean, but they have the Radio
Shack name, and you can get the repaired at any Radio Shack Store. The
model numbers are different then the Sangean. The ATS-909 is the RS
DX-398, but I have found my newer ATS-909 to be more sensitive and give
better reception than a new DX-398 that I bought and eventually
returned because of this. RS may come out with an updated model in the
future. The 909 had a silver case and I believe it's a bit newer and
perhaps improved. The ATS-818 is the RS DX-390, but they discontinued
this nice radio. You can still find it used on ebay.
idata:
ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS
ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_RADIO/FLUX
http://www.usascan.com/files/ats404.html
sangean 404 for $69.95