Shortwave Radio Diversity Reception
Shortwave radio diversity reception provides a way to combine several fluctuating signals and get a solid result. It provided the foundation for most radio news received in America for years.
During World War II, most countries around the world relied on Britain’s shortwave radio broadcasts for the latest news from Europe. In the days before transatlantic audio cables or satellites, distant news traveled fastest by radio. Networks in the America’s, Australia, New Zealand and elsewhere re-broadcast shortwave radio news domestically.
Getting reliable, good quality audio programs over shortwave is always a challenge because of fading. As signals bounce off the ionosphere, they split over multiple paths. Often they fade and flutter, sometimes significantly, as the nature of the layers change with time. Here are several examples of shortwave signals fading, so you know what it sounds like. Skywave radio signals are subject to complex patterns of travel and interference.
Eventually, domestic networks found a clever way to get better audio from these distant signals.
[…]Diversity reception works like this. Instead of one signal, you monitor several signals at once and blend them together. Harold Beverage and RCA pioneered work on shortwave radio diversity reception in 1920’s. Commercial solutions arrived by 1933. Typically, you would use three receivers with three different antennas, spaced 1,000 feet apart. When antennas are widely spaced, signals arrive with different fading. Just combine the signals and let the strongest signal dominate. As long as the fading is not correlated across all three antennas, improvement can be significant.
Diversity reception can be achieved in several ways. The most popular – spatial diversity – is described above. Other methods include frequency diversity – mixing together the same program received on several different channels.[…]
Many thanks to SWLing Post contributor, Dennis Kalinichenko, who shares the following review:
The Shoroh R-326 military radio
by Dennis Kalinichenko
I believe the piece of Soviet military equipment I recently bought to my collection would be interesting to all readers and contributors.
This is the R-326 “Shoroh” (“Rustle”) general coverage military tube shortwave radio receiver. These were produced decades ago, back in 1963. These portable receivers were in active military use in the Soviet Army until the early 2000s, when the R-326 was finally discontinued . Today, this set is no more a spy secret, but a great collector’s item and also a good receiver for home use.
My set cost me about $150 US, which is rather expensive for this radio. The R-326 was plentiful in the local market in 90-s, right after the fall of the Soviet Union, very cheap and popular between radio amateurs, but nowadays this radio has become more and more rare, so the price rises up.
My R-326 arrived from Khabarovsk city, the Russian Far East, where, I believe, for many years it was on duty in some of the Soviet radio intelligence and defense forces division.
The set includes the radio itself, original military 100 ohm headphones, original rectifier box for 2,5 V output, 12 meter long wire antenna on a reel, the 1,5 meter famous “Kulikov” mini-whip antenna, the isolator for placing it on top of the radio and some minor accessories.
Originally, the R-326 radio came with two batteries–1,25 V each–for field use, but mine are totally drained and need to be serviced, so I haven’t used them so far.
The radio is a light-weight, only 33 lbs, which is a real minimum for Soviet military equipment–the famous R-250 radio’s weight is up to 220 lbs–so, in comparison, this unit is really portable. You can easily put it in your car using the attached leather handle and take it with you on a weekend trip. No other military radio can be so “travel-friendly”; this is one of the reasons it was so popular in the ham radio and SWL communities.
The case is made out of steel and looks so solid you may want to use it as a nutcracker. And you can! In no way could you harm the box constructed to resist nuclear attacks. It is waterproof and sealed–so I can be confident that no previous owner has ever tried to solder something in the guts.
The radio is a super heterodyne containing 19 (!) special mini tubes and covering 6 SW bands, from 1 to 20 MHz. It works in both AM and SSB (CW) modes, having an on-board adjustable bandwidth control from 300 Hz to 6 kHz.
On the front panel, there are two scales: one is rough/coarse, and above is the precise one, a so-called photoscale, which may be adjusted to match real radio-frequency using the four screws near the sun protection visor. With this scale, you don’t actually need a digital readout. It also has a BFO control with a zero setting, adjustable AGC levels for AM and CW, and adjusting screw for matching the antenna input, as marked for 12 m long wire, 1,5 m and 4 m whip.
The radio has no built-in speaker. Instead, there are two output sockets on the front panel, for 100 ohm headphones and 600 ohm line-out.
The power consumption is very low for s tube radio, the rig needs only 1,4 A at 2.5 volts DC (including the lightscale). I use the original power transformer (transistor rectifier) and therefore switch the unit into the 220 AC outlet.
The sensitivity of the radio is extremely high and equals some modern transceivers. The selectivity is also impressive. No doubt it was really great for 1960s. But there’s negative side as well: the radio easily overloads even from the outdoor long wire antennas. The best fit is the “Kulikov” mini-whip that you can see in the photos.
When you switch on the radio, you hear noise, the level of which seems high, so you lower the volume down. Yes, the radio is sensitive and a bit noisy. But thanks to the tubes it sounds really amazing in the headphones. The SSB ham operator’s voice is warm and very clear.
The tuning is very smooth, being actually 2-speed: outer wheel is for fast tuning, inner wheel for precise tune.
It’s absolutely obvious that nowadays a simple Degen or Tecsun may be more useful than this old and heavy unit with big and tough knobs and switches. But what a pleasure sitting in front of this perfect tube radio at night, with the headphones on, turning the huge tuning wheels, looking into the moving dim scale, listening into distant voices and rustles, feeling yourself a Cold War times operator near the rig.
Isn’t this experience priceless?
Indeed the experience is priceless, Dennis! Better yet, your R-326 now has an owner that will keep it in working order and enjoy it on a regular basis. I personally believe keeping these vintage rigs on the air is one way to preserve, and experience first hand, a little of our collective radio history.
Thank you so much for sharing your review and excellent photos of the R-326!
Post readers: If, like Dennis, you have a vintage radio you would like to showcase/review here on the SWLing Post, please consider submitting your story and photos. Being a huge fan of vintage radio, I truly enjoy reading through and publishing your reviews. I know many other readers feel the same!
(Source: Micromedia Publications)
BERKELEY – A few poles, a couple new osprey nets, make up the new horizon of Good Luck Point’s marshland. Once home to hundreds of telecommunication poles that made up a ship-to-shore communication system, the poles were taken down from mid-January onward as part of a United States Fish and Wildlife Service project in the Edwin B. Forsythe Refuge which officials said focused on marshland sustainability.
The project removed several hundred poles from the old AT&T field in the marsh of Good Luck Point and scheduled 100 poles from its sister site in Manahawkin.
The long-decommissioned telecommunications poles were once part of a ship-to-shore network. The pole field is located along Bayview Drive in Berkeley and Beach Avenue in Manahawkin.
We’ve been following the story of the Good Luck Point site for serval months. Click here to read previous posts. Be sure to check out Dennis’ photos of Good Luck Point prior to WOO remnants being removed.
Many thanks to SWLing Post contributor, Neil Bolitho, who shares the following story in reply to our post yesterday Australian Codebreakers in WWII. Neil writes:
Never to march, never to be mentioned.
Since the end of the Second World War, many thousands of returned service personnel have marched at Anzac Day services throughout Australia.
My father never marched.
My father served in RAAF No 4 Wireless Unit, Central Bureau.
Central Bureau was under the direct command of General Douglas MacArthur, and was set up to detect, record, and translate all messages transmitted by Japanese forces in the Pacific.
Central Bureau was headquartered in Brisbane, but its Wireless Units worked in the field, moving forward with MacArthur, constantly intercepting and deciphering enemy messages.
As the war progressed, the units became so efficient in their work that they were monitoring all enemy radio traffic, and in fact frequently knew the Japanese intentions before the messages reached their intended destination.
The Wireless Units served throughout the Pacific islands providing vital information about enemy strengths and positions.
RAAF No 4 Wireless Unit was formed as a highly mobile unit, and served at Hollandia, Morotai, Labuan Island, and at Luzon, Philippines.
The U.S. High Command highly praised the Wireless Units of Central Bureau, stating that their work effectively shortened the War in the Pacific by at least two years.
At the end of the war, Central Bureau was dismantled. All personnel signed a lifetime secrecy order to not speak of their wartime activities.
No promotions applied. No evidence of their Central Bureau service was recorded, including overseas service. No medals were struck.
Family members, including children, were not told in any detail, of their father’s war experience.
It was only in the late 1990’s that the Australian government allowed information to be released.
In the early 1960’s, my father mysteriously went on an unexplained visit to Brisbane.
It was not until over thirty years later that I found out that he attended a twenty-year anniversary of his unit’s graduation.
I write this on behalf of the children and grandchildren of those Central Bureau personnel that served diligently and efficiently when called upon, and who, when the job was done, quietly went home. They are our heroes.
Indeed. Thank you so much, Neil, for taking the time to share your father’s story. We’re honored to post it here.
If you’re interested in WWII signal intelligence, here are a few fascinating posts from our archive:
Many thanks to SWLing Post contributor, Ian P, for sharing the following from the radio program, ABC Overnights:
The crucial role of Australian code breakers in World War 2
Thanks to the recent film, The Imitation Game, you may be familiar with the story of how British intelligence, led by mathematician Alan Turing, cracked Nazi codes during WW2. Did you know there were also two secret organisations in Australia working to break Japan’s military codes?
These were staffed with brilliant cryptographers, including some who had studied mathematics and the classics, and others who had lived or grown up in Japan. By patiently and carefully unravelling the codes in Japanese signals, their intelligence played a crucial role in the battles of Midway and the Coral Sea, as well as the push into the Philippines.
Trevor Chappell interviews Craig Collie, author of the book Code Breakers – Inside the Shadow world of Signals Intelligence in Australia’s two Bletchley Parks.
Duration: 36min 36sec
Broadcast: Mon 10 Apr 2017, 1:00am
Published: Mon 10 Apr 2017, 4:43pm
Listen to the full program/interview via the embedded player below:
I’ve also noted that you can pre-order Code Breakers – Inside the Shadow world of Signals Intelligence in Australia’s two Bletchley Parks at Amazon.com. There is no expected delivery time yet, however.
Code Breakers is available directly from the publisher in Australia–click here to view.