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Category Archives: Technical
DENIS O’CALLAHAN’S ADDRESS TO THE 2018 CONVENTION
It started for me when I was living in New Caledonia, having washed up there on a yacht and got a job with a local radio repair shop and a guy called Stan Clinch, who ran an outfit called Kiwi Radio. He’d been a wartime radar technician and had gone back to New Caledonia where he had been stationed during the war, to set up a radio repair shop.
Another benefit of belonging to the NZRDXL is use of a 4-channel KiwiSDR receiver located in an excellent receive location at Russell in the Bay of Islands. To obtain the password, just must be an NZ Radio DX League members, request it by sending an e-mail to email@example.com.
However to cover 20MHz of bandwidth for FM (88-108MHz) a single dipole design liek the Matchmaster will really struggle, with performance falling off the further from its design frequency you tune. So a combo yagi which is a hybrid log periodic yagi and standard yagi, sometimes called a “logyag” is a good way to go. It has 3 dipole elements, one cut for the lower portion, one for the middle and one for the top of the FM band giving much more even performance. There are also optimised yagi designs available on K6STI’s excellent site.
This interesting article forwarded from Bill Marsh was penned 80 years ago. In all that time, noise from electrical and electronic devices has grown even worse.
Bill Marsh has been experimenting with the ferrite sleeved loop design and has come up with a clever design. You can read the full article here.
Bill Marsh has been experimenting further with his coax loop for MW and the X-band. Here are the results:
X-BAND LOOP NUMBER 2
Washington state DXer Gary DeBock (above) who recently joined the League has posted this report of a DXpedition to his favourite cliff-side location on the northern Oregon coast last month. Thanks to Paul Rawdon for reporting this to the DX Dialog user-group.
- The Story Of The Pub on 14th June’15
- Brian Anderson – A Profile on 14th June’15
- Ted Manning – A Profile on 14th June’15
- Murray Lamont – A Profile on 14th June’15
- Evan Tombs – A Profile on 14th June’15
- Frank W Wilson – A Profile on 14th June’15
- Ken Mackey – A Profile on 13th June’15
- Alex Allan – A Profile on 13th June’15
Using Standard Signals From WWV
Possibly not all readers realise that very precise standards of time and frequency are available on the short-wave bands to anyone possessing a suitable receiver. This paper, prepared by engineers of the Aerovox Corporation, summarises the present transmissions and suggests methods by which the information can be used.
THE standard time and frequency transmissions of the National Bureau of Standards radio stations WWV and WWVH provide an invaluable service to laboratories and individual experimenters throughout the world.
Extremely precise audio and radio frequency standards, as well as accurate time intervals and radio frequency propagation warnings, are placed at the disposal of anyone having a receiver capable of tuning to one or more of the transmitting frequencies.
A summary of a lecture delivered to the Wireless Institute of Australia
on June 15, 1939, this article will be welcomed by all who are interested
in fading and skip-distance transmission on various frequencies.
By R. H. Healy, D.Sc., E. inst. P.
SHORT-WAVE circuits operating between wave-lengths of 10 and 100m. (30 and 3 mcs.) are dependent, in the majority of cases, on reflections from the ionised regions or layers of the atmosphere. In the absence of these reflections, communications by means of the ground ray alone is only possible up to comparatively short distances, the actual distance depending on such factors as the earth resistivity, the wave-length, and the height of the transmitter and receiver above earth.
STARS CONTROL WAVE-LENGTH;
USED TO CHECK TUNING FORK
An interesting development in checking the frequencies of broadcasting stations is announced by the A.W.A. Research Laboratory
THE stars in the heavens have been harnessed to prevent overlapping among broadcasting stations. By their aid, complaints of interference between any of the 121 stations in Australia have been practically eliminated.
To test whether a station is on its wave-length, the scientific staff at the A.W.A. Research Laboratory, Ashfield, employs a tuning fork of high-grade Elinvar steel. This fork, when vibrating, has a natural frequency of 1000 cycles per second, and when its frequency is compared with the frequency of a broadcast station or control equipment in course of manufacture, the slightest variation from an allotted frequency or wave-length is detected.
Typical Sales Advertisement from
The N.Z. Radio Times
February 2, 1937
It is generally agreed that if a receiver has to be operated where interference is directly radiated, the most effective way of improving reception is to attend to the aerial; the active span should be erected as far from any metallic conductor as possible, and the down lead which is incapable of picking up any radio voltages be used for connecting the aerial to the receiver.
HIGH EFFICIENCY AERIAL FOR SHORT WAVES
HERE is a short wave antenna that has helped me very much in my SWL work. I believe it is an original idea, for I have never seen or heard of one like it. It occurred to me when I was trying to figure out a way to have good directional antenna (all directions) without having to have a separate antenna for each direction. It has worked wonderfully well for the past six months, so I thought that others interested in the same field might like to try it.
FOR INCREASING R.F. GAIN
R. J. A. LITTLE, A.M.I.R.E. South Melbourne
From – The Australasian Radio Times – July 1947
A WAVE TRAP can be defined as a circuit containing at least one condenser and one coil wired in series or parallel to form a tuned circuit. A most common form of wave trap is one utilising a parallel tuned circuit.
Thanks to Tony King reporting on the DX Dialog reflector, here is a photo of Gary DeBock with his invention, the Ferrite Sleeve Loop. “Gary DeBock’s latest creation with which he is scoring many NZ stations on his Tecsun PL380. Probably about 200 ferrite rods on this “sausage roll” .pic attached. He’s in the right uniform, and his PL380 lives in an NZ emblazoned mobile phone pouch I sent him last year.” Rumour has it one or two Kiwis are building them!
And also from Gary is a Youtube video of his antenna picking up trans-Pacific DX from New Zealand.
Jim Brown K9YC is the author of an excellent guide to solving RFI issues around the radio shack. His very useful article “A Ham’s Guide to RFI, Ferrites, Baluns, and Audio Interfacing” has much information useful to SWLs looking for a way to reduce noise and there are a lot of instances where the noise-source is in the home. You’ll find a lot of interesting material on Jim’s website.
Historical article from Lamphouse Annual 1947-48
MANY excellent programmes are ruined by man-made interference. In order to locate the source of interference you should endeavour to obtain some clue to possible causes, and, by the process of elimination, determine the electrical system in which the trouble originates.
The local Radio Inspector of the Post and Telegraph Department is always willing to investigate complaints of continued interference, but before calling on his assistance you should endeavour to eliminate the possibility of the trouble being in your own receiving set, your aerial and earth system, or caused by some electrical appliance or circuit in your own home.