Re: Regen use for NDB ?
Stan,
I never used a homebrew regen for the beacons below the broadcast band.
When I was a kid, I built crystal sets that covered that range.
I had to wait until after midnight when the local 50kw clear channel BC station on 820kc signed off to hear them. Then I could hear DAL at Love Field in Dallas and RBD at Red Bird airport south of town.
Thought I was in tall cotton when I acquired a BC 229 TRF receiver in 1954 that covered 200 to 400 kc.
And I could actually make the 229 regenerate by connecting a wire from the antenna post on the front panel and lay it back across the tubes in the later stages.
Had the dual band coil set, and could copy CW on 40 meters.
Golly, that was a long time ago.
John
Re: Regen use for NDB ?
Posted by Stan on April 01, 2006 at 03:07:31.
In reply to Re: Regen use for NDB ? posted by John Litzendraht on April 01, 2006
Hi John, well I have not built a regen in about 50 years but think it might be the ideal circuit to play with in the 200 plus meter bands. The main thing is building up the coil set, not much else in one. hi I am thinking of one untuned RF stage, regen detector with one stage of audio and a old high impedance headset. If I really try I am sure I can find almost everything in my junk boxes.
Lot of regen circuits posted on the web for broadcast and HF regen tube circuits. I am considering a Jones handbook circuit from 1937 or 1938.
Stan ak0b
Reminder about eBay
Posted by Webmaster on April 02, 2006 at 20:45:47.
Sorry if this is an inconvenience to anyone, but I need to draw your attention to the Posting Guidelines for this forum, which prohibit the advertising of one's own sales and auctions on eBay or any similar service.
Many other message boards and e-mail lists have rules against this too. In part it's because such sales border so closely on commercial advertising, particularly if the person posting the item sells other things regularly online.
In addition, I personally find it rather like dropping in on a group of friends having a Final Four party...but rather than socializing a while and casually asking if any of them want to buy the item first, simply announcing "I thought you guys might like to bid on it against the entire universe."
If the board users wish, I am willing to consider an exception for items that are offered for sale here first for a reasonable time, and then placed on eBay if there are no buyers within the group. Your comments will be welcome.
John
Loop antenna
Posted by Martin on April 04, 2006 at 04:27:52.
I am making a loop antenna and could need some help with formulas for the antenna. The antenna is a square loop antenna for the VLF-frequenzy area. Re: Loop antenna
thanks
Posted by Warren K2ORS/WD2XGJ on April 04, 2006 at 09:46:48.
In reply to Loop antenna posted by Martin on April 04, 2006
Martin,
You should go to Reg Edward's web site:
http://www.btinternet.com/~g4fgq.regp/page3.html#S301%22
and download the program RJELOOP3, which should give you everything you need to design your loop.
73 & Good Luck Re: Loop antenna
Warren K2ORS/WD2XGJ
Posted by Warren K2ORS/WD2XGJ on April 05, 2006 at 08:46:06.
In reply to Re: Loop antenna posted by Warren K2ORS/WD2XGJ on April 04, 2006
If you'd prefer to crunch the numbers yourself, Will Payne has an excellent article on loops:
http://www.vlf.it/octoloop/rlt-n4ywk.htm
Warren K2ORS/WD2XGJ
Longwave Transmitters/Recievers?
Posted by AnthonyD on April 10, 2006 at 20:16:53.
I'm looking to run a test longwave station on the "experimental" 160-190KHz band. Unfortunately, a friend of mine who knows alot about radio says that I have to build my own transmitter/reciever. Does anyone know where I can find schematics to easily build a transmitter and reciever? Or can I just buy one?
Thanks, Re: Longwave Transmitters/Recievers?
Anthony
Posted by Warren K2ORS/WD2XGJ on April 10, 2006 at 21:12:20.
In reply to Longwave Transmitters/Recievers? posted by AnthonyD on April 10, 2006
Hi Anthony,
The only commercially available transmitter (that I know of) is a kit from North Country Radio:
http://www.northcountryradio.com/Kitpages/am88.htm
If you'd like to build your own have a look at the following web site:
http://www.mlecmn.net/~lyle/
Good Luck,
Warren
Re: Longwave Transmitters/Recievers?
Posted by John on April 11, 2006 at 10:23:10.
In reply to Longwave Transmitters/Recievers? posted by AnthonyD on April 10, 2006
Anthony,
Warren's advice is good, but it would help to know what you are trying to do. Is this for CW or phone operation? Are you planning to just play with this locally, or work over some distance? Do you already have a receiver of any kind?
John Andrews Transmitting ultrasonic
Posted by Jaohann on April 12, 2006 at 09:34:04.
How far can I transmit a signal with a 100 watt ultrasonic transmitter with speech modulation in AM, CSSB, SSB or DRM-mode? Re: Transmitting ultrasonic
Which frequency range is usable for this?
How far would a 100 watt ultrasonic transmitter reach in air by a carrier frequency of 30 kHz and how far at a carrier frequency of 300 kHz?
Is ultrasonic dangerous for animals? Will bats collide in the neighbourhood of ultrasonic transmitters?
Posted by Warren K2ORS/WD2XGJ on April 12, 2006 at 11:43:41.
In reply to Transmitting ultrasonic posted by Jaohann on April 12, 2006
Jaohann,
You would need an ultasonic transducer that is capable of handling 100 watts without overheating. That would not be easy to find. Air is a very poor conductor for ultrasound energy. At 30kHz sound is attenuated by over 900 dB in one kilometer! (Compare this to only 18dB attenuation at 3kHz).
Have a look at the following website calculator:
http://www.csgnetwork.com/atmossndabsorbcalc.html
Strictly speaking this is not long wave radio related and is off topic.
Good luck with your experiments.
Warren Re: Transmitting ultrasonic
Posted by John Davis on April 12, 2006 at 11:50:00.
In reply to Transmitting ultrasonic posted by Jaohann on April 12, 2006
:: How far can I transmit a signal with a 100 watt ultrasonic transmitter... ::
The question of distance cannot be answered without knowing the sensitivity of the receiving apparatus and the directional properties of the sending apparatus.
As a very crude approximation, one could drive a high-power speaker system with an audible high frequency tone at the same power, and walk about to determine how far it can be heard by ear. (Caution: high probability of neighbor annoyance, which could result in police inquiries!)
This experiment will not only yield a rough idea of the possible distance, but it will also demonstrate that sound energy of such short wavelengths exhibits phenomena characteristic of VHF and UHF radio waves; specifically, multipath interference and knife-edge propagation effects, unless the path is very carefully chosen to be line-of-sight. Furthermore, density variations in the atmosphere will cause the sound to be refracted in ways resembling the shimmering of distant lights when viewed on a warm or windy night (scintillation).
There is one additional ultrasound effect to which electromagnetic waves are not as susceptible: high frequency acoustic energy is attenuated more by its passage through the atmospheric medium than is low frequency acoustic energy. I see that, during the time I was still typing, Warren posted some actual numbers showing the magnitude of this effect.
This attenuation has obvious consequences for your choice of operating frequencies. If greater distance is desired, lower frequencies are better. A 300kHz signal will have its energy dissipated in a much shorter distance than a 30kHz signal. However, there is a trade-off to be made. A sending transducer for a lower frequency will also have less bandwidth, possibly limiting one's choice of modulation methods to SSB or very narrowband AM. In addition, animals will be more susceptible to lower ultrasound frequencies.
Other factors to consider with regard to modulation methods:
:: Is ultrasonic dangerous for animals? ::
Short answer: yes. High power ultrasonic energy, even if not perceived by the ear as sound, can cause disorientation, anxiety, headaches, ear pain, dizziness, nausea, and seizures--in humans, as well as other animals!
These effects were discovered at least 60 or 70 years ago, and were re-discovered the hard way in the 1970s, when ultrasonic intrusion alarms became common in commercial buildings. (Such alarms are still around, but now operate at much lower power levels. Very few department stores want customers clapping their hands to their heads in pain, vomiting, or falling to the floor unconscious as soon as they walk through the front door. Makes a very bad impression on the other clientele.)
In short, the area within several meters of an operating 100W ultrasound transducer is an extremely dangerous region. You wouldn't want people being within 20 or 30 meters of it for an extended time without ear protection, either. I imagine that a system operating below about 100kHz could cause considerable agitation among dogs throughout the entire neighborhood. And yes, bats and some insects would become disoriented if they flew into the beam.
John Re: Transmitting ultrasonic
Posted by Warren K2ORS/WD2XGJ on April 12, 2006 at 12:00:52.
In reply to Re: Transmitting ultrasonic posted by John Davis on April 12, 2006
John,
Terrific, thoughtful answer. But keep in mind that the atmospheric attenuation increases exponentially with frequency so listening for a lower frequency audible tone with the same power would not be a good indicator at all for the range of an ultrasound system. You mention 300 kHz, at that frequency air is an excellent insulator rather than a conductor; 300kHz sound is attenuated by more than 16,000 dB in a kilometer! You will have an unmeasureable amount of energy at 1 Km even if you are transmitting with a MEGAWATT of ultrasound!
Distant thunder sounds like a rumble because the higher frequency components are attenuated leaving only the lowest frequency components.
Warren K2ORS/WD2XGJ Re: Transmitting ultrasonic
Posted by Warren K2ORS/WD2XGJ on April 12, 2006 at 12:19:07.
In reply to Re: Transmitting ultrasonic posted by Warren K2ORS/WD2XGJ on April 12, 2006
I should have mentioned that in medical or industrial applications of ultrasound a coupling gel is used between the ultrasound transducer and the article under test as even a fraction of a millimeter of air would block the ultrasound signal. Medical and industrial ultrasound frequencies can go up to 100 MHz or more.
73 Warren K2ORS/WD2XGJ Re: Transmitting ultrasonic
Posted by John Davis on April 12, 2006 at 12:48:07.
In reply to Re: Transmitting ultrasonic posted by Warren K2ORS/WD2XGJ on April 12, 2006
You are right, of course, Warren--the additional attenuation at higher frequencies is so great that the experiment becomes invalid long before 300kHz. I should have been more explicit in stating the conditions of the experiment.
What I had in mind was the use of a frequency near the high limit of audibility, at least 15kHz. Factoring in the loss of the human ear, compared to a decent transducer operating with a small parabolic reflector, I estimate the result would be roughly comparable to an ultrasound system up to about 30kHz. That would quickly demonstrate how short the propagation range is...much less than one would suppose when thinking in terms of wattage alone.
It's the same problem one faces when trying to record a marching band on a football field with a microphone in the spectator stands. A glockenspiel's sound is very piercing, close up, as are the overtones of a trumpet; but one has to equalize high frequencies heavily to even remotely preserve their timbre from 50 meters away. The bass drum still booms away as before, however.
And, as we now know, elephants communicate with herd members scores of kilometers away, using infrasonic vibrations of a few Hertz frequency that can scarcely be felt by humans in their immediate vicinity.
The smaller the acoustic wavelength, the less interaction air molecules have with each other in direct response to the pressure stimulus, so the relatively coherent acoustical energy is rapidly dissipated as heat...also a form of mechanical energy, but not coherent pressure waves. Entropy devours all.
John
Re: Transmitting ultrasonic
Posted by Warren K2ORS/WD2XGJ on April 12, 2006 at 13:02:28.
In reply to Re: Transmitting ultrasonic posted by John Davis on April 12, 2006
Hi John,
Yes infrasonic waves travel virtually unattenuated. I have an article from Science News about detecting meteors entering the atmosphere by the infrasound waves. You need something between a low frequency microphone and a fast responding barometer to pick this up.
Warren
PC as a VLF receiver
Posted by Stan AK0B on April 12, 2006 at 17:36:01.
I have not seen this posted on the list.
http://www.qsl.net/dl4yhf/speclab/vlf_rcvr.htm
Using the soundcard the upper frequency is limited to 22 KHz, but you could build a mixer in front of the soundcard and copy other frequencies.
The program can also be used as a transmitter. Little complex to learn how to use, but DL4YHF has done a good job including hum filters, etc. It works well as a micro HELL transmitter and a QRSS receiver. I have not learn how to use the other features.
He has several links posted on various details on the use of the pgm.
It's free
Stan AK0B Re: PC as a VLF receiver
Posted by Warren K2ORS on April 12, 2006 at 20:13:55.
In reply to PC as a VLF receiver posted by Stan AK0B on April 12, 2006
Stan,
Lyle Kohler has a project on his web page that converts down and allows you to use Spectrum Laboratory as a software i.f.
http://www.qsl.net/k0lr/SW-RX/sw-rx.htm
73 Warren K2ORS/WD2XGJ
Transpacific LF Tests - Quick Summary (fwd)
Posted by Steve McDonald on April 13, 2006 at 17:08:20.
The recent Trans-Pacific LF Tests with New Zealand were undertaken on the nights of April 3-5, 2006. Although these dates were selected several months ago, it seems that we could not have picked a poorer time slot for our tests. The propagation Murphy was hard at work elevating the A/K index, producing solar flares and a strong geomagnetic storm resulting in an HF blackout and auroral displays visible well into the central states. In spite of the poor conditions, VA7LF (South Pender Island, B.C.) and ZM2E (Quartz Hill, New Zealand) managed to exchange signals on the 2200m band.
Using slow speed DFCW90 as well as DFCW60, signals from both ends were copied on all three nights. The third morning proved to be best, with ZM2E's signal suddenly elevating to 25 db over the noise and acknowledging our call to them indicating "O" (perfect) copy of our beacon signal. In our pre-determined communications protocol, this was an invitation to initiate the formal QSO sequence but, unfortunately, the sun was just rising at Pender Island and we quickly ran out of darkness before full calls could be exchanged.
The new amplifier and antenna system at VA7LF proved to work even better than anticipated. Evidently Murphy gave us a break with those!
While waiting for sunset on the third night, the VA7LF bunch took advantage of their strong groundwave signal and worked a number of cw crossband contacts with amateurs in B.C., Washington and Oregon. Hopefully we can do more of this on the next outing.
Although far from a valid QSO, the spirits at both ends remain high, as we look forward to another attempt. As Bob Vernall (ZL2CA) lamented, "The bottle of bubbly has been put back on the shelf for now".
Further information and photos are available at "The VE7SL Radio Notebook":
http://imagenisp.com/jsm/VA7LF.html
Steve / VE7SL
Re: PC as a VLF receiver
Posted by Alan G3NYK on April 13, 2006 at 19:47:55.
In reply to PC as a VLF receiver posted by Stan AK0B on April 12, 2006
Hi Stan,also Alberto has put up a early version of a program called WinSDR (same site as ARGO). Although it is inteded for I and Q inputs you can just put a single channel in....or in fact just put a wire antenna into the sound card and see all the Alpha stations and VLF signals....up to 48kHz if you have a 96K sampling sound card. A simple mixer a sig-geny and a few lash-up LP filters should enable you to fill in any gaps in your other receivers.
Cheers de ALan G3NYK
Re: Antenna
Posted by FRANK N3MUD on April 14, 2006 at 14:47:46.
In reply to Antenna posted by Art on March 15, 2006
THIS WILL SOUND A CRAZY,BUT I MARRIED THE COAX FROM MY RADIO SHACK DISCONE ANTENNA UP ON MY ROOF TO MY R75 AND I HEARD BEACONS I NEVER HEARD BEFORE.IF YOU CAN, TRY IT.NOT BAD FOR RESIDING IN PHILLY.73 & GOOD HUNTING Russian Alpha off air?
Posted by Jay Flynn on April 24, 2006 at 16:44:09.
From my location in Los Angeles, CA, I have regularly monitored the Russian ALPHA transmissions on 11.90/12.649/14.88 kilohertz. I have only heard one station on each frequency, which I presume is Komsomolsk in Asiatic Russia (the closest one to me).
Since 23 April 2006 0000Z, I have not heard the station on any of these frequencies.
Is it down for maintainence or repair? Are ALL ALPHA stations currently off air? Are these outages regularly scheduled and where might I find out more information?
Thank you. Re: Russian Alpha off air?
Jay
Posted by John Davis on April 24, 2006 at 17:48:08.
In reply to Russian Alpha off air? posted by Jay Flynn on April 24, 2006
It's pretty common for the Alpha system to be off the air. It basically only operates when there's enough money to pay the power bill.
Because the navigation technique upon which the system is based requires comparison of timing and phase between the individual signals, all of them will be down for a while.
It's rather surprising that they bother keeping it going at all, considering that there are so many better alternatives available, and that pilots cannot rely upon its consistent availability.
Re: Russian Alpha off air?
Posted by Jay Flynn on April 24, 2006 at 19:04:09.
In reply to Re: Russian Alpha off air? posted by John Davis on April 24, 2006
John =
Thanks for the info. I guess I had always managed to catch them when they were "flush" before.
I hope they had a party Sunday (their time) before they pulled the plug.
Will see if/when they return.
I agree, like the old Omega system, Alpha would be almost useless except as beacons for VLFers like me. But the Omega system was 95% reliable or better.
I have also noticed the BETA time signals are truncated - at least from RAB99 in the Far East. Their schedule is now just a five minute or so carrier on 20.5 kHz twice a day and nothing on the other four frequencies.
Jay Coming Back and a Question
Posted by Carl on April 24, 2006 at 21:56:21.
Now that I am pretty much retired and got the young 'uns all set up, I find I have the time to return to LF after years of inactivity. Found the gear stashed years ago, cleaned same,checked and good to go. Will get all joined up in a day or two.
Now the question: Is there any Part 15 operation on the F-M broadcast band. I have a couple of transmitters and was curious. There are LowFers, MedFers, and HiFers. Why not VeeHiFers??! Is it even legal? I think it's kind of like MedFer.
My primary interest, however, is in LF and below.
Thanks in advance. BTW: I am a Cave Dweller (Town House with the Dreaded Antenna rules). Gonna be fun!!
73 de Carl - K0BZV Melbourne, FL (Florida's Space Coast) Re: Coming Back and a Question
Posted by John Davis on April 25, 2006 at 02:35:17.
In reply to Coming Back and a Question posted by Carl on April 24, 2006
Hi Carl,
If you download the full FCC Part 15 Rules, a 392KB PDF document, you'll notice that the only provisions for FM band operation are in Section 15.239. It differs quite a bit from what was once permitted.
To be legal there nowadays, the device must keep all emissions within the 200kHz bandwidth of the channel upon which it operates, and it can only radiate a maximum field strength of 250µV/m at a distance of three meters. That's a very low field strength, and means you will pretty much only achieve line of sight propagation in the immediate neighborhood. There are no DX opportunities as with other Part 15 bands.
Also, there are no alternative provisions of such-and-so power into thus-and-such antenna for the FM band. At that low a signal level and that high a frequency, there are no reliable engineering rules of thumb to ensure limiting the field strength to the required value. Certification is generally only possible by actual measurement.
John
Re: Coming Back and a Question
Posted by Carl on April 27, 2006 at 04:37:34.
In reply to Re: Coming Back and a Question posted by John Davis on April 25, 2006
Thanks for the info. Looks to be a bit more trouble than it is worth. I believe I will be either a LowFer or a MedFer or maybe both. I will use the F-M for running the local Fire/Rescue information around the home. I thoroughly that facet of the radio hobby also. Now to see what is (or is not) on the MW band.
Once again, Thanks a bunch.
Carl - K0BZV (Melbourne, FL)
Re: Russian Alpha off air?
Posted by Alan G3NYK on April 28, 2006 at 18:57:25.
In reply to Russian Alpha off air? posted by Jay Flynn on April 24, 2006
Hi Jay A useful source to check the activity is the WWLL lightning sites which show a waterfall DC to 24kHz in almost real-time
http://webflash.ess.washington.edu/
is the main page. I use the one at Sheffield Univ in the UK at
http://togashef.sheffield.ac.uk/%7Esferix/vlf.png
I am sure you can find sites that hear your asiatic chain.
Cheers de Alan G3NYK Re: Russian Alpha off air?
Posted by Jay Flynn on April 29, 2006 at 11:29:13.
In reply to Re: Russian Alpha off air? posted by Alan G3NYK on April 28, 2006
Thank you, Alan! I will look at that.
It appears the Alpha that I monitor is back on after a week's absence. I caught it at 1400Z 29APR06 on all it's freqs. I will have to check what these sites hear on the BETA freqs.
Jay Alpha back on
Posted by Jay Flynn on April 29, 2006 at 11:31:07.
In reply to Russian Alpha off air? posted by Jay Flynn on April 24, 2006
I monitored the ALPHA station I can hear back on at 1400Z 29APR06.
Perhaps this was scheduled maintenance.
Jay
potrzebie