Fence Antenna
Posted by Frank Carson on November 02, 2002 at 20:51:02
I have a backyard that is fenced in with a chain-link fence. The shape is a square, with about 30 feet of the enclosed area the back of my house. Has anyone used such a thing as an antenna for LW/ELF type listening? Any thoughts? I thought this might make an interesting project this winter. Thanks!
Frank Carson
Broadcasting transmission via PLC-systems on telephone or powerlines?
Posted by Udo Maier on November 04, 2002 at 09:35:25
In which countries were or are broadcasting transmissions via PLC - systems on telephone or power lines in use? (I know from Switzerland, Germany and Norway)
Which frequencies were used for the transmission?
Are in some countries still such systems in use? If “yes”, where?
What are the disadvantages of these systems and why are most of them not in work any more?
Can they come again with modern techniques like DRM?
TH copy
Posted by Lloyd Chastant on November 04, 2002 at 16:39:33
Have been checking from time to time to see if TH was coming through and over the weekend had nice copy on TH at 189.5(a bit high from his posted)..As someone mentioned would be nice to see TH on QRSS...but guess we'll just have to continue with the cw copy HI!!
de Lloyd W3NF FM19MH P.S. I had no copy from DCH....
Re: TH copy
Posted by lloyd chastant on November 04, 2002 at 22:04:23
Th was coming in nice tonite(Monday) also.
new Tesla Technology website
Posted by George Trinkaus on November 05, 2002 at 12:33:40
See my new Tesla technology website at
teslapress.com
What is the true wireless? What is a magnetic amplifier? What is a third-generation Tesla coil?
This is a publisher's website augmented with readings and links regarding Tesla technology and magnetic amplifiers.
George Trinkaus author, Radio Tesla
Re: Broadcasting transmission via PLC-systems on telephone or powerlines?
Posted by John Davis on November 05, 2002 at 18:51:50
:: Which frequencies were used for the transmission? ::
I cannot answer comprehensively, because I am not sure of all the countries which used this technique. However, in general, they were common frequencies for which most people already had broadcast receivers.
:: Are in some countries still such systems in use? If “yes”, where? ::
I am not aware of any countries which use the method for general broadcasting to the public in modern times. However, the method is still used on many college campuses in the United States, and perhaps elsewhere in the world too. Its principal advantage in this application is the ability to limit coverage to a target area while not (it is hoped) interfering with regular broadcast services in the rest of the city.
:: What are the disadvantages of these systems and why are most of them not in work any more? ::
A single, centralized transmitting antenna is easier to maintain than the network of power couplers that would be needed to distribute RF evenly across a wide geographical area by electric or telephone lines. Uneven coverage was one significant shortcoming of the older systems, unless continual effort was expended as customers were added to the system. If a village could be served from a single telephone switching office, for instance, the system might be practical; otherwise it represented a lot of work for very little benefit compared to a "real" radio station.
In addition, uniform frequency response is difficult to maintain in such a system because of serious reflections arising from the power or telephone cables being poor transmission lines at RF. Wideband modes such as FM would not have been practical over a large territory--too much distortion would appear at some locations. Amplitude modulation, on the other hand, was very susceptible to hum and other electrical noises conducted along the lines with the signal. The end result was a rather low fidelity signal in some parts of the town.
Then, too, if a system used enough power to radiate more or less uniformly over a whole town, it also tended to radiate strongly enough to interfere with conventional radio stations at a distance. The power grid is an antenna whose radiation pattern is neither easy to characterize nor stable enough to use for frequency allocation purposes.
Thus, such systems are now deemed suitable only for distributing signals over very limited geographical areas. And, I imagine that some administrations prohibit their use entirely because of the difficulties they present for spectrum management.
:: Can they come again with modern techniques like DRM? ::
This is an interesting question. It is certainly true that DRM would improve the sound quality of signals broadcast over electric or telephone cables, and it might lower the RF power requirements enough to ease spectrum management concerns.
However, since attempts continue in some countries to use these conductors as "last mile" paths into homes for Internet access--sometimes with much interference to shortwave and AM broadcast listeners--I doubt that there will be much opportunity to transmit broadcast signals over those same wires.
For readers who are curious about DRM, this is a standard for digital audio broadcasting that can be used from longwave through shortwave frequencies. Find out more at:
www.drm.org
John
FAW copied in Minnesota
Posted by Roger Magnuson on November 06, 2002 at 08:16:01
Beacon FAW has been copied in Duluth, Minnesota, EN-36vt. I have been seeing FAW for several nights now. Yesterday a nice clear AW with the F a bit too fuzzy for a positive ID. This morning the full FAW came through. I've sent the screen capture to Chris. The distance is 1073.8 miles. Congats Chris, your beacon is working very well!! His freq is 185.1855
EIS TMO
Posted by lloyd chastant on November 06, 2002 at 09:49:16
Had very nice captures on EIS and TMO on QRSS30 and QRSS90 here in Maryland this morning..Hard to keep up with all these variations :):)
de Lloyd W3NF FM19MH
73 kHz Test
Posted by John Andrews (fwd) on November 06, 2002 at 14:47:52
Laurie Mayhead, G3AQC, will be beaconing on 72.401 kHz tonight from 2230 to 0700 UTC, in QRSS120 mode. Eastern U.S. listeners are encouraged to give this a try.
For some reason, I was the only one in the U.S. to hear him last November (W4DEX did later in the season), so it would be nice to have company this time.
John Andrews, W1TAG
Re: 73 kHz Test Nil
Posted by John Andrews, W1TAG on November 07, 2002 at 09:29:29
Reports from W1VD, W4DEX, WB3ANQ and W1TAG were all negative on the 11/6-7/02 test. W1VD and W1TAG both noted a weak signal approximately 0.1 Hz lower than G3AQC's 72.401 kHz frequency, but no ID was possible.
Laurie indicated that he might repeat the test in another week.
John Andrews, W1TAG
Re: 73 kHz Test Nil
Posted by Laurie Mayhead (fwd) on November 08, 2002 at 18:23:33
Subj: LF: Re. 73kHz Transatlantic Date: 11/8/02 5:19:06 AM Eastern Standard Time From: laurie@g3aqc.freeserve.co.uk (Laurie Mayhead)
To: rsgb_lf_group@blacksheep.org
Thanks to John and Dex also W1VD and WB3ANQ for looking for my signals on 6/7 Nov.
The Kp index was rather high that night (i.e. 3-4) and in my experience this is too high. Our 2001 crossing was made 15 days after an X class flare and following CME-but the index was low about 1/2.
There was an X flare on 31 Oct but no earth facing CME.
If the index drops in the next day or two I will try again. If not the next opportunity may be around 14 Nov. There is no doubt that a successful crossing requires a rare combination of events Hi.
73 Laurie.
DDH47 received on 147.3 QRSS3
Posted by John Andrews, W1TAG on November 08, 2002 at 19:27:42
The German DDH47 test mentioned on the LWCA home page is underway this evening. I have had partial copy of the 2345 and 0015 UTC QRSS3 tests. At this point, I can hear the CW, but there's too much noise to copy by ear.
John Andrews, W1TAG
Re: DDH47 received on 147.3 QRSS3
Posted by lloyd chastant on November 09, 2002 at 06:37:46
I have several nice captures on the QRSS3 transmissions here in Maryland between 0145z and 0345z that I monitored.
de Lloyd W3NF FM19MH
Re: DDH47 received on 147.3 QRSS3 + CW!
Posted by John Andrews, W1TAG on November 09, 2002 at 08:25:35
Conditions got better as the evening went on. I had good CW copy around 0100, and much better copy in the 0200-0300 hour. Didn't even have to concentrate! At that point they were looking for 80 meter cross-band contacts, and knowing the modest nature of my setup, I didn't try.
The DDH47 test guys have asked that email reports be sent to:
Juergen.Gerpott@dwd.de
John Andrews, W1TAG
Re: DDH47 received on 147.3
Posted by Denis Cote (fwd) on November 09, 2002 at 12:41:31
Booming in here on 147.3 KHz at 0339Z with audible CW ID. QRSS3 copy very solid.
RX Set up: IC-R75A and 7' hexagonal oop aimed E/W.
Denis
Re: DDH47 received on 147.3
Posted by Jay Rusgrove (fwd) on November 09, 2002 at 12:43:03
Friday, November 08, 2002 11:10 PM
Armchair copy here also.
BTW, LowFER VD is on and off some evenings while I'm listening but is usually back on for the overnight and during the day. Will probably be pulling the plug for a week or so soon for more receiving tests.
Jay Rusgrove, W1VD
73kHz Revisited-Tonight!
Posted by John Davis on November 09, 2002 at 13:59:16
Given last night's good propagation, two UK stations are going to make a transatlantic attempt around 72.4 kHz in QRSS120 mode (dots of 120 seconds) tonight, Saturday 9 November. Get details in the Top News section at LWCA.org.
John
Re: 73kHz Revisited! It Works!
Posted by John Andrews, W1TAG on November 09, 2002 at 18:51:12
I have successfully copied an "AQC" from G3AQC on 72400.95 Hz, as of 2340 UTC. Signal strength looks good, hopefully the copy will continue. No sign yet of G3LDO on 72.400.
John Andrews, W1TAG
73kHz Transatlantic Summary
Posted by John Andrews on November 10, 2002 at 01:14:27
G3AQC and G3LDO were both successfully copied on 72.4 kHz tonight here in Holden, MA. The AQC signal was visible before 6 PM EST, but LDO didn't show up until later.
G3AQC was first seen at 72400.95 Hz, and he slowly drifted up to about 72401.00. Here is the best shot of the "AQC":
http://webpages.charter.net/w1tag/files/AQC-8.jpg
G3LDO was first observed around 72400.3 Hz, and ended here around 72400.18. The "droop" can be seen in this shot, which has an extra "O" at the beginning:
http://webpages.charter.net/w1tag/files/OLDO.jpg
Watch for further test announcements, as we are trying to determine the conditions that make this path work. As of this writing, no other U.S. reports have been received.
John Andrews, W1TAG FN42ch
Re: 73kHz Transatlantic Summary
Posted by lloyd chastant on November 10, 2002 at 08:32:22
I monitored for several hours last nite and did not see any noticeable signals coming through here in Maryland.
de Lloyd W3NF FM19MH
RM Copied in MA
Posted by John Andrews on November 10, 2002 at 09:03:55
RM was visible here in central MA this morning around sunrise. I believe this was the first time that I've seen Roger's signal.
John Andrews, W1TAG
Re: DDH47 received on 147.3
Posted by Dexter McIntyre W4DEX (fwd) on November 10, 2002 at 20:59:13
Sunday, November 10, 2002 8:23 PM
Sorry for the late report on the DDH47 test. I was away from home for the weekend. I have uploaded Argo screen shots and a wav file of the signal I received during the test. Thanks for the effort.
http://www.gostanly.com/w4dex/DDH47/
Dexter, W4DEX
Lowfer RMQ?
Posted by Paul Stroud on November 11, 2002 at 10:49:07
While monitoring NC just below 185.3, I noticed RMQ abt 3 hz higher in frequency. Who is RMQ?
tnx, Paul AA4XX nr. Raleigh, NC
Re: Guided Wave LF
Posted by Alan Melia G3NYK on November 11, 2002 at 19:36:02
Hi Mitch, I'm a refugee from another LF group. Hi.
The article you quote is beginning to show its age now, and I suspect was written when most of the data was collected before the 1930s. It is generally agreed now that guided wave (sometimes called "wavegude mode") at LF only really affects frequencies below about 30kHz and occasionally up to about 50kHz. Propagation at frequencies above this are completely different, up to about your lowfer band, which probably lies on another "boundary". Between 50kHz and about 150kHz it is thought the wave is reflected off the D-layer in daytime and the underside of the E-layer at night. True as the author suggest the "fading" is slow, but only during quiet conditions. At the solar max and particularly in the fall when there are lots of geomagnetic storms there is a lot of rapid (10minute) fading (destructive interference) between multiple paths. I have analysed a lot of data on a 2000km path collected by Brian CT1DRP and daily signal plots over the last year are on my web site together with the text of a lecture I gave at the RSGB HF Convention last year. The "trigger" (to Laurie G3AQC) for the second 73kHz test was derived from this experience of solar effects on LF propagation.
73 de Alan G3NYK http://www.alan.melia.btinternet.co.uk
Kenwood TS-570D below BCB?
Posted by Henry Kolesnik on November 12, 2002 at 08:53:34
Has anyone tried to see how the TS-570 receives below 500 kHz? The digital dial indicates all the way down to 30 kHz but the one I have is all but deaf. I wonder if it needs a mod, pre-amp, or just doesn't have the circuitry? I beleive this radio has a filter or attentuator for the BCB and I'm going to find the mod to take it out.
tnx hank wd5jfr
CO copied in MN
Posted by Lyle Koehler on November 13, 2002 at 17:17:28
CO was visible here from 0445 to 0700 local time. The frequency was 187.5927 kHz, and the distance is about 775 miles. Argo screenshot at:
http://www.qsl.net/k0lr/CO_11-13.jpg
Congratulations to Doug!
Lowfer conditions
Posted by Lloyd Chastant on November 14, 2002 at 09:39:12
For several days past there was a point where I thought the antenna had come down--couldn't even see a trace of lowfers...But last evening I took a look at 185.3 area and there was IP,VD.WA(nice signal) and NC...and XSR(166.5) was coming in with a big signal..So if anyone knows what kicks off the propagation it would be nice to know---Only thing I can see is a small change in temperatures..but guess its still early in the season...OH..the European AM broadcasters on 153,163 and 173 were also coming in nice..all this around 8PM Maryland time..
de Lloyd W3NF
Re: Lowfer conditions
Posted by John Andrews on November 14, 2002 at 10:13:47
Lloyd,
It may have had a lot to do with weather condx here on the east coast this week. It was very noisy for a few nights.
I've been tuning around the AM broadcast band on my way home from work (5:00 - 5:30 PM EST). Last night, 670 (used to be WMAQ) from Chicago was solid copy, which is unusual at that time. I'm going to watch that as an indicator.
John Andrews
Re: Lowfer conditions
Posted by Larry Putman on November 14, 2002 at 11:14:43
Same thing here Lloyd!
It was like someone thru a switch and suddenly I had good strong signals from NC, WA, VD and another station just below NC with a key down for about an hour.
I don't know what is was but I am glad the conditions are back to normal again!
73
Larry WB3ANQ
Re: Lowfer conditions
Posted by Jacques d'Avignon on November 14, 2002 at 15:40:48
Is it possible that the noise was masking the signals? I know that up here, the noise levels have been extremely high and some NDB signals that were received regularly were just not there.
Jacques
Re: Kenwood TS-570D below BCB?
Posted by Peter on November 14, 2002 at 17:45:20
Hank,
Before you wack into that Kenwood for sub-BC band reception, might I suggest first to try a dedicated LF pre-amp in the feed line from a good LF ant. Such an ant. might be the popular box loop or an e-field probe type. You, others can find that info right here in the tech section of the LWCA site.
Briefly and bottom-line, E-probes should be mounted higher than near-by objects, whereas, a 6-8 foot loop can perform well at near ground level. Ha, these are merely generalities, however.
G L, Peter
Re: Lowfer conditions
Posted by Lewis on November 14, 2002 at 21:14:14
Same here in the South, a front passed through here a couple days ago, and just tonight it has quieted down NC coming through at 5:00 PM central time, real strong and at 8:oo PM started seeing others around 185.300.
Haven't Id. them yet.
Lewis IP new freq. 185.30285
Re: Kenwood TS-570D below BCB?
Posted by Henry Kolesnik on November 15, 2002 at 04:19:16
This site put up by the designer has some mods, I moved the BC ATT from NORM to DX and now the 570 hears fine down to 50kHz, that's as low as my sig gen goes. Now to listen.
http://www11.cds.ne.jp/~cqdx/eng1.htm
Re: FAW copied in Minnesota
Posted by Chris Spencer on November 15, 2002 at 18:46:31
FAW has been changed from QRSS60 to QRSS30 As of Nov 15, 2002. I hope this makes it easier to get a full ID.
Chris Spencer WB7FAW
[Hifer] GA in Norway November 16
Posted by Steinar Aanesland on November 16, 2002 at 07:21:18
Look at http://www.aanesland.com
Steinar
72 kHz Test Saturday Night
Posted by John Andrews, W1TAG on November 16, 2002 at 15:10:01
Laurie, G3AQC, will again be beaconing tonight on 72.401 kHz in QRSS120 mode, starting around 2300 UTC (16 Nov). Reports would be appreciated.
John Andrews, W1TAG
Re: 72 kHz Test Saturday Night
Posted by lloyd chastant on November 17, 2002 at 06:49:05
Listened for several hours last nite and did not have any capture results..just nice background noise..
de Lloyd W3NF FM19MH
"AQC" on 72.401kHz in Norway last night
Posted by Steinar Aanesland on November 17, 2002 at 09:00:40
I know this is a transatlantic attempt, but I hope you will accept my report. See www.aanesland.com
Steinar
Re: 72 kHz Test Saturday Night
Posted by John Andrews on November 17, 2002 at 09:36:35
Some fragments of G3AQC and G3LDO were visible here in central Mass. last night. The signals were identifiable only by their frequency, however. A storm on the eastern U.S. coast was producing a lot of static. Propagation conditions were likely pretty good, though.
John Andrews, W1TAG
Argo V1 build 130 released
Posted by Alberto di Bene, I2PHD on November 17, 2002 at 12:38:59
Hi all
I have just uploaded on the weaksignals site Version 1, build 130 of Argo. From the readme file :
V1, build 130 (Nov. 17th, 2002)
- NDB mode added
- Wave file read/write added
- Screen capture dialog rewritten (now should work as intended).
- Added the computation of the capture timing to specify for a screenfull.
- Corrected a few errors, one of which could cause random abnormal terminations.
- Ported to V6 of the C++Builder compiler
As usual, it is freely downloadable from :
http://www.weaksignals.com
Please read the readme file for information on the new functions.
Comments and bug reports welcome.
73 Alberto I2PHD
When you fix one thing...
Posted by Alberto di Bene I2PHD on November 17, 2002 at 17:25:42
.... usually you break another one....
This is what has just happened with build 130 of Argo.
If you find yourself unable to reload your favorite settings,
just saved under a given name, please download again build 130 of Argo from http://www.weaksignals.com I made a small silly error. Hope it's the only one.
73 Alberto I2PHD
DRM for amateurs?
Posted by Udo Maier on November 17, 2002 at 18:19:04
What equipment do I need to decode DRM - signals? Is this possible with my PC soundcard when I receive the PC to the audio output of an AM receiver with a special software? If yes, which software is necessary and where can I get it?
Do some LOWFERS experimentators and radio amateurs also use DRM for experimental purposes? In which countries on whch bands may radio amateurs transmit in DRM like modes?
Re: DRM for amateurs?
Posted by John Davis on November 17, 2002 at 19:56:42
DRM is not yet used in the amateur service anywhere, so far as I can tell. It has three major disadvantages:
(1) The occupied bandwidth is nearly the same as an AM signal of comparable frequency response.
(2) The encoder is neither cheap nor easy to build.
(3) Decoding the signal requires access before the AM detector in a receiver, so it is not likely that there will ever be PC-soundcard based software to do the job.
Someone might be able to program a DSP board to work with an IF sample from the receiver, although I suspect in the long run that most experimenters might simply use application-specific decoder ICs when they become available.
John
Copy Hifer GA in Texas
Posted by Tony Levstik on November 18, 2002 at 09:03:31
Got Good copy of GA 13.55545Mhz in Sherman Texas.
at 00:06 11/17/02
Here is the link to the jpg screen capture.
http://home.att.net/~levstik1/hifer.jpg
Tony Levstik levstik1@worldnet.att.net
Re: "AQC" on 72.401kHz in Norway last night
Posted by Laurie Mayhead on November 19, 2002 at 04:45:30
Many thanks Steiner for your report,all reports interesting and welcome.
73 Laurie
185.3 tonite
Posted by lloyd chastant on November 19, 2002 at 23:09:00
Took a quick look and WA was coming in like gangbusters and had a carrier type signal below WA and just below the carrier there was another signal -not sure of ID yet.Maybe this is all due to the new ARGO release???:-)
de Lloyd W3NF
R capture in Maryland
Posted by lloyd chastant on November 20, 2002 at 12:31:35
Had a nice Argo capture on Bob's R on 166.55 last nite.
de Lloyd W3NF FM19MH
IP in Maryland
Posted by lloyd chastant on November 22, 2002 at 07:44:45
Had a light trace on IP last nite(11PM local) but this morning had a nice capture with a fairly nice signal de Lloyd W3NF FM19MH
KPH MF Transmission on SUNDAY
Posted by Richard Dillman on November 22, 2002 at 12:38:12
Subj: [MF Monitors] KPH MF Transmission on SUNDAY Date: 11/21/02 9:21:31 PM Eastern Standard Time From: ddillman@igc.org (Richard Dillman)
To: MF_Monitors@yahoogroups.com
Because of other requirements we will be at the KPH transmitter site on Sunday, 24 November this weekend.
As usual transmissions will begin at about 1500 PST (2300 GMT) and continue until about 1700 PST (0100 GMT 25 November).
There will be a brief announcement on 500kc - perhaps more than once during the transmission - with the actual text transmitted on 426kc.
The text will consist of the ARA Free Press and Pacific weather. Transmission speed will be about 25wpm.
VY 73,
RD
======================================
New LW Amateur Allocation in Europe?
Posted by Keith Ballinger on November 22, 2002 at 14:17:07
An interesting statement from the Radio Society of Great Britain's report on the recent IARU conference, quote:
"An RSGB proposal to work for an amateur allocation around 500kHz was agreed by Conference...."
There are no further details in the RSGB report. Any European readers of this page have any comments?
Regards,
Keith VA3QF Ottawa - Canada
back issues of Lowdown available?
Posted by R Harrison on November 24, 2002 at 03:12:45
If I join LWCA will I be able to order copies of issues that were published earlier this year?
Reception report
Posted by Roger Magnuson on November 24, 2002 at 11:26:49
Stations copied on 185.3 last night are: WE, NC, and IP. When NC faded to nearly gone, IP came up to its best (5AM)
WGU-20 Recordings
Posted by Les Rayburn on November 24, 2002 at 11:33:25
I'm looking for any recordings made from station WGU-20,
which broadcast during the 1980's. I've got several short clips now, such as "This is radio station WGU0-20. The time is 12:26 exactly".
But I'm looking for longer recordings of the creepy,
emergency testing type stuff. Happy to trade radio related items, or even pay cash for any member who has recordings to share.
Can someone also please post this to the Lowdown? I'm desperate to get these.
Les Rayburn, N1LF
4919 Cox Cove Helena, AL 35080
TAG in Jason Mode
Posted by John Andrews on November 24, 2002 at 17:14:04
TAG is now running in Jason mode on 185.800 kHz.
JASON V. 0.94 may be found at:
http://www.weaksignals.com/
John Andrews
Linear-loaded 3 meter MedFER antenna? (links)
Posted by J. Jason Wentworth on November 25, 2002 at 09:46:01
Hello All,
I found two web sites about linear-loaded short vertical antennas. Unlike loading coils, the linear loading elements *do* radiate signal while also raising the feedpoint impedance of physically-short antennas. This linear-loaded antenna ^ http://www.qsl.net/pa3hbb/ll.htm ^ also has a capacitance hat to further lower its self-resonant frequency. The Meander Antenna ^ http://www.qsl.net/on7yd/136ant.htm#Meander ^ is an extreme form of a linear-loaded antenna. Conceivably, it could permit a 1/4 wavelength MedFER antenna to be only 3 meters long! Have any of you ever experimented with linear-loaded MedFER antennas? -- Jason
Re: Linear-loaded 3 meter MedFER antenna? (links)
Posted by John Davis on November 25, 2002 at 17:12:26
Sorry to be a spoilsport, but neither of these antenna types will scale correctly to 3 meters length at MedFER frequencies.
The Meander will be roughly twice the permissible length, while the folded-coupler antenna (I don't see where he comes up with the term "linear loading") will have to be substantially LARGER than the 80 meter equivalent...way, way over 3m.
Incidentally, I might add, it's not correct to say a loading coil does not radiate. It does...equivalent to a piece of wire the same length as the straight-line distance from terminal to terminal of the coil.
A more productive approach would be the helical antenna, where the conductor runs the full length of the antenna. Again, the radiating length is the same as a three meter straight wire, but the inductance (especially combined with a top hat) distributes the current more linearly, for a greater effective height than a wire or pipe alone.
John
Re: Linear-loaded 3 meter MedFER antenna? (links)
Posted by J. Jason Wentworth on November 25, 2002 at 18:34:17
John Davis wrote:
^The Meander will be roughly twice the permissible length...^
How does one determine the "straightened" length, fold width, and minimum fold height of a Meander Antenna for a given frequency? Also, is there a "best" point to connect the feed line? The drawing on the web site seems to imply an arbitrary connection point. The Meander Antenna looks like it might make a good Long Wave receiving antenna that could be stapled around a wooden perimeter fence. -- Jason
Re: Linear-loaded 3 meter MedFER antenna? (links)
Posted by Lyle Koehler on November 25, 2002 at 19:15:09
A few years ago, there was a discussion on the rec.radio.amateur.antenna newsgroup about a paper that someone had presented, describing a meander dipole which had spectacular efficiency and bandwidth in a very compact size. I seem to remember that it was about 2 meters long, and was designed for the 20 meter band. I tried modeling it, and one of the other guys actually built and tested one. Needless to say, it fell far short of the claims. A conventional pair of back-to-back whips with loading coils would have worked better. A search on dejanews for the word "meander" might reveal some other discussions on the subject -- I haven't subscribed to the newsgroups for a long time. Linear loading is not new, and has often been used successfully to achieve _some_ shortening of element sizes. The popular Force 5 series of ham antennas, for example, has a few models with linear loading. But if you try to compress a meander antenna to 1/100 of a wavelength or shorter in overall length, I'm afraid you will be very disappointed with the results.
Re: Linear-loaded 3 meter MedFER antenna?
Posted by John Davis on November 25, 2002 at 23:11:57
>> ^The Meander will be roughly twice the permissible length...^
> How does one determine the "straightened" length, fold
> width, and minimum fold height of a Meander Antenna
> for a given frequency?
Maybe some of those who play with them will share their formulas with us, though I suspect one would want to find the original IEEE Transactions article in an engineering library. My conclusion that it will run just under 6 meters in length is a simple scaling of the 64m size cited by Rik on the Web page by the ratio of the wavelengths at 1600kHz versus 136kHz.
The connection point is not arbitrary, but is selected for impedance match.
John
Re: Linear-loaded 3 meter MedFER antenna?
Posted by J. Jason Wentworth on November 26, 2002 at 07:29:48
I thank you all for the information. Since the common series-fed 3 meter MedFER vertical antennas are <1% efficient, if a Meander Antenna would be 2% - 3% efficient, it would be worth a try. -- Jason
Re: Linear-loaded 3 meter MedFER antenna?
Posted by John Davis on November 26, 2002 at 23:08:17
Jason writes: "Since the common series-fed 3 meter MedFER vertical antennas are <1% efficient, if a Meander Antenna would be 2% - 3% efficient, it would be worth a try."
Probably would--IF that were the case. Scaled down to a legal 3 meters and used at MedFER frequencies, though, there is no reason to assume they would be that efficient.
Reduced to such a tiny fraction of a wavelength, every antenna tends toward about the same poor efficiency for a given ground conductivity and quality of construction. This should not be surprising, as the radiated field strength of any electrically small antenna is the vector sum of fields from all the currents flowing in its elements. Three meters is 3 meters, after all.
If one takes measures to make the current as uniform as possible in that 3m --i.e., toploading-- one can increase the effective height and the radiation resistance, within reason. Other losses creep in, and/or you have to abandon the legal limitations to offset those losses (obviously something we don't recommend here). The Meander, if scaled this small, requires many folds of rather small wire to achieve reasonable impedance; but this translates directly to wire resistance losses, and more than stretches the notion of a single element not exceeding three meters in length. One then has to fall back on the Ken Cornell "anything that can fit in an imaginary cylinder of 3m X 3m dimensions" interpretation; which, it should be noted, is a concept that ANARC had requested on behalf of the LWCA, but the FCC declined to formally implement in the Rules at the last major Part 15 revision.
One can also choose antenna types to minimize environmental losses, such as picking a loop over a vertical when lossy obstructions are nearby. Not really any more efficient under ideal conditions, but definitely less excessively INefficient in certain real-world situations. Yet here again, one can only go so far without having to invoke a Cornell cylinder or other creative interpretation of the legal limits.
John
LF Beacon "RB" on the Air
Posted by Robert Bicking, W9RB on November 27, 2002 at 17:59:14
RB is back on from midnite to 8 am, CST (or 600Z to 1400Z). using QRSS5, at 186.92 kHz. Reception reports will be QSL'd. 73, W9RB.
TAG Running WOLF
Posted by John Andrews on November 27, 2002 at 20:37:21
TAG is in WOLF mode on 185.800 kHz.
TAG Off
Posted by John Andrews on November 28, 2002 at 20:04:41
It is.
John A.
Re: LF Beacon "RB" on the Air
Posted by Lewis Denton on November 29, 2002 at 16:56:22
Where are you located ? what kind of antenna ?
I am in south Ms. will give a listen Lewis IP@185.3028 Qrss30
RB
Posted by Roger Magnuson on November 30, 2002 at 11:33:30
Beacon RB was copied in Duluth, MN. Bob's signal faded in and out during the night but was mostly in. The last trace was at 8:16 AM, well into daylight. Nice signal Bob and good to see you.
Re: LW Loop
Posted by Ray Soifer, W2RS on November 30, 2002 at 17:46:13
Rich and Jacques,
Wellbrook has a new model out, the LFL-1010, which is specifically made for LF coverage. I've just put one up here, and will post an evaluation later. So far it seems good, though.
You can see more about it on their Web site, http://www.wellbrook.uk.com.
73,
Ray, W2RS
www.lwca.org
potrzebie