Re: HiFer Grabber VK2XV
Tom, Steve's grabber is at www.qsl.net/vk2xv/. Unfortunately, it is off as of this moment.
Best of luck on your transpacific journey when the grabber returns!
John
Re: Software Defined Radio
Posted by Douglas Williams on September 01, 2012 at 13:19:19.
In reply to Re: Software Defined Radio posted by Douglas Williams on August 30, 2012
Well, I found another possibility, the QS1R.
http://qs1r.wikispaces.com/
The e-ham.net reviews seem to be overall very positive.
Frequency range is 10kHz - 62MHz.
Claimed frequency accuracy is 1ppm, which should be sufficient for QRSS reception.
Claimed MDS is -121dBm (frequency not specified). Would be interesting to see the sensitivity claims at VLF/LF.
One thing I like is it has an audio amp, which is suitable for driving headphones or plugging into your computer's Line In jack. This should make it easy to interface with Argo or Spectrum Lab.
Re: Software Defined Radio
Posted by Douglas Williams on September 01, 2012 at 17:21:16.
In reply to Re: Software Defined Radio posted by Douglas Williams on September 01, 2012
Found the QST review of the QS1R. They did measure sensitivity down to 137 kHz.
From the article:
0.505 MHz: -117 dBm
0.137 MHz: -114 dBm
Also interesting:
"Spurious free dynamic range": 100 dB
I am starting to think the QS1R is the way to go for an "LF enthusiast" SDR. The code is all open source, so the purchaser is not locked into some proprietary software.
+/- 1ppm frequency accuracy should be good enough for QRSS60, or probably even QRSS120. If this isn't good enough, however, the unit has an input jack for an external high stability frequency reference. I have recently seen 10 MHz rubidium frequency standards on eBay for less than $200.
Now to convince the wife to let me spend some money....
NDB
Posted by Robert on September 02, 2012 at 03:33:12.
Tonight Sept first at 340.09khz heard NDB "SG" in slow cw repeating. It seems to be a small Taiwan airport but they list themselves at 310 Khz. Time was 9:16PM Mountain daylight time.
Re: Software Defined Radio
Posted by Lee on September 02, 2012 at 03:41:53.
In reply to Re: Software Defined Radio posted by Douglas Williams on September 01, 2012
http://qs1r.wikispaces.com/
Very cool. I want one.
Re: NDB
Posted by John Andrews, W1TAG on September 02, 2012 at 12:32:28.
In reply to NDB posted by Robert on September 02, 2012
Robert,
The NDB database at http://www.classaxe.com/dx/ndb/rna/ shows SG as being on 341 kHz in Santa Fe, NM (DM65wn). It appears to be about 5 miles NE of the Santa Fe municipal airport.
John, W1TAG
Former NDB SC Stockton, CA
Posted by Paul on September 02, 2012 at 14:37:11.
When they decomission an NDB, they mean business.
Was around SE Stockton the other day and decided to take a drive by the site where SC (271 kc.) was located for a look.
Not only is everything, including the building, gone.. There are already rows of grapevines planted and growing over the ground previously inside the (now missing) perimeter fence. It is as if it never existed.
Makes me wonder if they ripped out the radials too. If I didn't visit the site several times previously to know exactly where it was, there is no way one could ever know that LW signals once radiated from that spot.
Used to look like this-
http://t3.gstatic.com/images?q=tbn:ANd9GcRlURnv__6p8YLdVhiwa__EL-awmYdHStVaLDGKBDbTrGYaMm4i&t=1
http://t0.gstatic.com/images?q=tbn:ANd9GcTAijU6smqM4JhURW7ApViU-1baIKLPG5rQFxDjTZYRsnorqpaO&t=1
Re: New Lowfer Transmiter/Loading Coil
Posted by John Hamer on September 03, 2012 at 01:30:23.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by John Hamer on August 27, 2012
I finished my antenna today and concreted the insulator base and guy wire anchors. I'm having some friends over next weekend to help me lift the mast. Then I'll just be down to tuning. Should be on the air soon!
Beacon BR off-air due to Hurricane Isaac
Posted by Darwin Long on September 03, 2012 at 06:06:03.
BR 185.585kHz is now OTA due to complete structural failure of the antenna tower during Hurricane Isaac. Wind gusts exceeded 110mph at times for over 5 hours as the eye passed over and then became stationary just offshore, causing the lower two sections and buckle from fatigue, snapping the guy lines. A date of return to the air is not yet known.
-Darwin Long
Re: Beacon BR off-air due to Hurricane Isaac
Posted by Douglas Williams on September 03, 2012 at 11:30:27.
In reply to Beacon BR off-air due to Hurricane Isaac posted by Darwin Long on September 03, 2012
Wow, sorry to hear that, Darwin. Hope the antenna was the only damage you suffered....
Re: Beacon BR off-air due to Hurricane Isaac
Posted by Garry, K3SIW on September 03, 2012 at 11:44:46.
In reply to Beacon BR off-air due to Hurricane Isaac posted by Darwin Long on September 03, 2012
Very sorry to hear lowfer BR is down for the moment Darwin. It's been a great beacon. Hope you can get it QRV by winter when good/quiet propagation returns.
73, Garry, K3SIW, EN52ta, Elgin, IL
Beacon BR in Buras off air
Posted by EdWSlidell,LA on September 03, 2012 at 14:58:32.
In reply to Beacon BR off-air due to Hurricane Isaac posted by Darwin Long on September 03, 2012
Hello Darwin and all. Along with Gary and Douglas, hope you are OK, and any damage was minimal. Don't know if you are in the flood protection area there in Buras. When you mentioned "BR", I was thinking at first of the Baton Rouge beacon( "BT" ) on ~284KHz, but I checked the frequency, and it is still on the air. However, the New Orleans Airport beacon (" MS " Moisant) on ~338KHz is not. Guess the flooding along the eastern side of the Bonne Carre spillway was too much, or the winds got it. The general LF/MF frequency range seem quieter than normal for beacons. Here in Slidell all is still OK--the water stopped rising about 2 feet below the house, and all the trees fell the right way. The 143 ft. ENE longwire survived, which is amazing for #17 aluminum Fishock fence wire suspended between trees. Looks like the remnants of the storm are still creating problems for the folks to the north and east. Ed WSlidell,LA EM50cg
Re: New Lowfer Transmiter/Loading Coil
Posted by Douglas Williams on September 03, 2012 at 15:24:10.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by John Hamer on September 03, 2012
Curious what you used for an insulator base?
TAG Freq/Mode Change
Posted by John Andrews, W1TAG on September 03, 2012 at 20:33:59.
Lowfer beacon TAG in Raymond, ME will be off the air this week, and will return as a QRSS30 beacon on 185.297 kHz on 9 September. TAG has run for the last four years in WOLF mode on 185.800 kHz, and a for a few years before on 185.297/QRSS30. The WOLF beacon has been useful to a handful of listeners, but the QRSS30 slot in the "watering hole" should be of more general interest. Only the microcontroller program is being changed, so WOLF remains a later possibility.
John Andrews, W1TAG
Re: New Lowfer Transmiter/Loading Coil
Posted by Pat Bunn on September 04, 2012 at 13:44:02.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by Douglas Williams on September 03, 2012
I am in the process of building a 500 khz vertical with capacitive top loading. I hope to have a beacon at 497.0 kHz up in a few weeks. Initial power will be about 100 watts.
I was given three 15KV station insulators about 20 years ago by a friend who worked for a power contractor. They have bolt circle mounts top and bottom. I plan to use one on my 500 kHz antenna. It should work well and I'd hate to think what one would cost nowdays.
Pat Re: New Lowfer Transmiter/Loading Coil
N4LTA, WG2XCT
Posted by John Hamer on September 04, 2012 at 16:18:57.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by Douglas Williams on September 03, 2012
Im planning on using a short piece of pvc. I might machine something at work. We have some solid plastic bar at work.
Re: New Lowfer Transmiter/Loading Coil
Posted by Douglas Williams on September 04, 2012 at 20:29:11.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by John Hamer on September 04, 2012
Or perhaps a wine bottle cemented in the ground, with a short piece of PVC between the bottle and the bottom of the antenna. Of course, you must drink the wine first.
In the old days it was a soda bottle, but those are all plastic now.
Re: Software Defined Radio
Posted by Douglas Williams on September 04, 2012 at 21:02:44.
In reply to Re: Software Defined Radio posted by Douglas Williams on September 01, 2012
After further investigation, I am not all that enamored by the QS1R as a VLF/LF receiver.
The external frequency reference must be 125 MHz for optimum performcnce. Also, I had a couple of owners comment on the lack of sensitivity in the VLF range.
I decided to go ahead and take the plunge on a Winradio Excalibur Pro. I'll report back after I have used it for two or three months, and the LF DX season is well underway.
Re: Beacon BR off-air due to Hurricane Isaac
Posted by Darwin Long on September 04, 2012 at 23:14:16.
In reply to Re: Beacon BR off-air due to Hurricane Isaac posted by Douglas Williams on September 03, 2012
Thanks guys!
The only damage to my home was a few pieces of siding and a little water that blew through the front door warping a few Pergo floor panels - can fix that stuff in a weekend. Most others in my neighborhood were not so lucky - losing entire roofs or walls, or flooding under several feet of water. There will likely be no power at my home for a number of weeks, and scheduled convoys are the only way to get into and out of the neighborhood now (2.5 hour journey out to Buras/Boothville). Since I work in New Orleans (at the Audubon Aquarium), I'm temporarily staying downtown with my wife until the utilities are restored - most of the wood power poles were completely down.
I removed the transmitter and loading coil from the doghouse (that blew across the yard) before evacuating ahead of the storm, anticipating this might happen. Will try to get something up again before winter, though. Guy anchors, ground, tower base, power line, and doghouse are all still intact.
-Darwin
Re: Beacon BR in Buras off air
Posted by Darwin Long on September 04, 2012 at 23:21:56.
In reply to Beacon BR in Buras off air posted by EdWSlidell,LA on September 03, 2012
Glad to hear that you made it though OK too, Ed! I know some flooding was going on around Slidell, and hopefully that drains quickly for you guys.
In Boothville, with no power around, the band is FAR quieter. Large sections of some really noisy, old, arcy powerlines along Hwy 23 that gave me grief during listening were knocked flat down, so maybe (at least for listening), this might be a blessing in disguise if Entergy puts up some new hardware!
I also noted 338 MS off after the storm - major amount of flooding out that way.
Take care!
-Darwin
Re: New Lowfer Transmiter/Loading Coil
Posted by John Hamer on September 05, 2012 at 21:04:30.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by Douglas Williams on September 04, 2012
yeah, I don't have a simple way to use glass right now, I can change it later. I found some kind of hard high temperature scrap plastic that is supposed to be a good insulator. I am not sure of its dielectric properties but it will do for now.
Re: New Lowfer Transmiter/Loading Coil
Posted by John Davis on September 06, 2012 at 03:51:15.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by John Hamer on September 05, 2012
John. something you might want to consider in your insulator design is a shroud of some sort, to help extend the creep length of the insulator.
For anyone not familiar, the strike length of an insulator is the shortest direct air path a spark could jump from one end of the insulator to the other, while the creep length is the path any leakage currents would have to trace along the physical surface of the insulator to get to the other end. That's one reason why high voltage insulators are ribbed, and/or have a mushroom shape or other overhang built in. The strike length remains approximately the physical length of the insulator plus half its diameter, but the creep path can be made quite a bit longer than the strike length. That reduces the losses arising from dust and moisture.
Here's how I did my current base insulator, described in the March 2012 issue of The LOWDOWN. I don't necessarily recommend this exact approach, which merely happened to fit my own circumstances at the time. The significant feature to note is the shroud, which adds almost 10 inches to the creep path, over and above the length of the PVC pipe standing above ground.
The main circumstance was that I already had a length of 1.25" Schedule 40 PVC pipe marking the location I had surveyed for the antenna. It started out somewhere between 4 and 5 feet long, and over the course of a year and a half, I had managed to drive all but one foot of it into the soft ground. It wasn't going to come back out! A number of other insulator designs had proven impractical, so I decided to incorporate what I already had in place.
I drilled a 4" PVC end cap to just slip over the 1.25" pipe, poured some epoxy inside the pipe to seal out ground water, and epoxied the end cap at ground level to stabilize the base somewhat when the soil gets soggy. Since the insulator is supporting the weight of 40 feet of steel pole, plus the downward thrust of guy wires, and will also have to endure quite a bit of vibration in wind, I made the main load bearing element a pice of 2" Sched 40 pipe, cut to exactly the same length as the 1.25" extends above the base cap (length y in the drawing; in my case, 12 inches, but longer would have been better). A 2" end cap distributes the load between the two lengths of PVC pipe.
The pole rests on the 2" end cap through a hole (diameter z, the outside diameter of the pole) cut in a 4" end cap that was glued securely on top of the 2" end cap. Before that assembly was mounted atop the 2" pipe, the sleeve was secured in place. As seen in the photo, the pole sits nicely in its little recess and the gap is sealed against the elements.
There are undoubtedly many other ways of implementing a shroud, depending on the construction of your particular insulator. I'd be interested in knowing what technique you finally settle on.
John
Hifer K6FRC
Good early morning CW signals from hifer K6HFC to Illinois. Frequency 13565040 Hz. Only signal seen at the hifer watering hole at the moment is EH.
73, Garry, K3SIW, EN52ta, Elgin, IL
Hifer RY
Posted by John Andrews, W1TAG on September 06, 2012 at 15:07:18.
Hifer RY is off the air TFN - until May, 2013 at best.
John Andrews, W1TAG
Re: Hifer RY
Posted by John Davis on September 06, 2012 at 15:49:42.
In reply to Hifer RY posted by John Andrews, W1TAG on September 06, 2012
I will miss seeing the Starship Enterprise out here on the prairie.
JD
Re: Hifer RY
Posted by John Andrews, W1TAG on September 06, 2012 at 16:51:16.
In reply to Re: Hifer RY posted by John Davis on September 06, 2012
Who knows...there may be an RY-1701-A some day...
John, W1TAG
Late Night Message Board Tests Upcoming
Posted by Webmaster on September 06, 2012 at 20:55:33.
Due to new features I have been coding for the Message Board recently, some fairly extensive testing will soon be necessary. This will be done late in the evening, North American time (typically 0300-0600 UTC, or 10 PM to 1 AM CDT). Tests could begin as early as tonight, and might continue through several days.
These tests will not require shutting down the board entirely. Reading of existing messages will not be affected at all, apart from the temporary presence of a few cryptic test message. But if you attempt to post a new message or reply during those hours, there may be occasional inadvertent crashes while debugging is underway.
For that reason, and to prevent you from wasting a lot of time if you've been typing a new message or reply, I offer the following recommendations:
1. If you're typing between 0300 and 0600, keep your message as short as possible. If you click Submit but it doesn't get posted because of a temporary crash, you won't be out so much work. Alternately...
2. Consider setting your browser's Internet Options to allow persistent form data. This way, if you click Submit but there's an error or no response, you can use your browser's Back button to return to the message just as you typed it. Leave that browser window open, possibly minimized while you do something else, and then try sending the message again in a few minutes. Or...
3. Write the message, but before sending, copy-and-paste the contents to Notepad or another plain-text editor in case you have to re-send later.
I'll try to keep disruptions to a minimum, and apologize ahead of time for any inconvenience...but I think you'll find the results worthwhile!
John Davis
Re: New Lowfer Transmiter/Loading Coil
Posted by Lee on September 07, 2012 at 01:01:41.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by John Davis on September 06, 2012
Very interesting. Is this for lightning protection or to minimize RF leakage to ground. I am assuming the reading on the meter is 18.9 meg.
Re: New Lowfer Transmiter/Loading Coil
Posted by John Davis on September 07, 2012 at 01:16:01.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by Lee on September 07, 2012
Sorry, I forgot the caption didn't transfer with the photograph. The 0.189 reading is in nanofarads, aka 189 pF. The picture was of the first (or nearly first) capacitance measurement on the antenna, made in early 2011 after it was finally in the air. We just barely got it up and guyed between snow storms.
The reason for the shroud is indeed to minimize RF leakage to ground.
John
TAG QRSS30
Posted by John Andrews, W1TAG on September 09, 2012 at 12:34:51.
Lowfer beacon TAG in Raymond, ME (FN43sv) is now running QRSS30 on 185.297 kHz. The frequency should be pretty close -- will check it when I get home later today. Reports are always welcome.
John Andrews, W1TAG
Re: New Lowfer Transmiter/Loading Coil
Posted by John Hamer on September 12, 2012 at 14:09:08.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by John Davis on September 07, 2012
Does anyone know if the Aiken, SC beacon WI on 187.5~ is currently transmitting?
Re: New Lowfer Transmiter/Loading Coil
Posted by John Davis on September 13, 2012 at 03:29:16.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by John Hamer on September 12, 2012
Got an inquiry in to one of Walt's neighbors, relatively speaking. We should know something soon. He used to be pretty reliable about keeping his schedule.
John
Re: New Lowfer Transmiter/Loading Coil
Posted by Douglas D. Williams on September 13, 2012 at 10:44:52.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by John Hamer on September 12, 2012
WI was the first Lowfer I ever copied, way back in 1991 or thereabouts. Good times.
LowFER WI (was: New Lowfer Transmiter/Loading Coil)
Posted by John Davis on September 13, 2012 at 18:00:52.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by John Davis on September 13, 2012
Heard back from Dexter McIntyre that Walt suffered a damaging lightning strike not long ago that took out the beacon, among other household items. He plans to build a new one, but it may be a few months.
John
HiFer "OH"
Posted by Tom Lau on September 13, 2012 at 19:31:48.
HiFers:
Due to other radio activity in fall and winter seasons requiring my sole
antenna at this QTH, beacon OH had been shut down for fall and winter and
will return to the air on 1APR13. Note: If a special broadcast is needed,
please contact me via e-mail n8tl@woh.rr.com and I will try to fit that
request in.
Thanks for this season's reports, 73's,
Tom N8TL
Beacon JAM 187.015khz sched
Posted by Lee on September 24, 2012 at 01:13:47.
Beacon JAM 187.015khz is on the air RIGHT NOW for testing through Monday noon. Resuming regular weekend schedule Friday noon through Monday noon starting Friday 9/28. Of course running during the week during good conditions and by request. Re: Beacon JAM 187.015khz sched
Added extra top hat radials, new mid guy ropes, sanitized all grounds for your protection and found some bad connections and bad soldered coil taps. Should be way mo better this year. I can see that a complete tear down can be revealing and helpfull. Good DX to all.
Lee
Posted by Lee on September 24, 2012 at 01:41:10.
In reply to Beacon JAM 187.015khz sched posted by Lee on September 24, 2012
I forgot the format. The letter J QRSS30 3 times and a 5 WPM message that contains E-mail, Grid location, Beacon name.
Lowfer SIW QRV
Posted by Garry, K3SIW on September 24, 2012 at 23:15:45.
Bob, NK9M and I activated lowfer SIW this afternoon from his QTH in EN51uq. Signalling format is "SIW" at QRSS60, "SIW" at QRSS30, then repeat. The frequency changes daily at 1800Z. S,T,Th,Sa run at 185.2993 kHz; M,W,F run at 185.185 kHz. Since today is Monday the beacon is currently on 185.185 kHz. The frequency shift is to allow me to monitor the watering hole without being overwhelmed by the ground wave signal from 20+ miles.
73, Garry, K3SIW, EN52ta, Elgin, IL
Medfer,EH QRV
Posted by Sal,K1RGO on September 25, 2012 at 16:21:00.
Medfer EH will be on starting today on 511.904 kHz mode QRSS3 24/7.Last season was fruitless with 10 wpm cw, maybe QRSS3 will help. Re: New Lowfer Transmiter/Loading Coil
later....
Posted by john hamer on September 25, 2012 at 21:24:35.
In reply to Re: New Lowfer Transmiter/Loading Coil posted by Douglas D. Williams on September 13, 2012
Antennas up. Will be testing this week. 181.818khz
Longwave reception in London UK
Posted by Claude Moreira on September 26, 2012 at 19:09:34.
See my Youtube video regarding Long wave reception in London UK with a Sony ICF-SW7600GR receiver:
LINK: http://www.youtube.com/watch?v=DVnadMX5g9U
Re: Beacon JAM 187.015khz sched
Posted by Doug - KB4OER on September 26, 2012 at 22:14:42.
In reply to Re: Beacon JAM 187.015khz sched posted by Lee on September 24, 2012
Thanks for the update, Lee. JAM eluded me last season. Hoping to do better this season.
Re: Lowfer SIW QRV
Posted by Doug - KB4OER on September 26, 2012 at 22:17:20.
In reply to Lowfer SIW QRV posted by Garry, K3SIW on September 24, 2012
185.185 is a "no go" for me, due to a very close PLC.
Will be watching the 185.3 kHz "watering hole" this season, however.
Regards, Medfer Antenna Size
Doug
Posted by Andy on September 27, 2012 at 18:35:50.
I've completed a 512KHz medfer beacon test transmitter and am working on the antenna. I am building a transmitting loop but am stuck with the size issue. Does the 3 meter size limit the diameter of the loop to 3 meters or the circumference? I've found elsewhere references to a part 15 Lowfer wire magnetic transmitting loop that is 50ft vertical x 50ft horizontal. Is this the same interpretation that can be used for a medfer loop (3 meters high x 3 meters wide)?
Thanks.
Andy
Re: Medfer Antenna Size
Posted by jimvm on September 28, 2012 at 00:43:59.
In reply to Medfer Antenna Size posted by Andy on September 27, 2012
Check out the 'unfair radio transmitter' on Wenzel site. Re: Medfer Antenna Size
Google it, it describes a square loop antenna for part 15.
jim vm
Posted by Andy on September 28, 2012 at 03:07:14.
In reply to Re: Medfer Antenna Size posted by jimvm on September 28, 2012
Yes, I saw that, I have one in the basement ready to go. He described it as adhering to the strictest of interpretations of the part 15 requirements. I am interested if the liberal interpretation is the correct one (3m X 3m square loop).
Andy Re: Medfer Antenna Size
Posted by Andy on September 28, 2012 at 14:00:47.
In reply to Re: Medfer Antenna Size posted by Andy on September 28, 2012
http://www.we0h.us/Amateur_Radio_stuff/Transmitting-Loops/Bill-Ashlock-documents/Loop1.doc
If this meets requirements does the reasoning of height apply to a Medfer loop antenna?
Andy Re: Medfer Antenna Size
Posted by John Davis on September 28, 2012 at 17:18:43.
In reply to Re: Medfer Antenna Size posted by Andy on September 28, 2012
"If this meets requirements...."
That's the catch. It doesn't.
The FCC Rules say 3 meters for MedFER, 15 meters for LowFER, "total length of antenna, transmission line, and ground lead, if used." How you can go 50 feet out from the transmitter in one direction, 50 feet more in another, a further 50 feet in yet a different direction, and yet another 50 feet to return to the transmitter, and call it 15 meters "total" length is peculiar math, to say the least.
The Rules do not say "maximum length of whatever geometric shape you can stuff the antenna into," but instead, "the total length of the antenna, transmission line, and ground lead...."
Back about 20 years ago, this club, through the umbrella organization ANARC (the Association of North American Radio Clubs), formally petitioned the FCC to amend the Part 15 Rules to incorporate what was widely known as the Ken Cornell interpretation; viz, permissible antennas could be any structure that would fit within an imaginary cylinder having dimensions of 3m length and 3m diameter for MF, and 15m length by 15m diameter for LF.
Although many of us felt that was a reasonable approach which would keep interference potential low while simplifying compliance determination, the FCC rejected the proposal outright. End of story, so far as we're concerned.
Now, some people will do what they want and rationalize any necessary justification for it. I'm not the Riley Hollingsworth of Part 15. I have no enforcement powers, but I do have licenses of my own to protect and I also have a deep interest in preserving this hobby; so my goal is to put out the most reliable information I can, and encourage self-restraint and self-policing within the community.
For those who have not looked it up, the Wenzel MF rig loop antenna is 30 inches × 30 inches in size, which actually totals a couple of inches over the current "3 meters" wording of the Rules, but would have been strict antenna compliance under the earlier Rules which specified 10 feet. I'm not sure how efficient that output stage can really be, but Charlie is a very clever designer, so it probably works pretty well.
John
Weather Forecast, Sort Of
Posted by John Davis on September 29, 2012 at 17:59:00.
If you have plans to listen out for HiFERs, 600 meter ham/experimental activity, etc., this weekend, this afternoon and evening will be your best bets. Yesterday's CME on the sun has a good chance of causing strong geomagnetic activity tomorrow that could make propagation much less stable for a few days.
Natural Radio enthusiasts may be interested in listening for the storm itself, especially since the Radiation Belt Storm Probe satellites will be doing the same.
Find out more at the LWCA Home Page.
John
Re: Medfer Antenna Size
Posted by Andy on September 29, 2012 at 19:13:07.
In reply to Re: Medfer Antenna Size posted by John Davis on September 28, 2012
John,
Thanks for the background. I was questioning if the geometric interpretation was correct, it apparently is not, so I will default to the smaller 3m circumference loop. That's unfortunate. Still, there are many top loaded verticals in use that obviously have more than 3m total length of wire in their structures.
Since the loading coils of many Medfer verticals are quite wide (and long) in design and use a large length of wire for their windings, can we use a similar approach for a 3m circumference multiple winding small transmitting loop?
It would help increase the effectiveness of the loop as compared to a single turn STL.
Andy
Re: Medfer Antenna Size
Posted by John Davis on September 29, 2012 at 23:35:48.
In reply to Re: Medfer Antenna Size posted by Andy on September 29, 2012
"Still, there are many top loaded verticals in use that obviously have more than 3m total length of wire in their structures."
This is the other side of the interpretive coin, so to speak. Some folks try to reason that anything goes by apparently trying to show that "normal" antennas don't meet the strictest possible interpretation in some fashion, either, so maybe the field is wide open for any old interpretation.
But this is a false dilemma. Just as the rules don't mean the "longest single dimension" of an antenna is its total length, neither do they say anything about counting every individual strand of wire! Neither extreme really meets a plain-language understanding of the Rules. (For a short dissertation on exegesis of regulations, see my post of June 6. That was more about how to count ground leads, but the method applies directly to the way one should think about antenna length as well.)
An antenna is a conductive structure that provides a path for RF current, and in the process enables conversion of energy in that current to electromagnetic waves, or vice-versa. The structure may consist of a single strand of soild wire, a stranded wire, a steel pipe, etc., so long as the RF is traveling it as one path. The longest overall RF path length in the structure is the relevant factor. Understood in these terms, the most common interpretation of antenna length of a vertical as its structural height plus radius of the tophat structure makes perfect sense.
The tophat is a structure of its own, often separate from the mast but always connected. A symmetrical tophat doesn't radiate, but the question of radiating is not relevant; RF current travels from the vertical element out the distance of the radius along the tophat, and therefore must be counted. (The only real debate has been whether individual wires of a tophat count toward the total, or whether the overall structure should be regarded as a single plate. To me, that's the same argument as whether each individual strand in the wire of the antenna itself must count--an obvious absurdity. My view is that if the individual pieces of the tophat are electrically bonded at their ends, their behavior is the same as if they were a single solid plate. But if that view gets overruled some day, then I'll likely do a redesign and beef up my guying to accomodate a solid plate, so there will be no question. :))
Loading coils...sigh. As you may notice elsewhere in the linked discussion or some of its predecessors, there are folks who want to muddy the waters by counting the wire in the loading coil as part of the antenna length.
Well, a coil is most commonly and correctly understood to be a discrete component presenting a lumped inductance between its terminals. The "length" dimensions of all discrete components are measured from terminal to terminal, from end of form to end of form, or from one end of the body to the other--not by the length of wire inside a coil, nor the area of plates in case of a capacitor, nor by the volume of the resistive element in a resistor, etc. If the loading coil is just* a coil--a discrete, lumped inductance--then even if you are treating it as part of an antenna, the length of its form or the spacing between its terminals, whichever is greater, is what should be counted in the total length.
(*I emphasize "just a coil" because sometimes folks want to do the very thing you are asking about, and transform it into a radiating element inseparable from the rest of the antenna. Transforming a plain coil into a helical vertical or a multi-turn loop is a very different matter! If it's no longer a lumped inductance but has become distributed into the antenna itself, my view is that it's no longer a discrete component, but then is indeed part of the length of the antenna. If you can't legitimately say "this is a discrete component," it seems to me that it becomes just another variant of the geometric interpretation of antenna size.)
Now, in my own Part 15 systems, the so-called loading coil is not just a component separate from the antenna, it's an indispensible part of the transmitter. It's the inductor in the final output tank circuit, tuning the transmitter to resonance. In my LowFER, in fact, the hot end of the coil is my formal antenna terminal, and the cold end is my ground terminal.
Regards, Re: Weather Forecast, Sort Of
John
Posted by Ward K7PO on September 30, 2012 at 02:40:24.
In reply to Weather Forecast, Sort Of posted by John Davis on September 29, 2012
It figures. I have not received any reports of AJO lately, but I got an email today from a german ham who was receiving my 10m 1/2 watt beacon 5x3. 10 must have been wide open. Was hoping for good conditions for a while. Oh well. . .
Ward K7PO Re: Medfer Antenna Size
Tonopah, AZ
Posted by Andy on September 30, 2012 at 02:50:03.
In reply to Re: Medfer Antenna Size posted by John Davis on September 29, 2012
"Now, in my own Part 15 systems, the so-called loading coil is not just a component separate from the antenna, it's an indispensible part of the transmitter. It's the inductor in the final output tank circuit, tuning the transmitter to resonance. In my LowFER, in fact, the hot end of the coil is my formal antenna terminal, and the cold end is my ground terminal."
So what's the difference between that and making a multi-turn STL part of THE output amplifier Hi-Q tank circuit? It now becomes a necessary component of the transmitter output stage, much as was common in original loop antennas used in very early military transmitters (which eventually evolved to what is now the Patterson Loop)?
I think the easiest metric would be to limit the measured field strength at a certain near field distance. That would be difficult except for those of us with access to NIST traceable analyzers.
Andy
Re: Weather Forecast, Sort Of
Posted by Andy on September 30, 2012 at 02:53:03.
In reply to Re: Weather Forecast, Sort Of posted by Ward K7PO on September 30, 2012
(sigh) I miss the openings (and sunspot cycle) of the early 1970's.
This one is becoming a non-event.
Andy Re: Medfer Antenna Size
Posted by John Davis on September 30, 2012 at 04:00:16.
In reply to Re: Medfer Antenna Size posted by Andy on September 30, 2012
"So what's the difference between that and making a multi-turn STL part of THE output amplifier Hi-Q tank circuit?"
Not quite sure how you're using the term STL here...but the differences between a coil in conventional output stage and incorporating a loop antenna directly in the final to act as a tank are that in the latter case (a) the coil is no longer a discrete component, but is arguably a distributed inductance that (b) is an intentional, integral, and inseparable part of the antenna, basically (c) being the sole component comprising the antenna; and hence, counts fully toward the antenna length.
Remember that in the passage you quoted, the test I laid out was not just that the inductor in my transmitter is indispensible to the final tank circuit, but also that it is quite a separate thing from the antenna. You can disconnect the antenna from the output terminals of my rig, replace it with a dummy load, and still resonate the final for testing under full operating conditions, virtually without radiating a peep. It is a discrete component in this configuration, not an antenna, as we would understand the term in everyday language. Unlike politicians, I believe we don't even have to belabor what "is" means. :)
"I think the easiest metric would be to limit the measured field strength at a certain near field distance."
Depends perhaps on one's definition of easiest, but it would surely be the most unambiguous. And in fact, that's how compliance with most provisions of Part 15 is determined.
What we have in Sections 15.217 (LF) and 15.219 (MF) are labelled by the FCC as "Radiated Emission Limits, Additional Provisions." These power and antenna limits are alternatives to having to measure actual field strength. They are easier ways to demonstrate compliance than field measurements, which not only require expensive gear, but also necessitate a great many measurement points on an open antenna range to ensure that the field limits are not exceeded anywhere outside the specified radius.
Moreover, with even modest care in antenna construction and grounding, the simplified antenna and input power limits actually result in considerably stronger signals than the field strength limits do! That's one reason the alternative sections only apply to certain bands...ones where potential for serious interference is relatively low at the power levels in question. But beginning with stronger signals in the first place is also a double-edged sword. The more one stretches and stretches the wording of the Rules, the greater the potential to draw unwanted attention for interference anyway.
John Re: Medfer Antenna Size
Posted by Andy on September 30, 2012 at 07:33:43.
In reply to Re: Medfer Antenna Size posted by John Davis on September 30, 2012
"Moreover, with even modest care in antenna construction and grounding, the simplified antenna and input power limits actually result in considerably stronger signals than the field strength limits do! That's one reason the alternative sections only apply to certain bands...ones where potential for serious interference is relatively low at the power levels in question. But beginning with stronger signals in the first place is also a double-edged sword. The more one stretches and stretches the wording of the Rules, the greater the potential to draw unwanted attention for interference anyway."
Yep, the antenna and surrounding environment can be exploited to increase radiation either parasitically or in a combination to favor pattern manipulation. I've run several models using Empire Xcel and verified field measurements of wiring or metal framing within structures increasing fields at very low frequencies.
Ultimately, part of the problem is the FCC has left some of the part 15 wording ambiguous so that could lead to a more liberal interpretation.
I like to default on the side of caution, my licenses aren't worth risking either.
Andy
Re: Weather Forecast, Sort Of--AJO Report --28 Sept., 2012
Posted by EdWSlidell,LA on September 30, 2012 at 13:43:11.
In reply to Re: Weather Forecast, Sort Of posted by Ward K7PO on September 30, 2012
Hi Ward. Just to let you know, I did hear AJO on 13558 KHz or so on 28 Sept., 2012. It was about 0330 UT, and the signal strength was about 3-3/4-9, and fairly steady in strength. I was checking to see if a new noise source here had changed because of some rain we had earlier. Your beacon was heard between the periods of noise. It's something like a bad ballast on a HPS lamp--heating up, thermal cutout, quiet, then the cycle would begin again. This is now day and night, rain or shine. Nothing heard outside with a portable AM radio, either end of the band. S7 on the vertical and S5 on the LW. Will have to keep looking. Ed WSlidell, LA EM50cg
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