question about drilling holes in plastic coil forms
Hello Everyone:
I have a question about something I have seen in pictures of homebrewed coils, and variometers. whether they were wound on paint buckets, or large PVC, plastic trashcans, whatever, Some appeared to have holes drilled in the plastic. I have read on the net also that this causes the plastic to be more like an air dielectric, and maybe a little less lossy. Has anyone tried both methods, and saw any improvement with the holes versus solid plastic ?? I am about to begin making my matching network for my LOWfer beacon, and If the holes in the plastic are an advantage; out comes the drill !! --- Thanks for any replies:
73, Andy - KU4XR Re: question about drilling holes in plastic coil forms
Posted by J.B. Weazle McCreath on September 04, 2008 at 14:41:55.
In reply to question about drilling holes in plastic coil forms posted by Andy - KU4XR on September 02, 2008
Hi Andy, Lowfers,
Everything I've read about winding coils has made it
clear on two things in particular, if you're trying
for the optimum performance. The length to diameter
ratio should be as close to 1:1 as you can make it,
and the form should be low loss. By drilling holes
in the form, you're creating a "skeleton" former,
which is at least somewhat an air-wound.
For my combination loading coil/variometer, I used
a one inch hole saw to drill lots of holes in the
form. It took me several evenings with the drill
press, but I feel it was worth the effort, if only
for the psychological reason! See a pix of it on
my home page:
http://www.hurontel.on.ca/~weazle
It certainly made the form a lot lighter than it
had originally been!
73, J.B. Re: question about drilling holes in plastic coil forms
Posted by Andy - KU4XR on September 04, 2008 at 17:58:30.
In reply to Re: question about drilling holes in plastic coil forms posted by J.B. Weazle McCreath on September 04, 2008
Hey J.B. Actually the picture of your variometer is the one that I was basically referring too in the post. I saw the holes you had drilled in the bucket, and it made me curious about the benefits. There are some who say yes, some no, and some who said that they couldn't tell any difference. Re: Friendsville, TN. beacon " XR " status
Through my experience I have found that what will work for one, may not work for another, for whatever reason. I suppose trying for yourself is the best way to find out.
Thanks for the reply; 73, Andy - KU4XR
Posted by Douglas Williams - KB4OER on September 06, 2008 at 11:10:14.
In reply to Friendsville, TN. beacon " XR " status posted by Andy - KU4XR on August 11, 2008
I see you are just outside Knoxville. I am in the Tri-Cities area (Watauga), which should be about 100 miles east of you (just off the top of my head without consulting any distance calculators). I pulled my receiving setup out of the closet today and set it up for the listening season. Your signal will be the first one on my list to try for this season. 184.322 kHz QRSS30?
-Doug
Re: Friendsville, TN. beacon " XR " status
Posted by Andy - KU4XR on September 07, 2008 at 07:09:44.
In reply to Re: Friendsville, TN. beacon " XR " status posted by Douglas Williams - KB4OER on September 06, 2008
Hello Doug: nice to hear from you. My beacon is pretty much running 24/7 right now. It starts with a CW ID at 10wpm, then switches to QRSS-30 with the call " XR " . Any effort you give, I will appreciate. This is my first attempt with a LOWfer beacon. 73; Andy - KU4XR
Beacon " XR " mode change
Posted by Andy - KU4XR on September 07, 2008 at 07:21:58.
Greetings LOWfers; I have changed the mode on my beacon to an alternating CW / QRSS transmission. The transmission starts with a 10wpm CW ID: DE_XR_XR_XR/B 73, then 5 dits, followed by the QRSS-30 " XR " . I thought I would try this for awhile. I have had some of the longtime operators tell me they don't use software and such, so I thought I would make the beacon a little more versatile in case anyone wants to try for the CW portion. My carrier freq. is 184.322KHz. 73 for now; Andy - KU4XR
Re: Friendsville, TN. beacon " XR " status
Posted by Douglas Williams - KB4OER on September 07, 2008 at 09:54:22.
In reply to Re: Friendsville, TN. beacon " XR " status posted by Andy - KU4XR on September 07, 2008
I'll leave ARGO on all night doing screen captures for a few days and we'll see what we can fish out. Good to have a fellow lowfer close by. I've been inactive for a while, but the bug has bit me again.
73, Re: Friendsville, TN. beacon " XR " status
Doug
Posted by John Davis on September 07, 2008 at 21:28:54.
In reply to Re: Friendsville, TN. beacon " XR " status posted by Douglas Williams - KB4OER on September 07, 2008
Welcome back, Doug!
Re: Beacon " XR " mode change
Posted by Douglas Williams - KB4OER on September 08, 2008 at 04:05:37.
In reply to Beacon " XR " mode change posted by Andy - KU4XR on September 07, 2008
Good deal. That will give you both modes, and the entire CW ID will only be a dot on the Argo screen.
loop antenna question??
Posted by dave sampson on September 10, 2008 at 11:17:01.
hello
would like some opinions...of the various designs and configurations: what type of loop antenna design would offer the lowest noise. it would be used for receive only ,cover 160kc-540kc, and be mounted outdoors.
would appreciate any input,suggestions,ideas Re: loop antenna question??
thanks very much
73s
Posted by John Andrews, W1TAG on September 10, 2008 at 13:14:57.
In reply to loop antenna question?? posted by dave sampson on September 10, 2008
Dave,
Look for designs that keep the loop balanced with respect to ground, either by using a balanced preamp, or by a transformer. If that is done, you will see no noise advantage from using a shielded loop. Since the shielding decreases the tuning range, this is a useful point. Getting rid of the shield also considerably simplifies the loop construction.
A number of us have been quite happy with relatively large, square rotatable loops around 6 feet on a side. For the frequency range you mentioned, 8 turns would be nice, and even nicer if you can keep the turns spaced a bit from each other, thereby expanding the tuning range.
John Andrews, W1TAG
WD2XES QRP WOLF
Posted by John Andrews, W1TAG on September 10, 2008 at 13:21:14.
WD2XES is currently running in WOLF (10) mode on 137.577 kHz from Holden, MA (FN42ch). The transmitter output power level is only 4 watts, giving an ERP of about 10 milliwatts. This is approximately 20 dB lower than the normal XES power level. As of this writing, it has been copied both day and night at distances of 350 miles. Copy over much longer distances should be possible, and reports are welcome.
John Andrews, W1TAG/WD2XES
How are magnetic loop antennas better at rejecting noise?
Posted by Green Xenon on September 10, 2008 at 17:03:23.
Hi:
I've heard that magnetic loop antennas are better at ignoring static than regular antennas? How is this possible? In any form of EM radiation, a changing electric-field will result in a changing magnetic-field and visa versa. Hence, even if the the magnetic loop antenna is not directly affected by the time-varying electrostatic fields, the magnetic fields resulting from the changing electrostatic fields will be received by the magnetic loop and will cause noise on the radio.
Thanks,
Green Xenon Re: How are magnetic loop antennas better at rejecting noise?
Posted by John Andrews on September 10, 2008 at 18:55:30.
In reply to How are magnetic loop antennas better at rejecting noise? posted by Green Xenon on September 10, 2008
What you say is perfectly true in the far-field, where the electric and magnetic fields are nicely proportional (E/H=377). But near-fields are much more complicated situations, and you typically have several magnetic and several electric fields from each source. The static and induction fields can be quite high near the source, but drop off rapidly with distance, becoming negligible in the far-field.
There is a school of thought that says that with noisy conductors such as power lines, that electric fields will dominate in the near-field. In that case, a balanced magnetic loop antenna might offer a significant reduction of the noise. Alas, such things are not always that simple, but for antennas mounted near the ground in residential situations, loops do seem to offer quieter performance. An antenna like an e-probe may be very effective in the open and away from noise-carrying conductors.
John Andrews
Re: How are magnetic loop antennas better at rejecting noise?
Posted by Green Xenon on September 10, 2008 at 19:36:51.
In reply to Re: How are magnetic loop antennas better at rejecting noise? posted by John Andrews on September 10, 2008
What would be heard on a 40 Hz AM DX receiver that uses the most sensitive type of magnetic loop antenna? I doubt there would be any hissing since that artifact would involve high-frequency sounds and a 40 Hz carrier cannot transport modulation-signals higher than 40 Hz [violation of Nyquist theorem].
I also don't think power lines would have any perceptible affect on a 40 Hz receiver. In USA, the electric power has a frequency of 60 Hz -- in Europe, its 50 Hz.
Would any interferences from outer space be perceptible on a 40 Hz AM receiver? Galactic noise?
Re: How are magnetic loop antennas better at rejecting noise?
Posted by Gregg on September 11, 2008 at 00:54:15.
In reply to Re: How are magnetic loop antennas better at rejecting noise? posted by Green Xenon on September 10, 2008
Hi,
Have you checked out http://www.vlf.it ?
There's lots of additional info and RX techniques there for this kind of frequency range you speak of.
Just thought I'd throw this additional resource out there for you :-)
Cheers!
lowfer BOB
Posted by Bob Hoffswell on September 11, 2008 at 08:28:58.
BOB is back on the air after a long hiatus. Look for it at 186.978kHz (about where it use to be.) I'll leave it on all the time, except when I'm fooling with it, so please give it a try and let me know if you can hear it!
I still see Brice Anderson (BA) on occasion. He and his wife, Anna Rae, are in their 90's and, while not in the best of heath, they're still goin'. Brice is thinking of putting BA back on the air, too. I have his old set-up, will get it all going, and then he'll try to load his GAP vertical (isolated against ground). If all goes well, it may not be too long before the old-timer is back on the air.
73 es tnx de BOB
Re: lowfer BOB
Posted by John Davis on September 11, 2008 at 15:57:34.
In reply to lowfer BOB posted by Bob Hoffswell on September 11, 2008
Bob, it's good to hear from you again. Wonderful news, both about BOB being back on and Brice still being with us.
73 Re: lowfer BOB
John
Posted by Peter B on September 11, 2008 at 16:52:08.
In reply to lowfer BOB posted by Bob Hoffswell on September 11, 2008
Good to hear from Bob on BOB and about Brice. I'm a fellow ILL LowFER near DeKalb. I once heard BOB on CW a few years back. Never for BA. I'll give a listen come late fall. Re: lowfer BOB
--Peter
Posted by Paul Daulton on September 11, 2008 at 19:54:04.
In reply to lowfer BOB posted by Bob Hoffswell on September 11, 2008
Bob
I dont see you on current lowfer list. How about
updating your info with the webmaster.
Thanks I'll look for you this fall
Paul Re: How are magnetic loop antennas better at rejecting noise?
k5wms
Jacksonville ar
Posted by Green Xenon on September 11, 2008 at 21:32:29.
In reply to Re: How are magnetic loop antennas better at rejecting noise? posted by Gregg on September 11, 2008
Thanks for the link Re: lowfer BOB
Posted by John Davis on September 12, 2008 at 21:42:31.
In reply to Re: lowfer BOB posted by Paul Daulton on September 11, 2008
"I dont see you on current lowfer list. How about updating your info with the webmaster."
That's what he just did by posting here! :-) This is the best place in the whole world to be sure I notice beacon changes.
We don't promise instant updates of the list, but since this is fresh information on the board, it will likely be current in everyone's minds for a while.
LF Loop Antenna for Small Lot Dwellers
Posted by Gregg on September 13, 2008 at 01:11:41.
Hi Folks,
I've built a smallish loop for NDB DX that may be of interest to those who want to enjoy this winters DX, but are stuck with neighbors a few metres off your port and starboard ;-)
http://geek.scorpiorising.ca/GeeK_ZonE/index.php?topic=3929
Cheers,
Gregg
Re: LF Loop Antenna for Small Lot Dwellers
Posted by Douglas D. Williams - KB4OER on September 13, 2008 at 04:37:53.
In reply to LF Loop Antenna for Small Lot Dwellers posted by Gregg on September 13, 2008
Nice work! Thanks for sharing it.
Beacon LYQ Mystery
Posted by Todd WD4NGG on September 13, 2008 at 19:38:48.
Hi All,
This evening 09/13/08 in SC I am hearing NDB beacon LYQ off to the lower side of 530KHz. I was listening this evening to see if Turks and Caicos RVC was back on the air after hurricane Ike went through the area recently and noticed LYQ coming in quite well. LYQ has various postings on the web as being on 529KHz located in Manchester, TN. I assumed it was a regular NDB with a carrier on 529KHz and either a keyed tone in DSB mode or a 529KHz carrier with a keyed carrier 1020Hz higher for a form of USB compatible AM. The odd thing is I cannot hear any carrier on 529KHz but I can hear LYQ in CW mode on 529 or AM mode 529KHz next to the station on 530KHz.
It is as if LYQ is operating in CW mode on 529KHz. I can hear it in AM mode on 529KHz because the keyed CW carrier is mixing with the AM station on 530KHz but I cannot hear it on the higher side of 530KHz using a narrow 2.4KHz IF filter.
I wonder if anyone else is hearing LYQ tonite or recently in this strange mode or is that typical of LYQ? I haven't noticed LYQ before although I see it has had various reception reports in the past year or so.
Thanks and 73's - Todd WD4NGG
Re: lowfer BOB
Posted by Bob Hoffswell on September 14, 2008 at 15:06:01.
In reply to Re: lowfer BOB posted by John Davis on September 12, 2008
OK. Here's the information you requested:
beacon BOB
186.97 KHz
on all the time
Bob Hoffswell, AA9DH
harvey@hoffswell.com
PO Box 530 Mahomet IL 61853-0530
217 586 2128
..and a little more...
beacon BA
186.360 KHz
Currently, it's on all the time from the BOB location, but will be moved to:
Brice Anderson, W9PNE
301 W. 11th St. Apt C
Mount Carmel, IL 62863-1325
618 262 4134
Re: lowfer BOB
Posted by Bob Hoffswell on September 14, 2008 at 15:09:04.
In reply to Re: lowfer BOB posted by Paul Daulton on September 11, 2008
OK. Here's the information you requested:
beacon BOB
186.97KHz
on all the time
Bob Hoffswell, AA9DH
harvey@hoffswell.com
PO Box 530 Mahomet IL 61853-0530
217 586 2128
..and a little more...
beacon BA
186.360KHz
Currently, it's on all the time from the BOB location, but will be moved to:
Brice Anderson, W9PNE
301 W. 11th St. Apt C
Mount Carmel, IL 62863-1325
618 262 4134
Re: lowfer BOB
Posted by Bob Hoffswell on September 14, 2008 at 15:14:49.
In reply to Re: lowfer BOB posted by Peter B on September 11, 2008
Thanks for your notice, Peter, an good hunting! BOB has a pretty good signal 15mi from it: BA is quite a bit less, but has a poorer antenna. When it goes to Brice's, we'll have to see, but I suspect it will not be much better than it is from here. Ah, but no one knows the vageries of LF...!
73 es dx
Re: Beacon LYQ Mystery
Posted by Andy - KU4XR on September 15, 2008 at 13:12:25.
In reply to Beacon LYQ Mystery posted by Todd WD4NGG on September 13, 2008
Todd: LYQ is a NDB located in Manchester TN. They transmit an A.M. carrier on 529 KHz with a 1 KHz MCW tone. They are running around 25 watts I believe. They also have a voice ID between the MCW ID's. They announce their location, local weather, and wind speed. The airport is a small one, and is owned by a Shortwave Broadcasting Company in Middle TN. I am close enough to the NDB that I can hear the voice announcements as well, they are at a very low volume level and phoneline quality. Even when the beacon signal is very strong, it is difficult to understand the voice part.
73; Andy - KU4XR
Re: Beacon LYQ Mystery
Posted by Todd WD4NGG on September 16, 2008 at 09:10:36.
In reply to Re: Beacon LYQ Mystery posted by Andy - KU4XR on September 15, 2008
Hi Andy, Re: LF Loop Antenna for Small Lot Dwellers
Thanks for your info on beacon LYQ. But have you listened to LYQ in the last day or two at your location? When I listened last night there was definitely no steady carrier that I could hear on 529KHz. They were keying the carrier itself on-off in CW mode on 529KHz for the ID LYQ.
73 - Todd WD4NGG
Posted by Don Moth on September 16, 2008 at 17:16:05.
In reply to LF Loop Antenna for Small Lot Dwellers posted by Gregg on September 13, 2008
I can't open the loop address as written
Re: LF Loop Antenna for Small Lot Dwellers
Posted by John Andrews, W1TAG on September 16, 2008 at 18:00:51.
In reply to Re: LF Loop Antenna for Small Lot Dwellers posted by Don Moth on September 16, 2008
Don,
Try again. I "livened" the link.
John A.
Re: Beacon LYQ Mystery
Posted by Andy - KU4XR on September 16, 2008 at 19:14:00.
In reply to Re: Beacon LYQ Mystery posted by Todd WD4NGG on September 16, 2008
You're right Todd: I listened to LYQ in the car coming home from work today and it sounded different, and I couldn't hear the voice announcements anymore. After reading your post, I tuned LYQ in and it sure is pure CW. I looked with SpecLab, and there is no carrier whatsoever.
73; Andy - KU4XR
Re: Beacon LYQ Mystery
Posted by Todd WD4NGG on September 17, 2008 at 12:34:13.
In reply to Re: Beacon LYQ Mystery posted by Andy - KU4XR on September 16, 2008
Hi Andy, Re: Beacon LYQ Mystery
Thanks for confirming Beacon LYQ is indeed transmitting in CW mode on 529KHz. It is the only non-Amateur beacon I know of right now that is transmitting CW only in the NDB band. Interesting that you are close enough to hear it in the daytime. Their signal sounds pretty strong here at nite.
Thanks 73 Todd WD4NGG
Posted by Andy - KU4XR on September 18, 2008 at 10:06:10.
In reply to Re: Beacon LYQ Mystery posted by Todd WD4NGG on September 17, 2008
Todd: My home QTH is 100 airmiles from LYQ, and my work is 77 airmiles. It is a 44 mile road trip from my home to work and for the most part depending on the band conditions I can listen to the beacon on my car radio at 530 KHz. There is one place in particular that I can hear the beacon strong, in Vonore, TN. I cross the Little TN. river and the bridge is about 50 feet above the water ( no Earth attenuation ) there, the beacon will blow the radio out of the dashboard. On Wed. 9/17/08, on my way to work I listened and heard the familiar phfftt phfftt phfftt sound of a CW signal on an A.M. receiver. 73, OM: and have fun listening; Andy - KU4XR
mystery beacon "NEED"
Posted by RICK on September 18, 2008 at 19:02:14.
Anyone else hearing the beacon on 505 khz identifying as "NEED" ? Pretty good signal here in Pennsylvania. I copied for about 1/2 hour starting at about 9:30 pm local time.
Thanks Re: Towers of former Public Emergency Radio of the United States
Rick KA2PBO
Posted by Steve on September 18, 2008 at 19:53:21.
In reply to Re: Towers of former Public Emergency Radio of the United States posted by John Andrews, W1TAG on June 18, 2008
John is right. I've lived in the Denver area for decades, and used to design and install microwave sites all over the front range. Such a tower near Ault, CO never existed.
Steve KCoYA
Re: LF Loop Antenna for Small Lot Dwellers
Posted by Gregg on September 19, 2008 at 01:33:38.
In reply to Re: LF Loop Antenna for Small Lot Dwellers posted by Douglas D. Williams - KB4OER on September 13, 2008
Thank you much! I appreciate the comments so far :-)
Great news!!!!!
I upped the toroid balun to 34 bifilar turns and now she's a dream.
The balance is so well maintained from my ability to test it's range from 150KHz to 560KHz, that the low pass filter isn't even needed.
All common mode noise is gone. Even with the neighbor's TV and computer on, the broadband noise is gone and I can null out the SMPS fundemental to such a null I can hear weakish beacons over it.
I was running straight loop into the balun into the E5 and signal strengths were high enough that I didn't even need the preamp to pull out those stations I used the LPF+preamp the other night to get... only one S-unit lower.
Tuning "Q" is very sharp now - 6dB points are 1KHz on the lower end, going up to 7KHz into the lower AM BCB and about 3 KHz on the upper NDB range of 420KHz.
Cheers!
Re: LF Loop Antenna for Small Lot Dwellers
Posted by Gregg on September 19, 2008 at 01:38:29.
In reply to Re: LF Loop Antenna for Small Lot Dwellers posted by John Andrews, W1TAG on September 16, 2008
Thanks for the live link, I appreciate it!
There's new info added (also posted in a follow up here) and it's quite the little performer now.
Though I am not a member of the LWCA (yet), my projects are open-source, so feel free to repost/print with credit.
I would just love for those bound by the "antenna constrained" living to be able to participate in a better LF DX experience for this season.
Cheers!
Re: LF Loop Antenna for Small Lot Dwellers
Posted by Webmaster on September 19, 2008 at 08:15:32.
In reply to Re: LF Loop Antenna for Small Lot Dwellers posted by Gregg on September 19, 2008
> "Though I am not a member of the LWCA (yet), my projects are open-source, so feel free to repost/print with credit."
Thanks, Gregg, most generous. It would help to know, though, just how you would like it credited. We prefer to do normal author attribution, with full name and any contact information you choose to provide.
Please e-mail details to mb at lwca dot org. Thanks again!
John
more loop antenna questions?
Posted by dave sampson on September 21, 2008 at 08:38:31.
Thanks John for the info. on loop antenna construction!!
have some more questions...lets asume i have a square multi-turn loop with 10 feet on a side.ive read that you want to keep the turn spacing at a minimum of 1/4": how would you determine what the maximum spacing between turns before there would be no more appreciable gains in performance?
also.....could you use 50 or 100 turns of wire (or more) and just use a smaller variable capacitance?
Thanks very much Re: more loop antenna questions?
73s
dave
Posted by John Davis on September 21, 2008 at 10:30:24.
In reply to more loop antenna questions? posted by dave sampson on September 21, 2008
I can address one of these: "also.....could you use 50 or 100 turns of wire (or more) and just use a smaller variable capacitance?"
You could, but for a loop of the size John was talking about, there would be no advantage in using so many. It would make construction awkward if you were to keep the wire spacing adequate to avoid excess capacitance effects. (A hundred turns, spaced 1/4", would require a two foot wide frame!) Also, the additional length of wire introduces additional resistive loss, lowering the Q of the coil. And finally, impedance matching could become a little more of an issue.
A greater number of turns would be inevitable for smaller loops, of course, where you would not achieve the necessary inductance otherwise. But then, you cannot avoid closer spacing, and have to settle for the compromises inherent in smaller loops. They still work well enough for many applications, but you may not achieve as wide a tuning range, nor as sharp tuning, nor necessarily the deepest nulls.
John Re: more loop antenna questions?
Posted by dave sampson on September 21, 2008 at 13:33:10.
In reply to Re: more loop antenna questions? posted by John Davis on September 21, 2008
thanks for the input---
putting total weight,size,and construction problems asside:
would it be beneficial to have 100 or more turns if you had the room to compensate for the distributed capacitance and you could compensate for resistive losses by increasing wire diameter?
thanks
dave
Re: more loop antenna questions?
Posted by John Davis on September 21, 2008 at 13:48:33.
In reply to Re: more loop antenna questions? posted by dave sampson on September 21, 2008
"would it be beneficial to have 100 or more turns if...."
No. Beyond a certain point, there is no advantage if you are keeping the cross-sectional area roughly the same--that is to say, roughly, the same aperture size for the antenna.
More turns means you could achieve a higher terminal voltage (the voltage between the ends of the coil), but that comes at the price of much higher impedance. By the time you transform that down to a value that is compatible with your transmission line, you end up with the same voltage available at your receiver.
To look at it another way: The maximum amount of power you can extract from an electromagnetic wave passing through a given size of antenna aperture remains the same. All that changes is the way you will need to transform the impedance of that energy for best results with your receiver, plus the measures you will need to take to compensate for the extra losses and potential resonances that arise from having more turns.
Therefore, the ideal number of turns to use is whatever number allows you to cover the widest frequency range you are interested in with the capacitor(s) that are available to you; with a preference toward a lower L/C ratio rather than higher, where practical.
John
Finally finished my Variometer
Posted by Andy - KU4XR on September 21, 2008 at 17:21:07.
Hello LOWfers: loop inductance/impedance?
I finally finished constructing my LOWfer variometer for Beacon " XR ".
I have it sitting in my floor next to the window where the beacon feedline comes in. I had no idea how much inductance I would need, so I just put tap points in a few places, and started winding the wire until I ran out of paint bucket. The inductance ended up at peak being 5.88mH and at dip, 3.28mH.
I connected it in the line using the end tap points, and set the beacon to tune mode. My output was almost nothing, so I gave the handle a crank, and watched my field strength indicator start to rise, then it pegged the meter, and I got
kinda excited. But with the meter pegged, I couldn't tell when I had it peaked, so I turned on my scope and used it to peak the output. I changed the taps around until I found the highest output when peaked, and all I can say is: WOW !!! what a difference it made. Using the meter reading on my TS450S with the ant. disconnected, I had been getting an S-9 reading, it is now 25dB over
S-9. That should make a little bit of difference on the air.
Now, as long as the Yellowjackets And I can stay friends, The next step is to continue putting down some more radials.
73, and good LOWfer-ing; Andy - KU4XR - EM75xr - Friendsville, TN.
Posted by dave sampson on September 21, 2008 at 19:25:34.
In reply to Re: more loop antenna questions? posted by John Davis on September 21, 2008
you said a lower inductance to capacitance ratio is preferred...
is there an ideal ratio to shoot for?
also: is there a formula for figuring the the optimum turn spacing to achieve the lowest distributed capacitance?
assuming all other dimensions remain constant: is there a point where increasing the turn spacing further will have no effect or a negative effect.
thanks for answering all of my questions Re: Finally finished my Variometer
dave
Posted by J.B. Weazle McCreath on September 22, 2008 at 04:54:11.
In reply to Finally finished my Variometer posted by Andy - KU4XR on September 21, 2008
Hi Andy,
It's very rewarding to see that needle climb as you
crank the knob of the variometer, isn't it. You'll
now be all set for the 08-09 season! Good luck.
73, J.B., VE3EAR/VE3WZL New LF service on 30.2kHz & 48.25kHz (?)
Posted by Clive S Carver on September 22, 2008 at 05:04:21.
Today at 1155z when I switched my SDR-IQ and SpectraView on, noticed a 'new' transmission on 30.2kHz. This transmitts for a few seconds, then few seconds off. Does not appear to be fixed duration. However, when the transmission ceases, another carrier appears on 48.25kHz. Now at 1200z both transmissions have ceased.
Interesting!
Cheers
Clive
Re: Finally finished my Variometer
Posted by Douglas D. Williams - KB4OER on September 22, 2008 at 09:17:32.
In reply to Finally finished my Variometer posted by Andy - KU4XR on September 21, 2008
Your beacon is solid copy at 11am here in Watauga, TN. We are about 150 miles apart, so this is groundwave. Excellent work on your new loading coil. I never copied your signal with the old coil, so you have made a big improvement.
http://i81.photobucket.com/albums/j231/Goranothos/cap00011.jpg
-Doug Re: New LF service on 30.2kHz & 48.25kHz (?)
Posted by Gregg on September 22, 2008 at 17:50:16.
In reply to New LF service on 30.2kHz & 48.25kHz (?) posted by Clive S Carver on September 22, 2008
Hi,
Since you are in the UK, is it possibly the power company signals to/from the smart meters?
Cheers!
Re: New LF service on 30.2kHz & 48.25kHz (?)
Posted by Clive S Carver on September 23, 2008 at 02:36:47.
In reply to Re: New LF service on 30.2kHz & 48.25kHz (?) posted by Gregg on September 22, 2008
Yes, I am in the UK. (North Wales, about 2 miles west of the airfield at Hawarden/EGNR)
I'm not too sure about smart meter signalling in this instance. I know that there are LF transmitting stations in Germany (DCF39) and Hungary for this and other purposes, but the suggested UK system seems to be a two-way system which could involve GSM at the meter. This is a leaflet from the UK Energy Watchdog - http://www.energywatch.org.uk/uploads/Smart_meters.pdf
As for signalling via the power supply cable. I'm not aware of this for the electrical supply region that I am in (MANWEB ScottishPower), although that is not to say that it does not exist.
I would be interested for any further info re Smart Metering.
The signal I received on 30.2kH was quite distinct on SpectraVue at a strength 6dB greater than the HBG time signal on 75kHz and 3dB weaker than the DCF77 time signal on 77.5kHz. The 48.25kHz signal was substantially weaker.
Due to its few seconds on few seconds off nature, it stood out on the Spectravue's combined waterfall display. I have not observed it before.
Cheers
Clive
SJ tests
Posted by Sal, K1RGO on September 23, 2008 at 15:48:19.
Hanna blew down my lowfer antenna but its back up now. I am also testing a new antenna coil. I will be on slow cw around late morning at times and weekends for now if anyone wants to tune in (a primer for the lowfer winter season). SJ is still on 186.85kHz. pick-up loop questions?
...Sal, K1RGO
Posted by dave sampson on September 24, 2008 at 05:06:20.
hello
would like some opinions about pickup loops.
when using a multi-turn loop antenna: are there benefits in using a 2 or 3 turn pickup loop as opposed to a single turn and would it help the input impedance (that your receiver would see) to use a pickup loop of a significantly larger guage?
also have been using G4FJQ' rjeloop3 loop calculator and it is an awsome tool in designing multi turn loops!
thanks very much Re: pick-up loop questions?
dave
Posted by John Andrews, W1TAG on September 24, 2008 at 06:08:04.
In reply to pick-up loop questions? posted by dave sampson on September 24, 2008
Dave,
Here's one way to look at it. Think less about the impedance that the receiver sees than what the antenna sees. Let's assume a 50 ohm input impedance for the receiver. As an example, take a 14-turn loop that tunes to 137 kHz with a 1600 pF capacitor. The reactance of either L or C in that loop is 726 ohms at 137 kHz. And let's further assume that the Q of that tuned circuit is fairly high with nothing coupled to it. (A good assumption, as that unloaded Q should be greater than 100 if you've done a reasonable job building the loop.)
Now, consider what happens with a 1-turn pickup on the 14 turn loop. If the coupling is close to 1:1, then the impedance ratio is (14/1)^2 = 196. If the receiver input impedance is 50 ohms, then you are effectively placing 50*196 = 9,800 ohms across the tuned loop. Given that reactance of 726 ohms, the resulting Q would be (9800/726) = 13.5. That's a reasonable loaded Q, as it gives a 3dB bandwidth of +/- 5 kHz at 137 kHz.
But, watch what happens if you use a 2-turn pickup. The Q drops to 3.4, and the tuning is very broad. So, for this example, I would stick with the minimum of one turn, or perhaps even use less coupling by making that one turn smaller than the dimensions of the loop windings.
There are other approaches for connecting to the loop. You could series-tune the loop into a step-up transformer (wound on a ferrite toroidal core), or parallel tune the loop and use a step-down transformer. All of these approaches (including the pickup turn) keep the loop itself balanced, which should preserve the figure-8 pattern and minimize noise pickup.
So, if you think of the problem more in terms of what the loop sees as a result of being coupled into a 50 ohm receiver input, you'll be able to analyze the results.
John Andrews, W1TAG
Re: pick-up loop questions?
Posted by dave sampson on September 24, 2008 at 06:35:03.
In reply to Re: pick-up loop questions? posted by John Andrews, W1TAG on September 24, 2008
thanks john---im just a beginner: so all of your help is much appreciated. ill be building my first loop next month
and cant wait to get started!
73s choice of receiver
dave
Posted by Philip Evans on September 24, 2008 at 12:13:09.
Please can one of you, experts in the field, help this lay old man to choose a receiver - size and cost not so important - that will give him the best possible reception? Nostalgically attached to BBC Radio Four and now abroard, I miss it terribly. Thank you.
Re: choice of receiver
Posted by dave sampson on September 24, 2008 at 13:29:39.
In reply to choice of receiver posted by Philip Evans on September 24, 2008
loop height above ground?
hello
i believe the best (traditional desk top style) receiver for your money is the icom r-75.it has great dsp filtering as well as being sensitive and selective. it also covers a very wide frequency range (30kc-60Mcs) and has a ton of neat features...for longwave listening: you may want the optional 500cps or 250cps filters.
if your looking for one of the newest software defined radios: from what ive heard...the RF SPACE SDR-IQ or ONE OF THE winradio SERIES.
DAVE
Posted by DAVE SAMPSON on September 24, 2008 at 14:22:03.
hello all
wondering if the performance of a loop antenna would be affected if mounted only a few feet above ground?
thanks RYCOM 6040
dave
Posted by RICK on September 24, 2008 at 17:50:09.
Does anyone have a copy of the Rycom 6040 schematic/service manual? My displays ; both digital and analog are not reading.They only display a decimal point.The unit receives fine though.Id pay whatever postage necessary.
Thanks Re: RYCOM 6040
Rick KA2PBO
Posted by dave sampson on September 24, 2008 at 18:48:59.
In reply to RYCOM 6040 posted by RICK on September 24, 2008
Re: choice of receiver
hello
sorry i dont have one but did some websurfing and found a place called RIDGE EQUIPMENT has a manual for a 6041 which appears to be very similiar for about 15 bucks.
dave
Posted by Gregg on September 24, 2008 at 23:33:31.
In reply to choice of receiver posted by Philip Evans on September 24, 2008
The R-75 is a great suggestion, but for portability and economy, I love my Eton E5 :-)
They have a richer featured E-1 too.
Cheers!
Re: loop height above ground?
Posted by Gregg on September 24, 2008 at 23:43:04.
In reply to loop height above ground? posted by DAVE SAMPSON on September 24, 2008
Hi,
I tried my small loop near ground level and about 10' in the air. Same signals.
Same went for the internal RX loopstick at ground level and three stories in the air.
As long as your clear ob major LF obstructions (metal buildings, etc.) I don't think you'll see too much advantage until you're getting a halfwave up in the air.
Though some of the bigger loop owners here my have found some different results.
Anybody up for a DXpedition to the top of the CN Tower? :-D
Re: loop height above ground?
Posted by John Davis on September 25, 2008 at 00:05:04.
In reply to loop height above ground? posted by DAVE SAMPSON on September 24, 2008
Being too near the ground means some coupling will take place that can disrupt the "pure" ideal characteristics of the loop. But it won't render the loop useless by any means, even practically sitting on the ground. In practice, being above ground by two or more times the diameter of the loop renders these effects negligible and renders just about the maximum possible performance.
Mods done on " XR " Beacon, more power into the air now
Posted by Andy - KU4XR on September 27, 2008 at 12:41:08.
Greetings all:
I did a recommended mod to my xmtr, and the power is up to where
it almost has my field strength indicator pegged. I have no clue
as to how many more Milli / Micro-Watts it may have given me, but
every ounce counts, right ??? I'm going to need to redo my FS setup
and bring that meter reading down some, and then continue with
further hopefully improvements, and push this milliwatter
just a few more feet out into the grid-squares. Thanks to anyone
who tries to dig it out of the noise. Freq. is 184.322 KHz.
73, from Andy - KU4XR, Friendsville, TN. - EM75xr
loop motorized trimmer tuning?
Posted by dave sampson on September 28, 2008 at 09:08:49.
hello
checked out john/w1tag's loop antenna article,
you mentioned you had plans to ad motorized capacitive tuning.....
wondering what kind of results you have seen with this?
thanks Re: loop motorized trimmer tuning?
dave
Posted by John Andrews, W1TAG on September 28, 2008 at 09:55:47.
In reply to loop motorized trimmer tuning? posted by dave sampson on September 28, 2008
Dave,
I could tell you more if I had ever gotten around to doing it! Sorry...
John A.
loop motorized trimmer tuning?
Posted by dave sampson on September 28, 2008 at 15:14:47.
In reply to Re: loop motorized trimmer tuning? posted by John Andrews, W1TAG on September 28, 2008
john...not a problem most of us have way too many projects going on to finish them all at once:but ill be interested to hear more when you get to it!
dave
potrzebie