Author Topic: My home-made ferrite antennas  (Read 49231 times)

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Offline W3DRM

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Re: My home-made ferrite antennas
« Reply #100 on: May 06, 2014, 09:00:09 PM »
Don,
Glad the grounding of the shields did the trick.

A couple questions:  Did you have the shields on the PVC as someone had posted, but NOT grounded them yet?

After I built the ferrite antennas, I did not put them in the pvc right away because I wanted to see how they worked. A couple of days ago, I added the pvc pipes but did not shield them - again, wanted to see if there was any difference - there was not. So, I added the shielding. I used the same adhesive aluminum tape I had used for my V2 Loop antenna leaving a small slit along one side of the pvc. I did not attach any ground but it was soon apparent that my signals had dropped to almost zero and the noise levels went sky-high.

Quote
Did you have crappy efficiencies and noise and then placed the shields and did the grounding?

Yes, see my comment above. I added the grounds today and have been blown away by the change I am seeing.

Quote
Did you run a ground from the shields in to attach to the ground terminal on the pre-amp board or ground outside that?

The grounds are attached to each of the pvc pipes using another piece of the adhesive aluminum tape to hold the wire against the shield. That wire then goes to the ground-side of the atenna input terminals. There is one for each of the ferrite assemblies. BTW, I used some leftover 26AWG wire that I used to wind the ferrites with for the ground wires.

Quote
I just got some copper tape and hope to get things installed by this weekend since the trees with Oak Wilt are down and I hope to have some me time to work on this project further.

Thanks for the extra info.

Dale
  (I've always been wondering if I can put the shield tape on the pvc pipe when it is easy to access, and then ground later if I need to, or if it will goof things up by putting the wrap on the PVC and not grounding it to see what efficiencies I get with a different location.

I think the ungrounded shield actually acted as an antenna and picked up a lot more noise. Once I added the grounds, the noise dropped dramatically. I am currently seeing 47mvpp noise floor on the A channel and 46mVpp on the B channel. Prior to adding the grounds, it was around 120mVpp on each channel. That is a major drop in noise levels and was probably the cause of my poor performance.

I can't wait until I get the E-field kits so I can relocate everything outside and away from my noise sources.

Good luck with your setup. Hope these answers have helped.
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Offline dfroula

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Re: My home-made ferrite antennas
« Reply #101 on: May 06, 2014, 09:05:52 PM »
Both Jim McMurry and I had the same experience - the ungrounded shields pick up MORE noise than leaving the ferrites unshielded.

Don
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Offline Cutty Sark Sailor

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Re: My home-made ferrite antennas
« Reply #102 on: May 06, 2014, 09:18:26 PM »
Both Jim McMurry and I had the same experience - the ungrounded shields pick up MORE noise than leaving the ferrites unshielded.

Don
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And, back in the old garage sweet spot location, shielding helped not at all with the 300mm ferrites... just decreased over-all signal and noise level.  My weird location seems to prefer non-shielded since most if not all my noise is H field related. Strange...but that's the way it is here!  Arrrrggghhhh....

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Offline DaleReid

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Re: My home-made ferrite antennas
« Reply #103 on: May 11, 2014, 07:52:55 PM »
Well, I'm going to bite the bullet and apply copper tape shield to my ferrites tonight or tomorrow.

Having too much fun watching the real time display as those storms rumble by.

I know some here have NOT gotten benefit, I guess I could try to remove the copper (expensive) foil if it doesn't help any.

Question:

Is there a preferred orientation for the break in the surrounding shielding material?  Is it best to have the open notch vertical up, vertical down (rain won't run in the break and get under the adhesive), facing one or the other horizontal planes?

I assume since it was done that way in the project that each shield should have it's own separate ground wire run back to the amplifier board and under the ground screw with the associated wire from the ferrite?  I was thinking just run one wire to a shield, jump to the other shield.  Not that I'm short on wire, but why do more than needed?  I see the ground screw is on the same ground plane as the other one on the board.

If some of you guys can tear yourself away from the screens, I'd appreciate it.

Dale


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Offline scarecrow93

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Re: My home-made ferrite antennas
« Reply #104 on: May 11, 2014, 08:43:45 PM »
Dale-

I don't think it matters much.  I have my notch pointed toward the horizon.  My setup was only made for use inside the house.

If you're worried about rain getting under the adhesive, what about putting the completed antenna inside another, unshielded PVC pipe?  Maybe there is a rubber grommet or some other spacer you can use between the completed antenna and the outer PVC pipe.  That way you know the rain is a non-factor.

Just my .02   :grin:

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Offline dfroula

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Re: My home-made ferrite antennas
« Reply #105 on: May 12, 2014, 09:53:44 AM »
Electrically, the orientation of the gap matters not.

As for shield grounding, I have tried several configurations while trying to find a solution to my AS3935 detection issues.

I originally had the shield grounds tied to the "-" wire of each antenna from their respective shields. I also tied the grounded pair to the drain wire of the shielded cable I use to connect the antenna assembly to the amp board. At the amp, the drain wire and "-" antenna lead from each antenna are tied to the grounded "-" side of the amplifier inputs. Don't tie the grounded leads to the input connection of the amps or you will have all sorts of weird noise pickup!

I also tried separating the shield grounds from the antenna ground, running a separate ground just to the shields, and leaving the rest of the system without an explicit ground. DON'T DO THIS!!!!!! The noise pickup was incredible because of the potential difference between the shields and the rest of the system.

I finally just re-grounded the controller, took the single common shield ground wire I had installed at the antennas and reconnected the single wire to one of the "-" terminals at the amp input. This worked just as well as my original "dual-ground" setup and returned normal operation.

None of theses ground configurations caused my AS3935 to start detecting lightning, however!

Regards,

Don
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Offline DaleReid

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Re: My home-made ferrite antennas
« Reply #106 on: May 14, 2014, 09:17:20 PM »
This afternoon I decided to bite the bullet and get the ferrites shielded.

I used a wrap of copper foil tape, soldered the ground wire to each of the clever tabs I made, and ran the wire from each shield into the box and firmly but gently placed the tinned wire end under the - terminal.

I guess I was hoping for more.  Still get the burst of some noise once in awhile.  Gone into interference a couple times already.  The automatically controlled gain may be running higher numbers than I've seen for extended periods, but hard to know in just this short while.

I will try to get the E-field antenna together when it arrives and functioning well before I move things out to the shed, where I hope to find a quieter environment.

Nonetheless, as I try to get a relatively well thought out area to put the antennae, I have a couple of questions:

First, is there a way to 'plug into' the amplifier board and wander around sort of listening to it to see if the apparent noise fades or an intermittent local noise can be minimized?  I thought I saw somewhere that one of the participants was using an ear bud to listen for a good spot.  Maybe it was too much Cutty, although the Coors may have had something to do with it too.   Dunno.  But I cannot find that reference again, if there was something like this being done to listen to local noise.

Second, the auto gain function seems to be way better than the manual yellow LED setup, but since the system varies the gain all over the place, and other than looking at the Controller Board generated web page to see what the values are, I don't know of a handy little graph that Tobi generates that would allow one to look back, say two to six hours, and see a plot of what the gain settings were over that period.  I would think this might be helpful to see, in addition to the efficiencies, how much the gain can be elevated, and hence the relative quietness of the session.

There are graphs up the yazoo, so I would think that something like this may have been done and just isn't particularly obvious to me.  On the other hand, maybe this info is of zero value.

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Offline jmcmurry

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Re: My home-made ferrite antennas
« Reply #107 on: May 15, 2014, 08:11:18 AM »
Second, the auto gain function seems to be way better than the manual yellow LED setup, but since the system varies the gain all over the place, and other than looking at the Controller Board generated web page to see what the values are, I don't know of a handy little graph that Tobi generates that would allow one to look back, say two to six hours, and see a plot of what the gain settings were over that period.  I would think this might be helpful to see, in addition to the efficiencies, how much the gain can be elevated, and hence the relative quietness of the session.

Dale,

Not a graph, but I have a php script that I have running each minute that creates a log entry whenever there's a gain change on either channel, or a change in status.  The attached shows the log in action and you'll also see where my ISP went down for 1.5 hour at midnight.  If that would be useful I can clean it up, zip it and post a copy later today.

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Offline dfroula

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Re: My home-made ferrite antennas
« Reply #108 on: May 15, 2014, 08:32:24 AM »
I've installed a 1/8" stereo jack on all the amplifiers I have built. The jack is connected to the test output pins as follows:

sleeve---Gnd
TIP------Amp 2 signal
RING-----Amp1 signal

This puts channel 1 in the right ear and channel 2 in the left.

You cannot plug low-impedance earbuds or headphones directly into the jack, as they will load the amplifier too much and stop detections. You need to plug a stereo amplifier into the jack and the headphones into that. I built a battery-powered stereo "CMOY" stereo amp for the purpose.

You could conceivably unplug the amp from the controller, rig a 5-volt battery supply, manually adjust the gain with the pot, and walk around the house listening for a low-noise spot.

Nerd alert: This will make your friends and family think you have gone over the edge!

It does work, however.

Regards,

Don
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First, is there a way to 'plug into' the amplifier board and wander around sort of listening to it to see if the apparent noise fades or an intermittent local noise can be minimized?  I thought I saw somewhere that one of the participants was using an ear bud to listen for a good spot.  Maybe it was too much Cutty, although the Coors may have had something to do with it too.   Dunno.  But I cannot find that reference again, if there was something like this being done to listen to local noise.

Offline 92merc

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Re: My home-made ferrite antennas
« Reply #109 on: June 03, 2014, 11:06:11 AM »
OK, after reading all of this thread, I now know how to make a 300mm antenna.

But here's what I haven't seen in this thread.  What advantages are you guys with the longer antennas noticing?  On good days, I'm reaching pretty well with my 200mm.

So lower noise?  Better range?  Are you having to drop the amplification down due to longer antenna?

I'm just trying to see if the antenna change is worth the effort.  TIA
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Offline JonathanW

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Re: My home-made ferrite antennas
« Reply #110 on: June 03, 2014, 11:08:53 AM »
I have nothing to compare it with, but I went with Mike's 300mm, ~700 turn design (double heat shrink tubing).  After adjusting a few things, I'm detecting strikes at more than 3000 km nearly out of the box (before decent siting, packaging, grounding etc.).

Offline dfroula

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Re: My home-made ferrite antennas
« Reply #111 on: June 03, 2014, 11:52:11 AM »
Longer ferrite = more gain in the antenna and less needed at the amplifiers, resulting in better signal-to-noise ratio. That means longer distance detection.

There is a limit, however. Too much antenna gain will increase the sensitivity to local noise sources as well. Also, too long an antenna may drop the self-resonance of the antenna into the range used by the amplifier filters. This may distort the waveforms to the point that the system can no longer assign an accurate time stamp to a strike. Our antennas need to operate broadband, with low-Q - The opposite of a regular narrow-band radio receiver antenna.

The 250x7.5 mm antennas have test data to show the self-resonance range is well above what is used by the amp filters, so no issues.

The 300x7.5 mm antennas have not been characterized, but they seem to be working just fine as well for those who are using them..

That is using 26awg magnet wire, which is HIGHLY RECOMMENDED, as the tests were conducted with that gauge and the resulting number of turns.

Best regards,

Don
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OK, after reading all of this thread, I now know how to make a 300mm antenna.

But here's what I haven't seen in this thread.  What advantages are you guys with the longer antennas noticing?  On good days, I'm reaching pretty well with my 200mm.

So lower noise?  Better range?  Are you having to drop the amplification down due to longer antenna?

I'm just trying to see if the antenna change is worth the effort.  TIA
« Last Edit: June 03, 2014, 11:55:29 AM by dfroula »

Offline Cutty Sark Sailor

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Re: My home-made ferrite antennas
« Reply #112 on: June 03, 2014, 12:01:20 PM »
I believe my unshielded 300mm, 7.5mm are slightly more immune to the H field noise in my environment, while at the same time increasing the signal somewhat. I don't have equipment to measure. That's in comparison to the originals I ordered with the kit... Mine are oriented N/S E/W for several reasons, mostly because that's how I want them  :twisted:
I think my most distant strike detected was close to 4800km, back when Don F and I were the only two reds, and in 'serious bloody competition'  ;) over who was #1.... and the nearest just about 7Km, if I remember correctly.
(But this isn't really about distance... we should all remember this is about network efficiency)
When I attempted shielding, my initial impression was that the 'noise basement' had dropped about 10 db.  That was purely coincidental and situational, and proved not to be the case. Eventually I became convinced that the overall performance had degraded because of it, and removed the shielding.

My gains on H field are typically 10x10 both channels, depending on the axle factory's welders and assembly lines south of me. Then A needs to about 8x8 or 8x5, depending. My thresholds typically are 100-120 (without channel mapping) in either or both channels. With Channel mapping, because of the E field addition, I've been running them at 100-110. If old axle factory runs a second line, especially at night, I bring 'em to 120.

Nothing bothers my E fields... once in awhile a lawn mower, or some other thing that arcs nearby, might cause a burst of interference... only other way to get to interference mode is with simply too many signals. With my 370mm (15") probe, I'll have to knock gain all 3 channels down to 2x1 or even 1x1 and still detect strikes 200-300 mi away with E field alone, and H field at 1x1. I've run E field at 8x8 all channels, but typically will run at about 5x5, which is still too high for <300 miles and thresholds are always at 90.

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Offline JonathanW

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Re: My home-made ferrite antennas
« Reply #113 on: June 03, 2014, 12:05:46 PM »
Longer ferrite = more gain in the antenna and less needed at the amplifiers, resulting in better signal-to-noise ratio. That means longer distance detection.

There is a limit, however. Too much antenna gain will increase the sensitivity to local noise sources as well. Also, too long an antenna may drop the self-resonance of the antenna into the range used by the amplifier filters. This may distort the waveforms to the point that the system can no longer assign an accurate time stamp to a strike. Our antennas need to operate broadband, with low-Q - The opposite of a regular narrow-band radio receiver antenna.

The 250x7.5 mm antennas have test data to show the self-resonance range is well above what is used by the amp filters, so no issues.

The 300x7.5 mm antennas have not been characterized, but they seem to be working just fine as well for those who are using them..

That is using 26awg magnet wire, which is HIGHLY RECOMMENDED, as the tests were conducted with that gauge and the resulting number of turns.

Best regards,

Don
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Not to mention that going much larger/longer for ferrites is a needless increase in cost and space requirements.  The system as it is is more than sensitive enough for long-range detection with 250-300 mm long ferrites.

Once you're using that length/gain of H-field antenna, you're probably better off trying to reduce noise sources directly.
« Last Edit: June 03, 2014, 12:15:38 PM by n0ym »

Offline Cutty Sark Sailor

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Re: My home-made ferrite antennas
« Reply #114 on: June 03, 2014, 12:09:36 PM »
Longer ferrite = more gain in the antenna and less needed at the amplifiers, resulting in better signal-to-noise ratio. That means longer distance detection.

There is a limit, however. Too much antenna gain will increase the sensitivity to local noise sources as well. Also, too long an antenna may drop the self-resonance of the antenna into the range used by the amplifier filters. This may distort the waveforms to the point that the system can no longer assign an accurate time stamp to a strike. Our antennas need to operate broadband, with low-Q - The opposite of a regular narrow-band radio receiver antenna.

The 250x7.5 mm antennas have test data to show the self-resonance range is well above what is used by the amp filters, so no issues.

The 300x7.5 mm antennas have not been characterized, but they seem to be working just fine as well for those who are using them..

That is using 26awg magnet wire, which is HIGHLY RECOMMENDED, as the tests were conducted with that gauge and the resulting number of turns.

Best regards,

Don
WD9DMP

OK, after reading all of this thread, I now know how to make a 300mm antenna.

But here's what I haven't seen in this thread.  What advantages are you guys with the longer antennas noticing?  On good days, I'm reaching pretty well with my 200mm.

So lower noise?  Better range?  Are you having to drop the amplification down due to longer antenna?

I'm just trying to see if the antenna change is worth the effort.  TIA
Don gives us some very specific info here... and he's dead right.  If you check efficiencies, (right now all our eyes seem to be on distance,) and look closely, his antenna suggestions consistently come in way up there. Best over all might actually be Jumpin' Joe's 12 ball loop.
But 'detection at distance' isn't the best critera for the network. look on your station page, at your 'locating ratio'.... we get everybody consistently to around 20-40% we've got a good network... when it's low, below 10 especially, we're sending too many signals compared to strokes detected. There are any  number of reasons for this, but most of it is because we're running higher gains than a more denser network would require. And missing some percentage of nearer signals because of the clutter this produces.
« Last Edit: June 03, 2014, 12:15:25 PM by Cutty Sark Sailor »

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Offline Cutty Sark Sailor

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Re: My home-made ferrite antennas
« Reply #115 on: June 03, 2014, 12:16:17 PM »
oops... change "detection ratio' to "locating ratio" in the above...

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Offline 92merc

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Re: My home-made ferrite antennas
« Reply #116 on: June 03, 2014, 12:17:20 PM »
OK, a lot of that makes sense.

What I'm noticing on my 200mm is that on a good day, I can run 10x10.  On those days, I'm getting close to 1300 miles of detection.  I've seen strikes into Mexico and off the ocean by Delaware, from North Dakota.  A lot farther than I expected.

But other days, I have to drop the settings down to 10x5 or even 10x4 to get out of interference.  Then my EF ration drops to 20% or less.  Today is a good day, I'm running 67%.  But I just had to drop my numbers from 10x10 this morning to 10x5 again.

So with a longer antenna, I probably won't be running 10x10, probably 10x8 or so.  But still needing to drop that number down during interference.  That's basically the info I'm looking for.
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Re: My home-made ferrite antennas
« Reply #117 on: June 03, 2014, 12:18:13 PM »
BTW, I'm still waiting for my E-Field to arrive...
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Offline Cutty Sark Sailor

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Re: My home-made ferrite antennas
« Reply #118 on: June 03, 2014, 12:21:33 PM »
OK, a lot of that makes sense.

What I'm noticing on my 200mm is that on a good day, I can run 10x10.  On those days, I'm getting close to 1300 miles of detection.  I've seen strikes into Mexico and off the ocean by Delaware, from North Dakota.  A lot farther than I expected.

But other days, I have to drop the settings down to 10x5 or even 10x4 to get out of interference.  Then my EF ration drops to 20% or less.  Today is a good day, I'm running 67%.  But I just had to drop my numbers from 10x10 this morning to 10x5 again.

So with a longer antenna, I probably won't be running 10x10, probably 10x8 or so.  But still needing to drop that number down during interference.  That's basically the info I'm looking for.
Remember that 'efficiency' rating on the 'Participants' page is "network overall"... if all the storms are in Washington State, you'll have a very low percentage, but our West Coast stations, normally toward the bottom, will jump way the heck up there. Besides antennas, a big reason middle US stations are consistently up there is simply due to location.

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Offline JonathanW

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Re: My home-made ferrite antennas
« Reply #119 on: June 03, 2014, 12:28:59 PM »
OK, a lot of that makes sense.

What I'm noticing on my 200mm is that on a good day, I can run 10x10.  On those days, I'm getting close to 1300 miles of detection.  I've seen strikes into Mexico and off the ocean by Delaware, from North Dakota.  A lot farther than I expected.

But other days, I have to drop the settings down to 10x5 or even 10x4 to get out of interference.  Then my EF ration drops to 20% or less.  Today is a good day, I'm running 67%.  But I just had to drop my numbers from 10x10 this morning to 10x5 again.

So with a longer antenna, I probably won't be running 10x10, probably 10x8 or so.  But still needing to drop that number down during interference.  That's basically the info I'm looking for.
Remember that 'efficiency' rating on the 'Participants' page is "network overall"... if all the storms are in Washington State, you'll have a very low percentage, but our West Coast stations, normally toward the bottom, will jump way the heck up there. Besides antennas, a big reason middle US stations are consistently up there is simply due to location.

As they say, "location, location, location".  Try telling your spouse and your realtor that you need to find a house with good lightning detection characteristics the next time you go hunting.  See how that goes over :)

Offline DaleReid

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Re: My home-made ferrite antennas
« Reply #120 on: June 03, 2014, 12:45:26 PM »
Mark,
I beg to differ with you.

The reason that us MidWesterners are frequently high on the efficiency list is cuz we're such cool dudes.

Nothing at all to do with location.

"I don't often invite interference, but when I do, its Dos Equis..."

Now if I can just get my Efile done.

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Offline dfroula

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Re: My home-made ferrite antennas
« Reply #121 on: June 03, 2014, 01:00:08 PM »
This is just an empirical observation, from when I had Dave R's station running here (300 mm ferrites), comparing to my 250 mm antennas. It seemed that the longer antenna's exhibit greater directivity. I am somewhat concerned that carrying the "longer is better" philosophy too far may create some null area's in coverage at 45, 135, 225, and 315 degrees from the right-angle antennas. I know that when I have constructed tuned LF AM direction-finding ferrite antennas, "longer" usually also meant "more directional" and "sharper nulls".

Regards,

Don
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Offline dfroula

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Re: My home-made ferrite antennas
« Reply #122 on: June 03, 2014, 01:10:15 PM »
On a quiet day with no nearby storms and relative low lightning density in North America, I can run 16x10 on both 250x7.5 mm antennas, both thresholds at the default 120mv with "Auto Adapt to Noise" on. I will usually run at 100% effective gains with those settings, indicating gain up to the max I have set.

I need to back down to 16x8 to stay out of interference mode if there are local storms or a high density of storms in North America. I rarely bother to adjust the gains any lower, and just ride out any storm-induced interference mode.

The "Auto Adapt to Noise" handles local noise sources fine, which in my case seem to come and go in the afternoon. These noisy periods result in lower effective gains, but rarely induce interference mode periods.

These settings seem to scale well with Mike's settings, considering the 50mm longer length of his antennas.

That old cigarette ad comes to mind - "...a silly millimeter longer..."  :-)

Don
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Offline JonathanW

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Re: My home-made ferrite antennas
« Reply #123 on: June 03, 2014, 01:14:38 PM »
This is just an empirical observation, from when I had Dave R's station running here (300 mm ferrites), comparing to my 250 mm antennas. It seemed that the longer antenna's exhibit greater directivity. I am somewhat concerned that carrying the "longer is better" philosophy too far may create some null area's in coverage at 45, 135, 225, and 315 degrees from the right-angle antennas. I know that when I have constructed tuned LF AM direction-finding ferrite antennas, "longer" usually also meant "more directional" and "sharper nulls".

Regards,

Don
WD9DMP

That might explain the "greater noise immunity" Mike noticed.

In another life, I did quite a bit of antenna modeling with NEC--though never anything with ferrites.  Let me see if there's something that can be done to simulate these things.

Offline 92merc

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Re: My home-made ferrite antennas
« Reply #124 on: June 03, 2014, 01:15:30 PM »
OK.  I'll have to fess up a bit here.  I have already made a 300mm test antenna set and used it for a couple of days.  But what I started noticing is exactly what Don was referring to.

On my 200, I was getting strikes in Wisconsin before.  But with the 300, much less strikes in that general direction.  I didn't know if it was due to my lower amp setting or what.  So I put the 200 back in last night.  And now it seems better.  But of course due to storms in SD, I'm having to back the amp down.

I bought more cores, so I might have to try to make a 250mm next.

Oh, BTW, my antennas are NW/SW arrangement.  But that's because my house is set that way.  And my OCD says the antennas have to match the walls in my garage.  They can't be crooked.  :-)
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