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Author Topic: "Good" antenna noisy, "bad" antenna quiet  (Read 492 times)

N3WTK

  • Posts: 84
Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #30 on: March 02, 2021, 09:57:32 AM »

Yeah, seems to be working.

Also I should clarify, that when I added the 14 ft or so of coax and I said "...the noise went up" it didn't go up to S8 or whatever, it only went up to something like S3-S5 (but S1 without it). Anyway...

At some point I may build a simple dipole (or a 10/20/40 fan dipole) and see how that compares. For now you're right, use it -- I'm going to see if I can't work some stations with this antenna, so I don't spend ALL of my time tinkering and not using it.

I'm calling CQ in the mornings before work and in the evenings after work. So far I'm hearing a few US stations only, sometimes BC. No DX yet. I keep seeing posts (on Facebook) about people working Canary Islands or Spain on their dipole tucked under the eaves of their house...

This has been a fruitful discussion. I learned about building proper common mode chokes and where to put them. The MiniWhip has come down and put in a box (I got equal results from an odd piece of wire laying on the roof as a noise reference antenna). The initial question of this post was why the miniwhip was quiet when grounded and I guess that was all due to CM, which went away when grounded. The Alpha needs something to work against, so I'm still a little puzzled exactly how it works. It's funny, there are many end-fed you can buy or build from books; there are a gazillion dipoles you can buy or build from books, etc. Nowhere have I seen an "HF J-pole" in a book, and only one commercial one for sale. Not sure what that means; just an observation. The MFJ-1026 will get put away, kept on hand just in case, until I realize I never use it, or I use the coax for the reference antenna to feed a dipole, then will probably sell it.

If I ever learn anything new related to the Alpha HF J-Pole, or ever do a comparison between the Alpha and a simple dipole then I'll report back here.

Hope to catch y'all on the bands...
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Dave / N3WTK

N3WTK

  • Posts: 84
Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #31 on: March 06, 2021, 01:34:21 PM »

I'm not trying to work the ARRL DX contest for contest's sake, but I thought today's DX contest might be a chance I could work some DX. I heard some DX stations (Hawaii, US VI, Paraguay, ... HI was +10 over S9) but no one could hear me. It got me thinking, I wonder if I need that counterpoise after all, even though it adds RX noise. Adding that common mode choke brought my background white noise down, but does that mean it's an effective TX antenna? I mean, I could also bring the noise down by unplugging the antenna -- it'd be quiet all right, but wouldn't get out, either! Do I need to suffer S3-S5 background RX white noise in order to get out with this antenna?
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Dave / N3WTK

W1VT

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Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #32 on: March 07, 2021, 06:38:28 AM »

I think you need to be able to hear noise on a transmit antenna to work DX stations in a DX contest.  You are competing with many stations running full size antennas and amplifiers.  My 40 ft vertical for 75M is really noisy living in the suburbs but I've worked 34 stations and 23 entities including Australia.  Four new ones so just sixteen more for 75M DXCC!

Zak W1VT
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N3WTK

  • Posts: 84
Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #33 on: March 07, 2021, 09:38:12 AM »

So I did end up working Hawaii and New Zealand last night. They gave me 55 and 59 signal reports but judging by the number of times I had to repeat my call, I'm guessing those reports were not accurate. When I worked these stations it was late at night and no longer a million people trying to get it.

Even with the CMC there's still some noise; it's not like my antenna is dead-quiet. It's maybe S1, and without it maybe S8? I'll have to post a video some time. . .
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Dave / N3WTK

KL7CW

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Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #34 on: March 07, 2021, 05:05:07 PM »

It sounds like you have partially solved your problem.  I have found out that usually for TX on end fed antennas, the more counterpoise wires, vent pipes, or whatever is better, or at least the same but not always. One time in England, I hooked on to the steam radiator system as my counterpoise and it seemed to suck the signals out.  For RX you also need to try different configurations.  If you have a counterpoise system, it is possible that hooking onto a vent pipe, or ground wire run down through, or near the house that half of the antenna may pick up noise from within your house, even with a "good" choke on the feedline, so try it both ways for RX.  I have a RX array for 160 and 80 meters about 250 feet from the shack.  To get rid of most of the common mode noise pick up, I now have a choke in the shack, about 40 feet from the shack, and about 20 feet from the array.  I used approximately a dozen turns on an FT240-31 core.  Now most noise is directional and comes from various houses including my house.  All houses are at least 250 feet from the array.  I live in a semi-rural "quiet" area, so it must be really bad in an urban (noisy area). SMPS noise is especially bad on 160 and sometimes 80 meters, but usually more tolerable on the upper HF bands.  The next time a tree branch takes out my feedline in the woods, I may just add one additional choke at that point, just for insurance.  The loss in the chokes is nearly zero and the cost of each is only a few dollars.  I probably got more bang for the buck by putting my three chokes in different locations, rather than 2 or 3 in series in one location, but I was primarily interested in the low HF bands.  However the type 31 material and my chokes seemed to clean up a few noise sources near the top end of the HF spectrum also, so no type 43 material needed.  Also my directional Yagi also had better S/S + N ratio than my RX array in nearly all situations on say 20-6 meters.  These are just some of my observations, I am not an expert.  My feed line was Cat 5e cable, and used balanced circuits, but not all were optimally balanced, thus some of my common mode pick up was due to my design, so this many common mode chokes may not have been necessary.     Keep on experimenting and if at all possible a separate RX antenna as little as 20 or 30 feet from the house may be significantly better than any antenna on or near the house.             Rick  KL7CW
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N3WTK

  • Posts: 84
Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #35 on: March 08, 2021, 08:51:25 AM »

Thanks for that insight, Rick. I guess I should keep experimenting. I discovered a new way to test TX, via websdr.org. I tried tuning up a couple of stations yesterday and I could NOT hear myself in UT or DC. Yet, I was copying stations from Japan, Paraguay, Virgin Islands, etc. some at S9! (granted, they were running 1kW) And I believe the websdr was working because I could hear a station on my radio AND on a websdr station, at the same time. That was cool, but I didn't hear myself calling.

But the websdr might help me determine if TX is working, and I can try different setups without having to find a patient ham to listen for me and wait for me to make a change, listen again, etc.

What I'm thinking I'll do is first of all buy a short coax jumper then that'd get me the ~9' coax Glenn suggested and put my CMC right at the base of my feedpoint mast. I'll also buy some more toroids and make some additional CMCs to put in other places, and then I'll experiment with laying out counterpoises in combination with the above.

I know, I know, this is a lotta lotta work to avoid putting up a simple dipole. I even have a pair of trees for a dipole but then the feedline hangs down in the middle of the yard, and I'm trying to make my wife happy and make my antennas discrete. As it is, my radio is banished to the garage (which also puts the operating position a LONG way from those two trees). So the endfed over the house keeps the antenna and feedlines out of sight and puts the feedpoint right over the shack. Just trying to make the most of my situation. Here's what my QTH looks like, if you're interested. So you can see, those two trees are just begging for a N-S dipole, but then, not only does the feed point drop straight down in the middle of the yard (where she sits out daily!) the feed line is pretty long, has to go up over a retaining wall, and lay on concrete for awhile, to get to the shack.

Here's something new, an observation that I didn't notice before adding the CMC -- on TX now I get a buzz in my radio's internal speaker (or headphones) that I didn't used to have. I haven't done a direct in/out comparison to prove it's the CMC but it must be, since it wasn't there before. What does that tell you?
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Dave / N3WTK

W6MK

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Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #36 on: March 08, 2021, 01:52:24 PM »

I even have a pair of trees for a dipole but then the feedline hangs down in the middle of the yard, and I'm trying to make my wife happy and make my antennas discrete.

Most antennas are discrete but the wife-pleasers probably need to be discreet.

Regarding how the feed line hangs, keep in mind that dipoles don't necessarily have to be fed at the center.
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K0IZ

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Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #37 on: March 11, 2021, 08:02:40 AM »

Interesting topic and good info.  Dave, if you decide to try a dipole, given that you have two trees, you might consider a "V" beam.  This would basically be a dipole with center feed point at your house (roof peak, etc), and ends going to the two trees.  If angle between is at least 45 degrees, you should be good.  Pattern would be a little funky since in theory V beam best direction is between the angle.  But your angle would likely not be best on any band, so lobes will be wherever they decide to be.  (V beam is not an inverted V, incidentally).
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N3WTK

  • Posts: 84
Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #38 on: March 11, 2021, 01:21:00 PM »

... given that you have two trees, you might consider a "V" beam.

That looks interesting, thanks!

I drew on my map where I might put it. The angles look OK but the lengths are not great, only about 40-45 ft to those two trees from the house at that angle. What I read about v-beams is that they should be close to 1 wavelength long. But maybe I could try it. See photo below. Any dipole I put up would probably go where the Alpha Sr is, so it'd be < 20ft from the ground, hence mostly radiate straight up.

Also indicated in that photo is a new thought -- what about a vertical? I know, you're thinking, if you have noise problems then you don't want a vertical! But I don't know what my noise problems are; we kind of found (?) that they're from common mode current, since the CM choke largely knocked them out. Problem is, anywhere to put a vertical is right between my and my neighbor's house (see green area of photo). The two rectangular roof areas, one where my shack is (the #2) and the other under where the "0" label is, could be potential spots if I could place a vertical on the roof somehow.

Also, still wondering about this; I don't want this to get forgotten...
Quote
Here's something new, an observation that I didn't notice before adding the CMC -- on TX now I get a buzz in my radio's internal speaker (or headphones) that I didn't used to have. I haven't done a direct in/out comparison to prove it's the CMC but it must be, since it wasn't there before. What does that tell you?

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Dave / N3WTK

K0IZ

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  • Posts: 1176
Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #39 on: March 11, 2021, 04:29:16 PM »

Over the years I have had better luck with balanced antennas than either end fed or verticals.  Looking at your layout, if you could manage 45 ft legs, I would be inclined to install a G5RV and let the 6ft (102ft total) on each end dangle down.  Certainly a compromise.  Also feedpoint is some distance from your #2 location but possibly could be spanned by the window feedline of the G5RV.
Most V antennas are multiple wavelengths and give high gain and sharp directivity.  Yours won't have any gain but directivity will also be fairly broad, which I suspect in your case is an advantage.

I don't recall if you said what bands you would like to use.  One other possibility to take advantage of your current #2 feed point would be an off-center fed antenna.  Longest side towards tree like your end fed, short length (could be 33% or 20%) somewhere else.  Maybe the opposite house
peak from the V beam location?

Who knows, you might wind up with a real antenna farm!
« Last Edit: March 11, 2021, 04:32:26 PM by K0IZ »
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N3WTK

  • Posts: 84
Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #40 on: March 13, 2021, 11:59:17 PM »

I made a post in the antenna forum to ask a separate question about what an antenna sees as ground if the ground slopes. That question quickly evolved and I made some common mode current measurements. They are relevant to this discussion we've been having here.

Anyone interested in this saga might want to check out the other topic titled "How high is my antenna over this ground?" in the antenna forum. I know I said earlier in this thread that adding a ground wire made things worse, but that was before I built the K9YC-common-mode-choke. Now it's looking like this antenna may be improved by the addition of a grounded counterpoise, and the inclusion of a CMC.
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Dave / N3WTK

N3WTK

  • Posts: 84
Re: "Good" antenna noisy, "bad" antenna quiet
« Reply #41 on: March 15, 2021, 08:36:51 AM »

That last thread I just mentioned got locked, due to some inappropriate posts. A new thread has been started on common mode current and counterpoise measurements.
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Dave / N3WTK
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