I listen on 3885.. antenna questions

[Opcom]

On 3885 I can sometimes hear a carrier, a few words. Sometimes Don comes in real good when the weather's right but that's about it. There is so much noise here with my small wire antenna it's ridiculous. You'd think after 30 years in electronics I would have some experience with antennas, but the answer is no. Right now it's 40FT of wire, 10FT off the ground. It's useless to use amplifiers to force the issue if I can't hear anyone. A tuned preamp just makes everything louder including the noise. Most of the noise seems to be of the power line type, although there is some racket from the ethernet.

If I go to a 100FT dipole, 15FT off the ground at the ends and 45FT tall at the center, is this going to make as big (huge) a difference as I am told? It will be perpendicular to the power lines.

The tower will be a rohn 25 with three yardarms near the top: one with a halyard for the dipole center insulator, one for a VHF discone (100-175MHz), one for a UHF discone (200-500MHz). Might or might not put a 6M beam and some kind of vertical on top but I don't want to overload the thing.

I'm asking this stupid question because I'm about to spend the considerable cash and I don't want it to be a waste or to find out later once I am broke again that I should have put up something else. Your opinions might give me some comfort since you have no money interest in the job. I hope this will be done before summer.

[Sam KS2AM]

Hi Pat,

If I'm reading between the lines correctly it sound like you don't have any trees of any significant size to hang the antenna off of.
I think the 100ft / 45 ft dipole will make a big difference over what you have now but if you really do have that much noise coming from power lines or computer equipment it could be all for naught as a receive antenna.

The cost of a tower is a reasonble concern so why not try a temporary support made out of wood, pipe or monopole antenna mast ?  Even if its only up for a day or two it should give you and idea of what to expect.  I don't really have any experience with these supports but there are some web pages around describing their construction.


Good Luck

Sam / KS2AM

[KF1Z]

Yup, it will make a huge difference....

I assume only 100 foot long because of space issues...?

My 75 meter dipole is 65-70 feet from 3phase power lines, and parallel to them.
I get NO interference from them.
(well, yes I do, but below 1500kc)

If you could squeeze another 20 feet on to the wire length you'd do slightly better as well (120' total)

[WD5JKO]

Patrick,

    Many have reported that a FW horizontal loop up 40' or so will make a big difference with S/N ratio on receive.

    I just got off 3880 at 10 am, and my worst enemy is also noise. I use a Windom antenna. Some of the noise comes from 'stuff' in my house, power lines outside, and the neighbors outdoor bug zapper. Fortunately in the early evening (before 9 pm local), the ham signals come up considerably and in effect 'squish' out the noise.

    Part of the problem is that copying the guys in the east (w4's), and the Northeast (W1's, W2's, and W3's) is that many of these folks are pretty close together, and they copy themselves just fine with about 30% modulation. To make matters worse for us a long way away, some emphasize the frequencies below 500 Hz with about 80% of their sideband power. So all I experience here is S9 + carriers and muffled bassy audio that is in my noise level. Trying to copy requires some sophistication in your receiver. Some of the tools needed include, various filter bandwidths, passband tuning, Sync-Detection, Noise limiting, Noise blanking, DSP, or use SDR where all of the goodies are built into the software.

    Yes your antenna ideas will make a big difference. With the situation here at my QTH, two signals stand out that propagate well, are well modulated, and equalized such that an abundance of the sideband power is spread out to 3-4 Khz, and these two are consistently Tim Wa1hlr, and Don K4kyv. When either are in a roundtable with stations close in to them, I usually can only hear those two stations, even though several others have near equivalent signal strength.

    So Patrick, have you tried listening to the group in Texas and surrounding states? It would be interesting to hear from those in the E and NE to find out who they hear in the 5th call area.

Regards,
Jim
WD5JKO

[KA1ZGC]

Hiya Patrick,

I'd say you're probably already receiving all the noise you're going to from your power lines. What you're experiencing is likely direct EM coupling, in spite of being "perpendicular to the power lines" (I'm willing to bet you're perpendicular to the street primaries, not so much to the secondary feeding your home?).

If the power company is dealing with a particularly reactive load on your circuit, then it may not even be radiated garbage you're dealing with as much as just dirty power on the line. For that matter, if you have (or someone nearby has) a piss-poor ground connection at the pole, you're going to get awful trash in your receiver.

At any rate, improving your antenna should not, in this case, increase the noise floor. It will increase the strength of the incoming signals.

I'll also second what Bruce said: if you can make it 120', do so. You'll have a much better match.

Most of the problem you're experiencing is lack of height. At only 10' up, you can only send/receive energy at very high angles to the horizon, basically all your RF is coming in from straight up. That's why you can really only hear Don. Get that feedpoint up as high as you can. Your primary lobes will work their way down towards the horizon, and your receive coverage will shoot way up. The ends are less critcal, changing their height alters the shape of the lobe more than the actual angle of it. Focus on the feedpoint.

In summary: raising the antenna will likely not lower your noise floor, but absolutely will improve the signal-to-noise ratio, so the effect will be the same.

[kb3ouk]

I would definitely think you would have better luck with a 120' antenna since it is a halfwave on 75 meters. The noise problem could be from the power lines, I have a noise problem here that I hear during rainstorms but no other time, but I'm beginning to think that it may also be the receiver in the rig I was using, because I can't hear the noise on my other receiver.
Shelby KB3OUK

[WBear2GCR]

An ant tuned to the frequency of interest will definitely work better than one not tuned, of the same type.

Patrick, how much maximum length can you get on your property? That's an important consideration.

For example a Beveridge style antenna with a preamp on it will work very well, and have much less noise than a dipole... I once had a ~150 long steel wire that ran < 20ft above the ground that worked great as a low noise ant. Otoh, this is already (so far) a low noise location. If you could run 150ft or more low above the ground, more being better, you might find that it works out to be a very good receive ant. The dipole could be ur transmit ant.

I was told that many ops who worked into Europe from up this way used a Beveridge aimed at Europe for recieve, and a dipole for xmit - I could almost never hear the Euro stations with my dipole, but I could hear them working into Europe.

              _-_-bear

[KA1ZGC]

Let him figure out the dipole before throwing a seperate receive Beverage into the equation. One thing at a time.

Patrick, I just re-read your original post. Building a dipole is not much expense, and if it doesn't work you can just disassemble it and re-use the wire for another antenna. Of all the things you listed, that's the least expensive thing you'll be doing.

The unanimous answer is "yes", the dipole you describe will far outperform what you've got now. 120' would be the optimal length, but 100' will work (though a ricebox would probably want a tuner to load into it).

Rest assured, you will not be wasting your money.

[Opcom]

Thanks for the good replies.

The length is an issue. The lot is 150FT from west to east and 50Ft from North to South. This is not going to help me to the coasts, but I have what I have.

The clear overhead is approximately 100Ft by 40FT.

There is just a little more than 100FT of clear space before I am in the tree that is also in the power line that runs past my house. Therefore I must avoid the chance of having the tree contact the antenna and the power line at the same time.

I have no objection to a tuner. In fact I just reworked one that someone gave me years ago and it held 1000W into that 40FT wire on 75M. The tuner is a strange "backwards" configuration (attachment) but it works. Needs more C. I have almost all the parts for a balanced tuner, but that will wait, it's a big rackmount project due to BCST size parts. (I still need a matched pair of 15uH inductors - maybe I will wind them)

So that's it for space. I cannot go diagonally which could give more room due to the power feed location at the house (all above ground here).

The local trees that are not near the power lines are in the back neighbor's yard. It's a rent house and I don't want the hassle.

I could try first a temporary support, but I have no fit help here and do not feel competent to manage it safely myself.

The end supports I have planned, and the tower guys approved it, are each two sections of 10FT black natural gas pipe (the kind fit for burying), 2.5" diameter, will be sunk into a 18" diameter hole 5FT deep with concrete leaving 15FT above ground.

I could go maybe 5 FT higher for the dipole ends by adding another 5FT section, but it would make the one in front near the power lines a hazard if it ever did fall outward (unlikely but I am afraid of the high-line there). The geometry shows that 20FT of above-ground pipe would miss the power and telephone lines by only 5FT, so I better stick to 15FT above ground. I will put caps on the tops of the pipes to keep out water.

Ok, so the physical tower and its installation is definitely the biggest expense. The wire is not, although I have the somewhat unusual 4-legged dipole (Tekrad) that I would like to try first. It could be put up as shown in the manual (like a fan dipole?), but since the ends are going to have to be much lower than the manual shows, the two 'spare' legs could be sloped down to the north and south and when they got near the 8FT fence poles, could be hung off some big insulators I have and then sent in another direction (probably east-west; few options).  That way, I might get 'some' east-west direction, maybe better overall coverage. ?? Check out the manual though, because this is a very interesting antenna. I already have it, picked it up NIB at a hamfest for $15. The entire thing is made of 2" ladder line.

It should be sort of easy to change wires if this is unsatisfactory since there will be a halyard to raise and lower the center point and the main ends.

Height: It seems from your advice height is my best friend. I will talk to the guys doing this and see if I can go 10-20FT higher. The expense won't be that much more. I do not mind a bigger base, nor do I mind a base + guys + general ugliness as long as it performs.


Jim - by a horizontal loop, you mean one that is oriented flat/parallel to the earth, but elevated, right? I can try something like that later. A friend uses something like that, but his is huge and 35Ft high. Mine could reasonably be only 40Ft on each side and 20FT high. I will have to wait on trying that since this tower and dipole has to be the first thing now. I have tried the Texas guys, but don't pick them up well at all. I think I am inside the skip zone and too low to the ground.

Noise: I may have to do my own survey. The crack bums around here cut off the power pole grounds sometimes for copper.

I'd also be interested in comments about this odd tuner setup and the antenna on hand.

Many Thanks,
Patrick

[WD5JKO]

Patrick,

>  by a horizontal loop, you mean one that is oriented flat/parallel to the earth, but elevated, right?


Correct. Jon, AD5HR has one of these and he works all bands, and even on 75m works lots of DX. This needs to be a full wavelength long at the lowest band (~ 240' for 75m), and it has a feedpoint impedance of ~ 80 ohms. Feeding at a corner, or center of a span seems to make a difference. This can be balanced fed with twinlead, or maybe 75 ohm coax with a bunch of beads over it at the antenna side (makes a 1:1 current balun).

Your Tekrad antenna looks interesting. Is this more for SWL use, or to transmit?

   Take a peek at this antenna from Cecil W5DXP:

http://www.w5dxp.com/notuner.htm

  This is 137' long, but will be shorter (take less yard space) when set up as an inverted V, all depending on tower height. Also look at Cecil's analysis of the G5rv antenna which BTW is 102' long.

   Your tuner looks like the classic "universal transmatch", and with the proper parts, will match a 'wet noodle' (make transmitter see 50 ohms resistive). Still the antenna needs to be reasonable for good efficiency. A variation of this kind of tuner is to feed it with a 1:1 current balun, and then the outputs can feed a balanced feedline. This design is not the best as it still has an unbalance, but for 40-80-160m this approach works just fine. I did it once and used a 1:1 air coil balun based on the W6SAI radio handbook; alternatively a piece of coax with a sh_t load of ferrite beads over it like a necklace will work fine.

   I'd like to expand on my comment about long haul AM reception where many stations seem to be undermodulated. Maybe part of this issue (besides low actual mod %) has to do with the propagation conditions (how many hops the signal makes). The folks that come in well here from the E and NE, all have antennas that have good low angle capability. Maybe the effect of too many hops is that the multi-path reception somehow 'scrubs' off the sidebands such that the signal appears to be undermodulated. Whatever the case, those with emphasis to frequencies < 500 hz have little sideband energy left when I try to offset the passband tuning to try and 'chop off the bass' and capture what is left above that. Our old buddy, George W2WLR, addressed this issue with a lot of posts in the AM press exchange. Here is one of his posts:

http://www.amwindow.org/tech/pdf/eam.pdf

Regards,
Jim
WD5JKO

[Bill, KD0HG]

Inverted L. Maybe 60' x 60'.

Work it against a ground radial system or other counterpoise. Got a metal fence around your property? Use it! Or install a wire ring around the lot.

Best city lot antenna I ever used on 160-80-40.

Look at it as a tilted 1/2 wave inverted vee fed at one end instead of the center.

[W1AEX]

The tuner schematic looks like a version of the Lew McCoy differential tuner, which is in the attached schematic. The only difference appears to be the use of a split variable with one side going to ground rather than a fixed or switched-fixed to ground at the output.

When I put together my big tuner, which is usually in a simple T setup, I used banana type plugs and jacks and made all my jumpers between components simple to change around to allow different configurations. I haven't changed it out of the T configuration for years, because it matches everything, everywhere. You might want to use movable jumpers to allow you to change configurations, but a simple T setup seems to work great. I believe what you have pictured there should work fine as it is.

It sounds like you are going to great lengths to make this a safe installation that provides you with a low noise receive environment. My location here is usually fairly quiet, but it has its moments. I have found that a closed loop configuration is by far the most likely to offer rejection of local noise. Before you go to the trouble (and expense) of a tower as a center support for a dipole (potentially a noisy situation as vertical metal structures can be quite the noise collectors, and dipoles tend to not have great noise immunity), you might want to try a loop configuration. Even if it is lying on the ground (presenting a worst case scenario) for experimental purposes, it might give you some idea of its potential for cutting down on noise. By far, the lowest noise HF antenna I ever put up was a 260 foot loop, with an open wire feedline. It was a 90' x 40' rectangle about 40 feet in the air and it worked fine in a closed loop configuration from 75 - 10 meters. It seemed to have great immunity to noise on receive and was an excellent SWL antenna for the HF spectrum. I put a high voltage relay exactly opposite from the feedpoint and could remotely switch the loop open to make it a 160 meter halfwave for use on that band. It was by far the best bang for the buck antenna I ever put up.

At any rate, those are my thoughts. I would hate to see you go to all the trouble and find that you had created the ultimate noise gatherer. It largely depends on the source of the noise. If it is radiating from the nearby power distribution lines then I am doubtful that the tower - dipole arrangement will improve your immunity from electrical noise.

Good luck with the project, hope it turns out well!

Rob W1AEX

[KA1ZGC]

A dipole does not necessarily have to be in a straight line.

Optimally, yes... you want it as straight, as parallel to, and far away from, the Earth's surface as you can. That's the optimal case.

120' of wire in a 100' space will perform like any antenna with 100' of radiation aperture, but it will tune much more easily. You can run 100' laterally and let 10' of wire hang down at each end. Plenty of guys do that with good results. Since you're describing an inverted-vee taking up 100' of lateral space, you're going to have more than 100' of wire already, so you're almost there.

Also, I'd recommend looking into possibly feeding it with open-wire line fed by a link-coupled tuner (a balun should be your last option). You may only be interested in 75 for now, but you will probably want to expand your spectrum-coverage abilities someday. That's where having 120' of radiating wire really comes in handy; when fed with open-wire line a dipole can easily be tuned to its harmonics (in this case: 40, 20, and 10). Your pattern gets increasingly goofy the higher you go, but it gets you on the air. Coax-fed dipoles aren't so forgiving.

The loop idea certainly has merit, too. You may find you'll want to do both eventually (and maybe even add a receiving Beverage someday as Bear suggested), but you can easily get up a good dipole from the get-go. No such thing as too many options!

[WU2D]

Pat,

Because you said noise, I guess I would shy away from my first thought which was an inverted L. If you are strictly talking 80M, a simple loaded dipole might be a good choice. Feed it with coax and a 1:1 balun. At 100 feet, you would not need much loading and the efficiency would be good especially if you put the coils towards the ends. You could even add traps for 40M.

A delta loop or vertical square would make for some low noise and it only needs two supports. Can you get 240 feet of wire in some kind of rectangle? You can corner feed it with a 1:1 balun. In college I had a second story apartment and no antenna ideas except there was big maple tree out front of my window. I simply shot an arrow over it and pulled wire around the outside of the branches. It resonated on 80M as a full wave vertical loop!

For a quiet open line approach just put up as much wire as you can and feed it in the center with open line to a good tuner - done! 

Mike WU2D

[w3jn]

The Tekrad is a balanced antenner.  The BEST balanced tooner by far - if you don't aready have a Junkston Matchbox kicking around - is the K1JJ design as discussed multiple times in this forum.  One coil, one variable cap, some taps, and yer done.  You can literally build one in a half hour.

If you're not gonna use the Tekrad, get a W7FG antenner with the included ladder line.  You couldn't build one for what they charge; extremely robust and a good performer.  Ideally 120' is what you want for 75, but with the K1JJ tooner you can lop off equal lengths off each end and it won't make a bit of noticible difference performance-wise.  It'll work anywhere - mine even does a respectable job on 160 (make sure the tooner is stoutly made if you're gonna do this though!)

[Opcom]

The tuner is for transmitting and receiving. I have looked at Cecil W5DXP's setup, I like the switches for matching, that is ingenious. I am not a big fan of ferrites over the coax due to dissipation or losses but apparently they work fine.

The tuner I showed is temporary, a balanced one is in the works. I had a non-member e-mail me and tell me that configuration shown reduces harmonics better (low pass) that having it the other way around (high pass) like seen in MFJ tuners and all.

Getting 240FT of wire into a rectangle might be do-able with more planning. Easily available rectangle shapes are 40x40, 60x30, or an uneven trapezoid of 40FT+75FT+30FT+75FT.

The guy who sold me the Tekrad bragged on it, said he had one that had been up for 20 years. It is made with ladder line as the feed, which is nice. I have some large feedthrough insulators already for the shack.

I have no objection to letting the dipole ends hang, as long as I can support the ladder line it is made of at the bend and keep them away from metal structures. It would be a simpler engineering job to do that with just wire.

In the end, I will need the tower or I will never get 50MHz and up, so that's going to have to be done. I have a thing about 6 meters.

The HF antenna needs to cover all bands if possible, at least 80-10. With a good tuner made for the purpose, it should be able to do 'something' on 160M, for instance taking the ladder line abd shorting it and using the whole thing as one big mess, that would add some length to the equation as well as allow the somewhat vertical ladder line to radiate. The line or whatever is going to feed the antenna is going to come through the metal wall of the shack about 10FT off the ground. As it's a metal building with thin corrugated steel walls, I need to have the feed enter near the horizontal beam there so there is something decent to bear the stress. A rectangular hole backed up by a strong aluminum plate and L bracket should work for the insulators. I got a pair of insulators already. I thought to put the eventual balanced tuner in a rack right below this.

[ke7trp]

You will need the best and longest antenna you can get to hear 3885.  I am in arizona and I hear 20 DB over carriers all the time from people talking on 3885. But because they are running wide, broadcast type audio, They dont cut over the noise. As a result, You will need a good reciever and a good antenna to participate. Somtimes, one of the guys keys up on 3885 that has communications audio and a tighter bandwidth and they are clear at 10DB over signal. 

Its funny,  The other night I had 20 and 30 DB carriers and the normal Muted audio.. Then a guy on a stock valiant came on at 10 over an was TWICE the audio of the others.

Don, K4KYV is always very clear and pronounced on his audio. Even when the band is low, I can hear every word Don is saying.

C

[KM1H]

Pat, remember the old adage, if you cant hear them you wont work them. Id concentrate first on both minimizing man made crud in your house and a low noise receiving antenna.

A higher dipole is just going to hear the same noise at a slightly lower elevation angle as the NVIS cloud warmer in use now. Its only real benefit will be on transmitting. A large wire loop will gain you little as it will still pick up a good amount of atmospheric noise down in your area plus it wont help at all for the locally generated crud from power lines and neighbors.

A small shielded loop about 6' above ground on a TV rotator is one possibility. Another is a "BOG" Beverage on Ground (or a few inches above ground) as long as you can make it using 3 of the yards dimensions. ON4UN's 4th Edition Low Band DXing covers all types of receiving antennas in details and there is a good reason that chapter is before the transmitting antennas sections. Many 80/160M ops have amassed respectable DX totals on postage stamp lots with simple receiving antennas and they work just as well for 3885 AM.

Carl
KM1H

[flintstone mop]

I'll agree with the hi-fi bassy audio. It won't get too far.
Don has a very good balanced audio and a real antenna.

Your line noise and other manmade clatter needs to be isolated and eliminated or reduced

Gary, W2INR, on this forum, has a 50 foot "portable" tower for sale that you can check out, if you have absolutely no vert supports.

I'm still trying to wiggle a free 50 foot "portable tower" out of a former employer.

Fred

[KA1ZGC]

I have no objection to letting the dipole ends hang, as long as I can support the ladder line it is made of at the bend and keep them away from metal structures. It would be a simpler engineering job to do that with just wire.

I'm sorry, were you talking about a folded dipole? That's a different antenna. I was referring to a straight 100'-long dipole with 10' of wire hanging down from the end supports.

[WBear2GCR]

I'm with Tom on this one.

A 10ft hang down is actually an advantage. Makes it really easy to tune the ant.

Maximize ur height... doesn't have to be flat... if ur coax fed, keep the side with the center wire higher.

             _-_-bear

[Opcom]

KA1ZGC - No, you are correct in the first place. it is not folded. The "wire" of the dipole is made of ladder line. So the actual 'wire' of each 'pole' of the dipole is really two wires connected in parallel (at the center) and separated by a couple inches along its length. Electrically it is a 100Ft dipole. It seems strange but that is how it is made. The claim is to increase bandwidth.

In reality this antenna has 4 legs, like the manuals shows, but in any case it is not folded.

[KA1ZGC]

It seems strange but that is how it is made. The claim is to increase bandwidth.

Totally unnecessary. That won't perform any better than a normal dipole, but will be exponentially more time, money, and headaches.

That antenna might look good on paper, but try putting one up outside. All those solder joints, all those wires flapping in the breeze, all the support ropes you're going to need, all the different support points to tie those ropes to, all those wires to keep clear of any and all metal, etc.

That design has n² more failure points than an ordinary dipole, and won't give you any "bandwidth" that a good, ol' fashioned tuner won't give you.

You don't need anything nearly so complicated and gimmicky.

I only have a 200' flat-top dipole up 35'. That's not even resonant on any ham band, but the link-coupled tuner allows me to cover all of 80/75, 40, 20, and 10. If I feel like getting on 160, I just bypass the tuner and jumper the coax straight to the balanced line (and even that's only because I'm too lazy to find the tap points on the 160 coil I made last fall).

Seriously, you are far better off with a classic, gimmick-free dipole. Less investment, less maintenance, less reactive load, fewer single points of failure, and so on. Don't put up an antenna just because it purports to solve a problem that you don't even have the luxury of having yet, and probably never will.

Id concentrate first on both minimizing man made crud in your house and a low noise receiving antenna.

The problem Patrick is having is that he has a low-signal receiving antenna. Your ability to hear a station is determined by the signal-to-noise ratio of the circuit. Increasing signal has the same effect as decreasing noise.

If your antenna can't receive actual incoming signals worth a damn, then your signal-to-noise ratio is going to be horrible. Increasing inbound-signal strength must be the first order of the day. It's much less effort per dB of SNR than trying to devise "low-noise" antennas that may not be at all necessary.

If you try to listen to 3885 on a coathanger and all you can hear is your furnace's blower motor; it's because your antenna sucks, not your furnace. Always address the problems first, not the symptoms.

[WBear2GCR]

There will be an increase in bandwidth, but not worth the added windload and mass in the air.

Better to simply add a second conductor that at the end is some distance from the first conductor, like 2-3 ft. That makes it look like a "bowtie" sort of. That will add more "bandwidth" if you actually need bandwidth... few actually do.

If you put up the ant using some sort of pulley or rope to pull it up into place, you can lower it and experiment LATER. First get a basic dipole running, and get urself a basis for comparision.

             _-_-bear

[KA1ZGC]

...what he said.