End fed dipole question

[W2JMZ]

I live in an apartment and have been itching to get out on the HF bands.

So... The other day I went out and got myself a mfj-969 tuner, a 20m 1/2 wave end fed dipole antenna, and all the other bits and pieces I needed to connect everything together.

So here's my question.

I hung the end fed dipole up under my upstairs neighbors deck in a horizontal, rectangular configuration. The dipole begins and ends almost at the same spot but the ends are not touching.

It tuned up just fine with a 1.1-1 swr.

But for the life of me I couldn't really make any other stations out over the band noise.

Does anyone else have a similar configuration? Or have any other ideas (other the just to move... Trust me I'm working on it). Something seems off but I don't know what and I'm scratching my head trying to come up with something else.



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[K7MEM]

From your explanation, I am not clear on the antenna you are using. Do you mean you are using a 20M end fed antenna that is 1/2 wavelength long? Or, do you really have a dipole (which is fed from the center) but are feeding it from one end? Is this antenna purchased or home made?

In any case, wrapping the antenna back on itself is counter productive. There would probably be a lot of signal cancellation.

The noise on the band may have nothing to do with your setup. Does the noise show up as a reading on your S-Meter? I live in a very rural area, so unless there is a big thunder storm approaching, my S-Meter doesn't budge. Only when there is a signal does it move up. You could try putting a simple telescoping antenna on the back of your rig, to see if the noise persists. If the noise persists, the noise is probably being generated locally. In that case you would need to hunt down the source. It could be in your apartment or from the upstairs apartment. You could probably track it down using a small antenna on your rig and walking around the area. The noise could be coming from anywhere like flat screen TVs, computer power supplies, appliances, etc..

Martin - K7MEM

 

[W2JMZ]

It's a purchased end fed I got from radiowavez. And it is a 1/2 wavelength long.

The noise pretty much has my S meter pegged.

I'll have to look into maybe doing an inverted L if I have the room for such a setup, may have to get creative to hide it lol. But as I understand it the configuration must change no matter what.


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[ka3jjz]

If this is the antenna you're using....

RADIOWAVZ AMATEUR RADIO ANTENNAS

You shouldn't need a tuner...

In any case, changing the antenna isn't necessarily going to solve your noise issue. Martin's solution is correct - you need to chase down the source(s) of the noise, and if it's in your control, eliminate it.

Notice I implied the plural. It's entirely likely - seeing that you are in a multi home environment - that you could have more than one source. it is also possible that you won't be able to solve all of it. Repositioning the antenna may help, but that's only going to be a solution if your investigation shows it..

Mike

 

[W2JMZ]

That's the exact antenna. So other then a reconfiguration so it's not canceling itself out. Looks like the hunt for rfi begins.


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[popnokick]

Step one in your hunt could be to quickly eliminate your apartment as the source of the RFI. Get your radio running on battery power (may be simpler to buy a battery-powered shortwave receiver... something every ham should have anyway... doesn't need to be fancy, but you may want to get one that handles SSB... but any of them will work). Turn the battery-powered receiver on and tune the 20 meter band for a spot where the RFI is the worst. Now flip the main circuit breaker to your apartment to "OFF". Noise gone? Then you know it's you somewhere. Noise still there? Use the portable SW receiver to begin a wider search. Maybe the apartment above is on the same breaker? Oops. Well you just did a test for both places... and may have to figure out whether your place or the one above (again).
If you find it is your place, turn the main breaker back on and start unplugging stuff while the noise is still in the receiver. Likely suspects were listed in a previous reply (plug in "wall wart" transformers, TV sets, cable & satellite TV boxes, lighting, etc.).

 

[W2JMZ]

Thanks for the tip. I do have backup batteries for my station so I'll give that a shot.


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[Token]

So... The other day I went out and got myself a mfj-969 tuner, a 20m 1/2 wave end fed dipole antenna, and all the other bits and pieces I needed to connect everything together.

So here's my question.

I hung the end fed dipole up under my upstairs neighbors deck in a horizontal, rectangular configuration. The dipole begins and ends almost at the same spot but the ends are not touching.

It tuned up just fine with a 1.1-1 swr.

But for the life of me I couldn't really make any other stations out over the band noise.

Does anyone else have a similar configuration? Or have any other ideas (other the just to move... Trust me I'm working on it). Something seems off but I don't know what and I'm scratching my head trying to come up with something else.

Others have started you in what is probably the right direction with regards to noise, but keep in mind that apartment dwelling and HF ham radio can be a problematic arrangement. That does NOT mean it can’t happen, but it will always be sub optimal and may take significant effort to start to achieve acceptable performance.

But just so you know, your antenna is not a half wave dipole. It may be a half wave, but it is not a dipole. Dipole antennas do not have to be any specific length, although some configurations, such as the half wave, are more common / easier to use. But Dipoles do have to have two radiating parts. Most typically these two halves are symmetrical, but that is not strictly a requirement of a Dipole antenna.

Also, folding your end fed antenna back on itself forming almost a loop is not a great configuration. If you absolutely cannot find a way to install it relatively straight you might be better off with a zig zag type pattern, as long as the far end is as far away from the feed point as possible. To tell you the truth there is no “right” way to do it with your described conditions, so be ready to experiment with different configurations….all it cost is time. And it is quite likely that eventually you will find a configuration that works for your situation, even if it is not something you would find in normal use.

T!

 

[wb6uqa]

end fed antenna

If one of your neighbors has a plasma tv or a halogen light to a dimmer you will get a lot of noise. I bought the QSO king from Ebay, very good antenna.

 

[prcguy]

The Radiowaves EF20 is a true end fed resonant half wave and will perform similar to a resonant center fed dipole of the same band. The QSO King is a generic 9:1 balun with non resonant random length of wire and its not the same.

I have a report from a group that was using a QSO King with supplied wire about 73ft long and they were not making any contacts with it using a 20w radio. They switched to a resonant half wave version similar to the Radiowaves in the same location and then started making contacts. My testing of many home made 63ft 40/20/15/10m multiband EFHW types shows the same results. There is a big difference in performance between the 9:1 types and EFHW types and if you upgrade to an EFHW your signal will go up.

On the OP making a loop out of the Radiowaves EFHW, its probably not hurting the efficiency all that much and if you look at most of the 6m/2m/440 horizontal loops for SSB use they are a half wave dipole bent into a loop and fed by various methods. They radiate an omni directional signal just fine and an EFHW performs similar to a dipole with most of the current and radiation in the center of the wire.

The composition of the deck and any metal in or around it will determine if its going to work or not, separate from any noise interference problems.
prcguy

If one of your neighbors has a plasma tv or a halogen light to a dimmer you will get a lot of noise. I bought the QSO king from Ebay, very good antenna.

 

[K7MEM]

It's a purchased end fed I got from radiowavez. And it is a 1/2 wavelength long.

The noise pretty much has my S meter pegged.

I'll have to look into maybe doing an inverted L if I have the room for such a setup, may have to get creative to hide it lol. But as I understand it the configuration must change no matter what.

As someone else pointed out, you shouldn't need much of a tuner to make that antenna work on 20 Meters. But the tuner could be useful on the higher frequencies.

I think others have covered the noise issue. You need to tackle that problem before you start worrying about what antenna configuration is best.

An Inverted-L is a possibility. But don't expect much of a difference from your end fed because they are effectively the same thing. The Inverted-L is common for a 80/40 meter multi-band antenna. The vertical section is usually 1/4 wavelength on 40 meters and the rest of the antenna (horizontal) gets you resonance on 80 Meters. I have used them before and they work very well. But they also need a counterpoise so there should be radial under the Inverted-L. As many as you can put there. However, because much of the antenna is vertical it tends to be more susceptible to noise, than a completely horizontal antenna. Overall, it's a good arrangement, but isn't going to solve your problems.

Just to be clear on my initial post, there are End-Fed Antennas and there are End-Fed Dipole Antennas. The End-Fed Dipole Antennas often go under several different names, like Sleeve Dipole or Coaxial Dipole, and are mostly used vertically on 11 Meters or the VHF/UHF frequencies. However, it is possible to make a horizontal End-Fed Dipole.

In fact, I am using one. Here is a link to a experiment that I have been running.

Martin E. Meserve - K7MEM - End-Fed Dipole

Currently, the end points are at about 20 feet and I am running it on 20 meters. I think the Air-Core choke has too many turns on it, but overall it seems to work fine. I am mostly testing it with digital modes (PSK-31/CW).

Good luck with solving the noise issue.

Martin - K7MEM

 

[W2JMZ]

Would trying to go completely vertical possibly help?

The antenna is near the ground and is sandwiched between two buildings.

Thinking this maybe effecting my receive also


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[paulears]

Best is away from everything, and in the clear. If you have buildings either side, then the radiation pattern will suffer, and of course you may be causing considerable interference if they are that close. You also need to consider polarisation - horizontal, vertical or slant. This also impacts on how well they work. With any kind of wire aerial that is bent, the capture area of the aerial is effectively lower, because path of the aerial will be end on to the direction the signals drive from, and the overall radiation pattern a bit strange.

Sometimes this doesn't matter that much because all the lobes in the pattern you create could, by luck be in the right direction. The horizontal dipole I have out the back has a right angle bend in one leg. It still matches, but looking at a globe, Spain and Italy are about the same distance, yet I hear plenty of Italians, but never heard Spain at all, on any band.

 

[K7MEM]

Would trying to go completely vertical possibly help?

The antenna is near the ground and is sandwiched between two buildings.

Thinking this maybe effecting my receive also

A better antenna would help on receive, but the noise needs to be taken care of first. If you don't find the source and eliminate it, it doesn't matter what kind of antenna you have. The results will be the same.

But assuming you find and eliminate the noise, a vertical antenna might be a good idea. Verticals are very good DX antennas. They may be omnidirectional, but they have good low takeoff angles. But they come at a cost. A vertical antenna is more than just the vertical element. The vertical element is only half of the antenna. The other half is the counterpoise. Vertical antennas rely on ground radials. For a ground mounted verticals, you can get away with random length radials. But if the vertical is raised, tuned radials for each band are required.

My vertical is raised 18 feet in the air and has four radials for each band (16 total). That is probably bare minimum but it works well. Many hams use hundreds of radials. I don't have the patience for that kind of thing.

Martin - K7MEM

 

[prcguy]

The end fed halfwave in use by the OP doesn't need a counterpoise and it will work just fine hanging vertically. Some versions of the half wave end fed work well on even harmonic bands but if you hang one of those vertically the radiation pattern on the upper bands will suffer with a null at the horizon and power wasted up and down in lobes where they do no good. On their fundamental frequency they will work well vertical putting most of your power at the horizon.

In my experience its good to have a 1:1 common mode choke in the coax near this type of antenna because if you get very far from resonance they tend to light up the coax with some RF. I would use a good ferrite based choke with lots of resistive impedance in your operating frequency range and a coil type "ugly balun" does not give you that.
prcguy

A better antenna would help on receive, but the noise needs to be taken care of first. If you don't find the source and eliminate it, it doesn't matter what kind of antenna you have. The results will be the same.

But assuming you find and eliminate the noise, a vertical antenna might be a good idea. Verticals are very good DX antennas. They may be omnidirectional, but they have good low takeoff angles. But they come at a cost. A vertical antenna is more than just the vertical element. The vertical element is only half of the antenna. The other half is the counterpoise. Vertical antennas rely on ground radials. For a ground mounted verticals, you can get away with random length radials. But if the vertical is raised, tuned radials for each band are required.

My vertical is raised 18 feet in the air and has four radials for each band (16 total). That is probably bare minimum but it works well. Many hams use hundreds of radials. I don't have the patience for that kind of thing.

Martin - K7MEM

 

[K7MEM]

The end fed halfwave in use by the OP doesn't need a counterpoise and it will work just fine hanging vertically. Some versions of the half wave end fed work well on even harmonic bands but if you hang one of those vertically the radiation pattern on the upper bands will suffer with a null at the horizon and power wasted up and down in lobes where they do no good. On their fundamental frequency they will work well vertical putting most of your power at the horizon.

In my experience its good to have a 1:1 common mode choke in the coax near this type of antenna because if you get very far from resonance they tend to light up the coax with some RF. I would use a good ferrite based choke with lots of resistive impedance in your operating frequency range and a coil type "ugly balun" does not give you that.
prcguy

An end-fed half-wave can certainly be used vertically without any counterpoise. And it would also work on harmonic related bands. In fact it is a very common antenna for the QRP and portable op crowd. But that does not mean it would not benefit from a counterpoise. It doesn't have to be extensive. A single 1/4 wavelength buried radial would be sufficient to decouple the antenna from the rig and tuner. If you don't provide a counterpoise, it will find one. And that would be your feed-line and anything else connected to the system.

At low power, you probably wouldn't notice any of the issues, but at higher power you will. There are lots of articles on the end-fed half-wave vertical antenna on-line. Just do a Google search on "half wave vertical hf antenna". The first page of hits provides some pretty good reading.

Martin - K7MEM

 

[prcguy]

The commercial versions like the PAR End Fed, MyAntennas and my home made copies are very well decoupled from the coax and I operate them near full legal limit without any RF problems. It is recommended to use an inline 1:1 choke balun as I mentioned before and these antennas radiate and behave pretty much like a 1/2 wave center fed dipole and really don't need a counterpoise.

If anything, placing one vertically on top of some ground radials will detune it some, the same as placing a 1/2 wave center fed dipole on its side with one end almost touching some ground radials. Its height above ground will have more influence on its low angle omni radiation pattern when vertical compared to adding radials.

With radials laying on the ground this or any vertical antenna will have a radiation pattern skewed upwards slightly with some loss of signal right at the horizon. Place the center of the antenna at 1/2 wavelength above ground and that will pull the pattern down towards the horizon slightly. Move it higher in multiples of 1/2 wavelength and the pattern will pull down more until you get high enough (10-20 wavelengths?) where it will perform about the same as in free space with virtually no upward skewing of the pattern.

For the OP, if he can hang his EFHW vertically away from the building it will probably work better than wrapped into a circle and attached to a deck of unknown material. If you can hang it horizontally heading away from the building that would be great but it will have a radiation pattern broadside to the wire. I do this all the time with my EFHWs with great success when traveling but mine are 63ft long and more of a challenge to find an anchor point for the far end.
prcguy

An end-fed half-wave can certainly be used vertically without any counterpoise. And it would also work on harmonic related bands. In fact it is a very common antenna for the QRP and portable op crowd. But that does not mean it would not benefit from a counterpoise. It doesn't have to be extensive. A single 1/4 wavelength buried radial would be sufficient to decouple the antenna from the rig and tuner. If you don't provide a counterpoise, it will find one. And that would be your feed-line and anything else connected to the system.

At low power, you probably wouldn't notice any of the issues, but at higher power you will. There are lots of articles on the end-fed half-wave vertical antenna on-line. Just do a Google search on "half wave vertical hf antenna". The first page of hits provides some pretty good reading.

Martin - K7MEM

 

[jim202]

I might have missed it in reading the thread here, but if the siding on the building is of the aluminum type, your going to have issues with any antenna that is mounted close to the siding.

As for noise, you didn't explain what it sounds like. Just plain noise could be from a number of sources, like the newer TV sets, computer network cabling, fish tank heaters, florescent lights, light dimmers, cattle electric fence chargers, cracked insulators on the power poles, leaky cable TV lines. The list is almost endless. You need to try and cut down on the source, based on they type of noise your getting.

We can't even provide a guess without having a clue as to what it sounds like. Does it have a clicking type noise, does it sound like an arcing noise, is it just plain background white noise? Does the noise characteristics change with time? Does the noise change with rain or wind? Is the noise worse when it's cold outside?

Sometimes you can take a portable radio set on the AM band and in between stations. Walk around the neighborhood. See if the noise level goes up or down as you walk around. Sometimes using the car radio set on AM and in between stations can be a good tool. It's faster than walking and allows you to cover a bigger area in a shorter time.

Need some more detailed feedback from you before there will be any good feedback from the group here.

 

[W2JMZ]

The background noise is mostly white noise, it nearly drowns out what few stations I can barely make out most of the time. Also near 14.275 there is a high pitched whistling noise. My building is brick and mortar. And the deck the antenna is currently supported by is all lumber. I used coax cable staples to mount it onto the wood.

The signal noise was greatly lower yesterday during the day but rose again in the evening, so I thought maybe it wasn't so much interference as it was regular band noise. Then today during the day it was just as high as it was during the evening and still difficult to make anything out. What stations I can hear is like trying to listen to someone whisper while surround sound blasts static.

If it's something simple I'm gonna feel foolish.

Thanks for all your help guys and gals.


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[W2JMZ]

Update: so I went portable today. Backup batteries, coax, and the antenna. That was it. Made 3 contacts into Minnesota from New Jersey for their qso party. I only operated for about 30 minutes as it was pretty cold outside (40's). However I heard many a pile ups and other stations calling CQ. So my station barefoot works like a charm.

Before I did all that however I went on a semi rf hunt. Aside from using different coax (both lengths I have are lmr-240 one 50' the other 75') there really wasn't more then one s unit difference. I shut down the two laptops I have running near my station and that seemed to help very little if at all. I've basically come to the conclusion that, yes there is rfi in the apartment but aside from it not being near my radio I've gotta star looking elsewhere. Now to figure out how to start hunting down the most offensive stuff and mitigating it.

After I got back from my portable operation I re-ran my coax outside. Before I had the majority of the left over slack inside the shack near the radio but relocated it outside so I can in theory get a mast that I can put up and down when needed and have the antenna away from the building, as well as to mitigate any possible rfi from the coax itself.

I re hung the end fed antenna in a different configuration, twice. Once in a straight line that seemed to be the best in terms of lowering rfi noise and increasing reception. But the YL pointed out that it was now very obvious we have an antenna in the apartment complex and convinced me to try and relocate it once more.

It's final resting position is different from its original. Instead of having it run in a rectangular shape where the ends almost meet under the balcony in a completely horizontal position, I started off at the bottom of one of the supports ran it up, then down the length of the balcony, back towards the building, down again and then terminated it near the ground again. If you picture it in your head image a L shape where the long side and short side of the L end goes towards the ground.

This has also improved reception (though not as greatly as the straight line) and now my s units are down by roughly two compared to where I started. (Now sitting at 6 instead of 8).

I can hear people now, not as great as I could standing in a wide open county park but better then before.

Now the real question is can anyone hear me.


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