Outdoor Under the Eaves Loop vs. Active Mini-Whip Antenna

[ultravista]

I have been using an active mini-whip antenna (PA0RDT) at approximately 20 feet on a non-conducting mast. From my QTH, the mini-whip has been exceptional for RX.

Over the weekend, I ran a wire around the house under the eaves, approximately 200ft of wire @ 10 feet or more off the ground. As a loop, the coax braid connects to one side and the conductor to the other. It is two conductor alarm wire and I am only using one in the pair. No balun, just a simple PL-259 connector connecting the conductor and braid to the wire.

The mini-whip wholly outperforms the loop antenna. Strong signals present on the mini-whip practically disappear with the loop. On a scale of 1-10 for RX, the loop is a 1 or 2 compared to the mini-whip. Using the loop is like not having an antenna at all.

As a novice, I thought for sure, the long wire around the house would be at least as good if not better due to the electrical length. Not at all.

Can someone help me understand why the mini-whip @ 20 feet is outperforming the 200 foot loop @ 10 feet?

 

[prcguy]

The whip is a vertical and will pick up signals equally well in all directions near the horizon if not blocked by large metal objects. You probably have it up in the clear and away from the house and the whip is probably decoupled from the coax somewhat so the coax is isolated from the antenna.

A horizontal wire or loop 10ft off the ground has a major lobe that points straight up over most of the HF range and only a little to the sides at the horizon where you need to pick up distant SW stations. Since the loop runs around the house it will pick up more interference from stuff inside the house blocking out some reception. The shield of the coax is probably acting as part of the antenna since there is no balun at the feedpoint and if the coax passes any computer or similar equipment that can route noise right up the shield of the coax to the antenna to be picked up by your receiver.

 

[Ubbe]

I though that the coax where a major part of the mini-whip. Decouple it at the antenna with a current balun or something and it probably dies. Are shortwave signals mostly horizontal or vertical polarized?

/Ubbe

 

[ka3jjz]

Polarization often gets flipped as its bent around in the ionosphere.

Another issue is the construction of the eaves and surrounding structure. If it's all aluminum, it's almost like putting an antenna inside a metal box. Put that antenna out as a skyloop, away from the house, and perhaps feed it with a balun and/or transmatch, and you will see a noticeable improvement....Mike

 

[Ubbe]

Flipped, yes, but usually if you have an antenna that are incorrectly polarized you're looking at a 10-20dB loss. If the signal arrives as vertical and you have a horisontal wire between two trees then a 2 feet mini-whip will receive that signal so much better. Shortwave listeners must always have one vertical multiband antenna to complement their horisontal wires?

/Ubbe

 

[prcguy]

I think a reflected wave off the atmosphere is randomly polarized and will have little to do with good or bad reception and I don't think you will ever see pure horizontal or vertical polarity. Multipath and signal cancellation is probably the biggest problem we see with signal fading on the SW bands.

Flipped, yes, but usually if you have an antenna that are incorrectly polarized you're looking at a 10-20dB loss. If the signal arrives as vertical and you have a horisontal wire between two trees then a 2 feet mini-whip will receive that signal so much better. Shortwave listeners must always have one vertical multiband antenna to complement their horisontal wires?

/Ubbe

 

[Lauri-CoyoteFrostbite]

Hey Ultra

What you experienced is no surprise at all (at least to me.)

Let me explain--
First off, the length of this antenna wire is really secondary to the success of your antenna. A random length, like you described, strung about under roof eves etc. is just that-- a long piece of wire.
I am not faulting your judgement- its just that this 'antenna' is neither resonant, nor in the clear, or much of anything except just-- long. If it were slung high and away from objects, you might have been pleased with the results.

I see you are a 'novice' (heck, in so many things in life, aren't we all ?) - so I am going to take a little different tack in explaining why you found this wire lacking compared to your short active antenna.

First off, its how to conceptualize the thing call'd an "antenna." An antenna can be thought of as a device that is in tune with the Universe- it is in resonance with and couples radio frequency energy to the stuff we physicists call the ether. Its a transformer. This coupling transformer can be large, like a dipole, or beam antenna array- or small like your active antenna. At the heart of it all does it tune- resonant- with the Universe ?....
Know anything about string'd musical instruments ?.. I don't, except I've a friend whose a violin virtuoso. She can tune a violin to same perfect pitch that makes another instrument, placed across a room, vibrate to the same notes as if she was playing that one too.
If you resonate your antenna to the same 'pitch' as the station you wish to receive, your receiver circuits will "ring" loud- it will resonate- on that frequency also.

Am I making any sense here ?... Your long wire is just a dumb piece of wire; but your short, active antenna is a tuned Stradivarius---- short, tho the little thing's whip is, it couples flawlessly to the universe via its tuned circuits (think of my violin'st friend.) Add to this an active preamp- and its no wonder its works so nicely.
A good example is the AM of a car radio. They use very short, tuned antennas to pull in DX AM stations.

Experiment with resonate antennas- I think you will be surprised with the results.



Lauri

 

[ultravista]

Hey Ultra Lauri

Yes, a novice I am. I thought the random loop under the (wooden) eaves would be at least as good, or close to, the active antenna. Your point about the amplifier is well played, I didn't think about that!

I am in a small residential lot with little room to have a loop or similar up in the air. The active antenna is great, awesome for me in fact, but I would like a working alternative to compare results.

What do you recommend as an alternative to the active antenna for a small residential lot?

Thank you for the reply.

 

[Boombox]

With HF and shortwave, higher is better. That is one reason for the difference.

 

[nanZor]

There is a LOT you can do with a small residential lot. Aside from in-the-air traditional antennas, I've used and enjoyed a stealthy on-ground loop best and quickly desribed here:

The Loop on Ground Antenna - the "LoG"

This is just one of *many* options. Small vertical loops, like the W6LVP and similar are quite popular. The key for *receiving* is signal-to-noise-ratio along with desired directionality. In other words, don't compare antennas simply by the amount of band-noise or S-meter readings you get. It all depends.

Ubbe - time for you to get an HF receiver! You know you want one now.
Basically, polarization loss is a line-of-sight thing. Prcguy and myself would want to have antennas with the same polarization for local line of sight work. If we were cross-polarized, then yes, that would be bad.

However, if you are using your new horizontal dipole and are listening to prcguy or me using a vertical for transmitting on this side of the pond, it doesn't really matter as the polarity you get is a mish-mash of changing polarities as it bends through the ionosphere.

 

[Ubbe]

I got three HF receivers and don't need another one. If you have a random wire or even a long wire and use it to transmit it will send out it's major beam in the direction of the wire, out it's end. And depending of the relation between frequency and wire lenght and its heigh above ground it will direct that beam at different angles above the horizon and the beam will be vertically polarized when it leaves your antenna. If you point that in my direction, will I benefit from a horizontal dipole antenna with its broadside at your direction or a random-longwire vertically polarized pointing in your direction? You say the signal will be a mish-mash of different polarisation and it will be received by me as all polarities at the same time?

The vertical mini-whip is a short piece of antenna not long enough to be tuned to anything and there's no tuning circuit in the electronics that magicly tunes to the HF band I am currently listening to in my receiver.

/Ubbe

 

[ultravista]

There is a LOT you can do with a small residential lot. Aside from in-the-air traditional antennas, I've used and enjoyed a stealthy on-ground loop best and quickly desribed here:
The Loop on Ground Antenna - the "LoG"

Quick question ... how does a small loop on ground outperform a larger loop in the air? Albeit only 10 feet high, for HF, its immaterial compared to wavelength.

 

[prcguy]

Its not that the loop on the ground is outperforming a larger higher loop, it just has different characteristics that may work better for some things. Where the 10ft high loop will have most of its propagation straight up, a loop on the ground should have a pattern similar to half a doughnut sticking vertically out of the ground. It will have lots of high angle radiation but also low angle off the ends opposite the feed.

The big loop 10ft off the ground would be excellent for NVIS on the lower bands and would transmit and receive very well in the 0 to several hundred mile range as the signals bounce straight down when propagation is ideal. The signals from the loop on the ground would be maybe 20dB or more weaker but would have some advantage for distant signals off its ends and would also have a very low noise floor where a loop around a house might pick of lots of interfering signals from inside the house.

Quick question ... how does a small loop on ground outperform a larger loop in the air? Albeit only 10 feet high, for HF, its immaterial compared to wavelength.

 

[prcguy]

A long wire antenna that is many wavelengths long will have some major lobes off its ends and they will be vertically polarized, but any lobes that are more broadside to the wire will be horizontal polarized. You will not see this on wire antennas used by most SWL listeners because their antennas are too short to create the end fire lobes with gain and vertical pol.

If your within ground wave of the transmitter you will receive whatever polarization the transmit antenna has plus any high angle skywave that may be present due to NVIS propagation. You can receive multiple polarization at the same time and when they are out of phase you will see multipath fading. For distant stations, the ionosphere will randomly scramble the polarization and will also appear as multiple point sources from the sky depending on the shape and density of the constantly changing reflecting layer.

And depending of the relation between frequency and wire lenght and its heigh above ground it will direct that beam at different angles above the horizon and the beam will be vertically polarized when it leaves your antenna. If you point that in my direction, will I benefit from a horizontal dipole antenna with its broadside at your direction or a random-longwire vertically polarized pointing in your direction? You say the signal will be a mish-mash of different polarisation and it will be received by me as all polarities at the same time?


/Ubbe

 

[Lauri-CoyoteFrostbite]

Hi UV

Hmmmm... what type of antenna(s) for a small residence ??- a fairly open ended question.... smiles


I will go back to my original premise that what you need first off is a tuned antenna. Next we get into what frequencies- I am going to make the assumption that its for a fairly broad swath, like 2 to 30 MHz ?- if so, no one antenna is going to cover all that territory equally.

Never the less, there are ways.

First off, there is nothing wrong with a long, random length wire- but run it clear, high and away from the house. Isolate its contact points with decent insulators (like porcelain)- run it down into house thru insulators as well. You'll need a ground connection to work against- an attachment to a cold water pipe and a ground rod below the entry point to the house are good starters.

Next make it resonant.

The easy way to do this is to buy a ham radio antenna tuner... an MFJ for instance. When you get the hang of adjusting the wire with this tuner (ie: background noise peaks) perhaps add a tunable preamp... and connect all this to your receiver thru coax with proper connectors.....
This *might* give you an edge over your present active antenna, but don't expect miracles. In order to even hear a difference (requiring at least 2 "S" units to hear this, at a minimum)- that's going to have to be an ~12 dbs increase in signal strength --- your active antenna is may out shine that due to polarization, etc.
(For those hams reading this, please keep in mind that UV is asking for SWL antenna advice, not for the best antenna to work Northern Slobovia on short path HF-- I have tried and gear'd it to his question- not full of Flight-to-the-Moon theory)

I think this will put you on a good track- next approach it scientifically and use these suggestions as starting points... but get an antenna tuner.

Also UV, get at least a copy of - and start, cover to cover, to read the ARRL Antenna Handbook- old editions are fine (I actually prefer them and have several spanning many years- the material doesn't change much but the writing styles do.) Tho they deal a lot with transmitting, the theory also applies to receiving.

There are lots of cookie-cutter antenna designs, a tonne of third party advice, plenty of "Uncle Elmers" and so on to help you - but until you can grock what is meaningful thru all that noise its not going help you much. Become the inquistive scientist, take your time-

Read !

................... and experiment.
.
.
.


Good Luck Cowboy !

Lauri

 

[majoco]

Yes - to get the best out of a random length of wire - preferably hung up as high as you can get it - you need to 'tune' it. BUT you have to bring the wire down to the tuner and not with coax cable - just the end of the wire - the tuner becomes part of the antenna and does it's job properly - then you have a short length of coax from the tuner to the receiver. Otherwise if you have the room you can buy a PAR EF-SWL antenna - you'll need about 45feet between ends - or else you can make your own, the same length of wire and a matching transformer....

EFHW matching unit

Of course you could bring a wire down from your under-the-eaves loop to a tuner - not coax. Coax to an unmatched antenna is just a capacitor shunting your signal to ground and the outer of the coax picks up all the household electrical noise.

 

[Ubbe]

A tuner doesn't make any antenna resonate. It only impedance match between the tuner and your receiver/transmitter. I have heard that radio amateurs say that you should NOT use a resonating antenna.

If you have a wire antenna and that wire goes into your room, where you have your electronic devices, it will pick up all RFI there is.

/Ubbe

 

[nanZor]

Ubbe - If you have an antenna 1000 feet away from your room, but has poor common-mode properties from the coax, noise from your house / shack can travel right down the outside of the braid to the feedpoint of the antenna, and then right back into your receiver on the inside just like any radiated signal - so be careful. It's why ferrite chokes are popular in many installations.

You'd also be a candidate for discussing "conjugate system matching" and so forth.

Enough forum talk. Time for you to actually buy and HF receiver and set one up. I truly think you'd enjoy it greatly, experimenting with what works and what doesn't. Sometimes it surprises you when what you think is going on is something else - all the while enjoying the hobby.

I've made an appointment for you at your local radio dealer. Expect an email from them soon.

 

[ka3jjz]

When / If you go shopping for a transmatch - an 'antenna tuner' is a horribly misused, and in most instances, inaccurate term - don't buy these 1kw models. They're way overpriced for just listening applications. Low power models are fine. We have a couple of such links at the bottom of...

https://wiki.radioreference.com/index.php/Improving_HF_Reception

Mike

 

[nanZor]

I concur. And even at that, the wise swl'er (or amateur) will realize that antenna-reciprocity used for both transmit and receive is not actually necessary, when directionality and signal-to-noise is the major concern.

Example: One buys a very simple inexpensive antenna tuner which provides a better match to the receiver for his random wire. Great! But now, with the better match, sure signals smoking strong - the tuner did it's job, but the noise is also raised to ear-burning levels.

So after spending quite a few bucks, you end up punching in the attenuator, negating your improvement.

Zheesh - maybe I could have left well enough alone - even though there is plenty of mismatch in the entire system.

Yes, something like this is needed to make sure your *transmitter* doesn't burn up or shut down, but for receive, it's a different story if you are hearing what you want to hear (or what propagation allows).

I think that with all the instant communications these days, the tendency is to try and start off top-down - that is fill a virtual shopping cart full of stuff, and debate it forever before purchase - which in some cases leads to leaving or never starting the hobby.

Since propagation is rarely above 15mhz these days, even a ZIPCORD dipole, at low heights typical of a beginners setup, could prove to be entirely adequate. Maybe not. But if you try this first, and it works *well enough*, you've saved a boatload of cash for improvements and learning materials- if necessary - by adopting a bottom-up approach instead. It's a lot more fun than just opening the wallet and can lead to some serious study about possible improvements, rather than just looking at a pile of radio stuff from the shopping cart.