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Author Topic: More Wire, Higher Wire, Longer Wire  (Read 2026 times)

Offline i_hear_you

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More Wire, Higher Wire, Longer Wire
« on: May 24, 2019, 1911 UTC »
While I enjoy experimentation, I must balance cost and return, as I'm sure the vast majority of you do, as well.  I preface with this to head off the "just try it and find out" replies!

Over the last two months I've grown and improved my SWL antenna system passing through the following phases:

1) A long wire strung as straight as possible along the ceiling from one corner of my house to the other on the second floor,
2) 80' or so of wire outside the house leading off into the trees and connected directly to the center conductor of rg59 that makes ingress into the house to a wall plate, and a jumper leading from the plate to the radio,
3) Adding a 1:1 ferrite binocular isolation transformer between the coax center/shield and the radio's two antenna terminals,
4) Adding a 9:1 ferrite toroid isolation transformer, one winding connected to antenna wire and ground, with ground being a short wire leading to and soldered onto to a pile of old audio cables that are sitting on the ground (covered with woodchips for marital bliss), and the other winding to coax center/shield.

The final refinement I am considering is to add 100' or so of wire into the air, and push the coax connection off into the woods with a proper Earth RF ground.  The thing is, the steps I've taken so far have given me a very strong S/N, I'm very happy with the results. However, 15Mhz and up is very quiet, and I realize that is probably due to propagation conditions, and probably also my ferrite choices for the transformers.  I also have a lot of fading on some SW frequencies, but my understanding is more wire won't help that, and this requires tricks like diversity receive, antennas that are a wavelength apart, etc.

I'm interested to hear if anyone has made a similar jump and heard a noticeable difference by adding that last 100', and moving it terminus that extra 50' from the house.

Offline Josh

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Re: More Wire, Higher Wire, Longer Wire
« Reply #1 on: May 24, 2019, 1920 UTC »
I doubt an additional 100ft will add much save for in ambc and vlf work, I suggest a vertical antenna if you have none. On hf rx antenna length, the USN did a study and found a 6ft vertical probe, matched for maximum energy transfer to the feedline, would do in most any instance. That being said, they had a US warship and an entire ocean as the ground plane.

Dipoles and "longwires" are desirable antennas, but for low angle reception you can't beat a vertical, low angles are where you find the dx.
Conveniently located near Vincennes Indiana.

Offline pinto vortando

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Re: More Wire, Higher Wire, Longer Wire
« Reply #2 on: May 24, 2019, 2153 UTC »
Adding the additional 100' may help on longwave and AM BCB but don't expect much if any improvement much above
40 meters.  The material used in the 9:1 matching device also has a big influence... hard to get a certain material and
winding configuration to be optimum over a wide frequency range. 
Das Radiobunker somewhere in Michigan

Offline i_hear_you

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Re: More Wire, Higher Wire, Longer Wire
« Reply #3 on: May 24, 2019, 2154 UTC »
Thanks for the reply.

Seeing as this is for receive only, if I hung a wire over the tallest branch I can snag, let it drop straight vertically, would this be an improvement over the longwire?  Would it require a ground rod? Or whatever counterpoise I can muster?

My understanding is that for RX purposes, we are trying to deliver the highest signal voltage as compared to ground as possible, so a RF ground rod provides that "zero" against which the antenna can be compared. But a counterpoise is needed for TX because of EM fields within a wavelength of feed point. I have zero experience with verticals, but I can say that once I added my mess of wires as a "ground" to my random wire, there was a noticeable increase in signal strength.

It has been fun and rewarding so far, but my next steps will be more costly, time consuming, frustrating (I'm not very good with my wrist rocket) and its appreciated when the experience of others prevents the frustration of failure  ;D

EDIT:

Regarding the 9:1, I'm ready to experiment, I have two other mixture types, and enough to try 1:1, 1:4 and 1:9.

Offline ChrisSmolinski

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Re: More Wire, Higher Wire, Longer Wire
« Reply #4 on: May 24, 2019, 2221 UTC »
Any specific bands of interest? It's tough to beat a resonant dipole for a single band. 

If you're looking for general reception, consider something like a T2FD. It seems like you may have enough room for a reasonable sized one.They're fairly broadband for reception.

My experience with verticals has been limited. Mostly because each time I tried one, it was a noise magnet. So I have tried to limit my time wasted on them   :-X
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 670 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 120 ft T2FD/ 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline Josh

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Re: More Wire, Higher Wire, Longer Wire
« Reply #5 on: May 25, 2019, 1825 UTC »
On the vertical noise paradigm, it helps to place a say 100k ohm carbon comp resistor - or a high value choke - across the coax at the antenna to reduce static buildup and other noise. Also, you want it well grounded and as far from dwellings as possible to reduce noise pickup. A friend with a rosette of beverages has to replace his termination resistors often as they get popped by nearby lightning strikes, so use a higher wattage resistor in your vertical, bev, or whatever antennae if available. A high value resistor or choke across the legs of a dipole is also a good idea.
Conveniently located near Vincennes Indiana.

Offline i_hear_you

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Re: More Wire, Higher Wire, Longer Wire
« Reply #6 on: May 29, 2019, 1322 UTC »
This is meant for wide-band receive, so a traditional mono-band dipole is probably out for now.  I have some 300-ohm window line available, I'll look into the T2FD.

Josh, regarding the resistor for static discharge, would that be in addition to the ferrite isolation transformer at the antenna side? 


Offline Josh

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Re: More Wire, Higher Wire, Longer Wire
« Reply #7 on: May 29, 2019, 1745 UTC »
This is meant for wide-band receive, so a traditional mono-band dipole is probably out for now.  I have some 300-ohm window line available, I'll look into the T2FD.

Josh, regarding the resistor for static discharge, would that be in addition to the ferrite isolation transformer at the antenna side?

It can't hurt anything, if the antenna has a dc ground via the xformer it's not needed but can help in the case of a nearish lightning strike by sharing the pulse, possibly making the xformer last longer or comes open. This is one of the reasons I like any balun with a dc grounded antenna unput(s), free static drain! I think once you get above 10k ohms or so a resistor will do, I'd use a 2 watt or even 5 watt resistor and use lectrical tape or somesuch to waterproof it

On the t2fd, some people hate em, some love em. They're useful for rx on the hf band but should be tilted from horizontal if possible. I've not tried them in an inverted v config but they may work well there too. Also, if you ever get one of those insanely expensive B&W T2FD marked for RX/QRP only, don't tx thru it with more than a few watts or you'll discover why it's marked for RX only.


The odd thing is, a T2FD is a folded dipole with a resistive load placed at the center. A true folded dipole, aka one without a resistive load, rejects energy fed to it at twice the resonant freq, but a T2FD is fine with it.

Antennas are weird.

Here's some input on T2FD from a guy who knows antennas pretty well;

"It should not be surprising that the shorter T2FD shows much higher losses at the lowest frequencies of operation, since the antenna is about 0.2 wl long at 2 MHz. Basic antenna efficiency increases rapidly as the antenna length passes the 0.3 wl mark, which is well above 3 MHz for the shorter antenna. Indeed, we may call the frequency at which the antenna is about 1 /2-wavelength long the "knee" frequency. Below the knee, gain frops rapidly and losses (as well as dissipation in the terminating resistor) increase with equal rapidity.

The losses incurred in the terminating resistor occur in the form of heat. For reception-only applications, simple low-wattage non-inductive resistors may be used. For transmitting purposes, heat dissipation for the terminating resistor assembly becomes a major factor in antenna design."

https://archive.org/stream/ModelingTheT2fd/ModelingTheT2fd_djvu.txt

I tried to find the old NSA and Naval Research Labs docs on the T2FD, if I find em will post.
Conveniently located near Vincennes Indiana.

Offline i_hear_you

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Re: More Wire, Higher Wire, Longer Wire
« Reply #8 on: May 29, 2019, 1803 UTC »
Josh,

Thanks for the detailed information.

In other news, I had major storms last night and so was stuck listening to AM on inside antennas.  I've only just begun SWL in earnest April 1st of this year when I received my Tecsun PL880, and so this was a first.  I learned that the static crashes begin well before the first flash, and I was using this as a cue to look out the window in order to see some bolts.

Offline ChrisSmolinski

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Re: More Wire, Higher Wire, Longer Wire
« Reply #9 on: May 29, 2019, 1840 UTC »
I had a T2FD several years ago, before the famous 670 ft sky loop :)  It worked very well overall. From memory it was 132 ft long, so it worked well down into the lower part of HF. I have been toying with the idea of making another, for the Icom R71A that sits in the basement workshop, as a general purpose antenna. Although I actually find myself not using it, and instead using the Mac next to it, connecting to my KiwiSDR (which is on the sky loop).
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 670 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 120 ft T2FD/ 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline IZS4

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Re: More Wire, Higher Wire, Longer Wire
« Reply #10 on: May 29, 2019, 1843 UTC »
If your using the Tecsun PL-880 I'm not sure how much wire you could put up without overloading the radio and damaging it? Not sure if you have a different receiver your using with the outdoor antenna. I may have missed something.

Offline i_hear_you

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Re: More Wire, Higher Wire, Longer Wire
« Reply #11 on: May 29, 2019, 1944 UTC »
My true "first" is a CountyComm GP-5 SSB, and I remember thinking "this is going to f**king ROCK" when I hooked about 70' of speaker wire I'd strung on the ceiling to it.  There were images and ghosts EVERYWHERE across that thing and I immediately started looking to upgrade.

The Tecsun was my first serious world band radio, but I made some rapid acquisitions in the last month.  I now own an ICF-5900W, RF-2200, RF-1150, and ICF-2010.

I have ferrite-wound isolating transformers at the receiver and antenna ends.  I suspect this adds some attenuation, and most certainly it protects from static buildup.  There was only one night a couple weeks back where the Tecsun started having image problems, I assume from frontend overload.  Signals were just booming in.  I either did not see this issue with the other radios, or the issue was resolved by switching to "local" from "DX" on the offending frequencies.

I feel like Rain Man, but one of my biggest joys currently is A/B/C/D/Etc testing these radios and seeing how they stack up.

Offline ChrisSmolinski

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Re: More Wire, Higher Wire, Longer Wire
« Reply #12 on: May 29, 2019, 2018 UTC »
The Tecsun was my first serious world band radio, but I made some rapid acquisitions in the last month.  I now own an ICF-5900W, RF-2200, RF-1150, and ICF-2010.

I've often seen SWLs mentioning owning a bunch of portable radios. I'm curious, why not get one nice (used) communications receiver instead, for about the same total money?
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 670 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 120 ft T2FD/ 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline i_hear_you

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Re: More Wire, Higher Wire, Longer Wire
« Reply #13 on: May 29, 2019, 2114 UTC »
That's a great observation and question. 

Several reasons come to mind:

1) I enjoy portability. My first personal electronics were a Sony Sports Walkman that I took with me everywhere and I used until it finally gave out. I also preferred portable gaming systems to wired ones when I played vidya.

2) I am interested in off-grid comms, so I prefer battery-op radios, even for RX-only.

3) I enjoy comparing the various radios against each other.

4) I'm interested in preserving them and passing them down.  My little girls already have their own (RF-1170) in their room and are discovering a love for radio.  I intend to make a "radio room" with a museum feel to it.

5) I love the styling of all of them.  I would have a hard time picking a favorite, and while I've never had the collector's bug before now, I think it has taken hold.

When you say "nice communications receiver" I assume you mean something like an Elecraft K3, or top of the line Icom, Yaesu, or maybe something older like the Drakes that are highly praised.  These are amazing radios, but they can't be carried from room to room or out on vacation like a shortwave "boombox."  And there is a certain "fun factor" that I cannot explain, but I'm sure you understand what I mean, that I find in the several portables I now own that my KX3 does not have. 

If I decide to get more serious about radio performance, I've decided I'll go the SDR route.  Based on posts I've read of yours, I'm sure you appreciate this.  My understanding is that you need to start spending 5 figures to outclass a powerful computer with a good SDR attached.

Offline IZS4

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Re: More Wire, Higher Wire, Longer Wire
« Reply #14 on: May 29, 2019, 2219 UTC »
I feel you on the portability. Also if you take a portable radio into an area without RF interference and are running on battery power it makes a huge difference. Being a SWL and a Ham I would say buy a transceiver. If you ever decide to pursue the route of wanting to transmit then your ready to go, minus a tuner. I currently have an Icom 718 which is very basic and simple for both. Sure a JRC 545 is better, but I can go either way with what I have. Just a thought. As long as your enjoying what you do that's all that matters.