LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Useful information regarding antennas for SDR products.
Ian1951
Posts: 6
Joined: Mon Jun 03, 2019 5:36 pm

LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Post by Ian1951 » Tue Jul 02, 2019 10:08 am

I had hoped to follow glovisol example of making a single line post to allow edit and corrections to the main body of the text, but I've not posted enough for that privilege or to be able to send PM. Such is life

My brother in law is a hard core SW DXer. He has two tricked out Kenwood R2000 general coverage receivers, a separate demodulator with Inrad crystal filters, SAM, tone tilt, optional audio DSP, two Wellbrook antennas and the antenna described below. He paid a guy in Paducah to build it, so I have no idea what type relay is used.

I took my RSP1a over to demonstrate SDRs and he fell in love. This antenna might not be suitable for those who have strong MW stations nearby. There is a 1KW daytime only station about 30 miles away and it causes no problems with the RSP1a MW filter in place.
While the antenna is rated as 150KHz as the lowest frequency, we could receive NAA on 24KHz in Cutler Maine at ten o'clock in the morning. Of course NAA does transmit with 1.8 megawatts.

- - - - - -

LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna, Dallas Lankford, 1/11/07
This is a continuation of the development of a 15 foot noise reducing vertical antenna which was begun in my article “Some of my favorite small antennas for LW and MW;” see The Dallas Files. The antenna there specified a 4 foot ground rod; an 8 foot ground rod, indicated on the schematic at right, may give better noise reduction at lower frequencies. Output signal levels of this antenna are the same below 8MHz (low band), while output signal levels above 8MHz (high band) slowly increase as frequency increases up to about 10dB more at 30MHz compared to the original antenna.

The first obstacle to making a small noise reducing vertical antenna with excellent signal output from 150kHz to 30MHz was impedance matching. After much theoretical and experimental work I found that excellent signal output over such a wide frequency range could not be obtained with a single
matching transformer. Fortunately, when I tested three different matching transformers optimized for 0.1 – 2, 2 – 10, and 10 – 30 MHz they were more than adequate, and it turned out that two matching transformers, 0.1 – 8 and 8 – 30 MHz, were optimal. A single matching transformer with a tap
performed as well as two separate matching transformers, so that is what I used.

The second obstacle to making a small noise reducing vertical antenna with excellent signal output from 150 kHz to 30MHz was a satisfactory method of band switching at the antenna. A hermetically sealed mechanical relay with a wide temperature operating specification (well below freezing) and a high cycle contact life specification should be used. But try finding any. After weeks of searching a few showed up on eBay. They were small, the same size as TO-5 transistors, and manufactured by Teledyne, model 712-12. I bought some.

Later I discovered that Mouser had just started carrying the same (and other) Teledyne relay(s), catalog # 881-712-12. They are not cheap, about $22 each. But the specs are excellent: operating temperature range -55C to +85C, contact life rating of 10,000,000 cycles at low voltage levels, interconnect capacitance of 0.4 pF, and so on. The -12 means that the relay coil is 12 volts (16 volts absolute maximum). Other coil voltages are available.

For some voltages there are D models with built-in diodes for transient suppression. At first I was inclined to omit the transient diode suppression D in the schematic above, but after discussions with Terry Fugate I saw the error of my thinking.

Operation of the antenna is straightforward. When listening to signals above 8 MHz the relay is turned on.

When listening below 8 MHz the relay is turned off. At low noise locations with somewhat insensitive receivers a 10dB gain push-pull Norton amplifier may provide a better signal to noise ratio for weak signals.
LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna.png
LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna.png (66.71 KiB) Viewed 1542 times

BTW I am not nulluser, and I do not delete posts or retire quietly. And I find the insult I am a sockpuppet to be disgusting.
Last edited by Ian1951 on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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sdrom33
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Re: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Post by sdrom33 » Wed Jul 03, 2019 11:08 am

This "antenna" design contradicts many, if not all, antenna principles anyone however superficially involved with radio communications should be aware of. Just to name a few.
- If it is a ground plane it does not have the ground reflector. If it is not a ground plane, what is it?
_ It is claimed to be "noise reducing", but no scientific or otherwise practical reason why this whip should be a "noise reducing antenna" is given.
- worse, to connect the ground return to an earth stake is just about the worst one can do about noise, according to theory and practice.
- it is claimed to be "wide band", but no principle whereby this whip should provide wideband operation is given. To try and pretend to be wideband, it should at least have a large diameter, but no mention of diameter is given.

Furthermore the FT-114-75 core does not exist: must be FT-140-75, with an Al=5500 uH/100 turns, so 40 turns give an inductance of 8800 uH: reactance could now be calculated, but the low frequency side of the antenna is unknown. The FT-50-75 core does exist, with Al=2725 uH/100 turns. Assuming 50 Ohm at terminals A / G of T2, we have 50 Ohm on the other side, so there should be 5 KOhm across the 40 turns winding of T1. With the relay contacting the tap, the antenna impedance goes down to 312 Ohm. All this, without a well defined frequency plan, does not make any sense to me....An antenna output impedance of 5 KOhm? But there is more: in the original design by doctor Dallas, T1 primary has 80 turns..., so this must be considered an "improvement".

Sorry for these severe comments, but many inexperienced operators could be misled by this publication.

It does not matter if this design seems to be originated by "Dr. Dallas Lankford" (lost in the Arctic regions?) it still looks like something evidently not fit for the purpose and surely not delivering the claimed performance.

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vk7jj
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Location: Tasmania

Re: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Post by vk7jj » Thu Jul 04, 2019 10:25 am

Forgive me for wading in, no doubt Ian is very well intentioned and trying to be helpful, but as sdrom33 says the article is so problematic that it seems to be useful example of what not to do and anyway I love antennas so much I can't help myself.

It seems (to me anyway) that the concept is flawed from the outset as the "noise" being picked up by the antenna is in fact just RF, the stuff the antenna is designed to receive. The more noise, the more efficient it is and verticals are very good at picking up man made noise because of their low radiation angle.

Any attempt to reduce the noise using any form of phased coupling which seems to be what the aim is will also attenuate any useful signals that may also be present.

It does not seem even remotely possible given the values and configuration it could be made to resonate on a wanted frequency and be of assistance that way.

The only way to reduce the noise via phasing without also killing the wanted signals is to use more than one antenna and combine their output through a phase shifting system, eg. an MFJ 1026

Or even better an SDRplay Duo when the new version of SDRuno arrives :-)

I would add that using MMANA modelling software...

A 15 foot lossless vertical placed against an infinite and perfect ground has a feed point impedance on the 80m ham band (just to pick an example) of 0.175 ohms.

At 150KHz which is the lower frequency cited the feed point impedance is 0.0019 ohms.

The turns ratio on the transformers shows that it is stepping down not up. That is going to make the feed line match even worse as well as actively discriminating against the HF frequencies the lower down the band you go from 30MHz.

--

Commercial or home built small loops can make a very effective antenna on the HF bands including at the very lowest frequencies and there are many users on the Forum who would love to give examples.

Alternatively a cheaper and fun way to fiddle would be to buy a simple ferrite rod similar to those used in the old transistor radios, wind 20 turns of any old hookup wire around it and connect it to the zip cord feed line. That would be very much the superior antenna and could be fastened horizontally on the end of a wooden stick and rotated for best signal to noise.

Sincerely, Phil

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Ian1951
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Re: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Post by Ian1951 » Thu Jul 04, 2019 11:01 am

Sorry for the delay, I don't use the internet everyday, and there is the inherent delay for my missives to be approved for publication.

OMG I've posted enough to be trusted to be allowed to post without approval!

Dear SDR33, I don't especially mind if you think I'm someone I'm not, or that you like to nitpick everything I write, but the antenna I referenced works very well from the bottom of the nondirectional beacon, 198kHz through the US 27MHz chicken band.

The lack of a suitable ground initially disturbed me because I am used to working with ground plane antennas, center fed half wave length dipoles with traps for the specific ham bands I operate on, or my 500 foot Beverage over thin soil over limestone.

The Lankford Relay Switching Antenna works and works quite well. I'm not sure it's up to dealing with hunting down that low power DXpedition station from Terra El De Fuego, but my BIL routinely receives transatlantic LW broadcast stations from late November through mid February and has recordings of well over 200 non directional beacons.

My guess, and I freely proclaim to the universe I lack the technical education to model it, is the antenna presents a such a high impedance to the EM field it doesn't require a decent ground.

Let us review the design, for LW, T1 has 40:4 turns ratio.

If my math is right, the 40:4 turns ratio is 100:1 impedance transformation. The math is being done at 3:00AM so I could easily be wrong.

With a 120 ohm twinax lead, the antenna presents a 100 X 120, or 12000 ohm impedance to free space, which if memory serves me, is 366 ohms. Now I am not an engineer, but that strikes me as pretty insignificant loading of the EM wave. This it isn't as high as an active antenna with a jfet but it's pretty darn high.

And of course the voltage level drops by a factor of ten, for a 20dB loss, 03 3'S-Units". Given the naturally high levels of noise below 30MHz, even a less then ideal antenna can offer acceptable performance.

Does anyone know the loss of the PA0RDT active antenna? The source follower and emitter follower transform impedance but can't have any voltage gain?

The only differences between the article I posted and what my BIL uses is he used an 8 foot ground rod, feeds it with twinax.

He feeds power down the balanced pair and extracts it with 2 RF chokes, blocks the DC from the output transformer with capacitors.

The antenna might violate every accepted design principal you believe in, yet it works amazingly well.

If my BIL had asked me I'd have advised him to not waste his money, and I would have been wrong.

For some reason I'm reminded of Galileo said when he left the inquisition: "E pur si muove."

In English, "And yet it moves."

Or, for our purposes, "And yet it receives."


I've considered operating on the new VLF allocations on 2,200 Meters (135kHz), and LF 630 Meters (472kHz). For some strange reason the idea of erecting even minimally effective transmitting antenna for such long wavelengths and such low EIRP power level strikes me as a bad return on investment.

Here are some examples of antennas that, in your universe shouldn't work. I have not tested any of them because I don't need a ELF/VLF/LF/MW antenna.


Friedrich Krug, OJ3RV A Receiver for the VLF Time and Frequency Standard Transmissions from DCF 77

https://ia800200.us.archive.org/16/item ... DCF_77.pdf

Stephen P. McGreevy's BBB-4 (Bare Bones Basic) Natural VLF Radio Receiver Schematic for atmospherics, "whistlers."

https://www.transkommunikation.ch/datei ... _bbb-4.pdf

OMG he's trying to receive 200Hz to 12KHz on a short whip antenna!


Dual polarization, balanced, VLF antenna by Pierluigi Poggi IW4BLG

http://www.vlf.it/poggi3/dualpolarization.htm


I ran this parts of this past a real electrical engineer who reminded me a MW car antenna shouldn't work because it's only 1/75 of a quarter wavelength.

Some mathematical data.
1MHz Wavelength is 300 meters
1MHz Quarter wavelength for a monopole is 75 meters
Typical automotive MW monopole around 1M.
The antenna is about 1/75 of a quarter wavelength, at 1MHz, it gets worse at lower frequencies.

My radio software packages gives divide by zero error when I try to calculate the impedance or radiation resistance of a monopole that is 1/75 of a wavelength. And it gets worse as you tune to 540KHz where the 1 meter monopole is almost 1/150th of a wavelength.

I seldom listen to the radio in my car, preachments about "John Barley Corn and the Temptation of Eve," <Bonus point for the name of the song that was stolen from> endless adverts for male sexual enhancement products, pointless political ads and talk radio hosts who should be locked up bore me to tears. I use my iPod to play decently decadent music from the 1950s through the 1980s.

But, just to be sure the universe still works the way it used to, I checked reception on our car radio as we left home to go Lexington Wednesday afternoon. We are visiting our daughters and I have an doctor's appointment for a second opinion on having both knees replaced.

Guess what?

That little monopole antenna that is just under 1 meter fully extended allows me to pick up stations from Louisville, 120 miles to the east, Cincinnati, about 140 miles to the north east, though to be nitpikcingly accurate, WLW's transmitter is located in Mason Ohio. I could also receive stations from St, Louis, Nashville, it seamed there was a station, or mix of stations, on every 10kc allocation.

I wonder how that can be? Surely my 1 meter antenna can't possibly work if it's 1/75 of a quarter wavelength, can it? If so, how since it violates your rules of accepted behavior.

I am not ignoring the capacitive coupling between the car body and the ground and I'm embarrassed to admit I do not remember from my days of running a mobile on HF. But even if the car body is assumed to be an infinite ground plane, the monopole is still 1/75th of a wavelength.

And yes I know why it works, automotive radios have high impedance inputs, but guess what, so does the antenna that can't work.

This appears to be another example of an antenna that can't possibly work.

I have a 30 year old Radio Shack disk cone antenna that was rated for use from 25 to 1300 MHz. To say the specs were optimistic is laughable. About 15 years ago we had an ice storm. Two plus inches of ice took down all my antennas except for my 144/44 yagis and the disk cone. In shear desperation I connected the disk cone to my antique Sansui HiFi integrated receiver-amplifier to receive "local" FM BCB stations, 88 to 108MHz.

The radio had been left on 840KHz, and I was pleasantly shocked to hear WHAS. I could receive all the 'local,' and quite a few not so local, MW stations.

"Local" is about 30 miles away.

The disk cone is mounted about 70 feet up on a side arm off my tower. It uses 50 ohm coaxial cable.

So please riddle me this riddlemaster, how can and antenna that, most optimistically, have a lower frequency limit of 50MHz, feeding 90 feet of 50 ohm coaxial cable possible provide any signal to a MW receiver?

Again "E pur si muove."


Our daughters have a disk cone mounted above their DBS dish. I hope to have time later today, or tomorrow, to take some screenshots, and post them in a new thread, that shows how well, or how poor, their disk cone functions as a LF, MF, HF antenna. They live in the north end of Lexington about 11 miles from the blue grass airport which has a non directional beacon. This follow up might take a few days. I will try to find out the model of the disk cone and the length of the top hat elements. I do remember they removed the vertical element intended to improve reception in the 20 to 50MHz range.


I am not trying to be snarky; although my older says I don't have to try, it comes naturally; I am trying to point out that what we think we know might not be true.

Another point only tangentially related, in vocational school we were taught "vertical polarized antennas for HF are a bad idea because man made radio noise is predominantly vertically polarized."

So based on the accepted wisdom of 1972, a Beverage is a really bad choice for HF...just asking, after all, "man made radio noise is predominantly vertically polarized."

My engineer friend shared this with me.

<><><><><><><><><><><><><><><><><><><><><><><><><><><><>
Electrically-Short Dipole Antennas
Mark Connelly, WA1ION - 8 APR 2001

A dipole antenna normally is cut for approximately one half of a wavelength. The customary formula is (468/F) feet or (142.65/F) meters where F is the frequency in MHz. This works out to about 0.48 wavelength. The dipole antenna has seen little use at medium wave because of its impractically large dimensions: about 883 feet/269m at the low end of the broadcast band (530kHz). Furthermore, for the antenna to perform well, it has to be a minimum of a quarter-wave above the ground if mounted horizontally. If set up vertically, its top end is a half wave (or greater) above ground and if sloped at 45 degrees, the top end is at least 0.35 wavelength high.

In a quest for a compact omnidirectional passive antenna of reasonable dimensions, I did some measurements on vertical and sloping dipoles measuring only 33ft. / 10m total length (16.5ft. / 5m each side of the center feed point). This antenna is less than 0.02 wavelength at 530kHz and 0.06 wavelength at 1700kHz. Obviously, in this frequency range, such an antenna is a very poor match to direct 50 ohm feed.

The way to get a reasonable amount of signal capture out of such a compact antenna, without resorting to distortion and noise producing amplification, is through the use of passive devices to improve the match. A narrowband technique (a remotely adjustable inductive - capacitive (L-C) tank at the feed point) is ultimately the best approach in terms of efficiency, but it is difficult to implement and does not lend itself to frequency-agile DXing.

Matching with a broadband balun transformer is the other approach that can be used. The ratio to be used is fairly high because an electrically-short dipole presents a much higher impedance than 50 ohms. I did tests with two transformers: one had a 36:1 impedance ratio, the other a 16:1 ratio. The high impedance winding leads went to the antenna elements and the low impedance winding to the coaxial cable. I also had 9:1, 4:1, and 1:1 transformers available for testing if results indicated the 16:1 better than the 36:1 unit. This, however, was not necessary as the 36:1 transformer gave the better results across the medium wave dial. I set up a 10m (total length) center-fed dipole in a nearly-vertical configuration suspended by a nylon rope over a high branch on a black locust tree in the backyard at my home location in Billerica, MA (GC = 71.221W / 42.533N). The bottom of the antenna was about 1.5m off the ground and the coaxial feed ran about 20m from the balun box (at the middle of the antenna) into the house: I tried to keep the feedline close to a right angle to the dipole as much as possible. Daytime signal measurements on some groundwave locals were made using the Drake R8A in PREAMP ON mode. Across the band, the 36:1 transformer showed a 4 to 8 dB advantage over the 16:1.

Measurements with the 16:1 transformer (Mini-Circuits T16-6T-X65)
WEZE-590: S9+16
WRKO-680: S9+51
WEEI-850: S9+28
WBZ-1030: S9+27
WKOX-1200: S9+12
WWZN-1510: S9+35

Measurements with the 36:1 transformer (Mini-Circuits T36-1-X65)
WEZE-590: S9+20
WRKO-680: S9+55
WEEI-850: S9+36
WBZ-1030: S9+35
WKOX-1200: S9+20
WWZN-1510: S9+39

Homebrew transformers of various ratios may be tried in future experiments. One possible design is a 25:1 transformer consisting of a 40 turn high impedance winding on the opposite side of an FT140-43 toroid from an 8 turn low impedance winding. The larger core than what's used in the Mini-Circuits models would tend to reduce the likelihood of harmonic and intermodulation distortion in strong-signal areas. With the Mini-Circuits transformers I used, I did notice a slight amount of WRKO-680 audio under WLYN-1360 (680 * 2). WRKO's 50kW transmitter is about 5km from my home location.

The short dipole picked up less local electrical noise (relative to desired signals) than an active whip. If a 1:1 isolation transformer is used at the "shack" end of the coaxial cable, noise can be reduced a bit more in some circumstances. A broadband loop (square loop at 3m per side, coupled through 1:1 transformers on each end of the coaxial feedline) was still quieter than the dipole in terms of locally-produced TV / other electrical noise pick-up.

Signal levels produced by an efficiently-coupled short dipole are adequate for typical DXing.

When more gain is needed, a good high-Q regenerative preselector amplifier will bring marginal signals up out of the mud. The primary niche that the short dipole has is a very space-conserving antenna for small pieces of land. A broadband loop (as described above) can be located close to the dipole and the two antennas can be phased to produce a cardioid pattern.

When more land is available, you can phase two vertical dipoles spaced at approximately 60m on the desired peak-null axis.

Sloping the short dipole off true vertical only has a slight effect on directivity. An antenna of such small dimensions does not have much in the way of inherent nulls. If setting up two of these antennas about 60m apart for phasing, it might help to slope one the opposite way of the other to make the antennas a little "more different". Setting the antenna up in a horizontal position probably does reduce the low angle pick-up some.

If a tree or other support much taller than 10m is available, the dipole can be scaled up in size.

With a 20m antenna length, the transformer ratio can probably be lowered to something in the 4:1 to 12:1 range. As you approach a half wavelength, the required ratio goes down to 1:1. The closer the size of the antenna gets to resonance, the greater the sensitivity. Still I was quite surprised at how much signal can be obtained from an electrically short dipole when the correct matching transformer is used.
<><><><><><><><><><><><><><><><><><><><><><><><><><><><>
Now I'll admit a 10m, ~33 foot, dipole is about twice as long as the Lankford relay switched antenna, but it is still rather short for MW reception.
<><><><><><><><><><><><><><><><><><><><><><><><><><><><>

I did a net search and found this "update."

<><><><><><><><><><><><><><><><><><><><><><><><><><><><>
Copyright © Dallas Lankford - All Rights Reserved.
This is basically a Dual-Band "Relay Switched" Passive
{meaning Non-Amplified} Vertical Antenna using a Matching Transformer; Ground Rod; and Line Isolator.

If you did not want the AM/MW Band and Longwave Band coverage; and are 'only' interested in the Shortwave Bands between 3MHz ~ 18MHz: A 'non-relay' Single Band Passive Vertical Antenna would be simpler choice.

100% PASSIVE: +No Relay +No DC Power Required

The Original Lankford: For the 8MHz ~ 30MHz High Shortwave Band this Antenna uses a 4T to 10T (1:6) Matching Transformer at the Base of the 15-Foot Vertical Antenna mounted on a 4~8 Foot Ground Rod. Plus a 4T to 4T (1:1) Matching Transformer as a Line Isolator.

MODIFIED: For General 'Middle' Shortwave Radio Bands: 60M - 4400~5100KHz
49M - 5800~6300KHz
41M - 7100~7600KHz
31M - 9250~9995KHz
25M - 11.50~12.16MHz
22M - 13.57~13.87MHz
19M -15.00~15.825MHz

For a 4.4MHz ~ 15.9MHz Shortwave Band coverage this Antenna would use an 8T to 20T {-or- 7T to 18T} (1:6) Matching Transformer at the Base of the 15-Foot Vertical Antenna mounted on a 4~8 Foot Ground Rod.

Plus an 8T to 8T (1:1) Matching Transformer as a Line Isolator.

Antenna Side-by-Side : The Lankford Vertical -v- The Doty Inverted "L" It would be interesting to build one and run it along-side a "Doty" Low Noise Inverted "L" Antenna using a 10T to 30T (1:9) Matching Transformer at the Base of the 15-Foot Vertical-Up-Leg mounted on a 4~8 Foot Ground Rod with a 30~45 Foot Horizontal-Out-Arm.

Plus a 10T to 10T (1:1) Matching Transformer as a Line Isolator.

-Note- Separating both Bases of the Antennas by 30-Feet or more.
<><><><><><><><><><><><><><><><><><><><><><><><><><><><>
Ihave no idea what the last was supposed to mean.

Since you enjoy odd rambling bits of arcane fluff, My father was stationed in Rome, Italy, during WWII. They listened to WLW for news from home. WLW operated under a special license and ran something like 500K or 1MW. That was some DX.

My Mother was born in Mason County Ohio and when I was 8, 1959, we visited her family and passed by the WLW transmitter site. They had a massive "dry fountain" in front of the station. Mom's uncle [or cousin, it's been 59 years] was either the sheriff or a deputy and Mom talked him into taking me to the transmitter. The engineer explained the dry fountain was left over from WWII when they ran "high power," and the fountain was the secondary cooling loop. It cooled the distilled water that cooled the electronics. The transmitter building smelled the way such places should, old oil, with a faint whiff of ozone. There were racks of equipment taller then me, hey I was 8! It was spooky and magical. Dad told me about the fun of listening to WLW while he was in Rome on the way back to Elizabethtown. I guess the idea a signal from Mason Ohio could travel to Rome Italy might have been one thing that lead to me becoming interested in radio.

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g1hbe
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Re: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Post by g1hbe » Thu Jul 04, 2019 5:47 pm

Ian, in regard of the bonus points. The version of 'Let it All Hang Out' that I remember was by a certain J. King in (about) 1970, although I think it was his version of an earlier hit by someone else. Do I get a small prize? :D
Sorry mods for going off-topic, but any mention of bonus points gets me in a lather....

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Andy

vk7jj
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Re: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Post by vk7jj » Thu Jul 04, 2019 10:47 pm

IMHO articles on forums are posted there in order to be discussed and commented on so that the resulting discussion raises pros and cons and teases out other related issues for the benefit of everyone.

I've learned so much from making so many mistakes that I'm seriously considering making more of them.

Commenting on my own post above

- the reason I mentioned noise phase cancellation was because the words "Noise Reducing Vertical Antenna" in title of the post and the title of the circuit led to the possibility that Ian may have thought that "noise reducing" was what was happening with the switched inductances.

- in practice the antenna illustrated would likely work as an off centre fed vertically polarised doublet with the ground wire and earthing system being the non-obvious second part of the doublet, they would at as an RF source rather than a sink

- the ground losses and impedance of the ground wire earthing system as an aggregate would likely present as something above 15 or 20 ohms impedance in practice, meaning that the matching system as illustrated could well result in a halfway reasonable SWR

- if a person set out to design an antenna with the purpose of maximising its ability to pick up noise he would choose a vertical "ground plane" with a longish wire indirectly connected to a mains earth rod.

- if a person set out to design the least effective antenna possible for listening to medium and international HF he would choose a short end fed vertical, the shorter the better.


Phil

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Mike2459
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Re: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Post by Mike2459 » Fri Jul 05, 2019 3:04 am

Phil:
I think Lankford's 'noise reducing' design refers to the use of a 1) a ground rod at the antenna and 2) a balanced transmission line magnetically coupled at both ends. He uses this in several of his other designs.

Some of his other stuff can be found here: https://www.okdxf.eu/index.php/technika ... -lankforda



Ian:
I thought I might give the zip cord a shot with my mini-whip. I can power the antenna with a battery pack for testing. Lankford doesn't recommend using the transmission line as a DC supply line - says it will introduce noise into the signal path.


Mike

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vk7jj
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Re: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Post by vk7jj » Fri Jul 05, 2019 6:17 am

Hi Mike, yes I know, I did mention connecting to the zip cord in my first post and yes a parallel feed line is one of the pet things I keep pushing in all my posts and kudos for the inductive coupling Lankford used so as to create a balanced system.

If Lankford had used coax in that circuit I would have included it in the litany of antenna parts that acted as a collector of RF.

I use much the same here, after evolving various options in search of the best low noise solution I decided to home brew something similar using a lightly twisted pair of surplus eBay teflon as per mentioned in other forum posts. Its characteristic impedance is around 120 ohms which is the best compromise for my particular antennas. I was using home brew ladder line but couldn't get the impedance as low as that.

For example
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I've checked out zip cord, really handy for receiving but no good for transmitting. There are many other simple surplus options for receiving including CAT5 that actually work really well over modest distances.

--

I looked deeply into my heart and conscience before posting my criticism of the circuit, I cannot even begin to see how that 15 foot vertical and it's matching system (and earthing system) can in any way at all be touted as a "Noise Reducing Vertical Antenna". I think I could fill a detailed couple of pages setting out the proof of why it isn't and cannot be, I side wholeheartedly with sdrrom33's summary:
This "antenna" design contradicts many, if not all, antenna principles anyone however superficially involved with radio communications should be aware of. Just to name a few.
- If it is a ground plane it does not have the ground reflector. If it is not a ground plane, what is it?
_ It is claimed to be "noise reducing", but no scientific or otherwise practical reason why this whip should be a "noise reducing antenna" is given.
- worse, to connect the ground return to an earth stake is just about the worst one can do about noise, according to theory and practice.
- it is claimed to be "wide band", but no principle whereby this whip should provide wideband operation is given. To try and pretend to be wideband, it should at least have a large diameter, but no mention of diameter is given.
Put bluntly, touting that circuit as a wide band 150KHz to 30MHz "Noise Reducing Vertical Antenna" is getting very close to offensive rubbish.

Cheers, Phil

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vk7jj
Posts: 206
Joined: Thu Mar 02, 2017 9:56 am
Location: Tasmania

Re: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Post by vk7jj » Fri Jul 05, 2019 9:15 am

On a positive note, anyone looking to build a genuine wide band vertical can, it is absolutely possible.
TC2M Gain-2.png
TC2M Gain-2.png (3.98 KiB) Viewed 1244 times
TC2M SWR 30MHz.png
TC2M SWR 30MHz.png (19.51 KiB) Viewed 1244 times
https://www.tc2m.info/

Phil

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sdrom33
Posts: 123
Joined: Sun Dec 09, 2018 4:38 pm

Re: LW-MW-SW Relay Tuned 15' Noise Reducing Vertical Antenna

Post by sdrom33 » Fri Jul 05, 2019 11:05 am

I have been considering this TCM design and planning to do it with 300 mm dia. PVC water pipes supporting a steel mesh. In this case a self supporting wide band antenna could be made with minimum expense and no external supports. Non resonant ground reflector could be made with conducting cloth cheaply available in China. Phil, what do you think about this scheme? Your advice very important to me!

Cheers,

Thomas

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