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Noise – Quick and Easy things you can do

Noise makes me mad

This is a copy of the Talking Tech Power Hour on the Sandton Repeater on 27 April 2022 at 19:00 CAT, entitled “Quick & Easy Things You Can Do Today To Reduce Noise In Your Shack (and a few you shouldn’t)”

Click Link to download a PDF version –> Noise Discussion ZS6STN 

Outline Starts Here:

Good evening. Thank you for the privilege to modulate your airwaves for a few minutes. My sincere thanks to the Chair, Matthew, and all the other important guests, many of which I know and have met before e.g. Justin / Henry & many others and all the listeners.

Special mention to SK Willy Wilson F.I.L. who rescued me from raging teenage hormones when I was a young man. As an experienced radar tech his favourite saying was RF is art, not science. Wise man.

Also the invaluable inputs from Ian White, GM3SEK, and Bob Brehm, AK6R, and others who took the time to publish some of their knowledge.

Disclaimer: I’m only sharing my own personal experiences and opinions and while I hope you can find some useful hints tonight, you are solely responsible for your own results and you should at all times check our own data and keep safe.

  • Talking Tech Power Hour 1/

I was asked a while ago if I would like to share a few words about noise, a popular and sometimes emotional topic amongst amateurs.

Now I’m not an expert. I have burnt my fingers and/or or given up all hope too many times. But I have learnt a few lessons.

As an ex-electrical engineer I hate to admit this but occasionally I’m going to tell small white lies when I’m explaining something, to make it easier to understand.  Sometimes I might also sound (pun intended) controversial in order to highlight a particular issue. It is all in good fun.

So let me start with a very controversial point: We (hams) are making the most noise ourselves!  (at least 10dB more than the noise floor!)

Now before you hunt me down and poison me like Putin, let us go back in history a little bit – all the way to when radio started. Isn’t it true that the very first transmissions were created by – horror of noisy horrors – spark transmitters? Didn’t they deliberately create noise in the hope that someone else could hear them?

  • Talking Tech Power Hour 2/

The spark gap radios wanted their desirable noise to be stronger than the ambient or background noise. And this is an incredibly important point.

–> As long as your desired noise is stronger than the ambient noise, you can proceed to try and decipher/decode/interpret it.

This is critical: In order for you to hear and understand the sending party, you would search for his noise where it is higher than the background noise.

So take another more modern example: When you leave your cell phone too close to the car radio it will respond with a brrrrrrrrr. Is that intelligible? No, it is noise, unless you can interpret it. You must apply the right decoder (or demodulator) to the noise before it becomes useful and turns into information.

Therefore: The first principle of radio is that we create noise is the very thing we create (use) to communicate.

 

Yes, we shout harder.

  • Talking Tech Power Hour 3/

Which reminds me of the delightful story of the two guys who went camping. In the middle of the night they are woken up by a lion that is trying to rip open the tent and they are starting to run away with the lion in full chase of course.

Soon the guy in the back says to the guy in front: “Why are you running so fast?”

And the guys in front, without breaking stride, replies: “I don’t have to run any faster. I only have to run faster than you.”

This is the principle: You don’t have to be the loudest or the most powerful signal. You only have to be 10dB above the noise floor.

  • Tonight’s Focus Areas

I would like to use the first few minutes just to point out the environment in which we operate. It is really important to check out how we got to where we are and what is happening around us.

Then we will move on to look at how a little knowledge can go a long way to help us, but that it can also cripple us or confuse us. Shine some light on S/N

This discussion wouldn’t be complete without revisiting  two of the basic electrical formulas: Ohms Law and EMI  and how they help us.

Finally we can move on and talk a little about the specific things you can potentially try to improve matters.

Finally my disclaimer: You are on your own and I’m not responsible if you fall of ladders or do other silly things.

  • Focus Area One: Spectrum 1/

In the beginning when only a few stations could made the sparks fly, ether wasn’t considered a constrained resource.

Today, RF Spectrum is a valuable and scarce resource and the pressure to get more spectrum is immense. Mobile is pushing hard for more spectrum – and they have money. Just read the news on how many billions ICASA got for the auction of mobile spectrum. The “Golden Rule” applies – the guy with the gold makes the rules

Being a constrained and global resource, users are licensed or permitted. An amateur license is a privilege granted to experiment with all modes and types, not just to talk on 40 or play hamnet (*). As amateurs we have been granted a few generous slices of that valuable spectrum, but there is no guarantee that we will be able to keep it or that intruders will not encroach on it.

We can expect over time to experience much more push-back from industry and less sympathy from other competitive demands

Use it or lose it! Experiment more and talk less!

  • Focus Area Two: Knowledge 1/

When the sparkies started their sparkling experiments, they probably didn’t know how (or have the tools) to measure anything.

Today we have a much better understanding of the parameters and I want to focus on noise.

Definition time: dB – it is a ratio of power or voltage etc.
Easy to add or subtract. 3dB is double, 10dB is ten times.

S/N Signal-to-Noise ratio, like the guys who ran away from the lion
you only have to be slightly louder than the noise, usually 10dB
R = V / I or the important variation: I = V / R – current in a wire is what
radiates the RF, either good noise or bad noise

Typically one might expect to see a figure in the region of 0.5 microvolts for a 10 dB S/N in a 3 kHz bandwidth for SSB – basis?

  • Focus Area Two: Knowledge 2/

When we started tonight’s talk I promised not to tell the truth, not the whole truth, and definitely not only the truth. So here is my layman’s explanation of how the S/N ratio can spoil your lunch.

Way back in the beginning when I started with my radios with the older analogue radios, the MDS (Minimum Discernable Signal) was maybe around 90dB or slightly better and the limitations were mostly receiver noise in the front end.

Recently I purchased a Xiegu X6100 (same as Matthew) and I was picking up noise that my Yaesu was oblivious to. After much wringing of the hands and digging deep into the specs I found that the X6100 has a MDS of 138 dB … that is so sensitive and almost GPS territory!

And remember – we still only need 10dB S/N to decode a signal

  • Focus Area Three: EMI 1/

Electro Magnetic Interference according to the professors that know everything, has three elements and all three must be present before you can have EMI. They are:

1: A Source    2: A Coupling (or Path)   3: A Victim

Be aware that you could be or are part of the problem in all 3 areas.

With RF, multiple paths or couplings are very common:

Radiative – air.  Conductive – wire.  Inductive – wires. Capacitive – wire.

A Source: It’s all your fault with that big antenna!

( I used to issue an award jokingly called: “Worked All Neigbours”)

  • Focus Area Three: EMI 2/

Are you a Victim? Definition: “… a disturbance (ed: noise) that acts on an unintended receiver”    -> no FUN!

RFI Sources:

Ham Antennas (not only the one you are transmitting on)

Radiating Coax (our favourite Tri-pole)

Electronic Devices (they have become ubiquitous)

Solar Systems (not always the culprit)

Grow Lights (yassss!)

HVAC motors (or at least the controllers)

In the lounge: Plasma TVs and LTE / Fibre Routers

Switching power Supplies (this is a big one)

Washer/Dryer or other kitchen appliances

  • Focus Area Three: EMI 3/

Electrical Theory

I (RFI Current) =  E (TX voltage) /  R (Choking resistance)   [I=E/R]

à Objective: Reduce the current ( I ) that causes RFI

In order of priority:

  1. Shut down the SOURCE (Set E to zero)
  2. Choke the PATH (minimize E, increase R)
  3. Protect the VICTIM (Set R very high)

Elaborate somewhat.

  • Typical RFI Manifestation
  • Focus Area Four: Actions 1/

Ask any Ham (Amateur) what to do about noise and you will get a quick simple answer. Oh, the answers are not always the same but they are quick and precise and described in great detail!

This reminds me strongly of another indightful story.

I graduated at the Univ of Pretoria in 1974 and the story also goes back to the same year – 1974 – when the physicist Richard Feynman delivered his commencement address at the California Institute of Technology. During his speech he mentioned “Cargo Cult Science” which is defined as a pseudoscientific method of research that favors evidence that confirms an assumed hypothesis. In contrast with the scientific method, there is no vigorous effort to disprove or delimit the hypothesis.

  • Focus Area Four: Actions 2/

Cargo cults are religious practices that have appeared in many traditional tribal societies in the wake of interaction with technologically advanced cultures. They focus on obtaining the material wealth (the “cargo”) of the advanced culture by imitating the actions they believe cause the appearance of cargo: by building landing strips, mock aircraft, mock radios, and the like. Although cargo cult sciences employ the trappings of the scientific method, they fail to deliver anything of value.

Feynman adapted the speech into the final chapter of his book “Surely You’re Joking, Mr. Feynman!”. He based the phrase on a concept in anthropology, the cargo cult, which describes how some pre-industrialized cultures interpreted technologically sophisticated visitors as religious or supernatural figures who brought boons of cargo. Later, in an effort to call for a second visit the natives would develop and engage in complex religious rituals, mirroring the previously observed behavior of the visitors manipulating their machines but without understanding the true nature of those tasks. Just as cargo cultists create mock airports that fail to produce airplanes, cargo cult scientists conduct flawed research that superficially resembles the scientific method, but which fails to produce scientifically useful results.

  • Focus Area Four: Actions 3/

Action 1: I’m going to quote Terry Mackenzie-hoy In Engineering News: “The first principle is that you must not fool yourself – and you are the easiest person to fool.”

à Always check the facts.

Action 2: I’m going to quote Bob Brehm, AK6R, of Palomar Engineers who supplies ferrites to Amateurs: “When in doubt, add a choke.”

à Always use Chokes (ferrites).

Action 3: Never buy a box of ferrite rings (toroids) without knowing their exact characteristics. You will be disappointed. Aim for a choking resistance > 500Ω over frequency range used.

à Always buy from a reputable source

  • Focus Area Four: Actions 4/

Action 4: Speaking of which … I started with Ugly Baluns and they do have some choking effect, but are seldom sufficient.

à Always use a Current Balun – they have better choking.

Action 5: Dipoles are so … 1970’s …. but since many older people believe them to be superior (Cargo Cult remember), please do not deliberately turn it into a Tri-Pole

à Always use a Balun with your Dipole to prevent RFI feedback

Action 6: Consider ALL the other gear and equipment. While it would make matters much more simple if everything can be thrown at the Cheap Chinese LEDs (or solar or …). I wish I had a silver bullet.

à Always check every electrical apparatus for noise

  • Conclusions
  • The fight for spectrum is going to result in an ongoing escalation and conflict

–Our “rights” are not entrenched

  • Interference needs a source, a path, and a target

–Don’t leave the garden gate open

  • EMI Electromagnetic Interference is a complex topic with no simple answers

–Although the basics are well understood (by experts)

  • We have some very good tools to fight the interference
  • End Of Formal Presentation
  • What happens with more than one?
  • In Series – just add them

More beads = higher choking R (up to 30 MHz)

e.g. at 7 MHz:

5 beads = 400Ω

10 bead = 1000Ω

15 beads = 1600Ω

  • Extra Turns – SQUARE them

Ferrite resistance increase as (turns)2

  • If 1 turn = R, 2 turns = 4 x R,
    3 turns = 9 x R !!
  • More R = less RFI wire current = less RFI radiated from wire or induced into wire. (I=E/R)
  • General rule: choking R > 10X line impedance
  • (e.g. > 500 Ω for 50 Ω cable but 5000 Ω is 10x better)

e.g. at 7 MHz: 100Ω 900Ω 2500Ω

  • Is your Dipole a Tripole?
  • Coax outside of braid acts as extension of transmitting antenna and extra receive antenna
  • Choose choking resistance > 500Ω over frequency range used
  • Further Conclusions
  • There isn’t one silver bullet solution
  • There isn’t one super-supplier of toroids
  • Don’t buy a box of “rocks”
  • Don’t believe a word anyone “says”
  • Determine RFI interfering frequency & suspected path
  • Douse at RFI fundamental frequency
  • Choose best topology (slip, snap, ring) to fit the Path “Antenna”
  • Install ferrites – then retest for RFI suppression
  • Add additional ferrites or paths if RFI persists
  • The End – Thank you!
  • Further Reading 1/
  • Noise in HF radio systems definition: Typically the input voltage for a signal to noise ratio of 10dB is stated. For an HF radio communications receiver, typically one might expect to see a figure in the region of 0.5 microvolts for a 10 dB S/N in a 3 kHz bandwidth for SSB or Morse https://www.electronics-notes.com/articles/radio/radio-receiver-sensitivity/signal-to-noise-ratio-s-n-snr-formula.php
  • Very good copy and paste material (restaurant) https://kf6hi.net/radio/SNR.html
  • Good explanation of s/n over the noise floor of the receiver http://www.k0bg.com/signal.html
  • Refers to video https://qrznow.com/radio-receiver-signal-to-noise-ratio-snr-specification/
  • The moment your noise has some pattern – in effect becoming an interfering signal – all bets are off. (assume white noise)
  • http://play.fallows.ca/wp/radio/ham-radio/signal-noise-ratio-essence-radio/
  • Cargo Cult Science
  • https://en.wikipedia.org/wiki/Cargo_cult_science
  • Further Reading 2/
  • Common-Mode Chokes by Chuck Counselman, W1HIS
  • A Ham’s Guide to RFI, Ferrites, Baluns, and Audio Interfacing Revision 7 Jan 2019 Jim Brown K9YC
  • https://qrm.guru/the-truth-about-ferrites/
  • https://qrm.guru/category/qrm-kill-kits/
  • https://youtu.be/Ivr9VbSgjUU
  • https://youtu.be/p5vw3cq3DkQ
  • https://www.vkham.com/resources/reference-info/ferromagnetic-information
  • https://rrc.org.au/2020/07/10/some-ideas-for-rx-noise-reduction-and-a-mains-filter-for-your-radio-shack/
  • http://www.m0nwk.co.uk/mains-electricity-filter-for-emc-noise-reduction/
  • https://youtu.be/xF2wFJBpu_I (DX Commander)
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SWR Meters Make You Stupid

Vintage SWR Meter

I recently published a short article in the member magazine of a local radio amateur club about how unimportant the VSWR (Standing Wave Ratio) is relative to the power that your station puts out, yet how much the average Ham frets about it.

While doing my research I came across this humerous dissertation on the topic, written by Eric P. Nichols, KL7AJ. I’ve read many of Eric’s articles in QST and QEX and other publications. They are mostly of a technical nature and are always worth spending time on. Eric is a dedicated homebrewer and CW operator. He enjoys all aspects of low band operation, and fiddles around with some 2200 meter and 630 meter operation as well.  He has operated just about every HF digital mode at one time or another, and can often be found on plain RTTY.

The article I want to reference here “SWR Meters Make You Stupid” captures the essence of why Hams should not worry about SWR too much. Below is the link to download:

SWR Meters Make You Stupid

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Interference in the Shack (West Rand Club 10/4/21)

QRM Blockers

The West Rand Amateur Radio Club hosted a talk by Leon Uys ZR6N at 10:30am on Saturday 10 April 2021, titled “5 Quick & Easy Things You Can Do Today To Reduce Noise In Your Shack
(and a few you shouldn’t)”.

The published agenda covered three main parts:

  • Part 1: The Environment In Which We Operate
  • Part 2: Five Steps You Should Consider Taking
  • Part 3: Practical – Build Your Own Toroid(s)

The talk was well attended and stimulated quite a bit of feedback, but as Leon said: “I am only sharing a few of my own very limited experiences and your results will vary. Don’t fall off ladders and do other stupid things, because you are on your own and I can’t be held responsible.”

The entire presentation is available for download from here: Interference Discussion West Rand Club

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Grounding Systems in the Ham Shack – Paradigms, Facts and Fallacies

A while ago, Tim Ellison wrote about “Grounding Systems in the Ham Shack – Paradigms, Facts and Fallacies” with content provided by: Jose I. Calderon, DU1ANV – Makiling Amateur Radio Society. Member: Philippine Amateur Radio Association (PARA).

I strongly recommend that you read the full article here.

He goes through a case-by-case discussion in easy to understand English – with pictures – of the various types of problems one may encounter in a poorly grounded shack, and then he concludes with an interesting solution that could assist many amateurs.
The symptoms he tackles include:

Microphone bites (nasty RF shock!)
Gritty and or fuzzy audio modulation (Distortion)
Malfunction of electronic keyer (sending wrong characters)
RF shock when touching metallic objects within the shack
Power supply jitters (the regulated power supply becomes un-regulated!)
Crazy SWR meter readings
Desktop computer going crazy
PC Desktop monitor jitters
Fluorescent lamp flicker
Active TTL switch circuit going crazy (Turning ON-OFF-ON by itself)
Inactive panel meters of separate equipment moving on their own
When transmitting, a distorted audio is heard over the amplified speaker of the PC desktop.
Severe Radio Frequency Interference (RFI) to home appliances within the vicinity of the Ham shack.

His article helped me to “understand the importance of effective grounding paradigms and, the facts and fallacies of grounding in ham radio. To make a shack RF free coupled with sound electrical grounding technique is a responsibility of the amateur operator to address the aspects of grounding when dealing with high levels of RF energy in the operating environment. Effective grounding of equipment is mandatory to address the issues of personal Safety, damage to sensitive equipment and prevention of severe RFI in the operating community.”

Thank you Tim and the other contributors.

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FA tester instructions

 

User Manual

 

 

 

 

 

 

 

 

Theo Bresler ZS6TVB

September 2020

 

Release No. Date Revision Description
1.0 2020-09-09 Initial Document
1.1 2020-09-09 Red Dots on Jumper images for clarity
1.2 2020-09-10 Corrections and optimisation by Chris R. Burger

ZS6EZ

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Revision History

ZS6TVB FA Tester Instructions V1.2                                                                                                             Page ii

 

 

 

1.0 Table of Contents

 

User Manual

 

Table of Contents

 

Page #

 

  1. General Information………………………………………………………………………                                                                                                                      A-1

1.1  Background ………………………………………………………………………………                                                                                                                      A-1

  1. Using the FA Tester……………………………………………………………………….                                                                                                                      B-1

2.1  Connecting to your Vector Network Analyser …………………………….                                                                                                                      B-1

2.2  VNA Calibration………………………………………………………………………..                                                                                                                      B-2

2.3  Test your Device ……………………………………………………………………….                                                                                                                      B-3

2.4  Additional Applications ……………………………………………………………..                                                                                                                      B-3

  1. Miscellaneous ……………………………………………………………………………….                                                                                                                      C-1

3.1  Acronyms and Abbreviations …………………………………………………….                                                                                                                      C-1

3.2  Contact Me……………………………………………………………………………….                                                                                                                      C-1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ZS6TVB FA Tester Instructions V1.2                                                                                       Table of Contents

 

 

 

A  General Information

 

 

 

  1. GeneralInformation

 

1.1        Background

 

ZS6TVB designed the FA Tester as an Amateur Radio weekend project to

provide a means of simple and easy testing of QRP Labs filter board kits

and other filters or attenuators in a similar physical format.

 

Connecting cables and connectors to the filter kits for testing or calibration

of a Vector Network Analyser (VNA) is challenging. The FA Tester is

designed to enable filter kits and attenuators to be tested accurately and

repeatedly with a VNA, providing the correct calibration plane with on-

board calibration jumpers and termination resistors. The design was kept

simple with a single-layer PCB. Tracks were kept as short as possible for

accurate testing at higher frequencies.

 

The design is not intended as a commercial product. It is for testing

personally acquired QRP Labs kits. Use the board at your own risk.

Accuracy is not guaranteed.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ZS6TVB FA Tester Instructions V1.2                                                                                                           Page A-1

 

 

 

B  Usage

 

 

  1. Usingthe FA Tester

 

2.1 Connecting to your Vector Network Analyser

 

The FA Tester features two standard SMA-F RF connectors: One each for the

S11 and S21 ports on your VNA. Depending on your test equipment or

requirement for the device being tested, the FA Tester may be connected to only

the S11 port or to both ports of your VNA.

 

Your VNA should have been supplied with two SMA-M to SMA-M pigtails that

may be directly connected between the FA Tester and your VNA without the

need for any extra connectors. Connect the FA Tester S11 port to your VNA S11

or CH0 port. Connect the FA Tester S21 port to your VNA S21 or CH1 port.

 

Should you have a modern VNA such as the NanoVNA range with the 4” display,

you may use the pigtails supplied with your VNA or connect directly to the VNA

with the use of two SMA-M to SMA-M barrel connectors. The FA Tester was

designed with the same spacing between the two SMA connectors as provided

on the more modern VNAs, so that the FA Tester can be connected directly to

the VNA. Refer to the image below for more detail.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ZS6TVB FA Tester Instructions V1.2                                                                                                           Page B-1

 

Calibration Sequence S11 Jumper Position S21 Jumper Position
Open O O
Short S O
Load L/I O
Isolation L/I I
Through T T

 

 

B  Usage

 

2.2        VNA Calibration

 

To aid accuracy, the FA Tester is equipped with matched 50 Ω resistors on both

the S11 and S21 ports. A complete calibration sequence for Open, Short, Load,

Isolation and Through may be done by simply by placing the S11 and S21 jumpers

at their correct locations. Jumper positions are clearly marked on the board for

correct placement. Refer to the table below as a reference of where jumpers

should be placed during the calibration sequence of your VNA or VNA software.

The images below should provide more clarity.

 

Note: Once the calibration process is complete, remember to place both

jumpers back into the Open (O) position.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ZS6TVB FA Tester Instructions V1.2                                                                                                           Page B-2

 

 

 

B  Usage

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.3        Test your Device

 

Finally! Time to start testing.

 

  1. Ensureboth S11 and S21 jumpers on the FA Tester are placed in the Open

(O) position.

 

  1. Ensurethe filter is plugged into the FA Tester and that the IN and OUT

sides of your filter are aligned with the IN and OUT markings on the FA

Tester.

 

  1. Proceedwith testing of your device.

 

Actual tests are outside the scope of this document.

 

 

 

2.4        Additional Applications

 

Although originally designed to test filters, the FA Tester may also be used to

accomplish the following tasks.

 

• With both jumpers in the Open (O) position, connect your filter to a coaxial

transmission line.

 

• Use it as a calibration standard for your VNA or Antenna Analyser.

 

 

 

 

ZS6TVB FA Tester Instructions V1.2                                                                                                           Page B-3

 

 

 

C  Glossary

 

 

  1. Miscellaneous

 

3.1        Acronyms and Abbreviations

 

Acronyms and abbreviations used in this document:

 

PCB:              Printed Circuit Board

RF:                  Radio Frequency

SMA:             SubMiniature version A

SMA-F:       Female SMA

SMA-M:      Male SMA

VNA:              Vector Network Analyser

 

 

3.2        Contact Me

 

Should any of the content in this document not be clear you are welcome to

contact me. I am on QRZ.com.

 

73

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ZS6TVB FA Tester Instructions V1.2                                                                                                           Page C-1

Posted on

Q80 add-on for Q40 End Fed Halfwave Antenna

80m Add-on

HOW TO OPERATE THE “Q-40”or 40m EndFed Antenna ON 80 METRES

A loading coil must be added to a 40m  to operate on 80M. The overall length of the 80-10M version of this antenna is about 23 metres. See details below:

The nominal inductance of the loading coil is 110 μH to cover the 80m band. Use 50mm PVC plastic pipe for this coil. The PVC pipe needs to be about 70 to 80mm long, to allow for attaching strain-reliefs. Shrink tubing can be used for weatherizing (note that this changes the inductance slightly – but is not serious) the shrink tube openings of the coil can be made watertight by stuffing it with hot-melt glue from a glue-gun just before applying heat to the shrink tubing. You need to make this loading coil as waterproof as possible.

Use 0.7mm Ø enamelled copper wire. Wire length needed is about 8.5 metres, make it 9.0 metres. With 52/53 turns, and tightly wound, the coil takes up about 40mm of space. Measured 110.7uH on my inductance meter. Instead of wrapping red wire around the ends, rather use suitable plastic cable ties. I went to an electric motor repair shop to get the wire. If you have one of my LC Meters, you can measure the coil exactly!

Figure One: Typical loading coil.

Figure Two: Typical Antenna Layout.

Tuning the total antenna. Standard approach for tuning-and-pruning the antenna is to start with the band where the antenna acts as a 1/2-wave end-fed (40 metres for the 80-10 antenna). Measure the SWR in the portion of the 40 metre band that is of interest. Without an antenna analyser, this is do-able but definitely not easy…. If the frequency of the SWR dip is above that band portion, then increase the long wire by 5 cm at a time and repeat the measurement. Conversely, slightly decrease the length of the wire if the SWR dip is below the band portion of choice. Repeat until the minimum SWR is achieved. Now add the loading coil and 2.4 metres of cable. Then follow the same procedure for adjusting the 80 metre length of the extension wire for minimum SWR on the portion of the 80 metre band of your interest. Just fold back the excess and wind around onto itself. So it is best to start out with wires that are definitely too long. Do your SWR measurements on 7.100 MHz for 40m and 3.65 MHz for the 80m tuning operation.

Depending on your local environmental conditions you may have to use an antenna tuner for best results.

The typical layout shown above does not necessarily have to go over a house roof – this is just an example. I have hung the transformer box under the eaves, and strung the cable from an upstairs room and over some trees and bushes at a height of about 5 meters, and it worked beautifully.

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QRP-Labs QCW Band Conversion

QRP-Labs QCW

The CW Kit from QRP-Labs is a very capable transceiver and the performance matches just about anything available on the market.

There is a small problem, however, with the fact that it is a single-band device. So when I stared out I built a 20m unit which has been remarkably fun when the bands are open, but mother nature isn’t always kind to us and often times there was just no signal to play with.

So, I investigated what is required to change it down to 40m. Turns out it isn’t a lot. A few toroids, a few caps. Most of the components can be desoldered without hassles. My initial take is that the following components are affected:

  20m   40m  
L1 0.77uH 16 1.4uH 21
L2 0.90uH 17 1.7uH 24
L3 0.77uH 16 1.4uH 21
L4 0.40uH 10 1.0uH 16
C25 390pF “391” 680pF “681”
C26 390pF “391” 680pF “681”
C27 180pF “181” 270pF “271”
C28 180pF “181” 270pF “271”
C30 30pF “300” 56pF “560”
C5 none none 40m 39pF
C8 none none none none
T1 3t x 3 30t 5t x 3 38t
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Radiowinkel is the start of a new multi-language version of Radio-Shop. In theory – if the software works – most pages will be translated and kept in sync auto-magically. But you never know what can happen in the deep dark depths of the internet, so when you notice a problem please let us know?