long/short term “borrow” required
requires no machining or preparation beyond cable ties
high wind loading
ready-made solid structure
weight if tower falls
My main project for at least the last 12 months has been building a solid magnetic loop antenna and its companion automatic loop controller. I’ve been roughly tracking its progress at my magnetic loop antenna project page on this blog.
As usual, life has got in the way, but I want to get back on track and complete the project. To start pumping some RF current through it again, over the weekend I spent a short time playing with the loop on WSPR on 40, 30 & 20m. The tests were too brief but they certainly confirm that the loop is capable of transmitting a signal in spite of the fact the loop is only half a metre above ground and surrounded by metal garden furniture, a steel framed awning and gutters.
I used the WSPR Beacon android app to control my transmitter. There was some discrepancy (tens of Hz) between the actual output frequencies on the app and those shown on WSPRnet. I also found that tuning the loop to each WSPR frequency using the iP30 antenna analyzer was easy and the KX2 gave lower SWR figures.
The brief test became an exercise in understanding theWSPRnet results taking into account propagation and loop orientation which was aligned north-south.
This map view combines all 20 spots of the 1W VK2RH transmissions from grid square QF56oc. The first test was logged at 2017-05-07 01:36 UTC. (I’ve trimmed repeated info from the chart below to improve its fit on the page.)
40 metres favoured north-south, while 30 metres was literally an all-rounder and 20 metres was too brief. These results probably say more about propagation than the loop, not to mention the heavy lifting done by all the reporter stations extracting my down to -26 or -27 dB signals from the noise! Impressive all round!
I wonder how many people are using the Sotabeams WSPRlite antenna tester device. Certainly looks tempting, especially for longer term antenna evaluation.
In any case, the main purpose of today’s exercise was to re-start the loop project. The To Do list includes
- building & installing the SWR bridge into the loop controller,
- deciding on the best way to couple the stepper motor shaft to the tuning capacitor shaft,
- and wiring it all together with appropriate coax and control cables.
The Smartlock is an accessory for my SGC SG-239 HF Smartuner, and other ATUs they make. It can be bought ready made or built.
For reference – here are the indicators and connections on the transceiver end of the SG-239:
B.I.T.E.* Status LED Descriptions – *Built In Test Equipment
TND This LED will light when the tuner has found an acceptable match. It will remain lit until conditions have changed which will cause the tuner to find a different match. (i.e. A new transmit frequency has been detected, or tuner has been reset.)
L ‘Z’ This LED shows the status of the antenna impedance. When lit, the impedance is 50 ohms or less. When off, the impedance is greater than 50 ohms.
2:1 This LED will light when the VSWR is greater than 2:1. It will extinguish when VSWR is less than 2:1.
PHZ This LED indicates the status of the antenna reactance. When lit, reactance is inductive. When off, reactance is capacitive.
FWD This LED indicates the presence or lack of RF power from the radio. When transmitting, the LED will light to indicate RF is being detected. In receive, the LED should be extinguished.
OTHER All LEDs will blink on and off at a rate of 2Hz to indicate the tuner was not able to find a valid match.
The LEDs are very small and quite faint and almost impossible to see on a sunny day.
As the ad below indicates the Smartlock provides two controls that can be used remotely from the tuner and close by the radio – allowing the operator to lock or stop the ATU constantly retuning as the load changes and to reset which forces a retune the next time a signal is transmitted.
The Smartlock also indicates if the ATU managed to tune the antenna and if the lock is on. The lock can be invoked when the antenna is to be used for receive or when there are too frequent changes in the physical environment of the antenna such as when mobile and passing trucks or going under bridges….
Installation requires normal coax and a four conductor cable for power and control.
SMARTLOCK, FOR SG-230/237/239 SMARTUNER
From the product number, this seems to be the unit described above, on the SGC shop page at http://www.sgcworld.com/shopsite_sc/store/html/page5.html
This is the official circuit from the manual for the SG-239 (http://www.sgcworld.com/Publications/Manuals/239man.pdf)
Its simplicity and the cost of the assembled unit have inspired a number of people to roll their own.
The colour code of the cable to the Smartuner appears to be:
Phil Salas – AD5X – decided to remove the components making up the voltage regulator part of the circuit.
“I wanted to build a SmartLock to use with my SG-239. After studying the SmartLock schematic, I couldn’t figure out why SGC put in the transistor and zener diode. The ST-TNE input on the SG-239 is just a 1.5K resistor to an open collector transistor to ground. So I eliminated Q1, R3, D1 and C3 on the SGC SmartLock schematic. My final circuit is shown below. I used a DB9S connector to interface with the SGC tuner (I attached a DB9P to the tuner interface wires), and a PowerPole interface for 12VDC. This way I could use a standard DB9 extension cable as necessary for interfacing between the tuner and SmartLock. I used ultra-bright LEDs (3000mcd or so) to provide plenty of visibility.”
Phil Salas’s build of the Smartuner
There is another variation by Luca Molino IV3ZNK that can be seen at http://www.xluke.it/2016/07/28/smartlock-per-sgc-239
This uses a tiny PCB available on Italian eBay from a seller who wanted 50 € to send one to Australia!
I worked out a way to use a scrap of veroboard to hold the two capacitors and one of the resistors and to manage the wiring between the base and the panel of the enclosure which is probably more efficient and certainly faster. As well I noticed that the PCB seems to be designed for a different kind of DPDT switch where the centre poles are not in the centre!?! So I can add the satisfaction of saving whatever Euros I would have ultimately paid to the greater satisfaction of having nutted out the layout of the veroboard scrap…
Luca used the simplified circuit by Hans Nussbaum DJ1UGA which appears to have in turn have some subsequent input from OE7OPJ (who by the way has a very interesting website at http://www.qth.at/oe7opj/).
This circuit can also be seen at http://www.qth.at/oe7opj/homemade-smartuner-lock.htm.
The components required are
text of the italian site:
L’accordatore automatico SGC-239 indubbiamente è un gran bello strumento. Si collega e funziona ottimamente con qualunque radio (HF) semplicemente utilizzando un cavo coassiale e una fonte d’alimentazione a 12 volts. Non è particolarmente esoso di corrente e anche in utilizzo SOTA non va a gravare sull’autonomia giornaliera. Ne ho trovato uno usato sui soliti canali nazionali ad un prezzo decente e non mi sono fatto scappare l’acquisto. Accorda davvero di tutto gestendo potenze da 1,5 a 200 watt. Ottimo per il mio Yaesu 817, ma altrettanto utile per le “normali” radio munite dei canonici 100 watt. Per poterlo però utilizzare al meglio, si rende necessario l’acquisto di un interfaccia che permette di resettare o bloccare lo stato d’accordo del SGC-239. Tale interfaccia (SMARTLOCK) si trova però in vendita a quasi 100 euro, decisamente troppi per 2 condensatori, 2 resistenze, 2 led e un paio di interruttori. La prima idea è stata quella di prendere lo schema presente sul manuale dell’accordatore e realizzare su basetta forata il circuito. Cosa questa realizzabile, ma che avrebbe dato un idea di “precarietà” a tutta la realizzazione. La scelta a questo punto è ricaduta su un mini circuito stampato realizzato con maestria da Danilo Cramaglia (lo trovate su Ebay come utente Martelloman), che partendo dallo schema elettrico mi ha consegnato quanto riportato in foto:
The SGC-239 automatic tuner is undoubtedly a very nice tool. It connects and works well with any radio (HF) simply by using a coaxial cable, and a power source to 12 volts. It is not particularly power hungry and even practical to use on a routine SOTA outing. I found one used on the usual national channels at a decent price. It really suits around handling power output from 1.5 to 200 watts. Great for my Yaesu 817, but just as useful for “normal” radio equipped with 100 watt “cannons”.
But in order to make the best use, it is necessary to obtain an interface that allows you to reset or block the status of the SGC-239. This interface (SMARTLOCK), however, is for sale at nearly 100 euro, far too much for 2 capacitors, 2 resistors, 2 LEDs and a pair of switches. The first idea was to use the circuit in the tuner’s manual and build it on perforated board. While this is feasible, it could give an idea of “insecurity” to the whole creation. Instead I chose a mini PCB made with skill by Danilo Cramaglia (Ebay-user Martelloman), which, starting from the wiring diagram handed me what is reported in the picture:
I plan to use this wiring arrangement for the 4 pin plugs, socket and line.
As well Philip Storr VK5SRP describes his version at http://www.philipstorr.id.au/radio/seven/accessories.htm.
SGC Smartlock control
In the hand book to the SGC SG237 Auto Antenna Tuner there is a circuit for an interface they call the SmartLock and it allows some manual control over the AATU and more importantly, it indicates when the tuner has tuned successfully.
JH2CLV has documented his build.
These photos (from http://www5a.biglobe.ne.jp/~jh2clv/newsmartlockmaking.htm) give an idea of the layout which uses an external “chocolate block” connector for the 4 core power and control cable.
Case used is a plastic case – HA1593-KB of TAKACHI.
Also http://www5a.biglobe.ne.jp/~jh2clv/smartlockmaking.htm has details of changes – design and layout…
(2) inside the box configuration
The shielded 4 core wire is clamped in the cable tie through a pull through bushing. The case uses a diecast aluminum box TD 5-8-3B (55x30x80) by TAKACHI. The front of the enclosure has the Normal / Lock switch (2-pole, double-throw), the Tuned LED (Green), the Locked LED (Red) and the Reset switch (Make contact). It includes the three-terminal regulator. The bypass capacitors on the circuit diagram are omitted here.
(3) box overview and operation
Once tuning is complete the Tuned LED (Green) glows. If the Normal / Lock switch is pointing to the right, the Lock side, the Lock LED (Red) is lit and fluctuating SWR, etc. does not cause automatic re-tuning.
If the switch is set to the Normal side, normal operating conditions prevail, the SG-239 will automatically start tuning if SWR or the band is changed.
If you press the RESET (red) button, the ATU will re-tune.
Also check http://g3ynh.info/atu/sgc230.html for detailed description of using the Smartuner with a balanced antenna.
For some good ideas about how to protect the SG-239 see http://dg6hd.darc.de/html/sgc-239.html. He uses a large-ish electrical junction box and includes windings on toroids…
>So here is my effort successfully completed today…
I used the simplified circuit by Hans Nussbaum DJ1UGA and the front panel layout of Phil Salas AD5X. I managed to squeeze everything into a compact package – a small die cast aluminium enclosure 64 x 58 x 35mm which Jaycar sell for $9.95. And that was the main cost. Everything else was on hand.
I’ve yet to label the panel, but the green LED indicates a successful tune, the red LED is on when the switch is in the Locked position, and the push button switch is the reset. I used 4 pin sockets and line plugs to connect to and power the Smartuner. And I used a DC socket to supply 12V power. I had planned to use power poles but decided that would not fit comfortably in this small enclosure.
The ATU is housed in a plastic lunchbox which can be protected by a larger rubber waste paper bin as recommended in the SGC manual.
One of the most important documents for anyone who wants to know what makes a magnetic loop tick is Leigh Turner VK5KLT’s “An Overview of the Underestimated Magnetic Loop HF Antenna” which can be found on his club website.
Midway through building my version of Loftur Jónasson – TF3LJ / VE2LJX‘s Automatic Loop Controller, I came across Leigh Turner’s impassioned plea to consider this noise bridge antenna tuning design mentioned on page 32 of the “Overview”. As a concluding note VK5KLT states that he considers “The perceived need for a slick and salubrious auto-controller for properly tuning an MLA is oftentimes overrated and exaggerated, IMHO”.
He argued that elaborate microcontroller aided automatic loop tuning circuits are unnecessary and people should consider using this more covert and considerate approach. I think the bridge could be an excellent idea and a simpler way of staying in tune as you change frequency for all sorts of antennas. For a magnetic loop, it still requires a way to remotely adjust the tuning capacitor.
“The circuit goes inline between the rig and the antenna and sends a gated broadband noise signal to the antenna using a directional coupler and a noise bridge. You just listen on the desired operating frequency and watch your RX S-meter for a sharp dip whilst adjusting the loop tuning capacitor.
You simply remotely tune the loop with the aid of the receiver S-meter while you are on the wanted frequency without keying up and TX power output. This makes tuning a breeze without having to move off frequency and have the TX put out any RF power.”
VK5KLT mentioned the MFJ-212 Matchmaker that uses this same approach (and which is still on the MFJ catalog at US$99.95) and also referenced ZL3KB’s April 2001 RadCom article (pp17-21) as an easy and more economical way to replicate the same functionality.
“The distinguishing merit of the novel gated coupler/noise bridge loop tuning method is it’s completely passive and covert in operation; you don’t transmit any TX power whatsoever to attain an optimal loop tune setting. The technique makes for fast, QRM free, safe and easy QSY shifts and netting a frequency.” Leigh Turner adds that it’s even simpler if you use a pan adaptor or a modern SDR receiver as you can see the sharp null on the screen of the band scope display.
Kelvin Barnsdale ZL3KB’s RadCom article describes building and using the wide band noise bridge as a silent antenna tuning indicator. These four pages include circuit, PCB design and layout and full details of BOM and balun/transformer construction.
On 14 May 2001 ZL3KB published a 4-page follow-up pdf document “Instructions for Antenna tuning Noise Bridge” with info supplementary to the RadCom article about construction and operation. This article has an updated circuit and parts layout and refers to an issue B of the PCB. The new board includes places for the LED and dropping resistor R14, and pads for the two 100Ω load resistors and the two diodes D2 & D3.
This is the updated circuit with some updated values.
This indicates parts placement with the updated PCB.
Here is the foil side of the updated PCB
I contacted Kelvin Barnsdale and was lucky enough to obtain the PCB above.
I spent the pleasant sunny part of the final day of autumn testing a vertical antenna for 80 metres using Buddipole parts for home.
The back garden space here is barely 4 metres by 4 metres and for the moment the chimney is out of reach. While I have dreams of a magnetic loop for 80m, the vertical is more in reach now.
I installed a counterpoise wire a few feet shy of 66 feet length hidden on a timber fence that runs down the side of the property. The idea is to connect a short fly lead to connect the hidden counterpoise when the antenna is deployed and then disconnect when it’s all packed away. Buddipole components don’t lend themselves to permanent installations. The counterpoise doesn’t follow the recommended dog leg arrangement and is higher off the ground than the 2 feet suggested.
The purpose yesterday was to establish how speedily the antenna could be assembled and adjusted for a frequency of interest such as a net.
Here’s a list of the items used along with the counterpoise:
9′ telescopic whip
2 x 22 inch antenna arms
low band coil + clip
Buddipole short mast
I was surprised how easily it all went together. The adjustment wasn’t as fiddly as I expected such a short antenna for this band would be, and it appeared to give a usable bandwidth.
Assembly was straightforward. Set up the tripod and mast with only bottom two sections telescoped out. Attach the Versatee horizontally to the top of the mast. Connect the Low Band coil. Leave the red fly lead loose for the moment. Attach two 22 inch antenna arms to a long whip antenna fully extended. Then carefully attach that assembly to the top of the Versatee. I also connected a 1:1 balun between the Versatee and the iP30 SWR Analyser.
The next step is to simply drag the fly lead across the coil turns to identify the best spot to tap the coil. Background noise level rises as you get in the zone. I used the iP30 SWR analyser to narrow it down to a spot 16 turns up from the base of the coil.
This means I was shorting out the bottom 16 turns of the coil. The adjustment is too coarse on a turn by turn basis. You appreciate the value of being able to tap at 1/8 of a turn increments. (The coil is on an octagonal former.)
It took me a few measurements to realise that as I progressed left (from my point of view) I was decreasing the amount shorted out and hence increasing the loading inductance and so lowering the resonant frequency. It’s actually more confusing reading that sentence than understanding it in practice!
My target frequency was 3535kHz and this is a chart of the SWR readings I had when the coil tap was set at what I calculate to be 15 3/4 turns up from the base of the coil.
The 1.0:1 bandwidth was 10 kHz while at 1.5:1 it was in excess of 65 kHz.
From readings at the other possible coil tap points my guess is that at this frequency range each face of the coil moves the resonant frequency by about 4 kHz. One thing to be aware of with the Buddipole hardware is not to accidentally short out adjacent turns of the coil with the coil clip. It’s hard to do but I managed and it will throw your readings.
Next step of course is to make some contacts or at least activate the antenna on WSPR or JT65 to get an idea of whether the signal gets over the fence.
From checking the chart on page 146 of the ‘Buddipole in the Field’ book by B. Scott Andersen, NE1RD, I estimate that my shorting tap at about 16 turns from the base means I’m using about 39-40 uH of loading to achieve resonance at 80m. So that’s a starting point if I wanted to build a more permanent and cheaper vertical installation.
One of my favourite sites is Martin DK7ZB’s collection of pages detailing the construction of practical antennas for VHF and UHF.
I first visited the site following a link to designs for lightweight portable yagis that would be suitable for SOTA VHF activations. Under the link ‘2m/70cm-Yagis ultralight’, Martin describes a number of yagis for 2m and 70cm that use thin metre long aluminium welding rods mounted on PVC booms.
“These Yagis are constructed with cheap lightweight materials for electric installations and you can mount and dismantle them without any tools. The boom is made of PVC-tubes with 16mm, 20mm or 25mm diameter, the element holders are the clamps for these tubes.” DK7ZB
What makes the designs particularly attractive is that they can be quickly assembled from a compact (admittedly metre long for 2m) pack you can carry on your ascent, even designs using a 2 metre long boom.
The welding rods – used for TIG welding – are available in Australia in 2.8mm and 3.2mm diameters from welding supplies shops. I’m still on the lookout for 4mm diameter rods. PVC conduit and the mounting clamps are readily available in VK from hardware stores.
I’ve managed to cut a suitable slot in the end of a 3.2mm aluminium welding rod using a Dremel with a thin cutting wheel. One suggested way of attaching the feedline to the driven element is to crimp the lines into thin slots like this.
Also of interest to the portable operator are the J Pole designs based on Wireman 450Ω window feedline. There are dimensions for bands from 2m down to 40m. The J pole is essentially a half wavelength dipole where the high feed impedance is transformed by a quarter-wave length matching section (the tail of the J) tapped at a suitable distance to yield a 50Ω match. Follow the ‘Wireman-J-Pole’ link in the left navigation. These pages remind you that the J-pole can be configured in any way so a 40m J pole in a Zepp arrangement starts to look quite practical if you have just under 10m of 450Ω feedline available. I want to start with the 6m design and see if I can make it robust enough with heat shrink etc for portable work.
Kits for the DK7ZB yagi designs are also available from nuxcom.de, Attila Kocis DL1NUX’s website. Both sites are in German and English.
Last weekend I had a great time playing radio. Along with half a dozen other families and all our kids we went to spend the Easter weekend at the “mud brick mansion” at Bamarang on the Shoalhaven River, a few km west of Nowra on the south coast of New South Wales. Courtesy of the pod on my car I was able to take quite a few radio bits and pieces along.
We enjoyed perfect autumn weather while it rained back home in Sydney!
I even managed to build the neat little EFHW (End Fed Half Wave) Tuner designed by Stu, KI6J on a shady verandah. The kit had arrived a few days earlier and I made sure I had everything I needed to build it away from my attic/shack/workshop. In fact the weekend became a sort of trial for field day and a great way to identify the essentials. If there’s a lot of gear on hand an awful amount of time can be wasted deciding which bits to use and how.
I was inspired by reports about the EFHW tuner and the appeal of not having to worry about ground radials. What clinched it for me was a photo I saw on one of the (far too many) qrp email groups I try to follow showing a ham on a mountain side beneath his arching squid pole with the little tuner matching the hi-Z of the half-wave antenna to the 50 ohms expectations of the tiny transceiver which was probably an ATS3b.
So that was my mission for the weekend.
The tuner kit went together in a very short time. Before accepting my order Stu, KI6J sent me a powerpoint of the assembly instructions so I was sure I could handle the construction. The fiddliest bit was the tiny binocular ferrite core transformer for the bridge. Fortunately he provided enough wire in the kit for me to botch it the first time round and do it perfectly the second!
After a couple of leisurely hours mostly taken up with drilling holes in a tiny plastic box it was working on the test lash-up. The polyvaricon is delightfully sharp. You tune by dimming the LED – and then switch out the bridge to transmit.
I had a 10m (almost 33 feet) squid pole (aka Jackite or crappie pole) with a tiny pulley from a boating store attached to the top with cable ties. I used the guy ropes from my Buddipole setup to hold the pole up straight. It stayed up all weekend.
The half wavelength formula in feet is 477/freq in MHz, or just on 68 feet (20.7m) for the code end of 40m. The far end of this was held up – via a plastic button insulator – by a fishing line launched up into a tree using a half-filled plastic drink bottle. All too easy! The near end of the antenna simply terminates in a banana plug that connects to the little tuner. I also connected a short 5-6 foot counterpoise, which was essential.
I had a great time playing with the tuner and my new SDR-Cube pumping out a whole watt of RF, as well as the trusty little FT-817.
Now I have a clear idea of what’s required for an effective little kit of gear to take up a hill for relatively speedy SOTA style deployment. And maybe I’ll fill the water bottle for those trips.
If you’re interested in getting hold of one of these nifty little EFHW Tuner kits you should contact Stu KI6J at firstname.lastname@example.org. US$27 included shipping across the Pacific Ocean! Fast and very fair!
During a trip into the township to replenish supplies I found a fishing tackle shop with an Easter sale on, and bought a couple of handy Plano tackle boxes and some inexpensive 10m lengths of nylon coated stainless steel ‘leader line’ wire which I’m sure can be used for a handy weatherproof dipole. As long I don’t have to solder the stuff.
Over the weekend sunspot 1112 erupted and produced a strong solar flare. Now according to space weather sites there’s a 25-35% chance of high latitude auroras on 19-20 October.
And right now a group of four Norwegian friends are enjoying their annual DXpedition to Kongsfjord – well and truly in the high latitudes – at 70°43′N 29°21′E at the top of Norway.
Four of the main participants are Arnstein Bue, from Trondheim, Bjarne Mjelde (host), from Berlevåg, Odd-Jørgen Sagdahl, from Trondheim and Tore Johnny Bråtveit, from Trondheim. As you’ll see if you visit their pages these men are serious medium wave and short wave DXers, with impressive equipment racks and listening achievements to match.
Arnstein Bue’s blog DX Paradise gives a sense of some of the QSL trophies. DXpedition host, Bjarne Mjelde’s blog Arctic DX has an entry logging their first day last Friday anticipating the weather awaiting them:
“+2 Celsius, 15-20 m/s (35-45 mph) northerly winds, rain and sleet showers…”
As I write this it’s early afternoon there and according to their website it’s warmed up to +4 Celsius!
They also appear to operate remotely from this spot. Their antennas include a new 500 metre long Beverage aimed at the North Island of New Zealand which is clearly working very well. Two shorter Beverages (225m & 330m) and a Quad Delta Flag Array complete this dream DXing antenna farm.
And if you visit the website you’ll see ample evidence that they clearly know how to enjoy themselves at the dining table as well. Local King crabs are accompanied by the finest New Zealand wines. Their dining notes are as tempting as their DX!
Main course was pork sirloin marinated in garlic and chili, served with tagliatelle, basil, leeks and cherry tomatoes. With the pork we tried Kim Crawford’s Pinot Noir. Maybe a bit light for the quite tasty meat, but absolutely a super wine!
For dessert we had local blueberries with grappa – another Kongsfjord signature dish! And now we are off to listen to more recordings and prepare for another – hopefully eventful night. The solar indexes are going down and the K-index for Tromsø is now 0, and we hope that it will remain like this!
The main website is also the repository of a number of documents on DXing issues by Dallas Lankford. There are also data sheets for a large number of receivers (including AOR, Racal, Rohde & Schwarz, R L Drake Company, Siemens, Harris, TenTec, Icom etc) and information about antennas. Bjarne Mjelde has distilled his experience into a definitive article about the best antenna wire. The conclusion? A thumbs up for galvanised steel and aluminium. A number of his reviews are also aggregated on the site, including reviews of the IC-703 and the Perseus SDR.
Their sites demonstrate how much a part SDR plays in modern DXing and monitoring. There are some huge SDR recordings and mp3 files available as well. Retrospective analysis of these files enables them to find rare stations as well as – presumably – traditional live listening.
It’s been a delight checking in on their site each day to catch up with the activities of such a convivial group of friends. Truly inspiring to this reader on the other side of the globe.
Mads LA1TPA recently visited Julian G4ILO’s shack and was so impressed by his approach to cutting through the QRM using an MFJ-1026 Noise canceler and a pa0rdt-Mini-Whip active broadband RX antenna, he’s replicating the solution at his own QTH.
Julian G4ILO’s site has an extensive description of the MFJ-1026 explaining that it’s a noise canceler, not a noise blanker or a noise reducer – as well as a ‘look under the bonnet’. It’s most effective when the noise is coming from a single point source, not multiple sources. So the canceler can reduce noise from a neighbour’s switch mode power supply, TV or computer it may be less successful dealing with general powerline noise.
For Julian’s station it did the trick and as he concludes,
“The MFJ-1026 is expensive for what it contains and quite poorly made, so I don’t feel any pride of ownership of it. It’s also a hassle having to tweak its controls whenever I change bands. But pressing the button to take it out of circuit quickly reminds me just why I have it.
I’d probably had sold my equipment and quit the hobby if it wasn’t for the MFJ-1026.”
You can also preview the MFJ-1026 manual here.
The English-Dutch-Italian pdf about the pa0rdt Mini Whip explains,
“After several fruitless attempts to make an active loop work in a city environment, it was found that the electric field from local noise sources was contained within the house. The magnetic field of local noise sources was not contained inside the house, making weak signal reception at LF impossible.
Hence an electric field antenna was called for. Tests were performed using an active whip antenna, designed by G4COL. Results were encouraging and the whip length could be reduced from 100 cm to 30 cm without loss of performance. It became clear that at LF an active whip is a capacitance coupled to the electric field.
If it is accepted that a whip is a capacitance coupled to the electric field, shape becomes irrelevant, as long as the required capacitance is available. In practice the “whip” can be e.g. a small piece of copper clad printed circuit board.”
It never ceases to amaze me what wisdom is simmering away amongst those email discussion groups I read.
Out of the blue today – prompted by mention of a commercial solution on the Elecraft list – came a sequence of brilliant ideas about making effective and easy on the budget ladder line spacers.
The commercial spacers from K&S Ham Radio Parts look great, but the fact they’re made of nylon prompted concerns about their survival against UV. At 25 cents a piece I think they look fine!
In response there was a pointer to a YouTube video showing how to turn a box of ballpoints into very neat and secure spacers using black cable ties.
And then a pointer to another commercial solution from True Ladder Line, and a hint about how to replicate the effect at home using ‘drip sprinkler tubing’ which is the right size and and has just the right amount of rigidity for the job. And there’s Dave ZL1BJQ with his approach based on those plastic chopping boards you can buy at any $2 shop, cut into spacer pieces, notched then pushed on to wires and held in place with hot glue.
And then there’s this approach by VK2YE using plastic coat hangers, cut to length (5cms) and drilled to fit wire, and then glued to stay in place. In fact this is just one of 138 videos on his YouTube channel.