wythall radio club

Wythall Radio Club’s Christmas Contest is approaching fast!!  If you only have a basic 2 meter antenna or just a handheld, or you want to get out portable, here’s an easy-to-build 2 meter antenna to boost your signal – from Neil G1TZC. 

There is a link to a pdf version at the end.

Many years ago I read an article somewhere about the Slim Jim portable antenna.  It might have been in Practical Wireless, but was a very long time ago.

Thanks to the late Fred Judd (G2BCX) we have this great little antenna available to us.

I decided that now there is an antenna analyser in the workshop (see previuous post on the nanoVNA), it was time to revisit this old friend.  After a bit of digging around the internet, various measurements were found and duly scribbled on a sheet of A4 paper.

From my memories of the one that I built many years ago was made from choc-blok (electrical connector – 15A) and coat hangers.

Initial sketch

We had also better think about some sort of base as well, as this version will be a table top version.

Ingredients

4 wire coat hangers (10 for £1 from Poundland last time I looked)

3 choc blok electrical connectors (15A)

1 length 50ohm coax with suitable connector for your radio

1 bamboo kebab skewer (yes really)

Material to make a base and fixing screws.

Tools

Wire cutters

Pliers

Craft knife

Terminal screwdriver (small flathead)

Tape measure

Soldering iron (optional)

How we make it

Let’s start with the good bit.  Let me begin by apologising for the quality of photographs – they were done on the fly without a tripod or lighting and on a phone.

Take the choc blok.  Cut this so that there are three terminals per strip.  The ones used here were 6 way 15A, but you may be using something different.

Complete and cut connector block

Cut the hook section off the four wire coat hangers and straighten.  Remember if there is any coating this either needs removing or scraping to bare metal for joining areas.

You should now have four lengths of wire.  To absolutely maximise the available metal cut off two of the hooks from the twisted section and straighten.  These will make the two ends of the antenna.  Exact measurements for these can’t be given because your choc blok will vary in size.

Fold short lengths of wire with a pair of pliers

Loosen the screws and insert the wire as shown above.  Cutting these slightly long allows you to change the length of the antenna during testing.  Always handy to have a little bit of give, just in case.

Now take two of the long lengths of wire and cut them to 930mmin length.  In a perfect world these will slot through the choc block a bit like a trombone.  Take another two three way connectors and remove the metal terminal from both.  Do not throw these connectors or screws away as we will use them later.

Slide one of the three way connectors about half way along the two lengths of wire and tighten the screws.  This is simply used as a spacer.  Now use the other connector at the open end of the two wires and tighten slightly.  Again, we are going to leave the option to trombone the metal a little if needed.

Take one of the remaining lengths of straight wire and cut it to 580mm.

Now cut the last length of wire to a length of 497mm (500mm will be close enough).

Find the other end section that was made earlier and insert the two wires to make an unbalanced U shape.

More hunting.  Find the two metal inserts that you set aside earlier.  Here we have one of two choices.  If you don’t have a soldering iron to hand then simply slide one of the metal inserts on to each of the legs of the unbalanced U.

If you have a soldering iron, strip the end of the coax cable ready for soldering.

Solder the inserts as shown.  Note one screw hole on each is uncovered.

Once the ends are soldered and cooled slip them on to the unbalanced U section.  The inner is connected to the longer leg and the braid to the shorter side.  Pinch tighten these close to the base of the U.  This will allow you to adjust the feed point.  In the workshop this was set at about 50mm to start.

Now slide a 3 way as a spacer on the unbalanced U section and tighten.  Using the final 3 way slide it in to place so that the short section is just fed through the connector.  Tighten this connector on both sides.

Connect the long side to the original U section and tighten.  In the workshop version the kebab skewer was used in the middle of two of the connectors so that it strengthens the gap section.

Effectively, the antenna is now complete and ready for use.  You could now tie a piece of string to the top and hang it somewhere (or tie spare bit of bent metal to the end and hang it over something).

Alternatively, the antenna can be bent through 90 degrees to make a table top version.  Let’s come back to that later.

Testing

Connect the antenna to your analyser – BUT DON’T  DON’T WORRY IF YOU DON’T HAVE ONE!

Testing can also be done by connnecting your 2 meter transceiver, low power setting, with your VSWR meter inline.

(OR if you only have a handheld, and no VSWR meter, then try listening on the 2 meter band.  If you can hear signals (especially if they are stronger than on a rubber duck antenna), chances are it will work fine.)   

Adjust the feed point as required to give the lowest reading you can.  Once you have reached the lowest point you can also adjust the overall length of the antenna from the various connectors.  This may increase or decrease the VSWR readings.  This is a bit experimental but that’s what the hobby is about.  The analyser plot below gives 1.5 or better right across the band.

The antenna should also work on 70cms – two for the price of one!

Analyser plot for the coat hanger slim jim

Optional Base

If the option of base is required here is an option that was put together in the workshop.  A length of 30mm wide pine was left over from lining the workshop roof so this was used for my base.

Foldable wooden base                                       Close up of skewer

Cut the base slightly longer than the bent section of antenna.  Glue two 30mm square blocks on the underside, one at each end.  Measure another length to be fitted in the gap in the underside.  Make this section 20mm shorter than the gap to allow for rotation to make a foot.  Place this strip in the middle of the gap and screw so that strip can be rotated.  You might want to drill a pilot hole to allow free turning.  If you use a long enough skewer you can use it to stabilise the upright.  Drill a hole small enough for a tight fit and push the skewer in to place.

I hope these instructions worked for you and you enjoyed it as a little project.

You can print off these instructions as a pdf by clicking here.

Neil – G1TZC

Neil, G1TZC, a Wythall Radio Club member, writes about his experience with a little Vector Network Analyser….

My local club runs monthly activities and this month there are activities on 80m to 30m and 20m to 10m.

As good as the 1/2 sized G5RV is it just doesn’t cover enough bands for this.

Recently I purchased a four inch screen version of the NanoVNA. I decided to pay a little more for a premium version.

I hadn’t realised when I made the purchase that part of the extra money went on the fact it has a much better antenna connector – the N type connector – mounted to the metal case.

My main advice is read the menu flow chart and take the time to download the online manual. The windows software is the right side of basic.

This has given a great chance to make a couple of antennas for the 12m and 30m. Using the analyser makes the whole process so easy.  You can see some of the screen shots below.

I shall be purchasing some more pvc covered wire to add extra bands. I think this will become my portable “go to” antenna for holiday operating.

It has also allowed me to check my 3 element 2/70 beam and the two colinears. I’ve even found that one of the 2/70 colinears works ok on 23cm.

If you have a little bit of spare cash and you want a handy test tool this is great. It allows you to check that antenna from the end of the coax.

Check out Neil’s qrz.com (G1TZC) page for more of his blogs.

STOP PRESS – THE INTERMEDIATE COURSE IS NOW FULL.  FOUNDATION COURSE STILL AVAILABLE.

Wythall Radio Club will be running ONE online courses in September.

The 8 week Foundation course starts on the 13^th September .

The examinations for both these courses will be done under the RSGB’s new remotely invigilated on-line examination scheme in the candidate’s own home.

Practical Assessments for the Foundation course have been suspended until such time as the COVID lockdown makes it safe for them to be re-introduced and the Practical Assessments for the Intermediate have been taken out of the syllabus altogether.

There is no charge for doing these courses and we do provide individual tuition via quizzes etc.  Please note that there are specific IT requirements which have to be met for the online examinations.

If anyone is interested in doing these courses with us please contact Chris G0EYO g0eyo@blueyonder.co.uk  ASAP.

Join the world-wide amateur radio community with our FREE successful online course!

If you, or anyone you know, is looking to get into amateur radio then the Wythall Radio Club Online Foundation course could be just what you are looking for.

With amateur radio, you could be chatting to someone in the next street – or another continent!

With the need for practical assessments currently suspended due to the Coronavirus, together with the RSGB’s ability to offer remotely invigilated online examinations which candidates can do in their own home, we can take students from anywhere in the country.

Our courses are done through a Virtual Learning Experience called Edmodo and comprise a number of video lessons (via YouTube) plus lesson notes and lesson quizzes and other supporting information.

We mark the quizzes and provide individual feedback.  As a consequence,  we limit our courses to a maximum of 20 students.

There is no charge for doing the course.  You will need to book and pay for your examination direct with the RSGB through the exam booking website. You can also purchase the course book “The Foundation Licence Manual” through the RSGB online shop.

You also do not have to be a member of Wythall Radio Club to do this course although many of our Midlands based student do join us.

We will probably start this course in early September and it will run for 7 weeks. If interested please contact our Training Coordinator, Chris G0EYO on g0eyo@blueyonder.co.uk “ 

What countries can Wythall Radio Club members contact on the 80, 40 and 20 meter bands during July?

Some burnt the midnight oil in the hunt for rare countries!  “Inspired by the midnight/early morning efforts of Chris G0EYO and Kevin 2E0NCO, thought I’d explore the 40m band at 4.00 a.m. on Saturday” commented John M6KET.  “Surely there would be a VK/ZL waiting for that elusive M6 QSO?  ZL there was – but not audible here!”

The Challenge is part of a series, with a different group of amateur radio bands or modes being the focus of activity each month.  Previous months have covered 15,12,10 and 6 meters, and all bands Morse Code only.

Wythall Radio Club members spent their Tuesday evening on-line visiting each others’ radio ‘shacks’.

Using Zoom, 6 members provided guided tours of their amateur radio stations and antennas to a wider groups of about 15 members.  

An added high point was a visit to the fridge that Kev 2E0NCO keeps stocked next to his operating position!

The virtual tours were a big boost to those members still in lock-down. 

One member commented afterwards: “Last night was a lot of fun and a big pick me up for those of us imprisoned in our own home.” 

It showed the value of the Club taking part in the RSGB’s ‘get on the air to care’ initiative.

Don’t let a small garden stop you from getting on HF – including 160M! – reports Wythall Radio Club member Chris G0EYO.

End Fed (or long wire) antennas are the most simple antennas an amateur can make for the HF bands. However their simplicity does come with serious compromises when used as a multi-band antenna.

The physical length as measured in wavelengths of the transmitting frequency can result in very high or very low complex impedances at the fed end of the wire, so they need a very good antenna matching unit (AMU) to enable a good match to the transceiver and to deal with the high voltages or current that may exist,

The high currents or voltages at the end of the wire can also result in serious RFI problems for the amateur which are hard to control. This is because a quarter-wavelength in from the far end of an end fed antenna, the current is at maximum and the voltage is at minimum. At a half-wavelength the reverse occurs and so on.

So for a given length of wire and depending upon the band being used a wide range of complex impedances and currents and voltages may appear at the transmitter end of the wire. This is sometimes more than the AMU can handle, both in terms of impedance matching and voltages.

The end fed wire antenna produces quite complex radiation multi-lobe patterns unlike the simple “figure of eight” radiation pattern produced by a dipole. With multi-lobes come deep nulls in certain directions (diagram thanks to VK6YSF).

They also need a counterpoise or earth return to work well and avoid RF getting back into the shack. Ideally these should be about a quarter-wavelength long for each band the antenna is required to be used on.

We can avoid some of these issues if we can avoid wire lengths which are multiples of a quarter-wavelength of the bands being used.

So how long should our end fed wire be? A great deal of work has been done by others on the ideal wire length which avoids very large end impedances for the bands of interest and these can be found courtesy of Google.

My garden allowed an end fed wire length of approximately 25m to be accommodated in an inverted “L” format between a 10ft pole mounted on the side of the garage and a 20ft pole mounted at the bottom of the garden.

Alan Chester G3CCB in his book “ HF Antennas for Everyone” (RSGB) came up with a useful graphic which showed “practical” lengths for end fed wires. This allows you to pick a length and see which bands are will give you a matchable end impedance.

I wanted to work on all bands from 160m to 10m but ideally 80m, 40, 20m 15m and 10m. Alan’s calculations showed that a wire length of 18.5m would give an workable end impedance on 80m, 30m, 20m, 17m, 15m and 10m with possibly a little more troublesome end impedance on 160m, 40m, and 12m.

To avoid bringing high voltages and currents into the shack the AMU should be mounted outside and the signal fed into the shack via 50 ohms coax. Fortunately I had an SGC 230 Auto AMU that I had installed at my previous house in Hollywood.

The SGC 230 AMU is designed to operate with wire antennas and is configured as an “L” or “Pi” type network controlled by a microprocessor. The initial tuning takes several seconds to determine the transmit frequency and then select the necessary coils and capacitance to match the complex impedance of end fed wire to 50 ohms. These settings are stored in a non-volatile memory so the subsequent retuning of the same antenna on the same frequency only takes a fraction of a second.

The tuner has a ceramic insulated antenna terminal which looks as if it would tolerate quite a few volts, and a threaded nut for a earth counterpoise. It has a flying lead from the AMU with a 50 ohm coax and PL259 connector for the transceiver together with a 5 core cable for +12V DC, earth and “Lock Tune” control line and “Remote Tuner” indicator line.

On my installation I have a small plastic box next to the AMU which is a through line for the coax cable and a terminal block for the DC and control lines.  A 25m length of RG213 goes from the interconnecting box back to the shack in a bedroom at the front of the bungalow. Similarly a CAT5 cable is used to feed the DC and control lines back to a remote indicator and switch box at the operating position. This tells me when the SG230 has achieved a satisfactory match and locked on (and which can be confirmed by the SWR meter).

The SGC230 AMU is in a weather proof plastic box and is mounted under the eaves of my garage. A very short earth counterpoise is connected to the AMU earth terminal using copper braid and fixed to a 1 m earth rod driven into the ground. Overall the earth counterpoise is about 5m long and should probably be longer or with multiple earth rods. Chris G3YHF has suggested I do this modification to see if the efficiency improves. The antenna wire itself is Kevlar strengthened wire which is very strong but also very thin.

The pictures show the installation. I should say at this point that the inspiration to put in this antenna came entirely from Roger M0GWM who in 2019 said it was about time I put up some antennas having lived here for 3 years. Together we came up with the idea of using a long wire. Roger also did all of the installation work including running the coax and control cables around the bungalow just under the eaves.

Not long after the installation was completed, and always being a data mode fan, I got Ian M0LQY to set up FT8 on my computer and transceiver which is controlled by an old version of Ham Radio Deluxe. I limit the power to 30W (effectively carrier power – and probably equivalent to 100W PEP for SSB) and have been very pleased with the results.

Bands 160m, 40m, 20m, 17m 15m and 10m are rock solid. 30m suffers from RFI which upsets the wired mouse on the main PC in the shack and 30m seems to be constantly trying to find a good match. SWR’s achieved on these bands are between 1.15:1 and 1.35:1 which I am very happy with.

Strangely enough I never tried top band on any mode  until Chris G3YHF encouraged me to do so on FT8. I found it fun and challenging so made it my Wythall Radio Club DXCC challenge for 2020 (55 countries on 160M at time of writing). Chris has a similar set up with slightly longer wire length and bigger earth counterpoise. Analysis of PSK Reporter reports shows he just has the edge on me when it comes to performance, so don’t let a small garden stop you working 160M – 10M!

The VGC-VR-N7500 VHF/UHF FM Transceiver is the new kid on the block.

I was asked for help from a neighbour who had bought this and could not get satisfactory operation via Bluetooth to his iphone. Mindful of social distancing, he left the package on our doorstep for me to retrieve!

Unpacking it revealed the transceiver itself, heavier than expected and very solidly built, measuring 6” wide by 51/2 deep max (including the external mounted fan), a decent looking wired fist mic, mounting bracket, power lead (12v to 13.8v) and a PTT button to attach to gear lever/handlebars etc. and a Bluetooth fist mic. It seems some of the latter are available as cost extras but were included.

Being mindful that it was borrowed I did not wish to programme it beyond basic simplex or repeater use, nor set up the APRS or network capability.

On the bench, it was a matter of moments to connect the antenna (SO239),the fist mic via the now almost universal network cable type connection and the power. The rig was fused on both +ve and negative leads.

Downloading the Android app via Google Play Store and installing it took a few moments.

Enabling the app and Bluetooth on a Samsung Android phone (other makes are available), the rig and phone paired and the application started showing my GPS location.

Swiping the page brought up the programming screen and it took just a few moments to put in both 145.225 and GB3WL together with split and CTCSS as appropriate. No messing with usb leads, downloading drivers, finding a suitable programming app (or buying one) and reading/writing to the radio, this is where this radio shines. So intuitive, so easy and you can be up and running in moments. If going mobile (this in truth is the market sector targeted) the unit can sit in the boot and just operate via the Bluetooth speaker mic or indeed the Android phone.

On FM, it is rated at 50watts VHF and 40 watts UHF and those power levels were achieved feeding my “white stick”

Google is your friend the full specs and videos are easily found.

Works really well and although the price is around £190,this being twice the cost of say a Anytone AT778UV, its added capabilities may tempt folk.

Being SDR it is firmware upgradeable (by Bluetooth) which may well bring in more features and/or bug fixes as the product matures.

A 30 page manual is available https://www.moonraker.eu/downloads/dl/file/id/309/product/9250/vr_n7500_manual_v3_1.pdf

The Manufacturers website has more detail at http://www.vgc.net.cn/product/54-en.html

Please excuse the extraneous “QRM” on my desk- the unit to the left behind the rig is my MMDVM running YSF to my Yaesu FT2D.

This unit was on very short term evaluation so the photos were taken in haste!

Our Club newsletter archive hosts hundreds of Members’ articles covering all aspects of Amateur Radio.

Take a look using the link on our website and click here for an up-to-date index of Newsletter articles

73

Ian M0IDR

It’s May! And Morse Code appreciation month at Wythall Radio Club.

Everyone knows some Morse Code:  ‘ …  – – –  … ‘ = SOS!

At Wythall Radio Club during May we celebrate the skill of communicating by Morse Code in honour of Lew Williams, who was an expert at Morse and former Club President.

So Club members will be having fun by making contacts with other amateur radio operators using their Morse keys – which come in all shapes and sizes!

Many are ‘side-swiper’ keys, in which one paddle send dots and the other sends dashes.

Side-swipers are often used instead of the traditional ‘pump’ key, with its up and down action, because they reduce the amount of wrist action and operator tiredness.

However, pump keys are much better for learning Morse and for slower contacts. 

Here’s a short explanation for younger readers of how Morse Code was invented (you can skip the advert at start!).   

Ian M0IDR – a Wythall Radio Club member – reports on his build of this small low power transceiver.  This is the first in a series of reviews. His home is in a former orchard area, hence the title of these posts!

The QCX is a 5watt CW only transceiver with a very compact footprint which is available ready built or in kit form. Unfortunately the rather good aluminium case was discontinued in January 2019 and my purchase was a kit with case just as QRP Labs announced the change. The case can be bought elsewhere and details are on the QRP Labs website.

The kit and case shipped from America without any Customs charges, although it took some 5 weeks to arrive. Very well packed indeed with all components bagged by type.

Not for the faint hearted, I suggest, as assembly involved a fair bit of tricky intricate coil winding.

The assembly instructions are downloaded from the website and run to over 140 pages of very clear detailed instruction.

Having a fine tipped temperature controlled soldering iron made for perfect soldering first time around as removal of any multilegged component would prove very difficult. A desoldering station was on standby just in case.

The multi-winding coil was by far the most difficult to assemble but inductance measurements proved each winding before fixing into position (photo left).

Assembly proceeded in strict order of instruction and the completed board was mounted within the case (photo right).

Assembly complete – the unit on test (photo below)!

Since building this, I have purchased a second user GPS module – QLG1 – which can be added to effectively use the rig as a WSPR beacon.

This module is only available in kit form and interfaces to the QCX via a 4 core umbilical cord.

For the moment, I am pleased that the QCX assembly was trouble free and look forward to interfacing to the GPS module when time permits.