ANTENNA ANALYSER

MESSING WITH THE MFJ 259

Having spent some time putting together a 6M SlimJim, I decided to use the antenna analyser that I'd borrowed from my friend G0FRL to have a look at other antennas around the house.

Why?? Well after the simple Slim Jim made a fool of me, I wondered just how resonant all the Manufacturer's antennas that I'd paid good money for were. Surely, these giants of technology and knowledge would be pumping out antennas that were showing all signs of being resonant. And surely the antennas which came with radios should be spot on? 

Anyway, I got into the idea of testing them but without any idea of what the results would really mean. So let's get started - the analyser is an MFJ-259B which means that it's the older model without the UHF coverage. Despite its age, it still feels rugged and reliable. The rotaries work perfectly with almost no spiking.

The first test was to see if there's a difference between a FAKE Diamond SRH805S Stubby. Visually, it's easy to spot the fake! But how much difference is there in reality? I use these stubbies on my Yaesu and Kenwood handies with an OpenSpot2 and a DVAP Dongle. No need for a large rubber duck around the house and garden!

Result? Not a great deal. They both show high impedance and the fake shows a 30% higher SWR than the real one. In real life, they both do what I want them to.

I then wondered what the FT3 and D74 rubber ducks would be like.

As you can see, there's not much in them - the impedance is good on both, but the FT3 duck has a fractionally better SWR. Nevertheless I would have hoped for better SWR from both OEM antennas. With just 5W you don't want to be losing much to reflection.

Many people dump the supplied rubber duck and opt for an independent such as the COMET SMA3, so let's look at one of those....

Hmmm, not too good eh?? Probably better sticking with the OEM.


So what about a cheapo Baofeng rubber duck? Surely that's gonna be totally rubbish - The whole radio cost less than the Comet SMA3!

Oh! That's not as bad as I thought! Impedance is a little low, but the SWR is much better the the Comet.

The vast majority of people buy a UNIDEN UBC125XLT to monitor the AirBand and you'd expect the supplied antenna to be perfectly tuned to that band. Well let's have a look. I'll tune in to Manchester Airport's Tower frequency...

Rather disappointingly, the impedance of this rubber duck was very high at the EGCC frequency and if it was capable of transmitting, there would be an SWR of 2:1.  I did a bit of a sweep with the analyser and it found the best match at 160MHz - not much use. Yes, yes, I know it's not critical for RX, but if you're going to manufacture an antenna that will be tuned to the AirBand 90% of the time, might as well make it resonant there, no?

I wonder how my Discone would fair?? I'll test it on the AirBand frequency and then at 2M (you can transmit on this particular discone).

WOW!!! Very respectable! And how many snooty people mock discones??? So how does this compare with my Diamond S300?

SWR flat as a witches tit. Nice job Diamond! Impedance oddly inflated, but the antenna works superbly.

The last VHF antenna to be tested was the YHA63 which comes with the Yaesu FT-818ND. I tested it on 2M and 6M. I wasn't expecting much - and I wasn't disappointed...

Very high impedance in both configurations and pretty poor SWR to boot. No doubt fine at 1 or 2 Watts but I wouldn't want to have a lengthy 5W QSO with those figures. 


SO THAT'S THE VHF DONE!

Now for some HF readings. The ribbon cable Slim Jim that I just built for 6M works fine, but how does it do on other bands I wonder? Let's see if any are workable....

Well that's not too bad considering the simple light weight design. One could easily work all these bands with a tuner. How about my 66ft EFHW?

Pretty good! In fact, this antenna is pretty good on all bands (again, considering its super simple design). 

SO THERE YOU HAVE IT! No doubt useless, but it kept me out of trouble for a couple of hours, LOL. If no one else did, I found it quite interesting to see how far away from resonance some antennas appear to be despite being designed for a specific band.

I'm sure there's one hell of a lot more to this dark art and it's all a waste of time without considering many other factors, but it got me used to working with an analyser - something I've never done before.

I guess I'll have to give Bob his MFJ-239 back and buy my own. In fact, while I'm on the subject, I noticed that Bob had fitted 10 Zinc batteries inside the machine and so I replaced them with high quality Alkalines as a thank you for the loan.

Zinc batteries scare the bejabers out of me - especially when fitted inside something that only sees occasional use. They often develop a leak and end up destroying the battery case!

As you can see above, one of the batteries 
has become discoloured.

Notes about Zinc vs Alkaline

1. A zinc battery uses an acidic electrolyte while an alkaline battery uses a basic electrolyte

2. Alkaline batteries have much higher capacities compared to zinc batteries

3. The can is the anode of the zinc battery while alkaline batteries uses a zinc powder within the can

4. Alkaline batteries have a much longer shelf life compared to zinc batteries

5. Zinc batteries are prone to leaks while alkaline batteries are not

NOTE : ALSO SEE NANOVNA vs RIGEXPERT

Thanks for looking.

73, M7MCQ.

6M SLIM JIM

WHAT A PALAVER!

In readiness for a local 6M Net, yesterday I decided to have a go at making a 6M SLIM JIM and the Chairman of Bolton Wireless Club, Glenn Bates (G6HFF) very kindly gave me a length of 450 ohm ladder line to go with his construction diagram (originally designed by G4OAN).

The cable was about 5M long and the construction diagram showed an overall length of 4.3M, so I had a little spare. First job was to do the cutting with a sharp knife and a pair of sidecutters. Once that was done, I soldered a connector close to the recommended FeedPoint.

With hindsight, I can now see that I should have hung back on the soldering, but hey-ho, you live and learn. I cut the 80mm gap on the right side of the ladder line and then hoisted the thing up on top of a 7M telescopic mast.

Sadly, the SWR on the radio back in the shack was not very good. Even the MFJ-993B tuner struggled to tune it, so it was a bit of a fail despite following the dimensions to the letter!

I tried it on 20M and immediately got two good contacts - one in Bulgaria and Italy, receiving a 53 and a 56 using 10W.

So today I returned to the project and after borrowing an MFJ Antenna Analyser from my friend Bob (G0FRL), the job was made a hell of a lot easier! Having said that, I still felt like antenna building was similar to black magic!!

YES I KNOW that this is an extremely simple antenna build, but it drove me absolutely nuts trying to find that sweet-spot. Just as I thought I was getting closer, the reading jumped in completely the opposite direction. 

In the end, I realised that I needed to stop taking measurements at the feedpoint and take them instead from the end of the coax in the shack.

After much messing around moving the FeedPoint up and down, I eventually found a 1.1:1 match and ran some tests on the radio. It felt more like luck than anything else. All was well. At last!

I was very happy with the results at the end of the day and was glad I'd done it - until I passed a mirror and saw how this simple project had aged me.

Oh well, being a glutton for punishment, I decided to make a 1/4 Wave vertical with downward sweeping radials. It worked fine but offered no advantage over the SlimJim, so I packed it up and threw it in my rucksack.

73, M7MCQ.

WSPR RESULTS QTRWAVE

RESULTS OF WSPR TESTS ON NEW ANTENNA

I ran WSPR today using 5W and the new DIY Quarter Wave Vertical antenna just to see how it performed. It did pretty good considering its position at the back of the house.

It reached into China and Japan (twice), not to mention Anchorage, Alaska...

DIY Qtr-Wave Vertical (20M)

JESUS CONTACTS ME AT EASTER!

Being an atheist, I never thought I'd be making contact with Jesus, not even at Easter, but sure enough, he turned up right at the end of my hour of testing a new antenna!

Having been on "LOCKDOWN" for a couple of weeks, I started to worry about the future in terms of whether there's going to be a company to go back to and I awoke this morning from a dream where the bailiffs were banging on my door to take away my beloved radio gear!! 

Anyway, I ended up getting out of bed at 05:30am and sat at the 7610 with a cup of coffee. There was an atrocious amount of noise on the bands - and little else - apart from some Europeans on 80M & 160M looking for Stateside contacts only, so I switched off and flicked through some emails on my tablet.

It was then that I stumbled upon a message from Richard Newstead from SotaBeams (G3CWI) about making my own 20M QuarterWave Vertical.

I've been meaning to do this for months and just never got around to it. I guess I didn't really believe it was going to be worth the effort considering I've already got a great 20/40 Dipole, a half-size G5RV and a superb EFHW.

Anyway, in a bid to brush off the dark emotions of coronavirus, lockdown and the end of the feckin world, I forced myself to gather together all the bits I would need to complete the project.

I had a reel of antenna-wire which I purchased from SotaBeams (virtually any wire will do), a 1:1 Balun from Martin Lynch and a telescopic mast, 6M long which would conveniently sit in a parasol-base.

First job was to cut four lengths of wire - one for the driven element and three slightly longer radials. The driven element was cut to 5.13m and the radials were cut to 5.8m. Bear in mind that I chose these dimensions to make it resonant around the QRP frequency of 14.285MHz

Because the telescopic mast was only 6M high, I decided to wind the wire around the mast in a spiral shape so that most of it was up and away from the ground (the balun ended up being about 9ft high). This gives the added benefit of having the three radials going up at an angle instead of dragging across the floor.


To make sure the wire stayed in the spiral pattern, I added a little insulation tape every metre or so. I also taped the balun to the mast just in case the wind started rattling it a bit. It was actually a gorgeous sunny day (unusual for the UK in Spring) but the wind was picking up.

Once everything was taped up and a length of coax fitted to the bottom of the balun, I telescoped the mast to its limit and went to get the radio out.

I normally use the Yaesu FT-817 in the garden, but I opted for the superb ICOM IC-7100 because it has a very useful feature to help tune antennas. It has an SWR SCAN mode which takes a number of SWR readings across a frequency range. You can for example take about 7 readings across the entire band or you can opt to take smaller steps across a particular portion of the band that might interest you. I opted to take a few readings across different parts and here are the results...

 

 

 

Each of the screenshots above shows a portion of the 20m band and the centre frequency of the scan is displayed, meaning that you can see 10k readings either side. These readings were taken without the tuner connected.

So, overall I was pretty pleased with the SWR and if I'd have trimmed it a little I could surely have got it 1:1 somewhere on the band, but for now, it's good enough.  Let's get the radio connected!

As I setup the radio, the clouds blew in and covered that glorious sun. So annoying!! Most of the sky was still bright blue, but the light was dimmed by the clouds and it immediately felt 10 degrees colder.

I added power via a 13.2V 8.4A battery and started to tune around. The first station heard was W2RE BOOMING IN from the east coast of America with lovely levels of quieting. I was surprised at how low the noise was with this vertical because everything I've read about them said they could be quite noisy.

I spent quite a long time trying to reach Ray, but he just couldn't catch my QRP transmissions. I don't think it was anything to do with the antenna - he was just being swamped with lots of QRO operators. Eventually I decided to move on and see who else was out there.

There were LOTS of Europeans and they were all contesting, so every report was, of course, 59. Having said that, I could hear them all superbly and had little problem speaking with them. 

It quickly got cold and so I decided to conclude the experiment in favour of some late lunch. Just as I was starting to wrap it up, I heard Jesus calling! So I went back on and got him in the logbook! Praise be the Lord (or EC1KR).

I left the antenna erected and will go back to it over the next few days. I had previously spent time fully waterproofing the LDG Balun, so no harm would befall that if it rained overnight.

So in summary, I'm really pleased with today's little experiment and pleasantly surprised with the results. I feel confident that this will operate fantastically well up on the hills and is far more convenient to erect than a dipole.

So a big thumbs up from me.

Thanks for visiting :-) 

 73 de M7MCQ


This design is based on a post by Peter Miles

RSGB QSL BUREAU

QSL MANAGER

Well it's been over a year now and no one ever told me that I have my very own QSL Manager, LOL.

I've been sending out paper QSL cards (along with eQSL cards) to various stations and have never received replies apart from the one from DX Engineering. And then I saw an article in the RSGB Magazine that QSL Cards were building up and operators needed to contact their QSL Manager to see if they need SAE (Stamped Addressed Envelopes) to get their QSL cards posted to them.

So I looked it up online and found that my QSL Manager is Roy Taylor, M0RRV, so I emailed him and he told me that I have 5 QSL cards waiting, so I sent him a few SAE's and today the cards arrived on my doorstep.

With that knowledge, I can add "BUREAU" to my QSL list on QRZ.com

I know it's my ignorance that made me miss out on this, but this is EXACTLY the sort of thing that should be mentioned in that booklet which the RSGB send out to Newbies.

Anyway, here's the LINK to the relevant page.

73.