Apr 262013
 

Firstly I would like to publicly thank the two Micks, Robert, Karen and Tony who have been down to the shack and had a tidying up frenzy after the work we have been doing of late. The cables on the tower have now got plenty of cable ties and have been routed to the appropriate radios in the trunking. They have also got rid of quick a lot of ‘junk’ – in fact the shack looks enormous as a result and has a distinct echo :)

I have forgotten one or two things that have also been done – Robert will put me right. One thing is for sure we are making rapid progress!

Thanks for your hard work everyone.

I took a rather posh Rohde & Schwarz  ZVL Vector Network Analyser up to the shack tonight to have a look at the new 50/70 MHz dual bander. The tuning is not quite right, more on that later. Anyway here are the plot, still perfectly usable but we can make it better.

Click for full size images:

Screen grab of the return loss (RL) on 49-53 MHz. Maximum RL (min VSWR) is 50.398MHz - little high

Screen grab of the return loss (RL or S11) on 49 – 53 MHz. Maximum RL (min VSWR) is 50.398 MHz – little high

RL (S11) for 70 MHz. Minimum is out of band and needs to be improved.

RL (S11) for 69-71 MHz. VSWR Minimum is out of band and needs to be improved.

You may be wondering what this Return Loss or S11 is. I will do a little article explaining it, how it relates to VSWR and even links to a tool so that you can convert one to the other. To put things into perspective with the return loss shown on 50.398 MHz if you were to put 100W into the antenna a little less than 5mw would be reflected. This is a VSWR minimum of 1.01:1, pretty good! We just need to move it a little lower to the DX portion of the band, although the RL at 50.000 MHz dead is still 23dB which means 100W forward 0.5W reflected – actually quite good enough.

On 4m however 11 dB RL at 70 MHz means 100W forward just under 8W back, that needs some improvement I think.

I am fairly sure that the HF antenna is too close to the dual bander so we are hoping to get a longer stub mast.

Justin G0KSC has also suggested how I can improve the way that the choke balun is mounted – only a 5 minute job fortunately.

Mick and I were talking about the luffing winch and head unit bearing loading tonight, if we were to extend the stub mast appreciably and use a steel scaffold pole. He is a bit of dark horse that one, he knows a lot of stuff about a lot of things. It seems that our Mick has done some fairly serious mechanical engineering at some point.  So we’ll work stuff out properly and do the best we can. We all have a feel for these things but its always better to do the calculations and find a use for those redundant fag packets. Or we could do a spread sheet but then that would be like being at work for me!

The HF antenna is working marvellously though!

Apr 222013
 
Nice, straight and neat

Nice, straight and neat – click for full size image

Finally the antennas are up and working. Make no mistake some members of the club have worked very hard to make this happen, they should be proud. There is a lot more detail here than at first meets the eye. For instance Robert M0CRX took the time to make a very good balun former. This balun works extremely well on all the HF bands including 40m.

I am not an experienced HF operator but I have observed a lot over the years by being around. One thing that I can say for a fact is this: This is the quietest 40m antenna we have ever had up at G4NOK. It really is amazing to hear such a quiet band, the noise floor below signals is below S1 and then boom there is a huge s9+40dB signal there. This is also testimony to the HF rig’s good receiver, I was pleasantly surprised at how good the TS590 is in this respect.

The balun is not a true balun but a choke balun; it’s purpose is to prevent currents from flowing on the outside of the coax, you can see the balun structure in between the two antennas on the stub mast. The more observant will notice that the balun coil is at right angles to the feed. This helps to stop the fields from the antenna being induced on the turns of the coil. You will see this kind of thing all over the place. A standard way of preventing coupling between two inductors in a circuit is to orient them at 90 degrees to each other. The orientation of the balun simply follows this rule. The photos below shows the balun and feed in more detail, just click on the images for more detail.

Further out showing how the balun is clamped to the boom

Balun is clamped to the stub mast perpendicular to the antenna boom – Click for full size

A longer stub mast would allow the balun to come up from the underside of the driven element but this way is much stronger. This is important for us as we have an exposed hill top site. This way will also help rainwater run away from the cable. At the moment there are just ty-wraps holding the balun to the former but we will be coating the balun in a waterproof coating of some type in the near future.

 

Close up of the balun - maybe 'Ugly' but very effective

Close up of the balun – maybe ‘Ugly’ but very effective

Here is a slightly closer view, the inspiration for this implementation of the ugly balun came from Robert and the following site:

Build the ‘Ugly’ Balun

Notice the lack of connectors – cheaper , lower loss and nowhere for water to gather.

Close up of the A3S feed - Extremely waterproof

Close up of the A3S feed – Extremely waterproof

The tails to the feed are not super short like they would be for a VHF antenna but they are still quite low inductance at the frequencies we are concerned with here; namely 40m, 20m, 15m and 10m. There is a little give in case the antenna slips round in the 70 mph winds that we experience quite often. We have a plan to help ensure that there is no slippage of the antennas but you will have to wait to see what that is. I am a believer in letting the stub mast slip in the rotator a little rather than risking shearing the drive shaft of the rotator.

What I don’t like is the antennas slipping and thus damaging the feeds.Mick M6MWP has an idea how to stop this altogether.

Waterproofing 

For the A3S this consists of self amalgamating tape, heatshrink (2 layers), more self amalgamating tape and finally liquid rubber all over the eye terminals where they fasten to the boom. I don’t think that the water can get in unless the coax outer sleeve gets punctured. If you click on the image you will see that the photograph is so fresh that the liquid rubber is still dripping. It’s a bit tricky to get off as well so I recommend wearing some protective gloves.

VHF dual band yagi

As I may have said before the Innovantennas 12 ele dual band antenna is the best constructed antenna I have ever seen, it is extremely robust, chunky and yet reasonably light. You can tell the quality of the construction from how straight we have been able to get it when assembled. This antenna is dual band and so needs a balun that can cover both bands – once again a choke balun was chosen. Due to the higher frequencies involved the balun is quite a lot smaller. Also as we now on VHF it is imperative that there is no unnecessary inductance in the feed, so the coax tails are extremely short. I think that they are as short as possible. The cable passes through the boom and then the balun is formed by winding 6 turns on a furniture polish can. This is then kept in place with a few ty-wraps and the attached to the underside of the boom, once again at 90 degrees to the driven element – only this time in a different plane.

On 6m the antenna seems to be as good as my old M2 6M7 even though it is a little bit shorter. It is definitely a quiet antenna on 6m and GB3MCB in Cornwall was 559. On 4m the antenna is better than the old one but is a little off tune. The antennas have not been tuned at all yet.

Here are a few detailed photographs.

20130421_161333-1

Waterproof and low inductance – as recommended by G0KSC – click for full size

Choke balun under the boom

Choke balun under the boom

 

 

 

 

 

Apr 132013
 

Today we did some antenna work and boy was there some work involved. In fact we haven’t finished yet!

What struck me was the fantastic sense of teamwork involved, there was quite a few of us there and everyone did more than their fair share of graft.

Antenna work party attendees were:

  • Robert M0RCX
  • Mick M6MWP
  • Simon M6BRH
  • Karen M6KSD
  • Tony G0JVI

Simon, Karen and Mick took care of the huge task of pulling out the old coax and threading through the new Ecoflex 10 plus for 6m and 4m and the new run of RG213. All sorts of superfluous cable was also removed, a huge sweaty and difficult job well done!

Robert luffed over the tower and set about fitting the new 40m extension to the A3 HF beam. That thing is huge by the way. Due to the increased windload we replaced the stub mast with something considerably more substantial.

Tony and I assembled the new 6m/4m Innovatennas 12 ele dual bander. We spent a lot of time making sure everything was spot on. I wouldn’t want to ruin Justin G0KSC’s careful design work due to sloppy assembly. I have to say that the quality of construction of this antenna is without doubt the best I have ever seen. I can barely wait to try it tomorrow.

So we have some finishing off to do, but we will be there bright an early in the morning. There will be some photos as well.

Just to finish I’d like to say that I have never known such a spirit of cooperation and team work before, makes me really proud to be a member of North Wakefield Radio Club. I say this in all sincerity and I haven’t had a drop of alcohol! Credit where credit is due.

Thanks to all.

Conrad G0RUZ

 

 

Apr 112013
 

Just a reminder that we are doing antenna work this Saturday 13th from 10 am until its done.

These are the tasks

  • Re-align rotator on HF tower
  • Add 40m extension to HF beam
  • Replace coax on HF beam
  • Fit new 6m/4m dual band yagi
  • Fit new coax to to new 5m/4m dual band yagi
  • Tidy coax to VHF tower

So plenty to do, more hands make light work so please come along.

Apr 092013
 

I didn’t do a very good job of the 1st RSGB 70 MHz contest I’m afraid.

There were a number of problems.

  • I was very tired & very grumpy – this never helps!
  • The conditions weren’t great – so QRP operation such as ours is at the moment really finds it hard going.
  • The Stihl saw noise was a little distracting from out on the patio.
  • The antenna rotator was challenging – I didn’t know where I was pointing the antennas most of the time and I couldn’t go out and check because I would have been drenched as the patio was being jet washed :)
  • One unfortunate operator who was nearby developed an intermittent RF feedback problem and at certain times large portions of the band were wiped out – this can happen to anyone.

Apparently I had awful audio again but fortunately Peter G4IZH was on hand to give me some help with this. Peter is a very technically minded chap who knows his onions and I am now pretty sure that things are fine. There are some settings on the TS-570D that should not be used! TX bandwidth and TX-EQ! They were wrong and sounded awful, no wonder no-one would talk to me. Mind you that wasn’t a problem on cw and they wouldn’t answer me there either.

I discovered something very interesting about the antenna that we are using as well; the front to back ratio is very poor.  I suspect that it is an assembly  issue because the data sheet for the antenna indicates that the antenna has very respectable front to back and the data is reputable.

I feel sure that the new antenna will make a considerable difference to our station performance as well.

We certainly need an amplifier, this will increase our signal by 10dB. That will hopefully be completed by the end of the month in time for the contest on the 30th.

Can’t wait to do the antenna work this coming weekend.

Conrad G0RUZ

 

 

Apr 062013
 

Please Read – IMPORTANT stuff in ‘ere

Firstly thanks very much for the compliments on the website. I still have lots more to do and I hope to make the website a source of information for all amateurs and the forum the focal point of the club.

The Website and the Forum are different sites and each one needs it’s own login and a password.

I did this for a number of compelling technical reasons, in time I may be able to integrate the databases but there are risks with that.

So sorry you need to register for both sites.

There is absolutely nothing stopping you from using the same user name and password on both the website and the forum.

Members and none members and guests

At the moment the website does not have any protected content for members but it soon will have. Things like minutes of the AGM etc should not be visible to all and sundry.

If you want to leave comments then you will have to register on the website, leaving comments is helpful to other readers and me! There will be articles on there. I encourage people to submit their own articles soon. It can be anything radio related and don’t worry about spelling and grammar we have people who can do that.

Take G4RCG for instance, he has done contests from all over the place, a few photos and a few from John would be interesting. I’ll put some stuff up about VHF DX, little short articles are best. Tony could do a story about last years rally. The club does stuff and its time that people knew about it.

Don’t forget that you can subscribe so that when anything new is posted you are notified. At the moment I have to publish everything, we might change this. Once your first comment has been approved then after that your comments will appear immediately.

There are a few issues about membership types that I need to resolve:

Website

Some people are not paid up members but have done loads for the club – people like G4RCG and Gerald G3SDY, not paid up members but they should have access to to most things – I’m going to call  them Affiliates, I’ll set them up with the right level of access they need only register. It would be nice to get old lapsed members back into the fold I’ll stick them in Affiliates as well. If anyone has a better name  for this group let me know!

  • Guests may register on the website, they are known as Free members, they can then leave comments at the moment I have restricted them to 90 days but in hindsight I will lift this restriction.
  • Then there are members – these are paid up members or at least should be – I could do with a list :) I have guessed a lot of it!

Forum

  • Guests can read limited sections of the forum but they cannot posts
  • There is a members section which will be for members only and affiliates
  • There is a committee forum that is only visible to the committee and anyone that the committee may invite from time to time

A lot of the traffic will be in the general section, however things like organisational matters between members for Special Event stations etc will only be visible to members and affiliates.

The committee forum is for us to talk about you – most won’t even know it’s there.

This is posted on the web and to the email server

Apr 012013
 

I offered to do a website at the AGM last week and I have been true to my word, there is not much here yet but there will be.

So this is still

Under Construction

The forum is the place for quick chats and questions, it can also be used much like the current yahoo mail reflector. I hope that we will be able to replace that over time and I hope that the forum becomes the hub of the club and is useful for everyone.

The forum can be found here

Regards

Conrad

Apr 012013
 

This is where you’ll find news of events in the NWRC calendar as well as other items of general interest to the club members and other radio amateurs.

Member Login

Forgot Password?

Join Us

Password Reset

Please enter your e-mail address. You will receive a new password via e-mail.