Doublet Dilemmas

When it comes to installing my, yet-to-be-built, Doublet antenna my biggest concern is weight and whether it will need a center support.  If it does need a center support what will I use and how strong will it be?  My original intention was to install an 80M doublet just because I have the space but that antenna will be significantly heavier than one for 40M.  The QRP Guys Multi Z Tuner that I just completed only tunes 10-40 so an 80M doublet is definitely overkill so it only makes sense to only put up what I will need in the immediate future.  As well, I have my random wire that will be modified to be my 80M antenna with the addition of the QRP Guys EFHW mini-tuner kit for 80M.  Once these projects are ready to test I will do so using my FT-817.

Here is the image from the QRP Guys website:

If I still need support for the doublet I have a couple of options I've been contemplating.  I could use a guyed wooden support made from pressure treated 2" x 2" or I could use a guyed PVC water pipe mast with about the same 2" diameter.  I live in a windy location but the center of the doublet will be somewhat shielded from the wind by my small barn but I still worry about it.  The wind on the antenna wire is not my concern as much as the window feedline is.  It is both heavy and easily caught by the wind.  Only putting it up will tell how these factors play out in real life.  The height this antenna will be remains unclear but I am hoping around 40' up.  One end support is the 40 foot TV tower attached to my house and the other end is a tree over which the para cord will be tossed so the actual height of that end support remains to be seen.

The center of the antenna, since I am unable to 3D print at the library is going to be something I have used before for dipoles, although this one is a bit larger.  It is a PVC water line "T".  It's durable and lightweight and I can easily drill or melt holes for the wires to pass through :

Cheers for now,
72/73 de Scott

QRP Guys Multi Z Tuner completed

Carrying over from yesterday the last thing I had to do with the tuner construction was to wind and install the transformer.  There are 3 windings on this transformer: a primary with a center tap and 2 secondary windings of different sizes.  I wound it all up once but it was too sloppy so I removed all the windings and made it a lot tidier and tighter.  Below are the 3 stages of installing the first, second and third windings.

 Once that was wound I had to ensure all the enamel was off the leads and tin them.  I then fed them through the appropriate holes.  When I did this the first time I saw that there was some enamel still not scraped off so I pulled it back off the board and did a better job of stripping the enamel with the Xacto knife.  I then reinstalled it in the holes and soldered them in place.

Now the final touch was to install the PCB washer to hold the transformer in place and put the rubber feet on the back.

I have also included the circuit design which is also available in the assembly instructions on the Multi Z Tuner page on the QRP Guys' website.  

My next step now is to build my doublet and get it up in the air.  That will be happening in the next week or 2 weather permitting.

Cheers for now,

72/73 de Scott 

QRP Guys Multi Z Tuner started

I got down to making the QRP Guys Multi Z Tuner 10-40 this evening.  The first thing I noticed was that my eyes really aren't what they used to be.  Even with glasses on I could have really done with a pair of these:

                                  or this    


My ageing eyes aside, I dove in and got started.  The project does not have a lot of components so the construction isn't too difficult however there are some challenging bits to keep you on the ball but the instructions are top notch.  The first step is joining some PCB pieces together with solder to create the "chassis".  Once complete I began installing parts per the checklist:

Aside from the standard components there is a small toroid to be wound with a center tap.  This went fine.  It's been a while but it all came back pretty quickly.

By the end of the evening I had everything together except for the most challenging part, the large transformer.  For that I will wait until my eyes aren't tired and there is some natural light.  Here is the finished product for this evening.

Back at it tomorrow.  Cheers es 72/73 de Scott

During these times...Projects

With everyone pretty much stuck at home in isolation it's a great opportunity to think of antenna projects and other things like that.  I installed a random wire antenna last fall but with my Z11 tuner is not tuning it at all (I'm not sure if it's broken or just a bad setup) I can only operate it on 30M which is fine by me as it's one of my favourite bands.  That being said, i ordered 2 little kits from QRP Guys.  The first kit was the EFHW Mini tuner.  There are 2 versions to choose from and I chose the 80M version.  This little rig will hopefully help me turn that random wire antenna into a dedicated 80M EF antenna.  I will have to lower it down and add about 10 feet of wire to get to the recommended 135' starting point.  The below photo is from their site.

The second kit I purchased was for the Multi Z Tuner 10-40.  My plan with this little gem is to use it with the doublet I plan to install over the coming weeks.  I have the wire and space to install up to an 80M doublet and I figure I might as well go that route even though this tuner will only help down to 40M.  This kit is a bit more involved but shouldn't be too bad since there are no SMT components involved.  Here is the photo from their website:

A few years back I bought a good length of 450 ohm window line for a project that never came to fruition so now I can use it for this.  I have heard a lot about these antennas and the multi-band properties make it attractive.  I've always been one for using tuned dipoles but in my windy location they are a challenge to maintain.

I did have a plan to have the center support insulator 3D printed.  I found a nice one on  Thingiverse but the local library, which has the printer, is closed until further notice so I may just have to fashion one up.

I will post my progress with the Multi Z Tuner as I tackle that kit first.

Cheers es 72/73

Scott

Spring is Here Today

With the lengthening days, warmer temperatures and the reality of being stuck at home due to work policies surrounding the COVID-19 "situation" has me thinking about radio a lot more often these days.  Last weekend I decided to do some outdoor operating using my random wire antenna.  The temperature was 4C so it was quite bearable and I also had a nicer view than I would have had I sat inside looking at the barn wall.  Basically I sat just outside the barn window and ran a short length of RG-174 out the window to a chair.  The other end was connected to my LDG 9:1 Unun.  I set up and in 30 minutes I had 3 nice contacts on 30M and two of them were 2xQRP which always makes me extra happy.

 I have my rig, battery, key, clock and ear buds in a small Pelican case which I lined with "Cubed Pick Foam" from the local Canadian Tire store.  This allows me to keep everything organized and works a lot better than the computer carrying case I used to use.  The battery is a 7mAh and is heavy and would crush the other things in my bag.  Now it's held snugly in place by the foam. 

I have a small collapsible camping table and it worked great for keeping things off my lap.   I enjoy being outside again and with the COVID crisis looking like it's not going to end any time in the near future it will give me a chance to operate more often that I otherwise would have time for.  I am also taking some of my spare time to brush up on my code rx speed.  I started out using the standard G4FON program I installed years ago but have been found two other resources that are extremely helpful at increasing character and word recognition which will help with head copying and get past the barrier that exists when you try and write everything down during a QSO.  One of these resources is Kurt Zoglmann's Morse Code Ninja site which is full of links to Youtube videos he's created with all sorts of words, prosigns, call signs, etc at various speeds for aural practice for word and character recognition.  He has learned Morse Code to the extreme where he has even had books converter to code and listens to them.  He's pretty hard core on code.

The second site is called Morse Camp and it is quite simply laid out and easy to use for word recognition.  It plays words for you at a predefined speed (default appears to be 30WPM) and keeps repeating them until you think you know what it is and hit the space bar.  This shows the word or letter/number combination and you indicate with a left or right arrow whether you were correct or not and it moves on.  You can select word length but as you progress it increments on its own.

I think this seclusion we are all experiencing can be a challenge for those who suffer from anxiety or depression, let alone the rest of us who are also feeling the stress of the unknown be it job security, financial security, or even toilet paper security, apparently.  They say the key is to make sure to get out of the house for a walk or a hike or some other stress relieving activity.  Radio is that for me and I plan to do it as much as I can fit it in.  I don't need to sit there for hours...30 minutes is plenty and even just 1 QSO makes me happy when operating QRP.

72/73 de Scott ve3vvf

Change of plan

My plan a few days ago was to build a maypole-style antenna supported in the center with inverted vee antennas coming down around it.  I was worried about the wires coming down all over the place and I also realized that there must be another cheaper and more easily implemented solution.  I have done some reading in the ARRL antenna book and also done some youtubing and now have a new plan.  Now my plan is to install a single wire, centre-fed, with balanced window line.  As long as I am at least 1/2 wavelength long from end to end, on the lowest frequency I plan to operate on,  I can feed it to a simple tuner for multi band use.  My tuner of choice will be the QRPguys Multi Z tuner for 10-40M.  I like the way this tuner has an LED that dims as a match is obtained eliminating the need for an SWR meter which is a huge benefit if I take this tuner to the field.  I have watched a great Youtube video on the building and testing of this tuner and I really like what I see.  For $40 US plus shipping I don't think it can be beat.

My existing long wire can be used for an end fed half wave (EFHW) antenna on 80 meters.  My first option is to adjust the length and try and use my 9:1 Unun to make it resonant on 80.  Failing that I can feed this into a QRPguys EFHW mini-tuner for 80M.  I may need to add some length to the existing wire since the recommended length for 80M use is 135'.

If I cannot get it working well enough on 80 with the LDG Unun I will likely order both kits at the same time so I can save on shipping costs.  

Less than favourable results...sort of

So I installed my random wire antenna from my barn out to a very tall poplar.  I used #10 wire so that the strong winds at my QTH wouldn't break it and I have about 130' of wire up in the air sloping up towards the top of the tree with the last 50' or so being para cord over a branch and down to the ground where it's tied off.  At the shack end I am using a ceramic egg insulator to a rope tied through a pulley attached just above the barn window to a bucket of bricks so that strong winds won't break the wire.  I then have another wire soldered to the antenna wire which comes into the "shack" to my LDG 9:1 random wire unun.  From there I connect straight to the radio.

I used the Agilent Field Fox to look at the resonance points on the antenna and saw that it wasn't really well resonant on any band but it wasn't too bad on a couple.  I added some radials on the ground of varying lengths and according to the Field Fox this made things worse.  What I really need is a MFJ-16010 L-network tuner to finish things up for me.  As it stands now, when I hook up the FT-817, the only band that presents no SWR issue is the 30M band.  30 has always been one of my favourite bands (along with 17 and 12) so I'm not extremely upset by it.  We are in a dismal part of the propagation cycle and I was still able to have a few QSOs on Sunday (Jan 12th) including a QSO with Ron, K5WLT, at almost 1700 miles in Texas and a 2xQRP with Alan, KR4AE, in Cleveland Georgia which is almost 900 miles away.  It's certainly not as good a distance as I can get with far less power during better propagation periods but I like the fact that I can still make QRP contacts, albeit with 5 watts.

Of course, as with many hams, I'm thinking of other antenna ideas.  The one that interests me at the moment is the Maypole style antenna.  I am a proponent of the fan dipole antenna and this is a variation on that.  The problem I have at my QTH with wind can best be defended against with stronger wires but thicker wire is heavier making supporting the center more challenging.  What the Maypole antenna does is use a non-conductive centre support with the inverted-vee antennas equally spread out in all different directions around the circle (looking from above) acting as guy wires and also not interacting with each other as much as with the standard fan dipole.  This antenna can be fed with coaxial cable but you'll want to keep the run as short as possible to reduce losses.  You could use a 1:1 balun or choke at the feed point to reduce feed line radiation but I don't think it's really that necessary, especially at QRP power levels, based on my use of dipoles in the past and from what I've read on the topic.  The leg pairs will all be of different lengths making the "V" angle different on each band but this shouldn't change the feed impedance too much.  The legs should not touch the ground but can be attached to stakes or pegs with non-conductive guy ropes.  Since I am operating QRP power levels I am not worried about RF burns but at higher power levels you should keep the antenna elements out of reach of people.  The key now is to choose which bands I want to operate on and figure out the best type of centre support to use.  There's PVC piping but the strength is suspect if it gets too tall and there's also wood or fiberglass.  I'm not quite sure yet which is the best choice.  As it stands now, this antenna will take up a fair bit of real estate and cutting grass around it will be a pain but if it works well it will be worth the extra effort.