Showing posts with label dipole; inverted vee. Show all posts
Showing posts with label dipole; inverted vee. Show all posts

Tuesday, 20 October 2020

Moving shacks

 I don't really have a 'shack' of sorts as most hams do.  I operate from my yard close to where my antennas are.  During the inclement months I would go into my small barn and operate from a small table and chair.  I have a small space heater to take the edge off when it's -30C and that has served me well.  The problem with my barn is that I share it with raccoons and squirrels.  It is an unwinnable battle with the current state of the barn and access points the critters have to its interior.  I'm not terribly upset that they are there.  They don't cause me any other grief...they do not get into my garbage or anything like that.

I also had an old decrepit large shed/building which raccoons lived under and I could store some things in but the doors wouldn't shut properly and the roof was rotting.  It needed to come down.  I tackled the task which ended up being much more work than I had anticipated.  It took two 20 yard dumpsters and two 40 yard dumpsters to take care of it all.  It took me months to deal with this very well built shed.  Now that it's gone I am having a new, but significantly smaller, pre-made 10' x 14' shed delivered from Pine Grove Sheds in Alexandria, Ontario, just 20 minutes away.  This shed will be located on the opposite side of the yard from the barn and I wondered if I could use this new shed as a new operating position or shack.  It will be protected from the elements and the raccoons and I am excited at the prospect.  I was thinking of putting a vertical antenna up as I had originally thought I would also keep the old operating position in the barn until I went in the other day and saw raccoon poop on my table.  I'm done with the barn.  I will move my antennas to new trees and have a new permanent shack.  This will allow me to leave things there without fear of rodent destruction.  I am getting excited at the prospect of this new locale.  I will post pictures once it arrives in a few weeks.

When I was thinking of putting up a random wire vertical I did a lot of youtubing and reading and I learned a lot about the differences between the EFHW and the random wire antenna.  I learned more about 9:1 ununs and their proper application as compared to the 49:1 auto transformer used in EFHW antennas.  I really enjoy when these concepts that I didn't quite fully understand become more clear to me.  I had been trying to use a 9:1 unun for my 80M antenna at 1/2 wavelength.  I had purchased a EFHW 80M mini tuner that plays the role of tuner and matching transformer but a part was incorrect in the bag and had been waiting for its replacement.  I didn't understand why the unun was giving me an "ok" match but not a great one.  I made some contacts but the SWR on the FT-817 was still fairly high.  Now I understand the difference between the 2 antenna types better and the need for the 49:1 transformer and that the 9:1 just wasn't going to cut it.  Once the proper toroid arrives and I finish the 80M EFHW tuner the 9:1 can be put away until the next time I decide to put up a vertical or random wire antenna....with a proper counterpoise.


Cheers for now,

Scott ve3vvf

Thursday, 23 April 2020

Doublet Up and more to come

On Saturday I installed my doublet and the center hangs down to about 23' above the ground.  It's heavy over a long run so it does sag some.  I have decided to prepare my center support to take some of the load off and also to provide me with another use.  More on that later.

I tested my doublet with my tuner and found a very good match on 40, 17 and 15 and a reasonable match on 30, 12 and 10.  I could not match on 20M.  I made some contacts and was pleased with the flexibility I now have across the bands...except 20M.  I thought the issue was the length of my feedline so I trimmed 8' from it and still it behaved about the same.  Someone suggested that the length of the antenna may need some trimming.    I lowered the antenna and trimmed 2' off each end and raised it back up again.  The bands that were reasonable improved slightly in the SWR department but 20M stayed unacceptable.  Rather than fart around with this doublet to get something "reasonable" at the expense of the other bands I decided that I would prefer a tuned antenna for 20M so that I can get back to doing some QRPp work eventually.  I have decided to make a single 20M dipole and support it from the antenna support I plan to install.

In the QRP tradition I want this support to do the job with low expense and also with what I have on hand which is challenging.  I have wood.  I have a patio umbrella stand that anchors with patio stones in the NPM (non-penetrating mount) fashion since I'm not quite ready to dig and bury a 6"x6" or 4"x4" post as a base anchor point just yet.  I have a pulley and I have a 20' fiberglass Wonderpole with the tip broken off.  Originally I was going to use just the top section of this rod as I explained I was going to do in my post Still a Bit Chilly but I have changed my plan a bit to use the whole thing.  The only thing I am missing to get this support up are some hose clamps and some paracord.  I used up all the cord I had on the weekend so I will place an order at the local hardware store for a curbside pickup.

I am using two eight foot 2x2s end to end for the support and then I will strap the Wonderpole to it at the top.  This will give me close to 30' of support.  I may be able to get away with no guys at all, since the Wonderpole is light.   Just below the doublet I will attach a pulley and install a dipole for 20M.  The paracord attached to the legs will give me some added support.  Joining the 2 wood 2x2s end to end is a challenge and here is what I have come up with.


I ripped some 1x8 down to about 2" wide which is the same width as the main support pieces. the pieces are about 2' long.  I sandwich the support pieces at the joints and secured with some screws, wire and hose clamps.  The photos show wire I used but this won't be strong enough.  I don't have any fencing wire or I would use that and hose clamps are easily removed and adjusted.

I have strapped the support pole to the umbrella stand and will add the Wonderpole to it hopefully today,


More to come
Cheers de Scott ve3vvf

Friday, 27 March 2020

Doublet length

So I had decided to install the 40m (and higher) doublet to save on weight even though I had the space for the 80M doublet.  My original thinking was that some day it might be neat to compare the EFHW 80M antenna with the 80M doublet since my QRP Guys tuner that I plan to use with the doublet does not support 80M.  Then I read that a doublet will actually provide better performance on a given band if the antenna were resonant on odd harmonics for that band so I thought that since the doublet length is not critical I could play with the length to give a boost to a favourite band.  I knew there are websites out there that will calculate this for you so I went searching.

I looked at a couple and then found this page on Spookmate.com.  I was able to put in the frequency for 80M in the calculator and see what my options were.


As you can see where the harmonics are listed that 10.5 is the 3rd harmonic.  This is very close to 10.110 where I like to operate on 30M.  I then adjusted the frequency at the top until the 3rd harmonic was where I wanted it to be.  3.37 MHz does the job and the legs of the doublet would be 72.9' long.  The key with the doublet is that the antenna is not resonant on 80M if I want to use 80M.  It is not (although it may be too close) but I am not using the antenna on 80M so I'm not concerned about that.  Really I'm taking advantage of the 3rd harmonic which I would not have if I were to put up the 40M doublet.



The harmonic frequencies gave me no joy for the 17M band which I also enjoy so I will go with the 73' length.  This is what I plan to experiment with when I put this doublet up, hopefully this weekend, weather permitting.  I'm not sure how much luck nor do I have a way to get tangible results but my random wire is currently working well on 30M only so I can compare the two.

Now you may remember I was going to avoid the 80M doublet because of weight concerns but I have come up with a plan for a guyed wooden support pole.  It'll be a little "interesting" looking but I think it should do the trick.  I'm fine tuning my idea in my head daily and am almost there.

Cheers for now,
72/73 de Scott

Monday, 23 March 2020

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

Wednesday, 15 January 2020

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.  

Monday, 13 January 2020

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.

Sunday, 18 March 2018

1000 MPW ...Even with Poor Band Conditions

So I turned the radio on this morning for the first time since last September.  My wire dipoles are in a bit of a tangle from a winter of strong blowing winds but the SWR readings are still low so I ventured onto the bands.  I heard a fair bit of activity on 40 but I prefer the WARC bands so I moved to 17M.  The SWR was too high so I moved to 30M.  With the exception of someone already in a ragchew QSO I dialed around and found nothing.  I had my FT-817 set to 1W as usual and called CQ a time or two.  Then I heard a weak response from Roger, W4RFT.  I have him in my log on 20M but not 30.  It was a very brief QSO where we exchanged 559s and then it dropped off.  Roger shows as being 1100+ miles away in Florida so I was very happy that my first QSO in months was over 1000 Miles Per Watt.  I really love this hobby.

I can't wait to work on replacing these 2 fan dipoles (2 bands each) with the same but made from ladder line (see previous post).  I already ordered it from MacFarlane Electronics near Kingston, ON.  To save on the shipping (which is almost half as much as the wire due to the weight) I will be picking it up at the Iroquois Amateur Radio Club's annual Flea Market on the 7th of April in Iroquois, Ontario.

With snow still on the ground and below freezing temperatures I have no rush to start any antenna work just yet anyway.  I can wait a few weeks for the wire and I will never pass up the opportunity to stroll through a flea market...ham radio or otherwise.

Cheers for now,
Scott ve3vvf/qrp

Thursday, 15 March 2018

Silent Too Long

Well I went the whole winter without even turning a radio on and I was worried that I had lost my interest.  A lot has been going on which has had my mind on other things but all it took was listening to a couple of episodes of one of my favourite podcasts the QSO Today Podcast to get my mojo back.  I can always count on Eric (4Z1UG) to kindle my interests...especially on the QRP front.  I also believe some of my issue was the havoc the wind has been playing on my inverted vee antennas (not to mention the grim propagation these days).  The tangling that occurs with the fan dipole style of antenna is disappointing.  I need a better solution and I believe I may have found it.  I read an article in the ARRL Wire Antenna book that I bought from Amazon last fall.  The antenna from the article I read has the radiating elements made from ladder line/window line.  I can have a 2-band dipole that will not get tangled because the wires are evenly spaced/separated by the windows.

What is done is the length of the longest leg (34' for 40M) and the length of the shortest leg (24' for 30M) are added together making a 58' piece of ladder line the requirement for a 40/30 fan dipole.  Then you lay the cable out and measure 34' from one end and cut the top conductor.  Measure 34' from the opposite end and cut the bottom conductor.  What you have now, if you cut along the red line as shown below, is 2 pieces that will act as each leg of the dipole.  The long top wire is one side and the long bottom wire flipped over and end for end is the other side.

Then you need to strip the conductors bare at the double wired end and solder them together and attach them to the coax to create the feed point.  One leg connects to the center conductor and the other side to the braid of the coax.


Once this is completed you will have to raise the antenna and tune it for your desired operating frequency as with any dipole antenna.  I plan to build two of these.  One for 40/20 and one for 30/17 and I will post the results including photos of the tuning and testing process.

Cheers and thanks,
Scott, ve3vvf/qrp

Monday, 20 March 2017

Lessons Learned

I spent Sunday afternoon making and installing a replacement 40/20 inverted V for the flimsy one I had put up in the fall.  Here is one lesson I learned...QRP low power with lightweight wires is all well and good for temporary use but it is not robust enough to last through a windy winter.  The work was going pretty well and the weather was just above freezing and sunny.  Great for antenna work.  I had to raise and lower the antenna 4 or 5 times for trimming before I got it to resonance on both bands but I'm not quite sure if it's there just yet because as I was raising it the final time, a knot I had tied in the string I was using as a hoist came untied leaving 2 feet of string hanging from the pulley 40' up.   I had now been fiddling with this antenna for few hours.  I should have quit for the day and addressed this at a later date.  I didn't.  All I needed to do was climb the tower and detach the "yardarm" which keeps the antenna away from the tower.  The pulley is on the end of it.  Not too challenging.  Climbed up and realized that I had the wrong socket in my pocket for the U-bolts.  Back down and back up.  I ran a fresh piece of string through the small pulley and tossed the spool down to the ground keeping the loose end with me.  This was very challenging as the sun was directly behind the pulley.  I was clinging to the tower and struggling with the string.  I was cursing but eventually I got it after a few minutes.  I climbed down with the loose end and attached it to the antenna and started raising it up.  Half way up it got stuck.  The string (which is Mason's string) is very thin and quite durable however it jumped off the wheel and got stuck between the wheel and the side plate. I always knew this was a risk but figured the chances were slim of it ever happening.  No such luck.  My blood pressure and frustration level was maxed out at this point.  Luckily I did not have the right rope on hand to finish the job properly.  This gave me a good excuse to leave the task for another day.  This is a hobby and is supposed to be enjoyable.  We learn in many ways...from reading or watching videos or being taught by someone but the lessons learned through trial and error (mixed with frustration and possibly pain) are the ones we will never forget.