Category Archives: Antennas

Field Day Preps Complete!

My Field Day preps are done. Tested the EFHW and its ready to roll on 20m and 15m. There is 12Ahr of solar charged battery ready as well. I won’t be able to join the club at the NWS office as I have a commitment in the morning I have to deal with. I may start late but I am ready for operations in the backyard. Will get some water bottles and snacks for daytime ops. There is a 30% of rain tomorrow afternoon so I’ll keep an eye on that as well to see if I need to deploy the tarp tent. Rain means clouds so that may help moderate the heat. Today the NWS is advising people to stay indoors between 1pm and 5pm!

Tested the EFHW a bit and am finding Common Mode Current issues if I run higher than 90W. The SWR increases with power and foldback starts kicking in if I try and run at 100W. This should not be a problem on FD as I’ll be running at 5W where everything behaves itself. I’ll be trying computer logging this year as well. If things get real tough on Phone I plan to try PSK31 and have setup some DM78- macros for that.

Looking forward to a great Field Day in the outdoors!

Completed Linked EFHW

I completed the linked EFHW later yesterday afternoon and tuned the 15m, 17m & 20m bands. I removed about 6″ of wire to tune 15m, 2″ to tune 17m and about 3″ to tune 20m. The antenna is deployed vertically on a SOTAbeams Travel pole up 30 feet. I am using a TV mast tripod as a base. In the field I would lash the mast to a fence post or other similar support.

I tested the antenna on my base rig at 100W and made three easy SSB contacts. Two of these were EU DX contacts. I  left it tuned for 20m and ran WSPR for the last 12 hours. Here is the map:

2017-06-22_7-27-12

This works out to 112 unique heard spots with 66 unique heard by spots when running 1/2W. Looks like the antenna is a winner for Field Day! Only thing I will likely try today is adding a 1:1 choke as I am seeing the SWR swing a bit on SSB transmit.

Linked EFHW Coming Together

I purchased the following for $1 at Home Depot yesterday to form links for the EFHW I plan to use for Field Day:

Photo Jun 21, 10 47 20 AM

These are buckles to make paracord bracelets. Here is how the resulting link looks like using these, a couple of cable ties and a pair of Anderson Power Poles:

Photo Jun 21, 11 01 22 AMPhoto Jun 21, 11 01 32 AM

I have made initial wire cuts for 15m, 17m, 20m and 40m. I also cut 1/10 wavelength counterpoise wires for each band. I have also prepped the Travel Mast and the TV Tripod so I will hopefully setup later this afternoon (when it cools off a bit) and tune the wires. I’ll run 15m-20m as a vertical and 40m as an inverted V.

The only other prep I am working on today is I’ve taken the solar generator box I built last year and set it up outside with the two 15W panels to charge them up.

Update: Just did the calculations on the 40m inverted V and found that I probably don’t have enough space to lay that out in the backyard due to obstacles. Will configure the first half as a vertical and then the remaining half as a sloper which I’ll aim towards the north and terminate 4 feet off the ground. Only need a radius of about 16ft. A quick run on EZNEC show the following pattern:

2017-06-21_13-10-142017-06-21_13-10-32

Plan B for Field Day Antennas

I was pondering what I would do for a Field Day antenna after yesterday’s debacle with the Homebrew Buddipole and military mast. It just hit me a few minutes ago. I’ll run the EFHW antenna as a vertical on 20m and 15m. It is a proven performer and it is resonant thus no tuner needed. I’ll use the TV Mast tripod Cliff gave me to support it during the contest on the SOTABeams Travel mast.  What I will do this week is set that up and cut some links for 15m, 20m and possibly even 40m. Will be much more manageable as a vertical. I have 5 days to work out the details. Tomorrow morning I’ll put put the battery packs and solar panels to top off the charge. This should work!

Epic Fail! – Homebrew Buddipole on Military Mast

I took out the military poles and tripod today for the first time with the intent of getting the homebrew Buddipole up around 30 ft. The mast itself works pretty well with the tripod hub. I mounted the Buddipole on top as I have before with the painters pole except this time I replaced the thread adapter with a 3/4″ PVC pipe adapter and used a length of pipe to fit inside the mast section. I guyed it near the top. I sent it up and it promptly got swung around in the wind and tangled in a tree. After twisting and turning awhile I got it clear and up to 28 ft then tied off the guys. I left the last section off as I did not have enough coax to get it in the shack.

Started operating on SSB and made a strong 59 contact into Arizona then noticed that my SWR was swinging around. Looked outside and saw that one half of the dipole was swinging into more of a v-beam. Moments later it fell off completely. Doh!

Photo Jun 17, 1 25 23 PM

The section landed cleanly and did no damage but I had to take the whole thing down. Guy lines get tangled, the aluminum mast sections are burning hot to the touch and my temper starts flaring. Did I mention it’s 97 degrees outside with 51% humidity?

So I carefully sort out the guy lines, move the tripod a few feet away from the tree and place a wedge in to keep it from swinging as much. Sent it up again and adjusted the guy lines. Went back inside the shack and hooked up the SWR meter. It started a sweep and was looking good when I heard a SNAP and the meter SWR reading went full scale. I looked out the window and sure enough the half of the dipole fell again. On inspection I was not so lucky as I broke the whip off at the base. Doh!

So thus ends my Field Day Preps today.I am goign to use something much simpler next week. Either the Homebrew Buddistick which I have used before, an end fed vertical up about 30 feet or a 1/4 wave vertical for 20m with four ground radials. The Buddipole is going to be limited to lower heights using the painters pole. If I had more time I’d try an inverted V for 20m using the Spiderbeam mast.

 

Buddipole Tweaks

I was going to try and adjust the loading coils on the homebrew Buddipole but after reviewing the SWR plots in more detail I have decided against this. The resonance point is on the high end of the band but I’ll be operating mainly voice. The SWR is below 1.6 across the band and the reactance is within ±3 Ohms of the resonance point. Better to leave it alone at this point.

I did add a couple of cable ties to the arm to allow me to better control the antenna swinging in the wind. I am working to build another 1:1 current balun which I will replace the BNC to binding post adapter I am runing now. It will be interesting to see if adding this balun will change the SWR curve. Here are the current curves:

BUDDIPOLE CustomBUDDIPOLE CustomA

Hopefully I can retest the deployment of this antenna this weekend perhaps at 20 ft and with luck maybe at 30 feet on the military mast.

Some Thoughts On WSPR Data for Antenna Comparisons

I have been keen on using WSPR data to compare the performance of antenna systems. I haven’t worked out a detailed metric but I thought I’d share some thoughts on how the data can be broken down. When looking at 24 hours of WSPR data on a specific band I am seeing the the number of unique stations received is a clear indicator of the antenna’s overall performance and pattern. If this is enough to make the WSPR Challenge board for that period then another clear indicator. As an example, the homebrew Buddipole on 20m (even with resonance being outside the band high) came in at #22 on the WSPR Challenge site with 143 unique stations. I have been hard pressed to make the WSPR Challenge board with the end fed horizontal or the magnetic loop antenna (indoors). So the higher then number the better.

The number of stations hearing me on WSPR is a different story. The ratio of stations heard to stations hearing me is rarely equal. This really depends on the efficiency of the antenna, something that is not evaluated on receive. If I transmit at 1/2W I can expect fewer stations received than if I transmit at say 1W. This will not be a linear increase. What I am seeing is that some antennas have a high count of “heard by” stations for a given power than others. This gives a relative indication of the antenna efficiency. There may be a way to correlate this with a given antenna by testing at different power levels.

 

Vertical Weathers a Thunderstorm

We had some much needed rain at the QTH last night. I had taken down to work on the Homebrew Buddipole early last evening but left the 40m vertical in place. The storm blew through at about 4am and dropped over an inch and a half of rain with gusty winds up to 25 Mph. My wife went outside early this morning and came in to tell me we had debris in the back yard and oh by the way your antenna is bent. Doh!

Went outside expecting the worst. I have heard stories of fiberglass tubes breaking off in high winds. I was relieved to find that the antenna was indeed bent near the top, but only because the vertical wire had blow into and tangled into a tree branch holding it over. I shook it loose and it popped back vertical instantly. Three sections had telescoped back in near the base so after pulling them back out I am back in business. This SOTABeams travel mast has taken some real abuse!

Camera Tripod Adapter

The Homebrew Buddistick and the Magnetic Loop antenna both require mounting on a camera tripod. Up to now I had been using a tripod without the pan head and inserting the 3/4″ PVC pipe with a pressure fit. This worked OK for awhile but eventually the tripod fitting pulled out and the tripod was ruined. I have been thinking for some time about how to make an adapter that would fit the standard tripod pan head and allow me to mount the antenna. A trip to Home Depot this afternoon yielded a solution. I built a mount with these four components:

  1. 2″ Pipe PVC cap – These have a flat cap surface
  2. 2″ to 3/4″ PVC pipe adapter
  3. 2″ PVC pipe coupling
  4. A 1/4″-20 threaded insert.

Building this was simple enough. First drill an 11/16″ hole in the middle of the pipe cap. Then using a 6mm hex key drive the 1/4-20 insert into the pipe cap until it is flush. Here is the cap mounted on the tripod:

Photo May 28, 4 35 19 PM

To complete this adapter install the coupling along with the 3/4″ adapter and it will be ready to mount the antenna. Here is the finished adapter mounted on the tripod:

Photo May 28, 4 35 37 PM

I finished this just in time as I need it to start testing the Homebrew Buddistick as I’d like to compare it’s WSPR performance to the Homebrew Buddipole.

UPDATE 6/13/2017: This turned into a fail. I tested this mount on the mag loop antenna and the weight and balance was too much for the tripod head. The clamp mechanism snapped and rendered the head useless. I removed the head and and am back to using it as before, i.e. with the pvc pipe jammed onto the tripod vertical post.

Homebrew Buddipole Shakedown Testing

Sometime ago I built a homebrew version of a Buddipole horizontal dipole antenna. I only deployed it once to test and have not really used it much since. I am considering using this antenna for Field Day this year on the 20m band and wanted to test it out. Happy I did for several reasons. Here is the antenna deployed at 16ft with a painters pole:

Photo May 27, 1 47 33 PM

The antenna is guyed at two levels. The painters pole is inserted into a speaker stand tripod. Here is the SWR plot:

BUDDIPOLE Custom

Most of SWR is below 2 however the resonance point is outside the band on the high side.  So I have to lengthen the antenna slightly. The whips are already at their max so I will have to adjust the loading coils. One more turn on each should give me room to adjust with the whip lengths if necessary.

Something else that needs to be addressed is that the antenna swings around in the wind. I need to add an attachment point for a separate line to secure it from swinging. The old “Armstrong” method of swinging the antenna around. Finally, I need to put a true 1:1 current balun at the feed-point. I have the kit to build one and will do so this week.

The antenna has performed well. I called CQ this afternoon and made 5 contacts from South Dakota to Florida and North Carolina. Band Conditions have been fairly bad with considerable QSB. Europe will open up in a couple of hours and will try it again then.