Monthly Archives: May 2017

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 on WSPR

Here are about 18 hours worth of 20m WSPR data on the Homebrew Buddipole at 16 ft. So far 137 unique spots. Looks like it will provide good coverage for Field Day. I’ll be comparing this again the Homebrew Buddistick next.

buddipole wspr

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.

 

 

Reached 100 DX entities – unofficially

I made a 20m SSB contact to Guadalupe in the Caribbean yesterday which got my unofficial DX count to 100. It is unofficial because I don’t have the electronic confirmation either though QRZ or LoTW. My official tally is 85 for DXCC and 88 for QRZ DX World. It has taken awhile to get here and the new antennas I have been testing help quite a bit. Wish more folks could confirm either through QRZ or LoTW!

SWR Meter Bulb Replacement – Win!

I use an MFJ-822 SWR meter with my base rig and it has served me well. Only issue is the small incandescent 12V bulb burned out making it hard to read in a low light situation. I replaced the bulb with a white LED rated at 12V by MPJA. This did require a bit of careful surgery but was successful. One screw removed the case. The bulb is connected with a small Molex connector. The meter connections have to be un-soldered in order to get at the bulb. The meter movement is gently pried off the cover. Here it is disassembled:

Photo May 23, 3 20 57 PM

The bulb used in the MFJ meter is not field replaceable. It is glued into the meter plate. I gently popped it out and then drilled out the hole for the LED. A bit of super glue holds it in place. Reassembly was straightforward, just be careful to re-solder the meter correctly. Here is the meter with white LED goodness:

Photo May 23, 3 49 57 PM

Keep in mind that doing this retrofit likely voids any warranty you may have with MFJ so do it at your own risk and as always, Your Mileage May Vary.

Mini60 Bluetooth Retrofit – Epic Fail

I was going to make one last attempt at getting the mini60 Bluetooth module to work by removing it and redoing the baud rate programming step. Too many applications of the soldering iron affected the small solder pads and traces on both the module and the Mini60. I removed the module and put the Mini60 back together again. Everything is still working as before but no Bluetooth goodness. Better to just but the Mini60 with the Bluetooth module installed.

Mini60 Bluetooth Install – One step forward, two steps back

Per my last post, I found the jumpers needed to get signals and power to the Bluetooth module. I can now successfully pair the Mini60 with either the Amazon Fire or my PC. That’s as far as it goes though as neither application is transferring data. The USB link still works ok but nothing over the Bluetooth link. I verified continuity to the USB chip and even tried reversing the signals to no avail. Not sure what to try next. I’ll let it sit until I get a replacement power switch in. I burned up the original when I tried to solder it back on to the PCB.

Mini60 Bluetooth Progress – Nothing is Ever Easy!

I soldered the bluetooth module onto the Mini60 at the five solder pads. At this point I installed the battery and shorted across the switch terminals to test ot. The Mini60 comes up ok and I can place it into PC Link mode but the module is not powered up. Turns out there is is no 3.3V coming in at the pad I soldered it to. I have removed the module and rechecked the voltage and there is no power. Sigh…

There is not schematic or PCB layout for the Mini60 but it is very close to the SARK100. I found 3.3V coming out of the USB chip but have not found how its piped to the second PCB. So work has stalled and I’ll have to check all the required signals by tracing manually.

Update 5/16/17: Ok I think I found the problem. There are three pads that need to have jumpers installed to connect the top board to the bottom board. These three pads bring in the UART RX and TX signals and the 3.3V to the pads where the Bluetooth module is installed. Will solder the module back in place and test later today. The instructions at http://www.die-jetzis.de/bt_install.htm indicated only two pads. Looks like there are several variations of this board. I have noted that several folks have reported issues with the  Bluetooth module not responding. This is the likely cause as it is not clearly documented. Here is the board and the three pads are just left of the BT module:

Photo May 16, 9 34 26 AM