Category Archives: ham radio

Weller 9400

I typically use a soldering station as most of my previous soldering needs were largely soldering PCB. Soldering RF connectors and the like is quite another story. I invested in a Weller 9400 soldering gun this past weekend:


Wish I had gotten one sooner. It heats up in about 10 seconds and makes short work of soldering PL-239 connectors onto coax. It is very convenient to just plug in and use.



Measurement and Comparison of Common Mode Chokes

I have several common mode chokes in the shack today that I wanted to measure and compare against each other. This seemed like a good application for the low cost VNA I bought a couple of months ago. The setup is shown on the N4SPP website. Only the shield oif the chokes is connected to the center pin of each VNA input. The sweep is done in Transmission line mode and the result is Transmistion loss and phase. This was run after a calibration sweep using a short. I has some concerns over the overall accuracy but the results relative to each other is a good start for comparisons. The chokes I measure are two ugly baluns:


12T & 14T of RG-8X on an FT240-43 Toroid:


A 1:1 balun kit I ordered and made off of Ebay (after being outdoors pretty ugly in its own right):


and finally the guts of a MFJ-915 line isolator. I say the guts because the isolator originally was encased in PVC pipe but the connectors were off center and did not allow installation of the mating connector. I cut this off and wrapped the connectors in silicone tape.


This graph shows the resulting data on sweeps from 3Mhz to 15Mhz:


Overall, looking for damping in the range of 25-30 dB. At first glance all of these chokes all look about the same with the exception of the MFJ line isolator which although relatively flat has readings over 20 dB. G3TXQ has a great write up on the choking resistance. He notes that an issue with the “ugly” balun is that their impedance is almost entirely reactive with the exception of a small band of frequencies around resonance.

“Reactive chokes have the disadvantage that they can “resonate” with a CM impedance path that is also reactive but of opposite sign – in some cases actually increasing the CM current flow rather than choking it.”

I removed the ugly balun and replaced it with the 14T Toroid Choke at the feedline and added a 12T Toroid choke at the IC-7300 antenna input with a 1 S unit drop in the noise floor noted. I will replaced these with mix 31 toroids of the same size which should give a flatter, broader response below 15 Mhz. I also have a 1:1 balun on order from Balun Designs for use at the feedpoint. I’ll take some measurmeents on these and post and they become available.

Lowering the HF Noise Floor

Previous posts have reported on WSPR performance with my vertical antennas especially compared to data collected by a nearby Ham (Cliff – N5CEY) with a similar antenna setup. The metric is how well a given antenna receives unique spots over a 24 hour period as documented by the WSPR Challenge site. I have always seemed to lag behind Cliff’s receive performance in spots and in DX received. I have asked Cliff about the specifics of his setup and came to the conclusion that he has a significantly lower noise floor at his QTH in the country versus mine in the city. Cliff’s QTH is about 12.5 miles north of mine in a rural area. He is closer to the coast and likely has much better soil conditions as well. His antennas on WSPR are all 1/4 wave verticals on 40m, 30m and 20m. I have an “ugly” balun installed at the feed point of my vertical and about 30 feet of RG-8X to the shack entrance. There are about 8 loops of coax at the shack entrance. Inside the shack are various patch cables connecting switches, antenna tuners, SWR meters and the Timewave ANC-4 to the IC-7300. Lots of nearby noise sources including PC’s, cable modems, wifi routers etc.

So the task before me is how to lower the noise floor at my QTH to bring in weaker signals. I have done quite a bit of research and finally came upon some discussion of the effects of Common Mode currents on noise floor. My next post will detail some measurements on various common mode current chokes but for now suffice it to say that changing my common mode choke arrangement has had a positive effect on the noise floor. Here is what I did:

  1. Added a CMC consisting of 12 turns of RG-8X around a FT240-43 toroid core right at the IC-7300 antenna connection. This resulted in a 1 S (6dB) unit reduction in the received noise!
  2. Replaced the ugly balun with a choke as above. No significant change noted in noise floor.
  3. Replaced 30 feet of RG-8x feed line to the shack with 30 ft of RG-213 coax. No significant change in the noise floor was noted. this change should help in reducing losses though.

Adding the choke to the antenna input made a big improvement in lowering the noise floor. I adjusted the Timewave ANC-4 to further try and negate any remaining noise.

So the results are as follows after 20m WSPR was run for 24 hours:


Pulled ahead of N5CEY by 8 unique spots and made the DX list still lagging a bit behind Cliff. Here are my spots during this period (right image is Cliff’s and the one on the left is mine):

2018-03-18 (1)2018-03-18

So all in all a significant improvement by addressing Common Mode Currents. More on the Chokes in an up comming post.


The S9V31 is Working…but How Well?

I have been trying to collect some solid data on the performance of the S9V31 antenna configured for multi-band operation. It is currently configured to be non-resonant on any band and I go through an antenna tuner in the shack. WSPR results have been lackluster and possibly a little worse than when run as a resonant 40m antenna. FT-8 spots on on the other had have been quite good on early morning 40m. I am being heard all along the western Pacific rim consistently.

I have noticed quite a few stronger European stations in the late afternoon on 20m and have made several SSB contacts. I actually closed four all time new ones this week: St Eustatius on 12m, Republic of Congo & Easter Island on 17m, and Revillagigedo Island on 20m. Interesting that 12m and 10m have had brief openings in the late afternoon. Band conditions have been pretty bad with long periods of zero sunspot numbers.

I am still working on what to do to lower the noise floor at the shack. I feel that is the key to improve station performance and should be readily visible when running WSPR. More on that coming up….


The Alpha Antenna S9v31 is On the Air

After a full year of experimentation with vertical antennas I finally deployed the Alpha Antennas S9v31 antenna. It was a perfect day here for it as well. Mid 80’s with very little wind. A bit muggy for the work on the radial field but otherwise just a beautiful day in South Texas!

First up was finishing up the radial field. I set out the radial plate with 20 radials with lengths that vary from about 10 feet to just over 25 feet. The back breaking job was installing the lawn staples to hold them down. Tedious but straightforward. The yard was freshly mowed and I had tested three long radials and found no issues with the mower. Here is the finished radials:

Next I removed the 20m vertical element and finally lowered the SOTAbeams travel mast. This mast took a great deal of abuse over the past year or so and all told is still in serviceable shape. I highly recommend this mast!

The setup of the S9 was really simple. The mast is extended on the ground and a set of clips installed at each section joint to prevent collapse. The radiating wire is inside the mast. Once extended it is walked up and I mounted it onto the same aluminum angle I used with the travel mast. The hook ups remained the same with the junction box and ugly balance used before.

Here is the finished product:

I am running WSPR on this now so will report on performance after I collect some additional data.

Some Clarity on My ARRL DX SSB Post

The previous post discussed my operations on this year’s ARRL DX SSB contest which I really need to update on. I have recently started using SH5 log analyzer software to bring up some statistics on my operation. The actual final result works out to 95 QSO’s, 45 countries, 19,044 points and 5435 km /QSO average distance.

First up is a map of all my QSO’s across all bands worked (40m-20m-15m-10m):


Here are the QSO’s per time of day:


Here is the distance Histogram:



2018 ARRL DX SSB Contest

Worked the ARRL DX SSB contest this weekend and managed to get 100 contacts over the course of the past 48 hours. I did not operate to aggressively but did operate with spotting assistance. I worked 46 countries on 40m, 20m, 15m and 10m. 34% were in North America, 30% in South America, 16% in Europe, 7.5% in Asia and 10.8% in Oceania. No contacts in Africa this year. None of the worked countries were counted as new ones. All in all not bad and a lot of fun considering the band conditions were pretty bad (SSN=0 SFI=67). North America was dominated by 20m, South America with 15m, Europe on 40m, Asia split evenly on 40m and 20m and Oceania also split between 20 & 15m. All in all 20m was the more difficult band to work with many really weak signals heard here at the QTH. 40m comes alive in the early evening into Europe and Japan in the early morning. 15m had less overall activity but had many strong signals from central and South America. My score works out to 22,572 with 100 QSO’s. The DX stations responded with power of 1000W about 90% of the time with the lowest power as 100W. Good test of the vertical 1/4 wave antennas!

Fishing Pole Fail

I recently sourced three longer fiberglass fishing poles from Ebay that gave me a fully extended length of 5.9m. I have been using two of them to hold up my 20m half square. Went to check on it this afternoon and found that the lower section had cracked and snapped. Disappointing as the other poles I have been through major abuse without failure. Either a testament to the manufacturing quality or to the strength og the winds around here lately.

40m 1/4 Wave Re-build

I took down and rebuilt the 40m 1/4 wave vertical this past Saturday. I am using the same mast and vertical radiator as before but I have added the radial plate with 20 ground radials. I replaced the coax pigtail with the small vertical junction box I had been using previously. Overall, glad I made these changes as the connections were getting rusty and there was clearly some water getting into the feedline. I will start working to pin the radials down so I don;t have to pick them up when m,owing the lawn. I also plan to put up the 20m vertical element as before so I can have a resonant antenna on 40m, 20m and 15m (3rd harmonic of the 40m). Once the 20m vertical is up I can use it for A vs. B comparisons with the 20m half square. Also looking at a shortened 80m vertical to add to this set of “fanned” verticals.

The 20m Half Square is On the Air

It took several days of off and on work to debug the problems with the EFHW matchbox. I had to disassemble and rewire this several times before finding the issue. I noticed initially that the toroidal inductor seemed sensitive to motion. I ended up completely rewinding the coil then used some hot melt glue to pin down the winding.  Ultimately the problem was with the capacitor. I ended up modifying it so that the capacitance range was maxed out. Seems to be working now and the antenna tuned to 2:1 SWR across all but a small portion of the CW portion of the band. I made some SSB calls and completed the QSO’s however the signal reports were in the 56 to 57 range. I am running WSPR now and will collect some data as a comparison.