Two meter 3-element Yagi

You get everything from the local hardware store, 20mm square pipe, 8 mm tube, 5mm stick, all aluminum and 1 meter in length. Some polycarbonate, butterfly nuts, bolts, wire straps and hot glue do the rest. The balun is a 1/4 and 3/4 lambda RG58u coax balun, all dimensions and positions of the reflector, radiator and director are listed here. Here are some photos.

Yellow is the reflector, blue is the radiator, red is director
Backside of the reflector
backside of the radiator
backside of the director
Frontside of the radiator
Radiator and coax balun
Frontside of the director

I’ve tested it once in the garden, the 857D said the SWR was fine, the radiation pattern of this yagi suggests a 16 dB front to back ratio. The 3dB beam angle is approximately from -35 to +35 degree, it could be nice for fox hunting on two meter. Also, it is lightweight: 700 grams.

Last update: 17-sep-2017.

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Bandpass filters

During the last lighthouse weekend in Ouddorp Zeeland we found out the hard way that there is a lot of radio and radar equipment in lighthouses; this resulted in high QRM levels on the HF bands, the noise floor on my FT-857D was S7 to S9 on the 80m band near the lighthouse. Also, radio operators next to one another on different bands interfere with each other. The advise I got was to invest some time in set of a bandpass filters (BPFs). I got a DIY filter kit from DG0SA. His BPFs are rated at 200W, they are traditional 3-kreis filters and you can get them for all amateur bands. I have built the 80m, 40m and 20m BPFs and this is what you get:

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The documentation of the filters can be found on Wolfgang Wipperman’s website
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In the end this is what they look like, it took me 12 hours to build three filters. Tricky is the L2 torroid which comes with a trap. You can adjust C2 with tuning capacitors.
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Performance of the 20m bandpass filter.
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Performance of the 40m bandpass filter.
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Performance of the 80m filter.

The insertion losses of the BPFs within the amateur bands is less than 1dB, and the crossband suppression of each filter is approximately 30dB, if you want something better than this then you need to build higher-order filters. I thought it was too much trouble for what I wanted. Wolfgang provides tuning capacitors to adjust the C2 capacitor, but in the end I did not use them. I did check the resonance frequencies and the filter characteristics with my VNA, without a VNA you need to find a friend to help you out.

Receiver test with the Yaesu FT-991

I tested the 40m filter on a weak station, an S1 station on the 40m band with the FT-991 directly connected to the g5rvj antenna (DSP filtering was off, no pre-amplifiers: IPO and no noise blanker). The BPF was inserted in the 50Ohm segment before the tuner that I use for the g5rvj antenna. Once you insert the BPF the S1 station becomes somewhat stronger, possibly up to 2S points. Reason is that the FT-991 is challenged by strong out of band signals that enter the receiver. With a BPF you make it easier for the receiver to select only that signal you are interested in, reason is that the BPF suppresses everything outside the 40m band. This may be an explanation why the signal to noise ratio is somewhat improved with the BPF.

Receiver test with the SDR: airspy / spyverter combination

The test is similar, but also more interesting because the SDR comes mostly with digital filtering, nothing else reduces out of band signals and it is expected that the SDR will be more affected by large out-of-band signals. The SDR combination is connected to my favorite active antenna that I describe here. The consequence of inserting a 40m BPF is illustrated in the waterfall plot below, we are centered on the high end of the 40 meter band.

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The black bar in the center of the waterfall plot is the BPF switchover point, the lower part shows the waterfall where the BPF is inserted, the upper part sis the waterfall where the SDR is directly connected to the active antenna. All other settings in the SDR# software (gains for HF, mixer, IF and the AGC are the most important parameters) are the same. So here we also see a gain of a couple of dBs, I measured 5 dB, moreover you can see that the intermods caused by strong broadcast stations is significantly reduced. This test works best in the evening when the 40m propagation is enhanced compared to the daylight hours.

Intermodulation products are likely to be reduced by inserting a BPF before the receiver, the plot below is the same as others here, the lower part is without the filter, and upper part is with. The intermodulation product of a broadcast station is indicated by the yellow arrow, and it disappears when you insert the filter.

Presentation1

Last update: 6-sep-2017

Fieldday 31-jul-2017

On 31-jul I was in the field, a CG3000 tuner and a wire round around the mast up to the tip. The ground connector of the CG3000 goes to three 10 meter radials. Benefit of this set-up is that you are QRV on all bands from 160 to 10m. The CG3000 can handle up to 200W, the FT-857D produces no more than 100W. Use 10W AM to activate the tuner.

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12,5 meter glass fiber mast
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use the chair for the radio
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CG3000 tuner and three radials
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this is what you need to carry

Last update: 13-aug-2017.

800 Watt 1:4 Balun

The site of DG0SA Wolfgang Wippermann has a large collection of baluns. I replaced the 1:4 guanella balun with the 800 Watt 1:4 balun designed by Wolfgang, goal is to be able use it for higher power. Two ferrite cores are used, the first is a common mode filter to go from unbalanced to balanced for undefined impedance, the second is a 1:2 voltage transformer. I used volcanic wrap tape to isolate the leads between the transformers. As you can see in the images below, PVC tubing of 75 mm is well suited as housing, so this is what you eventually get:

And this is what is inside, the wiring is PTFE AWG18, so teflon coated rugged litze which is somewhat difficult to wind. This was the last view before I glued the cap on the side of the SO239 connector.

And this is a similar view at the other rise, I used plastic and metal rings to keep any water and debris out of the housing. Prefer to leave the cores loose in the tubing, the may generate some heat, once installed it does not move, could be done better but I ran out of ideas here.

And this is what the SWR looks like when I measure it with a 200 Ohm resistor terminated at the end of the balun.

Last update: 2-Jul-2017

New HF antenna

The last month I worked on a new HF antenna, there is no space for anything fancy in our garden, but one thing I could improve is the height of the antenna at the side of the house. For this I installed a mast right of the bathroom window for which I needed to put mounting brackets in the wall. It looks like this and it required me to drill 12 mm holes for 5 expansion bolts for which you need an SDS+ drill (the older drills only go to 10 mm diameter):

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Next is to install the mast, it consists of glass fiber army mast parts that you secure together with aluminum tubes and hose clamps. Four mast parts are put on top of an aluminum part that is clamped in the antenna mounts:

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The new mast
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The antenna is a G5RV junior, I could not fully span it so there is one arm going sideways to the roof of the garage block.
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Looking up under the mast, the matchbox is a 1:4 current balun, the coax-cable goes back over the roof under the roofing tiles to the shack.

What comes out of the antenna is 450 Ohm twin line that goes in the 1:4 guanella balun. For this antenna you need a tuner, and since I didn’t have anything free for this I used the T-match tuner that I built last month.

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The noise floor of this long wire antenna is substantially better than the CG3000 long wire running to the aluminum support mast at the end of the garden.

Tuner settings for this antenna

Freq         L     C1     C2
3603   16,25     +5    -45
3777   10,10   +90    -10
7080     3,50   +45    -20
7130     3,30     +0    -30
7160     3,25     45    -45
14195     1,50   +20    -45
14255     1,50   +20    -45
14310     1,60   +45    -45
14305     1,60   +45    -45
18130     1,50    -45   +45
28300     1,33   +80     +0

So the conclusion is, you can practically use this antenna for 40 to 10 meter, for 80 meter you have to be careful with the inductor, but it can be done, NVIS on 80m was fine up to 200 km away with my set-up. But probably the inductor will dissipate most of the power on the eighty meter band. Another thing is, tuners need to be in a closed case because the capacitors should not spark because of dust etc. What it also proves is that my two ring guanella 1:4 balun does work fine between 3 and 30 MHz for a power up to 100W. For higher powers I probably need to look at a larger ferrite ring.

Last update: 9-jun-2017