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

Manual antenna tuner

29-4-2017: The antenna tuner is something you can do yourself, variable capacitors, roller inductor and knobs are all used components and they come from the Rosmalen radiomarket. The case is from CONRAD. Unfortunately there is no step counter with the inductor, but it has a stop which you can feel, so just count the left hand turns.

The antenna tuner (also called matchbox or antenna coupler) is a T-shaped network, the inductor does something like 35 microhenry (and probably more), and the capacitors are 30 to 300 pf. I mounted the components on wood because they need to be isolated from the metal case. Straps keep them on the board, and rubber thules are used to isolate the components from the metal case.

Performance-wise this tuner is able to adapt a 200 dummy load to 50 Ohms between 1.8 MHz and 30 MHz, I checked this with my antenna analyzer, it works. There is still space to store a 1:1 or 1:4 balun if needed (see entry on 7-5-2017 how I solved this). I’m not sure how much power the tuner can dissipate, the heat could go in the inductor, or, the capacitors could spark, etc. These capacitors are rated for 1200 Volt, so maybe we can go up to a kilowatt. (hi) (see the entry on 4-5-2017 that discusses where the dissipation could occur in the tuner)

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Added on 4-5-2017, a note:

 

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7-5-2017: Added a 1:1 balun to be able to handle twin-lead lines. Glue, polycarbonate, green tape, some banana jacks and an extra SO-239 case part do the job. The balun is separate from the tuner, you need a patch cable to connect the output of the tuner that goes to the right most SO-239 connector to the left most connector which is the input of the balun. The input of the tuner goes via the middle antenna connector. The balun is nothing more than a common mode filter. The magnetic field lines will stay inside the ferrite core, and any forward magnetic field leaving the tuner will cancel against a returning current that has an opposite magnetic field. This will work fine up to 30 MHz which is the design area for ferrite (it is a 4c65 material), beyond this point you need another trick to design your balun. I added some green tape around the 4c65 core although it is not strictly necessary, on both sides you glue two pieces of polycarbonate and with two parker screws you attach the balun to the aluminum back plate. Check the end result with an antenna analyzer and a multimeter.

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Bill of materials:

  • three SO239 connectors, (relatively easy to get via stores in Rotterdam or Delft)
  • a 300 by 200 by 100 mm aluminum case (difficult to get, consider CONRAD)
  • two banana jacks and the matching case parts (a store in Delft had them)
  • a 4C65 ferrite core, you need it for HF and it shouldn’t saturate below 1 kW (got it from dx-wire in Germany, see also my article on the 1:4 guanella balun)
  • two 30-300pf variable capacitors (got it from a hamradio market)
  • roller inductor (got it from a radio market)
  • wooden ground plate, cut it as required
  • three tules, three knobs (hamradio markets have them)
  • 0.8mm or thicker copper wire (again, the ham radiomarket)
  • 30 cm of 50 Ohm patch cable with two SO239 connectors (I found a store in Rotterdam that I refuse to reveal, it is the only one in town, otherwise, CONRAD or radiomarkets)
  • various M4 nuts and bolts and straps (via any hardware store)

Options to consider: possibly an integrated SWR power meter, this is what I currently solve with a separate AV-CN600 cross-needle meter. The schematics is well known, however, I could not find a cross-needle microamp meter, the electronics is not very difficult, perhaps the calibration is.  Also, many transceivers already have a SWR/Power meter, so perhaps you can skip this step as well.

Last update: 7-May-2017

Field day with FT-857D

Got a second hand FT-857 last week, you can’t tell from the printed label whether it is a FT-857 or the D or the ND version, and also there are options like a TCXO and various filters. This one seems to be the D version because it has 60m and it has DSP filtering, and the CW filter is clearly there although I probably won’t use it. The receiver performs like a charm, maybe it seems somewhat noisier than the FT-991 but, if you play around with the RF gain and the filters, and if you listen on the headset then it is a very acceptable transceiver. No ATU, so your antenna SWR needs to be under 3 (probably), but to be honest, it is not very difficult to tune the antenna with a separate analyzer. Already did this for the vertical whip for 20m so I took the FT-857 in the field and made some QSOs.

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FT-857 on the dashboard, it ran for 1,5 hour on a 3S lipo and I made a couple of QSOs. When the 3S lipo goes below 11.4 Volt I normally stop.
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The whip got some tie wraps to prevent collapse, as you can see the weather was somewhat chilly, as was the 20m propagation on the 14th of April.
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I modified the magnetic suction clamp from MFJ and added three radials, and a choke balun. For 20 m my car roof is not large enough to form a decent counterpoise, with the radials it works fine. The farmer did not care whether I was there with the car, we had a chat about his smart dog and antennas.

I like this set-up for in the car, it is easy to do, easier compared to getting the FT-991 in the field. The 857 fits on your dashboard, everything (cables headset, mike, ropes) fits in one suitcase, with the 991 I end up carrying at least a bag next to the suitcase. Getting my tuner to work with this set still needs some work, the LDG YT-1200 is designed for the CAT interface, and not a CAT-IV interface, so I need a conversion cable and some conversion electronics.

Last update: 15-4-2017

Field day 2-April-2017

Two blue sky Sundays on a row, so I had to go outdoor with the radio.

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1:1 balun (diamond BU-50) mounted directly under the top mounting point of the guy wires, this prevents sagging of the glasfiber mast. Mounting it above this point is no success.
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Purpose of the day was to tune the 40m dipole, in this setup it is an inverted V with the highest point approximately 8 meter above the ground. Within 3 iterations I had found an SWR below 1.3 for the entire 40 meter band. You don’t need any tuner.
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The mast looks better I think than last weekend.
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The 40 meter conditions were not splendid, and there was a SP DX contest, I just made 3 QSOs.

Last update: 2-April-2017

Field day 26-Mar-2017

The challenge is, arrange yourself in such a way that you can hike for several km, carry a GFK mast, a 100 Watt transceiver, batteries, cables, tuner, and all antenna material without the help of anyone. Today I came close to this, I had a suitcase and a separate bag, and a mast attached to a tripod. It is not comfortable hiking, but it worked.

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20 meter antenna, 3 radials of 10 meter, and a MFJ 1979 vertical
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GFK mast with an end-fed 40-20-10 meter
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A bag, a suitcase and a mast+tripod
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Blue skies, guy wires and antenna

Last update: 27-Mar-2017