Shack RF&Safety combined earth

First of all, the subject grounding is controversial. Some say it's a need in your shack, some say the mains earth is good enough for safety. Since I use a safety transformer in the mains to supply 230V to my shack a mains safety earth is not working. So I made a separate earthrod outside the shack and connected it to the connectorpanel just behind the outside wall. Now this is just for safety, it's not a HF earth. However I am an experimenter and would like to test a HF earth, if it doesn't work I can simply disconnect and nothing is lost. 

I wrote about this subject before:

The RF surpression ground system myth
Making a second floor shack ground

The common way a RF or HF earth is made I think is explained in the figure above. To prevent earthloops everything is bonded to a single grounding point, however in my opinion you still create groundloops like this. The actual earth are the counterpoise wires that are 1/4 wavelength long for each band one or more (not really necessary if you use a balanced antenna). The star point could be connected through on of the counterpoise wires or better with a separate ground strip for safety.

Now in my case a problem with a earthloop was rising between the connectorpanel and the earthpoint in the shack which is best bonded to the last item in the coax chain, the antennatuner. Since the coax is earthed to the chassis of the panel a extra groundstrip would led to a groundloop. But I have the connectorpanel for safety, when the coax to the shack is unplugged the antennas and outside coax cables are grounded through the panel and I hope I'll not get dangerous high voltages on my equipment chassis when a lightning storm is nearby. So I made a two-way knife switch to choose between the shack earth and the panel. That way I will not create a earth loop. I don't really know if it is all worth the trouble, but at least it gives me a trustyfeeling when the counterpoise is grounded for safety. (I removed the switch in 2018 as it is always bonded to the connectorpanel)

Now some of you will think....why a counterpoise? That's only working when you have some sort of  impedance problem with a unbalanced antenna. A simple balun grounded near or on the antenna works ten times better. Oh, yes indeed that's true. But actually my RFI is related to my balanced 84 Mtr horizontal loop fed by a 450Ohm ladderline which I have only up in the winter and is used on all HF bands through a Palstar antennatuner. Actually I don't need a counterpoise with 1/4 wave length wires, but that's what still had from previous experiments. The goal actually is to bond as much metal in the shack to the common grounding point to get a equal potential on all equipment when transmitting. More information about this can be found on the website of W8JI. Best would be a conductive grid on the floor below the carpet or so, I will make that in the future.

Just for the record, normally you don't need this. Most shacks don't need a HF earth at all. A safety earth is more then enough. However if you have a antenna very close to the shack it could help against RFI. In my case I do have the horizontal loop in winter very close to my operating position (2 meters distance) and have som RFI into the the headset, deskmike and computerscreen when operating on 17m and 15m. Very annoying and I hope this will partly solve the problem. Only time will tell.

Left to right: Knife switch in relation to the panel, Knife switch in shack position,
Common grounding point, large grounding strip.

Loop up! Some pictures.

The start of the contest season was made with the CQWW DX SSB contest. Now some local contests are coming up. The first one is next weekend as the PA-beker contest is on. Since I need to go to the job I haven't got time to setup the NVIS horizontal loop this forthcoming week. So since the weather was excellent this weekend I planned it for Saturday. But things went different and luckely I had some hours at sunday. It was really great weather for antenna work. Actually never had this good weather before setting up the loop. Here are some pictures.

Het contest seizoen is weer begonnen en een goede start werd gemaakt met de CQWW SSB. Nu komen er eerst 2 lokale contesten. De eerste is komend weekend de PA-beker contest. Omdat ik de hele week incl. zaterdag moet werken en de rest van de week geen tijd heb moest het opzetten van de NVIS horizontale loop dit weekend. Ik had het op programma voor zaterdag maar de dingen liepen anders. Gelukkig had ik zondag nog wat tijd en was het weer prachtig. Eigenlijk heb ik nog nooit zo mooi weer meegemaakt tijdens het opzetten van de loop. Hier zijn wat foto's.

3 antennas in a row. Vertical, HB9CV, loop. Notice the free sight to the south.

The feedline I believe 450 Ohm

The complete loop incl. feedline on a roll.

Made the feedline a little longer as last year, see how near it is to the shack.

Feedpoint from a side.

Test HB9CV without cap

Oh yes, there are a couple of DXpeditions on and forthcoming that I really want to work. This is possible especially on the 10m band. But I need a better antenna and time to work them. Last monday I had limited time like always. Need to do some more painting on the house and all left me a few hours to experiment with the HB9CV. Luckely the weather was dry and a reasonable temperature. I first made a better connection between the boom and radiators. Then I experimented with the "gammamatch" till I had the best impedance possible. Tested it again in the shack and was not satisfied yet. Best SWR was on 27,9 MHz now and 1:2,5 on 28,5. I decided to make all elements 2cm shorter. A good gamble as the best resonance and SWR is now on 28,1MHz. At 14UTC I though I had to get my harmonic Anneli from school (a one minute walk) but asking my XYL it should be at 14:15. So I had 15 minutes to mount the beam on the mast and get it up to see how it does. I did manage it in 12 minutes. Then I did a run to the shack to see if SWR was right. It could be better, best SWR on 28MHz now 1:1.3 and rising to 1:2 at 28,5MHz with R=38 and X=6. A perfect antenna doesn't exist, but it  is good enough to get 100W out of my radio. I turned the radio on which happened to be tuned near the VK9XSP frequency. Had to turn the beam to east, VK9XSP was S9 and calling CQ up 5. Called once and was in the log. 14:14 now, 14:15 at school to get Anneli home. ATNO worked VK9XSP Christmas Isl. That's what I really like in the radioamateur hobby!

Now, later in the afternoon I wanted to make a video to show you the difference between the vertical and the HB9CV. As well as testing front-back-side ratio. Oh yes, there happened to be more DXpdeitions coming in real strong on the HB9CV. Easy as that I worked Madagascar 5R8M not a ATNO but a new one on 10. After that I worked FH/F4FET from Mayotte a all band ATNO. Wow, the HB9CV works again and does a incredible job. I'm always surprised how good this antenna works for the size it has. I'm ready to work the DXpedition of the year FT4TA on Tromelin Isl.