Sunday, June 17, 2018

6m vertical on the tower

Placed the 6m/UHF/VHF Watson W2000 (Diamond V2000 clone) antenna in the mast this weekend. It is not on it's final place but so far on top at 16m height. Didn't have much time to play with it though so really don't know how it performs. SWR is the same as on the low 6m long mast. I did receive a 4X4 (Israel) station on FT8 and some europeans. As soon as I made a CQ on FT8 I was spotted in Spain, Denmark and Germany. At least I made one QSO with a station in Germany. I don't think there was much ES at that time...however 6m can open within 10 minutes and close in the bext 10 minutes. Propagation can be very local, it is possible I work DX and a station 50km south of me does hear nothing at all. 6m is a strange and unpredictable band. And because of that it is attractive to radio enthousiasts.

I have changed my shack setup a little. Had to find a place for the rotor controller. Besides that you see 3 switches on the right side. Switching the digimodem, audio NIR-10 filter and a antennarelay at the bottom of the mast. Missing the voicekeyer in the picture since I didn't use it anymore so sold it. Well, the Icom IC-706 looks a little small in that space. Hopefully I will replace it by a IC-7300 in the future. The extra connectors you see are the jack plug for the footswitch and the mini DIN for the computer voicekeyer.

Next step is to install the 5 element 6m ZX-Yagi. I'm cleaning it and have to make some repairs. Hopefully I find some time to install it in the mast this week.

Friday, June 15, 2018

Lucky me!

Still busy with the tower. Arranging the radioshack desk and all the wires and coax cables. I need another lay-out on my desk as I have to add the rotor controller. But first of all everything needs to work before I will do a final install. I finally connected the rotor cable through a 13 pole trailer connector so I can disconnect as soon as there is a thunderstorm approaching. However, nothing worked at all. The nice green light came up and then the pointer stuck. Remember my Kenpro overhaul last year? I changed the scale and forgot to glue it, imagine what happened after a couple of months. The paper absorbs moisture that is always in the air and it will get slightly larger and so it did bulge. Had to correct this first. After the pointer could move freely I thought of how to search for the fault?
Actually it is very simple to measure a 8 wire cable like my rotor cable. Just
connect DC voltage from your PSU to the wires and measure at the other end. So, I connected the + to wire 1 and then moved the - from 2-8. Of course I had to walk all the way to the tower to measure at the other end. Anyway, when I arrived at wire 5 I had no 13,5V, same with wire 6,7 and 8. To make a long story short. It seems the pin-out of the male and female trailer connectors are not the same. That's why I hate those 13-pole connectors I think. After that was corrected the rotor rotates fine.

So, why the title then? I didn't feel that lucky when I was searching for the fault describing above. It did take hours before I finally found the connector problem. Still I feel very lucky.......look what I got for free:

A well known GPS company changed cables at my job a while ago. Since the old cable was going into the garbage bin after it was damaged a little I asked if I could have it. That was no problem. And indeed the sealed TNC connectors were damaged and there were some minor holes in the insulation here and there. It is about 29m (95 ft) long and would fit between my shack and the new tower for covering 90% of the distance. Now, I covered the holes with insulation tape and since the cable was used inside a building I expect no damage or very minor.

The MFJ-259B showed 1 dB loss @50MHz. The online loss calculator tells me 0,9dB loss @50MHz is normal. So, I guess there is nothing wrong with the cable at all.

Time to compare loss at several other amateurradio bands. Measured with the MFJ-259B and compared to the calculator.

MFJ-259B: @50MHz: 1dB, @28MHz: 0,8dB, @21MHz: 0,7dB, @14MHz: 0,6dB, @7MHz: 0,5dB, @3,7MHz:0,4dB, @1,8MHz: 0,2dB

Factory calculator: @50MHz: 0,9dB, 28MHz: 0,7dB, 21MHz: 0,6dB, 14MHz: 0,5dB, @7MHz: 0,3dB, @3,7MHz: 0,2dB, @1,8MHz: 0,1dB

The differences are small. And of course different from each other because the factory is calculating the losses and I measure them with a meter that is not calibrated. However it comes close and it shows this is a very low loss cable which I will use for 6m/UHF and VHF. This cable is not really interesting for HF I think. H2007 might have a little more loss but you hardly notice that, at least I hope so.

Now continue working on the tower and shack before the ES season is over....

Tuesday, June 12, 2018

Superantenna MP-1 modifications and experiments

Some years ago Hans PE1BVQ bought a Superantenna MP-1 after seeing mine. Especially the compact size of the antenna when travelling was something to go for and of course how the antenna performed. At that time we exchanged some e-mail about the length of the antenna and how to get a even better performance out of it. We were not alone and it has been tried before. But we are both stubborn radioamateurs and never believe what others tell till we have prove it ourself.
Besides that Hans was on vacation in my area and it's always fun to do some experiments together.

These days you can find these antennas at Remember we bought ours long before this site even existed. You can buy so many gadgets for this antenna these days. So, it is a good product. I bought mine second hand from a english HAM (M6RDP) who was very active before but only does SWL now. That was almost 10 years ago and still the antenna does well.

The experiment goal was to determine the effect of length on the signal, receive and SWR of the antenna. Theoretically current in a antenna is high at the bottom, so the coil needs as high as possible for higher efficiency. We are not the first ones that tried this. You can read all about this shootout here.

First of all we did a test with WSPR. Hans his vacation QTH is about 20km south of my QTH. So we tried a quiet 10m band to conduct a experiment with a normal and a longer MP-1 and finally compared with a vertical polarized endfed. All transmissions were done with 1W. The first 2 spots are before the experiment. I was the receive only station. We kept a log via whatsapp (modern times ;-)).

See WSPR reports on 10m. 19:16-19:24 are with the original MP-1 (2 rods below the coil). 19:34-19:38 are with the shortened MP-1 (1 rod below the coil). 19:54 and 19:54 are with a 7m long endfed on the ground. What you see is actually no difference. That's because WSPR is not a good tool to measure difference between antennas. Propagation/conditions may differ too much during testing. However, it was a nice experiment.

MP-1 long/short. 1W WSPR signal as received at PE4BAS over 19km
This experiment might not bring the result we expected but we observed other interesting things. For instance removing one rod below the coil does not change the SWR much.

Hans his vacation was almost over last week and as he planned to visit me at home we decided to do a fieldstrength experiment with my MP-1. So after a good cup of coffee we setup the MP-1. Hans brought his analyzer so we could change bands fast.

We decided to measure at 14MHz first as being approx. the center of HF bands covered by the MP-1.

(Click on the photos to view a larger one). At first we tried 3 rods below the coil. A reading of 2,5 stripe on the FSM. With only rod it is 1,5 stripe. There is a difference but it is not that big. How many dB it is? Wish we had better measuring tools. But at least we showed there is a difference. We expect with the original 2 rods the reading is 2 stripes. It was interesting to see the SWR hardly changed with 1 or 3 rods below the coil, something we didn't expect!

Next we tried 40m as we expected to see more difference because of the band length.

You hardly see 0,5 stripe difference between 2 rods or 3 rods. 1 rod is not possible because the antenna is too short then and you can't get the SWR right. So, actually if compared with 20m it is the same difference. It probabely has something to do with ground losses I think.

It was already near sunset when we decided we quickly should have a test on 10m as well to complete the experiment.

Fieldstrength looks larger now but that's just because of the frequency. Probabely the diode picking up the signal is more sensitive here. Besides that the antenna length on the FSM is more efficient on higher frequencies of course. You see a larger difference now, But still it is only a few stripes.

Well our conclusion is that making the antenna larger with a 30cm rod will add some more gain but it will not be noticed at the receiving station. It is more a psychological thing thinking that bigger is always a lot better. However we didn't test it on receive. For that we would need 2 MP-1 antenna's and a switch. A experiment we could do probabely next year?

Did we prove anything new? No, but it was interesting though and a nice experiment to do together. There is another experiment that I want to do. It has to do with the feedpoint impedance of the MP-1. DD7LP claims that there can be a 20% improvement in fieldstrength if you use a beta match at the feedpoint to match the impedance to approx. 50 Ohm. He does this with a 1 microH coil connected parallel to the coax at the feedpoint.

Find the experiment (in German language) here:

To end this post I inserted a photo from both Hans and my FT-817 after sunset. Hans FT-817 looks a little odd as it felt off the stairs and he removed the broken screen protection. You get a complete other colour backlight then and a bigger screen.