Thursday, 21 July 2016

​After nearly two decades, a spy "numbers" station is back on the air

Actually this is "old" news but I'm surprised no other blogger has picked it up yet.

I was unable to find a youtube video or any other recording of their "show" from last Friday. I'm shure it exists. If anyone knows, please let me know and I ad it to this post.

However, it's puzzling why they started to send coded messages via the old medium radio again as it's easy to send coded messages via the internet these days. It might be they lost contact with one or more secret agents? Another approach is that they just want to scare South Korea to show them they still have spies around. 

Saturday, 16 July 2016

Vertical antenna rebuilt

I collected all the neseccary ingredients for this simple upgrade from Alu tape antenna to Cu tape antenna. Now, this monday was the right time and coorperating weather to disconnect te vertical and rebuilt it with the I-max 2000 as base. Before I started I made a photo from the field strength at the shack on 15m I expected a increase with the "new" antenna. I was wrong but I think I know why. More about that later.

When I had the old antenna down to dismantle I now had the possebility to inspect it closely. Actually in 7 years time it had been damaged so much that there were holes in the insulation especially at the top part. Even the copper wire was broken at one point. The antenna obviously suffered a lot from the weather.

 It is a miracle I still could make DX with this antenna even with QRP! Since there were holes there was water inside which resulted in heavy corrosion of the tape were it touched the copper wire. Of course I know copper and aluminium are not good together when air can reach it. But since a aluminium wire was hard to find I had no choice. At least it did hold for several years.

I dismantled the antenna and built the "new" one. The I-max is a very flimsy antenna compared to the size. Actually I hope it holds this winter and with the large winds that always come up once or twice a year.

Anyway, the tape was applied on the antenna and just to be shure I taped a copper wire on the first layer of tape again. Everything was taped in with insulating tape. That's a lot of tape isn't it ;-)

Actually everything went smooth. Till I had to fasten the radials again, it started to rain. Rain is something we get a lot this year. It is probabely a forecast that the next half of the summer will be very dry, we'll see. Back in the shack I noticed SWR on all bands was close to perfect and below 1,5:1. Looks good, so now a look at the field strength meter on 15m. The needle dropped? Strange I expected a improvement. I moved the field strength meter away from the radio and it went "dead" no reading at all. I probabely measured a radiating coax cable? Or I measured radiating radials as the old vertical was in such bad shape that it almost couldn't radiate anymore? If anyone knows better?

Well, I'm just a antenna experimenter. I like to experiment with unconventional designs. I don't know much about antenna theory and certainly am not a antenna expert. Actually I'm just doing it for fun, to learn something from it and hopefully it works out. I tested the antenna in the afternoon and noticed I was spotted in Paraquay on 17m and in the USA on 20m. Received stations from Japan on 20m. I made some contacts on 20, 17, 15 and 10m and it all works fine. Propagation was not that good at the start of the week I think. I used PSK and JT digimodes for the test. Listening on SSB before going on digimode I heard nothing on those bands! A strange experience!

I had some time to do more tests in the next few days and was not disappointed although propagation was rising. A amazing 17m JT65 QSO with BD0AAI from China wednesday evening into a dark path doesn't happen to me often. His signal was very good actually, could it be longpath? At the same time there were conditions to South America, excellent signals from that part of the world...Thursday evening I read PC4T's post about the quote from K2WH "bands are only dead if you believe they are". So I started calling with JT65 on a "dead" 10m band and immidiatly got response from IZ2NAB and later from UB6AAK. Signals were weak but it was not bad for a dead band. Again confirmation that the antenna works especially for weak signal communication, something I really love in this hobby.

At the moment I only tested with digimode. Through the week I have been listening on SSB but hardly heard any interesting (DX) station although digimodes showed propagation was there. I probabely have to wait for a nice contest to really test the antenna out. The results so far are promising. Of course it is not as good as a (3 band or more) directional antenna. I think it can be compared with a endfed antenna although this one can match to about 50 Ohm everywere from 1,8 - 30MHz, a real multiband vertical.

Friday, 15 July 2016

Guest post: Interference from a LDG Z-817 autotuner

This actually is a guest post from PE1BVQ Hans. Hans did suffer from heavy noise (S9) on his FT-817 affecting his receive especially from digital weak signals like WSPR and JT modes.

By coincidence I discovered that the noise on my FT-817 with the laptop connected only appeared when the CAT cable is connected through the LDG Z-817.

When the CT-62 CAT interface is connected
directly to the radio the noise disappeared. When searching for the problem I noticed the noise came up even when I touched the Z-817 connector with the CAT cable connector, it was not even plugged in!

The noise disappeared when connecting the PL259 chassis to the earth of the CAT connector. This problem never occured to me as I use the Yaesu FT-817 + LDG Z-817 as a combo as the Z-817 is sticked to the radio. Opening the ATU reveals 2 circuits, one that tunes the antenna and one that controls the memory.

Both circuit negative sides are connected with each other through coil L14. I didn't bother measuring this coil and just made a connection between the connector earths, that solved the problem.

I hope Hans can now finally enjoy digimodes again and actually decode weak signals.
If you as reader has something interesting about the hobby to share and don't want to post it yourself please contact me, I'll be happy to publish it for you here on this blog. The only thing I need are photos and a small story. Dutch will be translated by me. And if desired I will place dutch text as well.