LZDX 2012 – the one with the RX loop

Actually not too much LZDX unfortunately. I try to be in this contest each year because it’s a good workout for next week’s CQ WW CW. As usual I’m going through busy times here so I decided to set up the station already this weekend so I can rest and work some DX the coming week. WX forecast predicts calm weather so why not.

Usually I do all the preparing antenna work on Friday afternoon since this is my free afternoon. But with two kiddos it’s a different ball game especially when I have to play ‘single dad’ because the XYL has to work late. Get kid A from kindergarten, get kid B from day-care, run errands, prepare dinner, feed and try to eat, and then put ‘m to bed. In the mean time I was desperately trying to find an exotic relay to fix a broken dishwasher so ‘doing the dishes by hand’ was another job to be done too. The relay got smoked and some pins were evaporated. Ashes to ashes, dust to dust.

Raising the tower went smoothly and routinely, an extra elevated radial for 80/160 was put in place. FINALLY the time had come to put up the ALA1530 RX loop that has been here for over two months. Oh yeah: ‘collect box dropped at neighbour’s by parcel service’ was another item on the already busy schedule. This box contained the simple TV antenna rotator I ordered to turn the loop. I did my best to get it all done. I laid out the coax to the loop and the rotator cable. But by 15.30 I had to abandon the work and trade the ‘antenna hat’ for the ‘daddy hat’. No more ham radio on Friday. But I got up early on Saturday.

  • Put rotator control box in shack, connect cable to the multi-pair control cable that goes to the garage. Check.
  • Go to appliance dealer and try to get hold of a relay. Check.
  • Solder relay, mount dishwasher, start program. Check.
  • Back outside. Mount motor to iron tube. Check. BTW is was cold outside!
  • Connect control cable to motor. Check.
  • Connect cable outside to cable in the garage (coming from the shack). Check.
  • Put loop on rotator. Check. Did I mention it was cold?
  • See if rotator turns? Success!
  • Check dishwasher: it washes but the water remains cold: broken heating resistor after all. Darn!

After lunch it was supposed to be contesting time but in stead I had to go back to the service centre for dishwasher parts. Parts are pretty pricey and still no guarantee for a fix. So in the end I did what I wanted to avoid: buy a new one and turn in the (not so) old one. It seems that these things aren’t made to last anymore and certainly home repair is out of the question. The burnt relay was a strange part and apart from the Chinese relay manufacturer’s datasheet, no where to be found. Even the local service shop had only a similar replacement. I had to cut a pin and the coil voltage was 6V DC i.s.o. the original 5V. Google showed people with the same problem. It is said that the heating resistor draws more than the 10 amps the relay is rated for. Nice German design! Furthermore the quality of the PCB was poor, with very bad solder joints. Again confirmed by several Google sites. Hence the disappeared pin: high resistance carrying 10 amps or more causes a hot spot on the PCB. Hot spot gets too hot, solder pad and relay pin get smoked.

Back home I went into the shack and connected the loop’s coax to the K3’s aux RF input. I had to read the manual again and tried to receive some signals on 40m in broad daylight. The loop was deaf. Completely deaf. Tried the transverter’s AUX RX input for the main receiver. Deaf. Completely deaf. I tried to listen on 80 and 160 but heard absolutely nothing. There you go: wasted money.

So I went to play on 10m and 15m and waited until I made 100 QSO on each band. Just for fun. Propagation was acceptable but it did not seem very good. Especially on 10m. A few weak W6/7. East coast was loud. After that I took a long break for some family time since competitive scoring was out of the question. In the evening I returned and worked some 80 meter. I didn’t bother to work PT0S with all the QRM-comments I read but since they got spotted on 80m and I was there anyway I tried to call them. They were loud and then I realized why: it’s only 6000 km away from here. Hardly DX in kilometers. I worked them after a few calls but with the usual QRM circus on top of the DX. Tuners, jammers, cops, simplexers – “The Lord needs to have his numbers of all kinds” my late Uncle would say. Again the RX loop turned out to be deaf. Completely deaf. Removing the coax didn’t make a difference. Unplugging the power to the pre-amp outside didn’t make a difference. As if the loop wasn’t there.

I set the alarm for ON sunrise and went to bed. I refused to believe the loop was this deaf. So I decided to track the problem down on Sunday. I got up and had a nice run on 40m, contrary to 80 which was already deserted. Then off for breakfast with the family and waiting for the rain to stop which it didn’t so I kept on playing on the higher bands for a total of 550 QSO or so.  As soon as the rain stopped, I connected a 50Ω dummy to the shack’s end of the coax and took my DVM outside. I unplugged the BNC from the loop’s feedpoint and measured… “OL”. Overload – open circuit. That makes sense: no RF goes into the shack and no DC reaches the pre-amp. Hence the deaf loop. I went into the garage and unscrewed the coax cable coming from the shack from the one that went outside. Sure enough I had 50Ω on the N-plug’s pin but nothing on the barrel connector when screwing it back on. The culprit: a retracted pin on the N-plug. The pin didn’t slide into the barrel’s centre piece. Then it hit me: all my efforts over the previous years with loops, K9AY and BOG’s where I concluded they didn’t work: must have been this dreaded pin!?!? You probably think: why didn’t you check that before? Well, this thick low loss RG-217 coax with N-plug was the very first cable I had coming from the shack out into the garden in early 2003. I had successfully used it until October 2004 when I inaugurated the tower and switched to another pair of coaxes. It worked then, and the cable didn’t move ever since. Apart from my other low band RX endeavours. I wonder what made the pin slide back more than 5 millimetres into the N shell. I have heard stories about low temperatures causing the inner conductor to crimp and pulling back the pin along the way thus breaking the connection, but it wasn’t that cold and 5mm is a lot. I use a lot of N plugs both male and female and never witnessed a problem.

Anyway I cut off the N plug and resoldered it. Then I reattached the BNC to the loop’s pre-amp and sealed it with quality vinyl tape and a length of self amalgamating ribbon for 100% waterproofing. Pretty confident of myself this time. I went back into the shack around 19.00 utc and found the loop absolutely NOT deaf. I didn’t bother to actually compare it to the TX antenna but put the K3 in ‘diversity receive mode’ with the 80m GP on RX A and the loop on RX B. I managed to work a weak RW0LBM for almost 8400km. The QRO was off and I had to use all 100 Watts to make me heard; 45W only achieved a question mark as a reply. But I managed to work him. He was weak but solid copy. I will try later this week to do some more A/B comparing to evaluate the loop. Let’s hope for a pleasant outcome!

6 replies on “LZDX 2012 – the one with the RX loop”

Been going through some similar iterations here – we had our 1-yo granddaughter for 4 weeks so radio time was sporadic and no preps for CQWW at all. I’m now trying to get mentally into “that mode.” Normally by now, I’ve had a week’s worth of daily sessions with MorseRunner and have worked a few DXpeditions that are gearing up for the contest.

But not this time…

Good you got the loop working, hope to work you on lots of bands this weekend. I will be SOAB HP as SJ2W. Unforuntately it looks like propagations will suffer from the recent flares, but I’ll try to go for the SM record anyway.

Cu Franki, always a pleasure to read your blog.

Hey Mike – Thanks for your note!

I saw the flares reported too. Fingers crossed, maybe the effect will be minimal. At ‘only’ 50° North. It might be worse up there on your side.
GL chasing the SM record. Let’s hope for good and stable propagation.


N connectors are evil ! I used to have them on some monster RG-17 coax. In the cold WX, they center conductor would shrink back, pulling the pin out of the female connector. I have since soldered an RG-8 jumper directly to the RG-17, and used UHF connectors on the RG-8. No more problems !

So you’ve also been a victim of the thermal effect on N-connectors. Knock on wood but so far I haven’t had that problem. I think mine was a mechanical problem. I bought a drum of 100m RG-217 years ago, because it was very cheap and has good specs (it’s 1/2″ thick). The seller had only 2 matching N connectors so I was happy to find a few used ones at a hamfest. They were labeled ‘for RG-217’ but I think they were not really designed for that specific cable. Or the parts of the plug were a mixture of other parts.

I bought a pair of UHF plugs for Ecoflex-15 cable and tried to solder those on, but I had a bad experience with it in Fieldday 2011. It turns out the fit isn’t really mechanically stable ‘as is’, while it had electric continuity when I just soldered it. I should redo it and stabilize the outer shell of the plug over the coax’s jacket.

First of all – thanks for your patience to get my calls on high bands !

About your dish washer : 🙁 what are the most common three words together? every positive minded person would answer – “I love you!” … Unfortunately, however – the world is not what it was … the correct answer is “made in China”

And finally – it’s nice you found the defected N-connector and put your RX-loop under employment.


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