This weekend I built the WARC band switch box for the antenna switching system at the station. This was the last box to be finished so the only remaining thing to do now before the new switch system will be taken into use is to get the 12 & 17m yagis up the tower as "multiband" antennas are banned in the new switchsystem. I used power splitter cards from SJ2W but have omitted the transformers so it will only be possible to use one antenna on each WARC band. But It's possible to add transformers later if there would be use for power splitting but I doubt that on WARC.
As described in the previous post I have been working on a 12m 5 element monobander that I designed from old Hy-Gain scrap we had lying around at the station. Last sunday I picked up Thomas SMØCXU/PY2ZXU and Hans SMØBYD who also took theese pictures. Myself and Thomas made the Beta match feed arrangement for the beam. The calculated Beta match length was 15 cm but it became rater 30 when we hoisted the antenna up for tuning. Driven element tips had to be shortened by 2 cm on each side and that gave a perfect resonance in the middle of the 12m band with a flat 1:1.1 SWR over the whole band. Now I will build a similar 5 element design for 17m and after that both antennas will get a new home in a WARC band tower.
Here's the design measurements for the SMØW 5 element 12m yagi.
|Boom 5,08 cm – Place||T1 – 2,225cm||T2 – 1,113cm||Total|
All measurements are in meters if not otherwise noted. All tube diameters are hy-gain standard diameters, I recalculated "inch" into cm for the design.
Last summer we organized all aluminum scrap at the station. I found several Hy-gain antennas in really bad shape. Still I did not want to get rid of the stuff rather reuse them for some project. Last fall I was reading some stuff in the ARRL Antennabook and found remodeled versions of popular Hy-gain monobanders for 20, 15 and 10m. So I started thinking and got the idea to build 5 element monobanders with high performance on 12m and 17m. So I remodeled the ARRL versions yet again, firstly re-scaling the ARRL design down to 17m and 12m, then making additional tweaking to get just the right performance. I knew I had a big bunch of Hy-gain 2" booms, and lots of element parts and clamps so I could design pretty freely.
Last fall I took the bull at it's horns and took all rusty and corroded parts into pieces with the angle grinder and gave them a good cleaning, and assembeled the new elements and clamps with new hardware. Last sunday myself with the help of Thomas SM0CXU assembled the 5 element 12m yagi. Boomlength is nearly 7m. Now I will have to prepare the feed details for the beta match and then get it up the tower after final tuning.
Last weekend myself and Thomas SMØCXU/PY2ZXU decided to participate in the CQWW 160 contest. Knowing we had several RX antennas broken we decided to do it "semi-deadly-serious" only and just for the pure fun of working DX's on "topband". Propagation was excellent on friday evening before the contest but never picked up quite to the same level during the contest. On saturday the magnetic field was also disturbed by the sun which gave the impression that somebody had disconnected the antenna from the transceiver. Here's a summary…
Contest : CQ World Wide 160-meter Contest Callsign : SM0W Mode : CW Category : Multi Operator - Single Transmitter (MS) Overlay : --- Band(s) : Single band (SB) 160 m Class : High Power (HP) Zone/State/... : 14 Locator : JO99BM Operating time : 30h43 BAND QSO DUP DXC S/P POINTS AVG -------------------------------------- 160 1086 26 70 14 5833 5.37 -------------------------------------- TOTAL 1086 26 70 14 5833 5.37 ====================================== TOTAL SCORE : 489 972 Dupes are not included in QSO counts neither avg calculations Operators : SM0W, SM0CXU Soapbox :
Finally after months of work the 3 element 3,5 MHz yagi (80m) is up again! Around noon with the snow slowly falling down from the skies and -7 deg C it was there again on top of the tower. The real hero, with all hats off goes to Dag SMØKDG who climbed the tower and stayed up there for some hours in the cold!
The rest of the ground crew on the ground was SMØW Teemu, SMØSHG Adde, SMØDZB Tor, SMØCXU/PY2ZXU Thomas and crane man Lasse who did a superb job manouvering the "monster" around.
Theres still stuff to be done, the coax and control cabled for the rotator and antenna relay boxes has to be hoisted back up the tower again.. to be continued.. here are some pics from yesterday!
Last week I started building the new RX Antenna Distribution System. I don't own a good accurate inductance meter so I built a small probe with two alligator clips and a capacitor of known value that I hooked up to my Vector Network Analyzer. Placing a coil in between the alligator clips creates a LC parallel cirquit that displays it's resonant frequency in the VNA. Using the formula f=1/2*pi*sqrt(LC) it's easy to calculate the L (inductance) value of the coil. Played around abit with that and started assembling and tuning the bandpass filter cards. Will probably give you the finished filter cuves in the next post.
I also started assembling the Combiner card and Patch card of the system, now I ran out of components so I made an order of the remaining ones so hopefully next weekend I can continue the build.
Here are som pics.
During last year I have been thinking alot about how to distribute RX antennas to different operating positions at the station. Like the rest of the antenna switching the scope is different, allowing contest operations in different configurations like SO2R, M/S, MM. Working regular DX and also good remote switching capability. All ideas and possibilities was cooked down to an RX Antenna Distribution System.
Main parameters that I had to do was:
1. System should be able to be controlled by the openASC system.
2. As little electronics as possible at the beverage switching hubs in the forrest 150m away from the house.
3. Three operating positions should be able to use any of 14 possible RX antennas, even simultaneously!
4. Few feed cables into the forrest
5. Few control cables to the forrest.
6. Low loss even when several RX'es use the same antenna.
7. Possibility to switch on preamp.
8. Good filtering not to blow RX'es if several transmitters are at use simultaneously.
The RX antennas (beverages) are fed into two hubs which are about 150m away from the shack/house in the forrest. From there I will run three 150m long 1/2" hardlines to the house. The two hubs 50m apart are also connected by three RG-58/RG-213 feedlines. There will be a 2x10pair control cable from the house down to the forrest as well.
This is a basic scetch of the whole system. Two relay switching cards (antenna hubs) in the forrest are connected to the 150m long feedlines going up to the house. In the house I will build an 1RU box containing the following cards:
1. RX Antenna Combiner Card
2. RX Antenna Patch Card
3. openASC Driver Card
4. Arduino Microcontroller
5. 3×3 Band Bandpassfilter Cards (160,80 & 40m)
Here is a layout of the current Beverage antenna park. 10pcs of ~500m long beverages.
The relay cards in the forrest (RX Antenna Selector Cards) are controlled by the 2×10 pair cable run down from the in-house unit. There are about 60 relays in the RX Antenna Selector Cards that needs to be individually controlled so I decided to multiplex the control signals from the house down to the forrest and de-multiplex the signals there so with just 4 bits per "RX-Line" (total of 3) = 12 bits = 12 control lines I can control all 60 relays. It will also be very easy to control antenna selecton this way through the openASC system since I can assign several driver outputs for each antenna in the system. Each of the three "RX-lines" has the possibility to use any of 14 RX antennas.
RX Antenna Selector card. Schematic here. RX_Antenna_Selector
So when any of the 3 operating positions that will have RX antenna capability selects an antenna in the openASC system the RF signal from that antenna is routed up to the house and into the RX Antenna Combiner Card. This card assures at all times that in and out impedances are correct. If two RX'es use the same antenna one of the incoming feedlines from the forrest is disconnected at both ends by relays and if the RX'es are on different bands the signals just pass on to the Bandpassfilter cards. If the RX'es are on the same band there will be 0 degree hybrid combiners connected to always assure the right impedances are used before the signal is passed on to the Bandpassfilters. If the RX'es use the same antenna on different bands the Bandpassfilters work like passive splitters only introducing the low passband loss of about 0,5-2 dB (frequency depandant) between the antenna and each RX since the filters only filter out the incoming energy of the actual tuned frequency and blocks all other signals with the high impedance input outside the passband.
RX Antenna Combiner card. Schematic here. RX_Antenna_Combiner
The Box contains three independent Bandpassfilter Cards originally designed by OH2U for 160, 80 and 40m. Mike SJ2W made PCB designs for the filters that I will be using in the box.
The selection of the correct filter is also done with the openASC system. openASC detects the band that the RX/TX is on and activates an output in the driver card. To minimize the amount of outputs used in the driver card I have also decided to multiplex the signal by 2-bit encoding. The multiplexing between the openASC driver card and BPF cards are done on the RX Antenna Patch Card that also distributes and filters signals to and from the driver card and forrest. Filtering includes lowpass filters on all control lines and varistors. The RX Antenna patch card also distributes the 4 bit antenna selection data and 2 bit band selection data to an Arduino microcontroller that I will program to control the Combiner card depending on all different scenarios of:
1. Different antennas/different bands
2. Different antennas/same bands
3. Same antennas/different bands
4. Same antennas/same bands
Picture of the RX Antenna Patch Card. Schematic here.RX_patch_card
This project will be continued! =)
Since I now have the openASC system up and running at the station I want to implement the rotating possibility from the system. So this last week I visisted Mike SJ2W in Luleå, Northern Sweden and made 10 rotator cards that can be built into rotator controllers and hooked on the sytembus. The PCBs are coated with soldering paste and all small SMD components are picked with a small needle with vacuum suction and placed at right spot on the PCB's. Then everything is heated in a special oven and out comes finished cards in no time compared to doing everything by hand with a soldering iron. Some pick and place pics =)
The day before Christmas eve we gathered at "The Hill" and managed to winch the 80m yagi into it's position on top of the top section of tower. The next step after Christmas holidays will be to get a crane to the site and lift the whole shabang on top of the tower. Few days ago I measured the antenna to see if the resonance was in order before we lift it to the top. The relay/coil boxes I built on each element enables the yagi to work in 4 different segements on 80m with each segement about 40-50kHz wide with reasonable SWR. All resonances seems to be in order!
Here is a few pics from the antenna party.
73 de Teemu SM0W
This weekend I mounted the relay switch box for the 80m yagi back on the driven element again after bringing it home for repairs. I also made a new common mode choke, 30 turns of RG393 on 110mm (7") PVC tubing. The Hi-Q coils on the elements had old splicings in the connections to the coils and they were really bad after years of weather. So I decided to re-do them properly. First I took away all old oxide, then wound new copperwire around the splicings and soldered with a big 300W soldering iron! After that the whole thing got a cote of fresh warnish to protect them from the weather. Also the coils lost some of their warnish over the years so they were sprayed as well. All and all a good weekend! The only remaining thing now is to add some paint to some stupp that needs to be rust protected, I need to go over all elements once more and check that all hardware is tightened properly. And then it will fly again! =) Some pics for the weekend, if it looks cold and frosty it was! On saturday we had -6 degrees centigrades, on sunday a little better with a few degrees above zero but very windy.