September 05, 2014

Pimping Elecraft KX3 for VHF and up

Long wait is over, the 144 MHz transverter module for my Elecraft KX3 has arrived!
KX3-2M transverter module shipment kit
The transverter module came in the way all Elecraft users have got used to; well packed, all small bits and pieces in ziplock bags and  with very detailed installation manual.

The transverter board is a very high-tech piece of electronics not only due to the physical size constraints, but the RF performance is quite outstanding, merely required as the sole RF performance of KX3 is so outstanding.

Looks like the KX3 has been originally designed quite well having optional internal transverter modules in mind as, even it is a tight sandwich, the transverter module has its well-planned position in the radio. Also the antenna connector hole already exists in the radio body, so does the LO signal output connector on the main board.

I have the optional antenna tuner board and the roofing filter installed in the KX3, both needed to be removed during the installation to access the LO signal output connector and to install the SMA antenna connector.

 The SMA connector for 144 MHz antenna fits just in between the toroidal coils of the filter part of the main board. I had to move the closest coils so the connector body would not make contact with them. This was mentioned in the installation manual too, so I'm not probably the only one needing to make some space for the connector.

The LO signal for the transverter is available next to the roofing filter connector on the other end of the main board.

Both the antenna cable and the LO signal cables use UMC (Ultra Miniature Coaxial) connectors which are small but tough.

Mating the contacts first time requires impressive amount of force comparing the connector size. The LO cable connector is below the roofing filter board, which was required to be removed during the cable installation.

The transverter board fits directly on top of the optional antenna tuner board, utilizing the same connections the tuner board uses.

The power transistor of the transverter is attached to the side wall of the radio body between the antenna connectors, and there's also a screwhole ready for that.

The sandwich consisting only the optional tuner board was already a tight fit, and even more tight it got with the transverter module installed! There is still some clearance between the modules and the cables run freely.

I noticed later when getting the radio back to one piece that the transverter antenna cable is bit on the way of the loudspeaker and extra care needs to be taken when closing the lid so the cable won't get squeezed between the metal sheets.

Finalizing the installation required me to upgrade the firmware of the radio, which was no pain using the KX3 utility. The installation manual clearly went through step by step the required parameters to be entered so that the transverter module would be recognized and available.

I briefly tested both FM and narrowband operations and everything looks good. Getting FM to work was bit tricky but thanks to the manual again I was able to get both repeater offset and PL to work :) I'm getting old as I need to read manuals!

When I get a chance I will do some basic measurements on the performance of the transverter module to proof the sensitivity and output power. According to the manual it should put out 3 W on 12V, and about 1 W on 10V which is the case when running on batteries.

144 MHz is a nice addition to the KX3. The module supports also +5 V bias voltage on transmit for switching transverters to TX, which makes me want to try KX3 as the IF radio for microwave stuff too :)

February 05, 2014

Wonderful small filter kits for HF projects!

Ok, I admit I'm degrading. More and more I've found myself wondering about projects and stuff related to shortwaves, which I was not at all interrested in the past. It might sync with the gray hair? :)

Anyway, the RTL-SDR technology and development which I've been following closely has made me want to make few direct-sampling RTL-SDR based receivers for the community use through the WebSDR's I run.

I bounced to a universal low pass filter kit at W8DIZ Kits and Parts online shop. I purchased few kits, one for lower HF bands and another to cover up to 28MHz. The kits were $8 each, shipping was $14,40 which is hilarious in the relation to the price of the actual goods :)

The kits arrived in the mail pretty fast, including small bags for each filter ordered.

Constructing the kits was easy and I just was able to measure the filters with my DG8SAQ VNWA.
Insertion loss is the blue curve, return loss (matching) is the red curve. In general the filter responses are as expected. Insertion los at the passband section is only fractions of a decibel so they will work great for a RX project.

14 MHz low pass filter insertion and return loss measurements

The 14 MHz low pass filter needs bit tweaking as the insertion loss starts to increase bit too early, having already about 2.5 dB loss at the 14 MHz band. It still works for my purposes as I plan to make 80m and 40m RTL-SDR receivers.

28 MHz low pass filter insertion and return loss measurements
The 28 MHz low pass filter performs as should, the insertion loss starts to increase about at 30 MHz. The attenuation curve could be bit deeper but this is a good start to put in the front of the RTL-SDR's

January 14, 2014

GREAT news for OH2DMR MotoTRBO repeater!

Our DMR-activity group OHTRBO has successfully been running multiple DMR repeaters, but lacking some total coverage for the Helsinki 'Metropolitan' area. We gained a huge improvement in this area recently when the first Finnish DMR repeater OH2DMR repeater was moved from Juhanila TeliaSonera cellular tower in Espoo to a tall tower in Pasila, bit north from downtown Helsinki. The tower is a huge landmark next to the HQ for Elisa, a mobile/data/telco operator, peaking at 100m AGL with the base standing at 31m ASL.

The tower has few antennas left from the analog MPT1327 trunking 'AutoNet' mobile telephone network ran by Elisa (dismantled by us a decade ago) The highest antenna on the tower was a monitoring antenna for the AutoNet-system, a humble 8dBd Kathrein vertical, kindly left there for the greedy amateurs to come and take full advantage of it some day :)

With co-operation with Elisa Radio Club OH2AQ, the site could be used for amateur radio services too.

In the near future a new 70cm FM R.Net repeater is to be installed to the cabined with the DMR repeater. Estimated coverage for the FM repeater is quite similar to the DMR coverage. The site earlier had OH2RUA 70cm repeater installed also.

The roughly estimate of the repeater coverage from Pasila using Radio Mobile Online shows a huge coverage area, which is now proven correct by few distant DMR users.

Cabinet installations are still mid-way, the Motorola XPR8300 DMR repeater and Sinclair Q3220E duplexer are the only ready parts in the cabinet. The duplexer seems to perform nicely with only 2.0 MHz split, with just over 80dB notches. Internet connectivity is next on the To-Do list, and also wiring the RX-multicoupler and TX measurement panel, both visible in the middle of the cabinet.

OH2DMR continues to operate at same frequency 434.575 MHz (-2.0 MHz input), CC1. When internet connection becomes available, slot 1 will be DMR-MARC linked (TG1 WW, TG2 EU, TG24 Nordic etc.) and slot 2 will remain domestic in the OHTRBO network (TG244 Finland, TG8 regional, TG9 Local)

As mentioned above, we took care of dismantiling the Elisa trunking network at 2004. It was the same room where we carried out ten cabinets full of radios and equipment, of which the RX multicoupler and the TX monitor used for the current project are from. So they returned home in some means :)

November 25, 2013

Monitoring the horizon with RoofCam

A long-boiled idea of having a camera next to my antenna at the remote radio site is now reality and I can literally monitor the horizon :)

I have long experience about webcams in general, I've had few at our summer place almost for a decade now, recording the conditions in a fixed interval. It's very nice to observe the differences of a same day yearly, how much snow and how much no snow at all for example on christmas eve :)

I installed a Ubiquiti AirCam to my antenna setup, the camera turns with the antennas and looks at the horizon. Many times when doing some antenna work at the roof, I've admired the beautiful skies and clouds and hoped to be able to observe them more often. At the seafront, cloud formations and generally weather fronts are spectacular to view. Hopefully I can grab some good snapshots in the future!

The camera provides JPG snapshots as seen below, but also a MP4 stream for live viewing. Resolution is not the best possible but it works for now!

I can now also monitor how the antennas (well, only the static omni antennas on the other pole) are doing in high wind situations. I also thought of putting a small wind sock to the tip of the 1296MHz yagi antenna (the one which is on the right side of the picture), so I could more easily adjust the antennas towards wind.

I hope to catch something special through the camera too. It's not too long to the new year,when this should be quite good observation view of all the fireworks. No matter which direction the camera points, I'm quite sure :)

 There are not yet publicly accessible address available for the snapshots. I'll try to make one so you could see how's the weather here, and see to which direction the antennas and the camera are pointing. I can extract the position from the antenna rotator system, but superimposing that to the picture needs some work still.

September 12, 2013

Monitoring VHF and UHF conditions with a WebSDR

SDR is here to stay and one of the most useful service around the topic the WebSDR system by PA3FWM.

WebSDR is a linux application which hooks to a soundcard for I/Q input (softrocks etc.), or to a FuncubeDongle or a RTL-SDR (a DVB-T TV reception USB dongle) and provides the RF spectrum received by any of the receives, to a web window as a waterfall display, spectrum analyzer display etc.

Monitoring 70cm beacon sub-band 432.402-432.498 with my WebSDR system. OH2UHF beacon (and it's I/Q mirror) well visible!
My experimental (but more stable already) WebSDR is located with the VHF/IHF remote station, and I must admit I like to check the conditions using this first rather than firing up the remote system! Currently I have two FuncubeDongles as receivers, they provide a coverage of 96 kHz which suits for the beacon sub-bands perfectly, being both 100 kHz wide.

The setup uses Big Wheel antennas which I have on the roof for 144 and 432 MHz. 1296 MHz will be added shortly, I'll plan to use three stacked big wheels and probably a preamplifier for that band.

You can all access the OH2LAK WebSDR from this link

Update to the Pusula HF/VHF remote station

My first remote station was built to our summer house in Pusula already long time ago, and also the experiments with RemoteRig began there when building the system for Martti OH2BH. Then the "rack" with all the required equipment and radios was just a quick-and-dirty setup on top of pile of cardboard boxes in the garage but this summer I finally did a big renovation to the system. I put everything into a real rack cabinet with a door, floor, and walls so that everything really is in there, out of sight and not for mice or other to build a home :)

The rack has now all the installations needed and lots of spare space for the upcoming PA's and antenna relays etc.
The top of the rack is dedicated for telecomm stuff, the telephone line terminates to this rack now for the ADSL modem, as there's no landline phone anymore for other purposes. Before the ADSL line was terminated in the house and only a cable for the remote setup ran to the garage, now the setup is inverted so that the cable running *from* the garage to the house, provides network for the PC and other appliances there.
Next are the antenna relay and rotator controller, a Microbit WebSwitch which allows antenna to be turned from a web client. I'm planning to replace that with a Arduino setup
Bottom of the picture shows the Kenwood TS-480 and Icom IC-706mk2G remote radio setups. Very nice 2U-high rack enclosure for the radio and RemoteRig box!

Of course during the 'renovation' we had a single strike thunderstorm in Pusula, and the lightning hit something few kilometers away when I was in the garage building the setup. I saw an arc somewhere in the cabinet, and later found out that it came through the telephone line and broke another ADSL modem. Luckily enought I've been collecting spare modems, and another came in handy then :) I added a Krone lightning protector bar to the Krone panel where the telephone line terminates and connects to the modem below. I routed the line through two pairs of the protectors just for extra protection :)

I also added lightning protectors to all antenna lines terminating to the roof of the cabinet. It was a really tight fit, the connectors make it barely so that they do not touch to roof all the time!

All N, even for HF. That's because I did not have
any UHF lightning protector, but N works OK for HF too :)
The bottom of the rack is dedicated for power supplies and the server computer. All 'critical' AC is fed through the small UPS which takes care that the server won't face short power interrupts. Also the other non-radio power supplies are fed from behind the UPS to protect the power supplies and systems from electricity net based spikes. The server is a Linux server and it's main purpose is to provide web outlook for the weather station on the roof.
Server and power supply department of the rack
During the rack upgrade I decided also to upgrade the firmware of the TS-480 radio. After spending some time figuring out what's wrong, I can with honours tell you all now that the Kenwood upgrade software does not like and even recognize USB serial ports!

Kenwood TS-480 upgrade process on the livingroom table

Both of the radios, Kenwood TS-480 and Icom IC-706mk2G sit nicely in a 2U high open rack box which I found from OH1AD Flea Market 'Lutikoiden Tuuletus' few years back (Yes, they most propably still have those!) The box has a top cover with lots of holes in it, so it works also for the heat transfer.

Only thing I miss in these great cases is a full front face for the box to hide the equipment in to the box, but I've given up finding such as a leftover somewhere. It needs just a one-piece aluminium sheet which I can find from  a hardware show for sure

The antenna setup in the Pusula remote setup is pretty simple. For HF currently there's only a 80m loop spread into the woods. Putting a 6:1 Balun on the loop was a good choice as the antenna was 'naturally' tuned to all bands needed :) For 6m and 4m there's a dual band yagi built by Egil LA8AV, and a 15-el antenna for 2m. The vertical on the top of the tower runs to a Icom FM dual bander for repeater talk etc.

August 07, 2013

New APRS digipeater on the air

There's been an apparent gap in the APRS network coverage around Karkkila, and we already several years ago acquired a ex-police VHF network basestation location from Alhovuori. Every time I have driven pass the tower I've looked up and confirmed the antennas are still there, so there still has been hope to put the digipeater up :)

Finally last week I came up with a solution of a 'temporary' digipeater OH2LAK-2 to put up to the tower. Well, it ended up being quite good looking setup, so it might not be temporary, only the callsign might. It might be easier to apply a real digipeater callsign for the long run.

The digipeater setup consists of a MDR VHF radio modem which is very famous in Finland for APRS which it's rewritten firmware HaMDR, the rack chassis is a controller chassis of another VHF base-station from Elektro-Arola. It featured a nice AC to 12V power supply, power switch and fuse panel, so it was a great choice for the digi.

From old habit I equip all the things I build with a Cisco-style console port, so a RJ-45 jack. I have an endless supply of the blue RJ45-D9 cables, and it can be considered as some sort of a world standard. Below the console port jack there's a configuration switch, which enables the configuration mode during power-on for the HaMDR radio modem.
We drove up to the Alhovuori site with Marko OH2BUF with clear plans to leave few hours after with a working digipeater running at the site. Alhovuori is a ski center, but during the summer season there are variety of activites around, which this time means horses. The very rough road up to the site which is next to the ski slopes, passed a grassland for horses which was fenced around. Luckily the fence could be opened to get through :)
I knew that the very last POVI basestation would be waiting for us at the site. I felt quite nostalgic dismantling it from the chassis as it was truly the last of its kind, still installed and capable of operating and hooked to antennas. (I've listened quite much of the fellow policemen talking through this thing in the past!)
Unfortunately the DC power feed to the base station was removed, so we could not check it's functionality any more :(
The digipeater sits nice on the same TELENOKIA rack cabinet, we also found by accident some spare front plates and filled the front of the rack with them, so the installation was even cleaner.

The antennas of the digipeater are the very topmost antennas, three dipoles on each side of the tower to create an omnidirectional radioation pattern. The antennas are sturdy Aerial Oy dipoles with a reflector grill, model AV1523-3

The computer model of the expected coverage of the station using Radio Mobile Online matches quite well the results derived out by the system with the data of the actual traffic relayed through the particular station. The digipeater itself is configured to relay packets only from a distance of 50km or less to avoid overlapping with other digipeaters. The tropo conditions experienced lately have made the OH2LAK-2 digipeater to be heard in Sweden though, so it is most probably a working setup by all means.