Last days we have strong tropo conditions. Currently i run a Openwebrx with FT8 monitor on 2m and although i only use a small vertical monopole the maximum distance of reports are >800km. Some 2m FM relais from Hamburg was audible very loud. The 70cm band was full of repeaters (i think most of the signals were DMR). This evening i gave 70cm a try. I was surprised to hear LA1UHG beacon from JO59FB (>900km). Other beacons heard: DB0VC (JO45), OZ7IGY, OZ5SHF, DM0UB. I worked SM7LCD in JO86 over 600km with only 30W and Quados-6 antenna.
Over the past months there was quite some activity here and there but i found no time to document it. For vacation i took my FT-857 and the small duoband yagi and tried some FT8 in the evenings. I also tried some meteor scatter on 2m here and there. In November i found some time to participate in the Marconi contest with the DM7A team from JO60OM which resulted in a 3rd place in DL as multi-Op station. Some small activity was to collect some equipment for watching the local analog TV repeater which was reactivated during the year. After months of searching i found a nice portable FM satellite receiver. The repeater transmits on 10200MHz. With a normal satellite LNB with 9750MHz LO this will be far outside the tunable IF of the receiver. From previous experiments i had some cheap PLL LNB with 25MHz crystal. From previous experiments i found that it was not that usable for narrow band QO-100 acitivities as the 27MHz referenced Octagon LNBs but i knew that the PLL locked down to a 23.3MHz reference. So i ordered some 23.70625MHz crystals and exchanged it. With this crystal 10200MHz is converted to about 950MHz which is just at the lower end of the sat-IF range (the receiver tunes down to 900MHz). From the roof window i can now receive the DB0TUD ATV repeater 10GHz output. I do not know the frequency response of the LNB yet. Most probably the LNB is not very sensitive since the frequency is quite low compared to the satellite band. For some reason i broke my old DVB receivers AV input. So i used a cheap USB video grabber card to watch the video.
Recent days showed some more sporadic E conditions. I worked EA and LZ. Monday evening i went away from the PC and when i returned i saw a CQ from 9K2YM. Unfortunately it was too late. Later on i also catched a CQ from S01WS. PSKReporter showed some really interesting spots by DK2EA. He received stations from the Carribean sea and others received transmissions from Japan and eastern China.
CQ of 9K2YM
4m ES condition on July22 2018.
BTW: the very nice and useful DXMaps page has changed to openstreetmap. Now its possible to show screenshots which was not possible because of license restrictions before. Thank you very much!
This week some people from here work from Estonia under the call ES0UG (and ES0UG/8). Since there are no good ES conditions currently we tried MSK144 meteor scatter. I did not think there will be a lot success since i can only run 25W ERP. But finally i god some of their CQ.
ES0UG/8 calling CQ in MSK144 from KO18
During my lunch break i did not have success. In the evening we tried again and were able to complete the QSO to KO18 field within about 1.5h.
Since yesterday evening the crew is qrv from the next island in KO19. We tried again in MSK144 and this time we had bursts rather early. It still took more than an hour to complete the QSO and this time i have a nice screenshot.
ES0UG in KO19
Since i did not expect that it will work at all i am quite happy with my first two QSO via MS. I also got some spots from G3SHK. Many thanks!
Now i started soldering the 9cm transverter kit that was in the shelf since years. The filter caps look already a bit oxidated. But soldering still worked fine. The new 9cm will get into a box together with 13cm at some time.
I assembled the Iceni 70cm transverter kit from G4DDK. Instead of the ADE-13 i used a ADE-751MH+. Sam was so kind and sponsored one of his mixer samples he used for testing. Unfortunately the manufacturer of the mixers uses different pinouts for almost every type. In this case i had to swap RF and IP ports. The good one: It is not difficult with the layout. In the picture you can see the short semirigid.
G4DDK Iceni transverter for 70cm
The next picture shows some IM3 measurement for the RX part of the transverter. The estimated input IM3 point is around 0dBm now (21dB gain).
The P1dB is about -9dBm (2x -12dBm).
Iceni ADE-751 IM3
I also checked the output signal. The 2nd harmonic is about 53dB below wanted signal and the LO suppression is about 58dB. So some extra filter might be required to the comply with regulations.
Overall i am very satisfied with this transverter block. With the alternative mixer the performance is even better than it was before.
Next i need to add a amplifier and other unimportant things like sequencer, RX/TX-switch, chassis and so on ;)
I was searching for a small driver for 2m in order to have enough power for my microwave transverters. I usually drive them with about 500mW. Since i have a transverter block with about 0dBm output it needs some gain. Again i found something from China. The advertisement told something about 1.5W, the pictures showed a PCB with a print 35dB/3.2W. However, i thought it could be good enough to get 0.5W out of it.
A small VHF/UHF amplifier
When the device arrived i noticed that the manufacturer milled the top of the two amplifier IC. Very funny that the guys there try to save their designs from unwanted copy ;)
At the input there is a 6dB attenuation pad which are followed by two amplifier stages of unknown type. The first stage is supplied via a 5V regulator, the second one is connected to the supply input directly. I used 12V to do some measurements.
The first action was to know the gain of the circuit. I wanted to see if it is really working from 1 to 700MHz.
In the picture you see the little noisy measurement. The drive from the analyzer was set very low.
Gain of small VHF/UHF PA
From the gain curve it can be seen that the device is probably not working that well at the lowest end of the shortwave. But at least from 30MHz on it should be usable. Towards upper frequencies the gain is decreasing a lot but still 27dB at 700MHz. For the 2m band roughly 43dB gain is achieved and about 33dB in the 70cm band.
Finally i wanted to know which output power can be achieved in the amateur radio bands.
VHF/UHF PA output power
At about 1W output the output always gets compressed. You might add about 0.4dB on 70cm and 0.3dB on 2m to my measurements since the graph does not include the attenuation of the output cable. For me it means that the amplifier should work well for my purpose.
Just for fun i tried to collect some components from the shelf and plugged together a simple monitoring receiver for 9cm.
I have a DF9NP PLL OCXO for 2592.2MHz and a pipe-cap filter tuned to 3400MHz. From China i ordered a wideband LNA some month ago. It has about 15dB gain on 9cm. The mixer is a ZEM-4300+ (+7dBm LO). The setup results in a IF of 807.8MHz which is received with an RTLSDR and the very nice GQRX software.
With a short wire attached to the input of the LNA i was able to receive the local 9cm beacon DM0TUD.
Since i use Quisk for my HiQSDR i found it interesting to experiment with FreeDV again. Quisk can directly support using the FreeDV API and work in this digital mode without building lots of cables. Since i wanted to try the latest mode 700C i had to compile the library from the scratch and add the mode to the configuration of quisk. Below you can find recordings of my CQ call in the modes 1600 and 700C which were made loopback.
Now i search for a QSO partner preferably on 2m somewhere in the area around JO61. I can work relatively well direction southeast. So east OK might be good.
Please remember the 700C mode uses only 1kHz of bandwidth.
If you are interested in some tests just send me a email to firstname.lastname@example.org
Usually i do not post links to foreign content but here is a really interesting talk by Bruce K6BP on the state of digital voice and open source usage within amateur radio in general.
Thanks a lot to Hamradio Now for making this talk available !