Improvement of the QO-100 Uplink.

 Today I received a new helical feed antenna for my QO-100 uplink system, and tested it with the power amplifier I made an initial test with in the previous entry.

The amplifier mounted indoors, and with the previous unaligned feed arrangement did give a readable downlink SSB signal for people with a well optimized RX system, and I made QSOs with it.

As I am not very good at mechanical work, I used a DX-Patrol helical feed with a hole and mounting option for some LNBs. I did mount one LNB, with a TCXO, and modified for down conversion to 432MHz. I will use that for monitoring my uplink signal to the satellite.

Right now I am using my IC-905, driving the SG-Lab Power amplifier directly on 2400MHz, and a GPS stabilized LNB, mounted in a 60cm dish. This has quite good performance, although I want to try it with a larger dish. I have some lying around, so it's a matter of finding time and energy to do it.

Now, the test with the new feed gives about 15dB S/N via the satellite, and I can easily read my own signal. With the previous feed I could read my own signal with a little difficulty.

I can still improve the uplink signal, mounting the PA near the antenna, but it is quite nice to have it inside, so no weather proofing is necessary.

This is the test setup (with the LNB not connected).

2400MHz Amplifier Test.

Finally, after the winter solstice, I had a bit more energy.

I purchased the 2400MHz amplifier from SG Lab in Bulgaria. This has a good reputation for reliability, and I wanted a bit more output than the 2.5W I already had.

This is the v3, needing less than 40mW to deliver a typical output of 20W @28V power supply and 17W @24V.

I did have a signal generator using a computer control Windows program, but no usable Windows machine with a CD-ROM drive. Oops! What do we do now?

Well, well. I do have my IC-905 with variable power output up to 2W nominal.

The RF unit is in my "shack" on the ground floor, and the lab with all my test equipment is in the attic, so I picked up the controller unit and a piece of cat8 network cable, so I could control the thing from the upstairs lab. Now to get the RF power upstairs. As I only needed maximum 40mW, I could use some cheap SMA cables, RG174, two lengths of about 5m. 

This makes for a neat cheap attenuator. With the 2W output from the TRX I could measure about 30mW, using the peak indicator of the spectrum analyzer. That is good, as I can't overload the amplifier.

Because the output of the PA is 10-20W max, I needed to bring that down the level. I used a directional coupler (800-2500MHz), with 40 dB coupling. Bingo! 10W becomes 1mW. Of course a dummy load capable of dissipating the output power was connected to the "through" output.

Connecting the system I could measure about 10W out with a drive from the TRX of about 33% (650mW minus the cable attenuation) Result: 0dBm out of the directional coupler 10W from the amplifier.

Increasing the drive gave about one more dB.

This looks like to low output, but I would consider it within the tolerances of the test equipment. There is some extra loss in the connectors, adapters and cables after the output of the amplifier, and the spectrum analyzer, as well as tolerance of the input power measurement of the spectrum analyzer. so measuring 12W maximum output is within the tolerances of the minimum 15W specified from the amplifier, by about 1.5dB. That is good enough for me.

The amplifier test setup was the module attached to a cooling fin, with Kapton tape, and using some good thermal compound. 

It did not get hot to the touch by normal operation, even using full carrier FM.

I intend to use it for a while indoors, and if it looks stable, I will likely mount it outdoors. this will require a better mechanical construction, but also provide more power available to the antenna.

This setup is intended for QO-100 uplink use.

If this works well, the next step is some more power for 1297MHz FM.

1296MHz Tropo.

The past week end made for some surprising propagation on VHF/UHF into my area (Greater Copenhagen)

I did not work much o 144MHz, apart from what I call "local tropo) propagation. That is distances up to about 300km (200mi). We had some good contacts within that distance, running FM with a vertical.

The more interesting band for me this time was 1296MHz.

Both Saturday and Sunday provided beacon reception (by ear), from several countries.

Of course, the local OZ7IGY is always audible here., then 2 other OZ beacons, further away.

3 German beacons were there.

The Swedish SK1UHF, on the island of Gotland at quite a distance.

The Norwegian LA3SHF at 370km (230mi)

The Polish SR1KOL at 270km (170mi)

Finally, the Czech beacon OK0EKL at 580km (360mi)

The only antenna available at this moment is a monoband 23cm vertical with over 10dB gain. All beacons transmit with horizontal polarization, so the attenuation is considerable. With a good horizontal antenna (yagi etc) I estimate the signals would have been 10-15dB stronger, and I would likely have heard several more beacons.

Best 2-way DX was DC7QH in Berlin at 345km (216mi). This was unusual. I heard him call CQ in FM and called. When he heard "OZ" he pointed the antenna in my direction, and the signals disappeared.

Then, when he pionted the antenna about 180 deg. away from me, the signal went to S9+. Probably a reflection. He was working with 200W into a 1.5m (5') dish with horizontal polarisation. ( am running only 10W, at the antenna about 4W.

During all this there was a lot of noise from radars (at least 3 different ones), sometimes wiping out most signals. I had good use of the narrow CW filter (250Hz) when listening to the beacons. The radar peaked far above S9.

On Sunday afternoon I decided to get my radio running with WSJT-X, so I can run some DX tests. That took a few hours, but it finally worked.

Best distance "heard" with FT8 was UR5WCE at 1029km (about 600mi).

Come spring, I need to mount a (small) yagi on a tiny rotator I have available. It will be very interesting to see the improvements, including raising power to about 40W at the radio. Perhaps later a PA/preamp near the antenna, raising the power at the antenna to about 100W, also running digital modes like FT8.

This was a spectacular week end on 1296MHz, let's see what's in my future.

Nice Bargain at VHF Day.

 Yesterday, 11th January I went to the Winter VHF Day in the town of Ringsted.

As always great to meet other VHF-up people and exchange tall tales.

There is also a small flea matket, and I got two things home.

A programmable attenuator 0 - 120dB in 10 dB steps. specified up to 2 GHz. Another addition to the test equipment for the higher frequencies.

The second thing was a bit of a surprise. Someone had a Uniden scanner, the 3300 on the table, and when I asked the price he said DKK 20.- (about $3) so I took it home, thinking that if it's a brick, it doesn't matter.

I tried to switch on with the battery - of course it was dead. I found a suitable DC connector and connected 12V. Switch on, and the4 display showed something that looked like a functioning radio. Neat.

Now to find out how to program frequencies, so we can see if it really worked. Downloaded the manual and spent some time to get the right menu going. Finally I could enter a frequency. 

When I looked up the spec, the scanner should be able to run from 1240-1300MHz, so I entered 1297.500MHz, and restarted the radio, transmitting on that frequency. 

Bingo! Signal received. (Hearing audio feedback) The receiver works. 

I have not yet tested sensitivity, but even if it has poor sensitivity, I can use a preamp, and possibly a filter.

Now, a $3 radio that works on 1300MHz, that is what I call a bargain.

Temporary 28MHz Beacon.

 Fun little story from today.

I was, as usual, listening to the International Beacon Project (IBP) beacons on 28.200MHz.

Suddenly a big signal was coming in. I reralized that it was a test beacon from an Italian station.

S9 signal drowning the usual 18 beacons on the frequency. 

I found the email address on QRZ.com, and wrote a mail to him explaining the situation, quietly.

After a short while the signal diasppeared, and I got a reply mail telling that he was not aware of the IBP project, and he would find a suitable frequency.

All in the good ham spirit, and I do understand that we don't know every aspect of the activities, and we are usually, like here, willing to correct a mistake.

No, I am not going to reveal the call, because all went absolutely well. Mistakes happen, we have all made them.

CB Radios From Long Ago.

Yes, I have started doing a bit more radio again, let's see how long this lasts, as I need to de-clutter a lot.

Some time ago I got a box with a few CB radios, totally for free.

4 radios in different states, and all FM rigs.

First one (40 channels) tested worked in TX and RX. Power on and 3.5W TX output.

Second one (40 ch) had no TX output (nominal 4W) I had found that before, so not such a surprise

Third one (40ch) had about 2.8W out, and needed an external speaker to receive.

The last one was a 23 channel FM rig with 700mW out (nominal 500mW), b

I could probably find a replacement for the blown final transistor in #2.

All sets had, to my ear, poor sensitivity of about 2uV (-100dBm) for a well readable tone.

All worked on receive. #4 had poor audio., probably a defective electrolytic capacitor.

I think all those radios could use an alignment

Are any of those radios useful for anything ham related? In my view, yes.

- one or more could be used as a monitor receiver on 27MHz, for propagation monitoring (maybe a good use for the one with the blown final.)

- one could be modified and used for monitoring or transceive on 29MHz FM. I already have such a rig, so not so likely.

- I could use the casing of those radios, and build some home construction transceiver or receiver. The channel switch could be replaced with an optical encoder, and the squelch/volume pots for volume (duh!) and RIT control.

I have been thinking of some simple low power transceiver projects.

Anyone with other ideas?

23cm DX With the Vertical.

 This evening I had a bit of fun.

Listening on 23cm, well, I was simply having the IC9700 stand by on 1297.5 FM, and nothing.

Looking at the spectrum display (waterfall) I noticed a line around 1296.912. I had not heard any signals on that frequency before, so I checked, and out of the speaker I heard the DB0XY beacon in JO51EU. The signal was easily readable at the other end of the room, so actually quite strong at times.

I was a bit surprised, as this was with my vertical 23cm antenna, and most beacons work with horizontal antennas.

Distance 438km. Not bad with such a simple setup.

I need to get a horizontal antenna up again, and also getting a power amplifier up and running.