NAC on 1296MHz.

Yesterday I was up at the local hill with the '905 to operate a bit in the Nordic Activity Contest.

This time I brought a bit more equipment, apart from the 23cm yagi antenna:

- a tiny 3 band FM handheld, the Standard C710

- a 2400MHz long yagi.

Among a few contacts with SSB on the '905 and the 12 element yagi, with the local OZ4HZ, after the 1296MHz QSO we tested the 2400MHz band.

On 2400.500 we worked a nice QSO on FM with S9 signals noth ways. Now, with the correct polarization and operating from the hilltop, that was a massive improvement from the first test.

The test with the handheld radio was actually quite a lot of fun.

The radio operates a maximum of about 300mW on 1296, and some of the strations in the Copenhagen area had excellent signals. This radio comes with a tiny 10cm long "rubber duck" antenna, so I was a bit in doubt about the range. The first QSO was with OZ1GIN, working with an indoor antenna 2 small yagis, and reported S9 signals from the radio at about 25km. Yes, he was running horizontal polarization, so it was simple to turn the hand(held) for that.

A bit later I tried with OZ4HZ, and again wee had S9 exchanges, and a less local station, SM7FMX, just over 40km away)  came in for another handheld QSO with good signals.

All worked well, and then I noticed that the radio was in low power mode, so all those FM QSOs were actually worked with a mere 100mW. Now, that is fun portable work on 1296MHz.

I will probably try going light-weight portable on the hill with the handheld and a somewhat larger antenna, so everything can be carried in the rucksack.

QSOs on a New Band. 2400MHz.

 A few days ago I got a mail, someone was planning to do activity from the island of Moen. A distance of about 77km from me.

The operation was planned for this afternoon, and they would acttivate both 1296 and 2400MHz.

I went out about 2km from home and set up the IC905 with small antennas for the 2 bands.

I think they stopped activity about the ime I got set up, so I called some of the locals who had 2400MHz capability.I was not on the hilltop as the earlier tests, so it's always interestingt to see how a new band works. I called OZ4HZ, who had a station with antenna on a balcony. Signals on 1296 were booming in, so we decided to test 2400. Signals from Hans were weak, but readable, and we made a marginal QSO in SSB, exchanging callsigns and reports both ways, 52-53 reports. Not bad for a first test on the band.

I had texted OZ1GIN and told him about the activity, and h came on after a while. Also with booming signals on 23cm. The test on 2300MHz had weak, but easily readable signals in CW. We exchanged 559 reports at 25km distance. This is a special case as Allan was running with a completely indoor system, including the antennas.

After the experiments I started listening for beacons on 1296, and heard 2 in SM6, at least one in LA, and also OZ5SHF at Yding, one of the highest points in OZ, and the whole time, most of the time booning in, and audibl with the antenna in all directions. There was most certainly tropo today. It's now about 2200 local time, and with my vertical at home it's still coming in with  solid copy, even at the other end of th4e house.

There is still a lot to optimize in the portable microwave system, so maybe better results next time.

Right now I am not complaining.

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.