QRO or Not QRO? That Is the Question.

Some years ago I got myself a used HF power amplifier for 1kW.

The ACOM 1000 is regarded as a solid amplifier that holds it promises from 160m to 6m. That is also my experience.

However, with quite short distances to neighbours' houses, I am not quite comfortable with using it.

In fact I used it briefly on 10m with about 400W out. That was when the solar activity was still quite low.

Then I used it on 50MHz, also with about 3-400W. Tha antenna that could endure that kind of power was removed, and for some years I have used the V-2000 for (2m, 70cm and) 6m. Under no circumstances would I use more than 100W with that one, especially with  FM or digital modes like FT8. The capacitors will not stand that, and will be transformed into carbonized components.

So today the ACOM 1000, which has been on the radio shelf for a few years witout being connected to the power outlet (or a transceiver), was taken down from the shelf. I am probably going to sell it and get some more UHF/SHF equipment.

I will not abandon HF completely, but focus more on VHF/UHF/SHF, going a bit back to my old interests.

Over 30 years ago I was working a lot on 2m, 70cm and 23cm with relatively low power and decent antennas, and over 40 years ago I was working crossband 50 or 70MHz to 28MHz, and had a lot of fun with that. Now I want to try the even higher frequencies, too. probably mostly portable from hilltops, but also with a (very modest) station at home.

Outdoor LNB for QO 100 Mounted, and Quick TX Up-Converter Ideas.

The LNB for the OSCAR 100 downlink receiver was sealed after the modification, and has replaced the temporary one mounted at the 60cm dish.
I still need to complete the indoor buffer circuit, but some preparations for other stuff had to be done first.

Next comes the transmitter up-converter to 2.4GHz. I am still waiting for a passive mixer module specified up to at least 2.5GHz, and they are on the way.

The configuration will likely be as follows:
432/439MHz transceiver frequency -->
attenuator and the LO *) signal -->
Passive Mixer -->
amplifier, probably made with the RF amplifier of a modified (filters) MMDS converter (when using 432/439MHz as IF, these filters should provide sufficient image rejection) -->
20 - 50mW amplifier -->
1W amplifier -->
cable to feed antenna system -->
"8W" amplifier, likely providing 4-5W at the feed -->
feed antenna --> dish antenna **)

*) LO signal provided by a ADF4350 synthesizer board controlled by an Arduino Uno board -->
about 20mW amplifier at 1962/1968MHz.

**) experiments with other antennas will be done. I already have a panel antenna for RHCP and a 1m long yagi, as well as a cheap, probably not very good, 17elm yagi about 40cm long, as well as a PCB LPDA antenna for test as a feed antenna.

This should provide a decent up-link signal to OSCAR 100, useable for SSB, and certainly for CW or digital modes.

The building activities will be halted for a few weeks, but mid april they should resume.
More than enough experimentation before the refinement of the system starts.

The buffer for the RX reference LO should be ready and tested soon, though.

Using the PA for both HF and 6/4m transceivers.

I have a IC-7300 covering HF, 6m and 4m, and a IC-7600 covering HF and 50MHz. I would like simultaneous use through the PA of both transceivers to a R-6000 antenna and a 6m 1/2 wave antenna.

How to proceed? Here is my idea. Between the radios and the input of the PA I can use (lazy as I am) a commercial diplexer, like the CF-360 from Comet or the MX-62 from Diamond.
The problem with using those at the output of the amplifier is the limited power they can handle. 600W PEP or about 200W continuous. Not exactly fitting for the 1kW capability of the amp.
Looking a bit around on the net I found this : https://www.ka6wke.net/hf-vhf-diplexer , describing the use of a IC-7300 with an HF antenna and a 6m antenna with a home construction diplexer. There is a design that I could use, albeit with components capable of withstanding the higher power.
What about 4m ? At the moment of writing this, the power limit for 4m in Denmark is 25W, so the PA is not really necessary. If the limit goes up, I might think of a modification to the existing PA, or using a second transceiver for 4m and building a separate amplifier for 4m.

Next step is to find those components.

At the moment the amp is running low power, 200W, with a CF-360 at the output, connected to a vertical 1/2 wave 6m antenna, at the VHF port and the R-6000 at the HF port.

Now, here is the question some will ask :Why use a separate antenna for 6m when the R-6000 does 6m, too ? I have compared the two antennas, and I find that the 1/2 wave antenna for 6m performs far better than the R-6000 on that band. Further, since I do not intend to set up a HF beam, but at a later stage I do intend to have a small 6/4m capable of accepting the full power of the amp, so here we go !
I may design some high voltage capacitors , maybe made with PCBs, if I can not find some suitable for the 1kW filter I prefer to design for higher power than I intend to use, so I can avoid burnt components and/or equipment.

Oh, Boy ! Yet another project added to the pile ;)