Mini project #4B: Small 70cm Flexa Yagi, and Some Thoughts on the Higher Frequencies.

When I purchased the small Flexa Yagi antennas some time ago it was the intention to make a compact, not too visible antenna system for 2m/70cm/23cm SSB/CW etc operation. At the time I had chemo therapy, so everything went too slowly, and the project almost died.

This project has now been resurrected, and I got the 3 antennas assembled. 

- 4 element yagi for 144MHz

- 11 element yagi for 432MHz (strictly speaking 8 elements, as there are 3 reflectors making a reflector plane).

- 16 element yagi for 1296MHz

The Flexa antennas have very thin steel elements (and a not too heavy boom), reducing the visual impact of the antennas, as I wanted

All these antennas are made for mounting in front of the mast, i.e. "behind" the reflector, so the mast will not interfere with the function of the antenna by blocking part of the elements, especially on the higher frequencies.

Having all antennas front mounted will create an imbalance of the load on the rotator, so I am thinking of making a compromise here: Mounting the largest antenna (the 4 el. for 2m) on one side of the mast, then mount the 70 and 23cm antenna in the opposite direction. This will make the operation a bit more cumbersome, but I think it can be done.

I may add a Moxon Rectangle for 4 and 6m to the system. This is a rather small antenna and will not add significantly to the visual impact.

Further, some small antennas for the 2400MHz and 10GHz band are expected to be added. No parabolic dish there, just some tiny yagi or patch antenna for 2400 and a small horn antenna with a transverter for 10GHz. This is for later, but initially a LNB (frequency stabilized), maybe with a small horn extension will be mounted for 10GHz monitoring purposes.

I will need to mount this on a rotator. No need for a heavy duty one, so I am looking into options.

I intend to mount the system on top of an old apple tree where I have some antennas already.

For SSB/CW (DX) work I have had a clover leaf ("Big Wheel") antenna mounted right on the top of the tree, essentially invisible, and it has provided some DX on 2m.

What kind of performance can I expect from this system.

On 2m, the stated gain of the 4 el. antenna is 7.6dBd. This may be exaggerated, but compared to the old clover leaf antenna I expect to mount the 4 el. 2-3m higher and less obstructed, so I would expect a performance improvement of approximately 10dB over the clover leaf antenna. With a good preamp at the antenna, and also an added PA in the shack I should have a solid performance boost, compared to the current system.

On 70cm, with a stated gain of 10.2dBd the system is a very modest, but some DX activity should be possible.

On 23cm, with a stated gain of 14.2dB (exaggerated?) I would expect some interesting occasional DX activity, especially if a preamp and a PA (25W?) is mounted near the antenna.

On 13cm this system will just be playing around , maybe with some interesting DX in the best directions I have, but I do not expect much there. 

On 3cm  the system is very modest. I may be fortunate enough to make some DX under excellent tropo conditions, and possibly some rain scatter QSOs. 

For the higher (microwave) bands some hilltop operation is probably a much better option, but the capability of some modest home operation is good to have.

Found at Rally: Triplexer.

 A few weeks ago I found this at a local get-together taking place at a repeater site. At this meeting they sell (often donated) stuff for the benefit of running the repeater.

This year I found an unknown set of band filters in a box, I suspected that it would be a kind of triplexer, and toady I got my NanoVNA out, and yes it is.

The connector at the far side is the common one. On the near side we see two very recognizable labels, VHF and UHF. I did not know what the third one was, but measuring I found.

Testing from the common port:

TOS: Low pass filter, flat up to 117MHz, then a small dip of up to 5dB, then a 3dB cut-off at about 134MHz.

VHF: Flat from 135MHz - 270MHz, but some feed through up to about 315MHz. Good attenuation below 100MHz and above 400MHz.

UHF: High pass filter with 3dB cut-off around 336MHz. Attenuation on 1300MHz was about 3dB.

Residual attenuation:

Below 100MHz: Practically flat with <0.5dB attenuation

VHF: <0.5dB at 144MHz

UHF: <0.5dB at 435MHz

Attenuation between band ports was more than 22dB at frequencies where I would expect to transmit, so that is insufficient for a transceiver triplexer. For a VHF-UHF monitoring receiver system, this would work nicely.

I got a few of the filters for experiments. I had decided that the shielded boxes, at least, could be useful for other RF projects, and there were some decent looking (SMD) capacitors for VHF and UHF. There were quite a bit of these filters,  so I might have got a few more. If they are there next year I may get some of them again.

 Yes, finally I got to use my RF test equipment, now it is time to get some construction done.

Quick Test of Some Receivers for Monitoring.

Over the week end I found some older scanner receivers etc that I want to use for propagation monitoring and general (local) traffic monitoring.

Because I like to have the monitoring running for hours every day, and using solar power, I want to limit the power consumption.

Monitoring FM channels:

I have a 10m FM transceiver that I intend to use for monitoring 10m FM on 29.600. Draws 160mA on receive, which is acceptable, though not ideal. Current consumption is still about 160mA, but it is better than using the IC-703. For 10m FM it is also possible to use a Bearcat UBC92XLT handheld scanner running 6V with 70mA current consumption. A voltage regulator reducing the 13V to 6V will be necessary for this (easily built).

For 6m FM, monitoring frequencies in the 51-52MHz segment I can use my older Yaesu VX-5.

The best results of those came with 2 handheld scanner receivers, Bearcat UBC65XLT. These are 10 channel units capable of running in the 4m, 2m and 70cm bands. They draw 5mA when off, and 50mA when receiving. 

I think that one of those should scan the 4m FM segment - 70.300 - 70-500 - 9 channels, and 69.900. the frequency pair 69.900/70.500 is allowed in Denmark for use with repeaters - yes 600kHz spacing, just like the 2m repeaters.

The alternative would be using a (Wouxun?) handheld for this purpose, if I can find out how to program its memories.

The second one can be used for 2m, and the 143.625 MHz, all in 25kHz spacing system. 143.625 has been used by the space stations Mir and ISS for communication with the ground stations in Russia.

For 2m FM I could also use my older Kenwood handheld TRX, or a Baofeng as monitor, again if I can figure out how to program the beast. Since I have no intention of transmitting with those I have no problem using those Chinese radios for monitoring.

For 70cm I could use the Baofeng's again.

Now, what to do for 23cm? I do have an old Kenwood TM741 triband radio, and that could be useful for FM monitoring on that band. I will have to test the power consumption of this one, but it does have the advantage of being capable of running 3 bands simultaneously, with additional transmit capability. I can likely find a low power scanner capable of running 23cm. We shall see.

I am well aware that some antennas will be necessary for all this (and more) monitoring.

The advantage of receive-only antennas is that the preamplifier, if it is necessary, can be placed close to the antenna, so a low cost coax cable (cheap satellite cable) can be used.

The 10 - 6 - 4m, and 8m bands could be covered by a TFD antenna about 2.5m long, hanging in a tree in the garden. Essentially invisible.

For 2m, 70cm and 23cm a short tri-band vertical can be used, with a wideband preamp, and stilll the low cost cable. Not invisible, but relatively discreet. Yes I am aware of the possible overload of some receivers when transmitting, but that is, for now, an acceptable compromise.

For reception on bands in between - such as air band and FM broadcast radio of both Western European and Russian stations, a wide band antenna, such as a discone or a log-periodic antenna could be used with a wideband preamplifier.

The next level will be some monitoring using FT8 and beacon reception, and this requires more sophisticated reception systems capable of SSB. I have some ideas, but this will have to wait for another time.

30m Wire Antenna Update.

 The 30m long piece of wire has found its place for a while.

The feed point is placed 2m high at the end of the out-house under an apple tree. It then goes up through the tree and lead to the second apple tree - the largest in the garden, then down to a smaller tree where the end is attached. Most of the wire is about 5m above ground, not particularly high, but definitely better than 1m above ground. 

The antenna now has a counterpoise added, about 50m of wire, about 2m above ground (and lower).

The system works nicely on 30m, and does not need a tuner when operating from 80 - 6m. On the resonant bands of the dipole, the dipole mostly works better, but on 20m in particular the wire gives signal mostly equal to the dipole. On 30m the dipole is useless, as it is not resonant at all, and the wire works nicely. A TZ station (Mali) was coming in nicely with up to S9 signals, but 5W was (as expected) not sufficient to break the pile -up. I will have to try again when signals are good, and less stations are calling.

The present set-up of antennas and transceivers for the 80 - 4m bands is now as follows.

IC-705:  Wire antenna, workable on all bands 80m - 6m.

IC-7300: Dipole working on 4,6,10,15,20,40,80m

IC-7600: The old R-6000 antenna running 10-12-15-17-20m, and the 6m part of the V-2000 antenna.

IC-7100: A vertical Sirio half wave antenna for 4m, mostly used for the local FM traffic.

Update On the QRP Challenge.

 Almost every day I have been working QSOs with the 5W output CW, mostly from the IC-705. QSOs have been made on 10-12-15-17-20-40-80m.

Now we wait for 4 and 6m to open - and 2m in the summer Es season. I suspect that I will mostly run more power on those bands, but some 5W work will be tested in the big openings.

New antennas are needed, so I can include 30-60-160m. Initially I expect to make and use a 30m vertical 1/4 wave GP, usable on 30-10-6-4m, probably good enough to listen on 8m (40MHz).

Next antenna will probably be an EFHW wire antenna for 80m. That should work on all HF bands except 60m, and with an extension coil it should be extended to work on 160m. I do have the transformer (49:1), it must be built into a box, but then it should be ready for deployment when the weather gets a bit warmer. Yes, I am waiting for spring weather. It may be variable, but I think I can find some warm and dry spells to play with antennas.

We have got more sunspots than I have seen in several years, and we are getting more daylight, so the HF propagation is already better than I have seen it in years. Good times for HF QRP operation ...

The Higher HF Bands Are Good Again.

 Now that we have more daylight in my area (55 deg. N), the propagation on the higher HF bands is improving again.
On top of this, the solar flux numbers have been above 100 for several weeks, with very few days below 100 SFU, I is now about 60 days ago we had no sunspots visible. Cycle 25 has started in earnest.

In my 5W challenge I have now had QSOs on the 10-12-15-17-20-40, and 80m bands.

Testing the SWR with my 5-band dipole showed that it is also useful  for a few more bands than the design frequencies - 10-15-20-40-80m. The dipole can operate on 4-6-12 and 17m. SWR is too high on 30 and 60m, and far too high on 160m. But not bad to be able to operate 9 bands on a 5-band antenna. This may change when I get the feed point higher up, as it is less than 4m above ground. I will have to improve the HF/MF antenna system, so I can include the remaining bands, and maybe try out the 630m band, or the 2200m band.

Last night I made what I refer to as a real CW QSO on 80m. F6BBQ with much more exchange than calls and report. Nice and moderate tempo, perfect for my modest CW capabilities. 

As it is right now, I am using the IC-705 for all the 5W QSOs. When I add an antenna for 30m (planned as a 1/4 wave ground plane), that should be usable on 10m (possibly with a tuner), 6m and 4m on thr 3rd, 5th and 7th harmonic. Not ideal, but probably slightly better than the performance of the low dipole on 10-6-4m, until I can get my 4-6m Moxon rectangle assembled and mounted.

The 30m vertical could be expanded to other bands with parallel (band) elements. This antenna would most likely be used with the IC-7300, with higher power on 4 and 6m, and likely set to 5W on the HF bands. Spring is allowed to begin, but I will probably have to wait another month here.

Another Personal Challenge. QRP.

This year I will make an attempt to get 365 QSOs in the log, all with just 5W output or less - no matter the band.

The most used transceiver is likely to be the IC-705, but other transceivers, either with a 5W power limit or higher power transceivers set to 5W out may be used. e.g. I intend to get the IC-7300 up and running with a 30m vertical. This antenna will also work on 10-6-4m, so I can get some summer sporadic E, and maybe some other band activity going. 

This requires me to build a new vertical. It will be a ground mounted 30m quarter wave with a good amount of shorter radials on the ground. Other bands in between may also be added with extra (wire elements), e.g. 20, 17 and 15m.

Idea Box: More Simple HF CW Transceiver(s).

 Here is another one for the idea box.

While I am doing stuff for much higher frequencies I am still thinking of this in connection with my "one QSO per band with home made gear" challenge. I was thinking of using a kit (or two) for a simple HF CW transceiver using a direct conversion receiver.

Some examples of those kits are the Pixie, the Rockmite, the Frog Sound and the 49'er. I have a box with some of those kits, and some of them should be quite easy to convert to HF bands up to 18MHz without too much loss of performance.

For higher frequencies I suspect that the receiver sensitivity will be insufficient for efficient work on those bands (21/24/28MHz). Here it is probably a good idea to use two kits, one for TX and one for RX, adding a preamplifier for improved RX sensitivity, and possibly a PA for higher TX power.

Each transceiver would be modified to use a SI5351 synthesizer board. This board should be controller (programmed) by, e.g. an Arduino, so I will have to learn another skill: Micro-controller programming. There are libraries and some programs in existence, but the programming skill will come in handy if I want to extend functions.

A simple 28MHz model could possibly be used as base transceiver for transverters to higher bands. This would not need RX modifications and could possibly be using just a simple TRX kit. I am well aware of the lack of CW activity, especially on the VHF/UHF/SHF bands, but a single QSO, or a few, should be possible.

I do have two other kits for CW transceivers, the QRP Labs' QCX+, with components for 20m and 60m. Still need to be built, but that is a matter of finding time to add those.

Do I have too many kits and projects? Yes, but I will not have any time to be bored, that is certain ...

Another one of the ideas stacking up ;)

Some 2m Sporadic E (Es).

 Yesterday my FT8 monitoring system detected a single Italian station, most likely a short Es opening, or a long meteor burst.

Then this morning I went to the radios and found that 10 minutes before there had been Es signals on 2m. 2 stations in Southern France and 4 stations in Northern Spain were detected with up to +11dB S/N.

Away from the station I have set up a rudimentary 2m Es monitoring system using the PSK-reporter and the DX-maps websites showing my own 2m FT8 spots and the Es-MUF map for Europe, as well as stations spotted on 6m FT8.

This monitoring system has been running essentially 24/7during the Es season, and I would like to be able to add to the system, so I can monitor 28(/40)/50/70/144MHz 24/7, especially during the Es season, so here is an addition to the "Idea Box":

For this I do have usable receivers, but the antenna system is not yet ready for this. For the purpose I am thinking of mounting a TFD (Terminated Folded Dipole) vertically, with an added broad band amplifier, hidden in the trees at the far end of my garden, at least for the 28 - 70MHz bands, and probably some kind of wideband antenna, usable for the FM broadcast band, air-band, 137MHz satellite band and 2m, also with a preamp.

An alternative for 2m would be a simple vertical or a horizontal V-dipole or a halo, with a narrow band preamp for 2m.

Most Active Es Day For Me This Year.

Today was quite a day for sporadic E propagation (Es).

2m:

While I have received Es on 2m a few days ago, I worked my first 2m Es today. One Russian and one Italian. Both were worked with FT8 because I only had low power available at those moments. I discovered the opening to Italy a bit late when I checked the PSKreporter while in a local QSO, then I got busy. I probably missed the main opening, but at least I got one.

Here is the map of received stations via 2m Es today. Quite a bit of propagation.

Initially I tried to work SSB or CW, but at that moment the PA went on strike. After the openings I checked, and with a power disconnect-reconnect it works again. I suspected the RF input level to the PA was too high in SSB, so played with the levels for DIGI modulation and Mic Gain, as well as limiting the RF output level of the radio, and now all works nicely again.

4m:

The other day I worked a single station on Es, today there was a bit more (yes, just two). The antenna used is still the HF dipole. not ideal, but it does provide QSOs.

6m:

This band has been humming with signals every day the past week. Today I got just under 20 QSOs on 6m, all with trying 2 and 4m in the mean time.

Oh, the weather was perfect for working on the radio, raining much of the day.

Week End Activities, P.1: Sporadic E.

 This week end has provided some sporadic E propagation on 10m and the lower VHF bands

My 4m vertical is still not functional, so I tested my low hanging 5-band HF dipole, and with the tuner in the IC-7300 it could be used on both 4 and 6m. At least, I could try to work on 4m, so I set the receiver to monitor 70.200, and sure enough, on Thursday (13th) a signal popped up. S57L called CQ in CW. I got the key connected in time, and made the QSO. Yes, I know! I need a better system to use my memory keyer for more than one radio.

I have now made my first 4m Es QSO of this season.

After this I went on 6m, still keeping an eye, well ear, on 4m.

8 QSOs in SSB and CW were made.

The rest of the week end I had the radio monitoring 6m FT8, and there have been signals every day, but not enough time to work QSOs.

Amplified RX Loop Test and a Little Outdoor Antenna Work.

 This week end I have been active with antenna work.

Small Receiving Loop.

The first was a test using a low cost Chinese amplifier for the NCPL (loop).

The amplifier is actually "overkill", stated gain/bandwidth is 32dB/1-2000MHz. Not surprising, the gain is too high, both attenuators are in action on the FRG-100 receiver, and the base noise level (not interference), especially on 5-10MHz, is still very high.

Considering that the antenna is till tested indoors in the noise field I would expect things to improve when the antenna (properly weather proofed) is placed outdoors, but there is still one problem. The high gain causes intermodulation, maybe also cross modulation. I have not tested this, but in addition it is possible that the amplifier is oscillating in the UHF range. 

Which signals cause the intermod etc? I suspect it can be the MW broadcast band, but given the bandwith/gain of the amplifier it could be FM broadcast stations, too.

As I suspected this type of amplifier is simply unsuitable for such low frequencies, but I had to test it.

A simple 2 transistor with negative feedback is in my thoughts, along with a pre-selector. N1KPR has published a simple design that could be made on simple perf-board. 

Outdoor antennas.

The weather was pleasantly warm today, so a little outdoor antenna work was done. Since I do it all alone things may take a bit longer.

First outdoor thing was removing the lowered 6m half wave vertical antenna. There was a bit of rust, so the WD-40 was in action. This antenna was mounted on a satellite dish mount on the lawn, so this is now freed for other antennas. In addition, the cable was freed as well, and put to good use.

The 5 band dipole (10-15-20-40-80) had been connected together with the 4m vertical (now partly lowered) with a HF/VHF diplexer, which this was removed. The dipole is now connected to the old 6m antenna cable. Testing from indoors, the dipole/cable system seems capable of operating on 6m and 4m, so for the moment the dipole is used for 4m, because the 6m reception is quite noisy. The performance is expected to be quite poor on 4 and 6m, but until a better solution is available this will have to do.

The (partly taken down) 4m antenna is now connected to the old cable, running indoors, so a very limited 4m reception is possible, until another 4m(6/10/30m) antenna can be tested. At the moment only a transceiver capable of running a repeater is connected.

For now the 4m will be run on the IC-7300 with the dipole, and 6m on the IC-7600 with the V-2000 vertical.

It looks like the weather will be quite good tomorrow, too, so I may find time for more antenna work.

4m Antenna System Temporarily Out of Order

 Because I have the intention to replace my 4m vertical with a multiband vertical the antenna has been partly taken down.The mast is standing/lying in about a 45 deg. angle, so while it is connected, it is useless right now. When the weather permits I will seek to change that situation.

Initially I should test a set-up of a 30m vertical (GP) which will resonate on 30, 50 and 70MHz. This could, initially (tor testing) be set next to the tree where the old 4m antenna is now quite useless.

As soon as the weather permits this is the next stage of outdoor antenna experiments.

Sporadic E on 2 Meters

Yesterday and today I experienced Es on 2m for the first time this year.

In the morning of yesterday I detected an opening, but only after looking at my FT8 PSK-reporter map.

There was a solid signal from the Ukraine and a weak one from UA6, just East of the Black Sea.

Then, today the following appeared, almost while I looked at WSJT-X:

1016 RT3G   KO92up

1028 RK2T   KO93ad

Both were in the -15 - -20dB range, so quite weak, but they were there, none the less.

The past week there have been substantial Es openings on 28, 50 and 70MHz, but I did not detect anything on 2m until yesterday. Also, today Russian FM stations were there aplenty on 70MHz.

A few days ago I detected signals on 50MHz from Japan. No North America on 6m yet.

The season has really started. Interesting to see what this year's season will provide.

2020 Has Started, And A Brief Look Back On 2019.

For me, 2020 started in the sign of the cough. It stared e few days before the New Year, and is still there, though it seems to be subsiding now.

2019 was a year of travel, and not too much radio activities.
The QO100 geostationary satellite was activated, and the amateur radio transponder went on line in February. I got a decent system up and running for receiving the narrow band transponder down link. This is actually not too complex, as a TV satellite LNB is sufficient for converting the 10GHz down link signal from the satellite. A bit of modification, and adding an external reference oscillator placed indoors proved necessary, was constructed and has been in use since then. An improved version is in the making.
Next step is - still - getting to transmit on the 2400MHz up link for the satellite.
Also on 10GHz, a simple experiment has been running: Using a LNB for reception of terrestrial signals, via rain scatter and tropospheric propagation. I am still impressed that I receive a beacon about 36km from here, certainly non-line-of-sight. It is there all the time, received with the LNB alone, no extra gain from a dish.
Also, a fair amount of sporadic E openings over the summer on 6m and 4m, with a few new countries worked on each band, and getting a fair amount of components for projects (mostly via eBay).
Not too many projects finished, and many more ideas appeared. It is a fact of life that getting ideas is easy, putting them into practise takes much more time.

2020 should probably see me finishing just a few projects, like:
- QO100 uplink capability
- receive antenna system for monitoring several frequencies simultaneously
- some QRSS activity, mostly grabbing (receiving) QRSS signals  and other weak signal modes

The beginning of 2020 (and the end of 2019) has seen some spectacular tropospheric propagation over the Atlantic.
On 2m the European distance record was broken for tropo signals, with a spectacular QSO between Cape Verde and Northern Scotland.
On 70cm the world record was broken with a QSO from Cape Verde to Scotland.
All this has been made possible by using weak signal modes, like FT8. I would not be surprised if those records will be broken again later this year. Exciting times on VHF and UHF, and possibly the microwave bands.

Happy New Year to all from here. Hope to work some of you guys.

The Beginning of the "Summer" Sporadic E Season.

10m and 6m have been buzzing with European activity today, and some yesterday, too.
Also, I saw someone reporting Es on 4m.
The season has started.
This does not, of course, mean that we will have Es every day for the next monts, but it is a nice beginning.
My 10m map for the last 24 hours show (I think) Es-linked F2 propagation to South america and probably to the Middle East. At least 2 stations from the Arabian peninsula were reported here. Hundreds of reports from European stations and places like EA8, etc.
I am now changing my FT8 listening frequencies to 10m and up. Right now it will be 10m, 6m and 2m, even if I only expect tropo signals on 2m the next few weeks.

Busy times ahead, this time with operation on VHF bands and up, plus, of course, my favourite HF band: 10m.

IC-703 Modification.

For the first time in almost 2 years I have been traveling (more than about 100km from my home) for a bit less than 2 weeks, and I am back now. This was a non-radio-related round trip From my home near Copenhagen through Northern Germany, The Netherlands and Belgium, then to Paris. On the way back via Köln (Cologne). Last year I spent getting rid of a colon cancer, and I am now free of it, just going to control visits every few months.

Today I modified my old IC-703 for receive output/input. Will likely use that TRX for 10m with aux RXs for 10/11/12m propagation monitoring, using the TRX with the 10m PA running about 200 - 250W CW or about 150W FT8. Should work nicely.

Why do a modification like that ?
Well I wanted to be able to add some kind of spectrum/waterfall display, and possibly use the same antenna with several monitor receivers, e.g. beacon watch, FT8 watch etc.

I was using a kit purchased for doing the trick on a IC-7300, but decided to try it with this one first.

The mod took a bit of filing off the outward side of the new adapter and filing a bit of the bottom cover, and removing the connector for the external ATU control. The external control is not necessary as long as the built-in tuner works (or is not needed at all).

It now fits nicely into the casing.

System check of the RX shows that it is working nicely in through-mode.

It is likely that the modulation circuit will need an equalizer, because the reports on the modulation are not good enough. Initially, I will check the adjustment of BFO and SSB filters.

Second use for this low power TRX could be driving a transverter to 4m, including RX output for AUX RXs, such as spectrum waterfall.

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 ;)