AR8600 Filters and Add-on.

As mentioned earlier, the AR8600 receiver originally has a poor SSB filter. 

I do have an old Mk1 and a newer Mk2, and the filters are different. Also, the Mk1 stops at 2040MHz, and the Mk2 continues up to 3GHz, so it is useful for reception on 2400MHz, too. 

I suspect that a preamplifier will be needed for those high frequencies. I can find one, or use a module I have for that.

I made a search on Ebay after looking at a video on updating the receiver.

I did locate one SSB filter suitable filter, and ordered it from Japan. This is an 8-pole Collins SSB filter that should be much better that the original Murata filter in the receiver. The post mentions the AR8600, so I hope that the filter fits in the PCB. I am hoping to receive the filter some time in February.

The filter I ordered looks like a fit for the Mk2, and that suits me fine, as the Mk2 has the wider frequency range.

I suspect that I will have to find an alignment procedure for the AR8600s, as there seems to be some misalignment, at least in the Mk1 I have used until now.

I do have an AR7030, too, and I also ordered a 500Hz CW filter suitable for that one.

When I look into my crystal ball I see some upgrade activity in my future ;)

An added Idea Box entry:

The other part is the audio output of the AR8600. The built-in speaker is very small and not very loud. So I am thinking (ouch! ;) ) of building myself a new audio device with an external audio amplifier, possibly with an equalizer circuit (I have PCB a module for that), and an audio CW filter.

I do have a stereo amplifier suitable for use with at least two radios. With a little mixing trickery that could easily become 3 radios simultaneously, one in the left channel one in the right, and the last one in the middle. With an external switch box (that I already have) more radios could be added to the external audio system, albeit not all radios simultaneously.

QO100 Reception Using HF Transceiver?

 I have been using an old AOR AR8600 with a stabilized LNB (indoor reference oscillator on 25MHz). This is essentially a glorified scanner receiver with SSB capability.

This works OK, but is far from ideal.

The filters for SSB are cheap ceramic filters. Those are quite wide, and lacks some good suppression of the opposite sideband. This was noticed when I operated at a frequency with interfering stations . The wanted station were sometimes weak, and were swamped by the neighbouring stations.

So what to do to improve the situation? The AR8600 does have an output for the IF band, used for add-ons like a TV demodulator. Maybe that could be used together with an old fashioned HF receiver. I located a suitable cable for the experiment and set things up, with an easy-to-read frequency.

Oops! No.

The conversion in the AR8600 inverts the down converted IF band. Further, the IF output only works with the AR8600 in WFM (wideband FM) mode. The second part could be eliminated by a minor modification of the radio. The inverted band is annoying, however. I could live with using the other sideband, but the frequency readout goes "backwards" , so I have to recalculate the frequency.

What do I do now?

First option would be an up-converter, converting the band up to 19,29,39 etc MHz, using a local oscillator above both frequencies.

There may be another option. the HF radio is my IC7600. That model has a transverter input(/output). There is one drawback with that. There is no setting for ah"high LO" , i.e. I cannot invert the band frequency readout once more. More oops.

Update:

I used it today, and it does work, even if it is inconvenient.

This leaves a second converter with high LO.

Yet another project to add to the already long list. This is no longer a very simple solution, but neither is it a very large project.

This Year's Challenge. Small and Mini Projects. And Antennas.

This year, as opposed to last year, I have the intention to do some more building and construction activities. Last year was the year of 365 QSOs with 5W, later 365 with just 5W and solar power.

This year is more about getting some physical things done. This does not mean that I will not do much operation. Especially as propagation is among my great interests.

My antennas need an overhaul, and an update. At the moment I have:

For HF: R6000 for 10,12,15,17 and 20m (6m usable for some monitoring). Then a 5 band dipole, 10,15,20,40,80m, passable on 4 and 6m. Also a 30m long wire antenna with some limited counterpoise. This is passable for all HF bands and barely usable for 6 and 4m, and should be usable if I want to listen on 8m (40MHz). a 1/2 wave antenna for 10-11m is OK.

For VHF/UHF I have the V-2000 vertical from diamond running 50, 144 and 432MHz. A cable is running into the shack to a triplexer, running up to 3 different radios. A short (1m long) dual or triband antenna is used for monitoring 2m and 70cm, and a clover leaf ("Big Wheel")  for 2m. My 4m vertical is not standing upright at the moment, so it is not very useful.

This year I want to get up and running on a few more bands/modes. That requires new antennas and some kind of rotating functionality.

For 2m I want to do some more SSB/CW etc. (DX) activity. The 4 element yagi mentioned in an earlier post should do that.

For 70cm I also want to add DX activity. The 11 (really 8) element yagi is intended for that.

23cm: I have had some activity on that band a few decades ago, and because there is an activity group active now on this band I want to get some activity going again, this time with better equipment than I had back then. The 16 element yagi is intended for that.

I am (a bit) active on the QO100 geostationary satellite, transmitting on 13cm and receiving on 3cm.

I want to become active  with terrestrial on those bands, even if it will be with small antennas form home. Those are more directional than the VHF/UHF antennas, and need to be rotated as well.

I suspect that some portable operation from hilltops will be good for the microwave bands (above 1GHz), as I have obstructions in several directions, so range is a bit limited. This means that both a home station and some portable equipment is needed. I am building up my stock of equipment and antennas, and no, I do not expect to finish all of it this year.

In any case I want to be able to extend the number of bands where I have made at least one QSO. In this case we are talking about 2400MHz and 10GHz, and maybe later on the two bands in the other end of the spectrum, 630m and 2200m.

Then there are the small projects and mini projects, I have the goal of making at least one or two of those every month, as they are limited in scope.

One (two) of the somewhat larger projects are about assembling two QCX+ kits I have, one for 20m and one for 60m. Those are 5W CW transceivers, and should provide much fun in the future.

Mini #5: Test of low pass filters.

When I picked up the PM2B mentioned in #3, there were two 30MHz low pass filters included in the price.

Further, I had some older low pass filters, a 30MHz  and a 50MHz one, so I got them all tested today:

Out came the NanoVNA F (4" screen). The tests were made with a wideband calibration setting, so the absolute values are not perfect. 

All filters are in good working order.

This means that I now have three 30MHz low pass filters and a 50MHz filter, all fully functional:

The old one I have is a Yaesu filter with a 100W rating. I have had that for decades.

The second one is a Trio/Kenwood filter, 100W rating.

The third one was a bit of a surprise. An old Drake filter rated 1000W.

The fourth one is a BNOS low pass filter for 50MHz. No rating on the filter, but I suspect it is 10W or so. It is a much smaller filter than all the others.

I reckon that all those ratings will be reduced to about 50% of the stated rating if I want to operate 100% duty cycle modes, like digital modes, e.g. FT8.

I opened the 1kW filter, and all looks clean, a beautiful mechanical construction with silver plated coils and high power capacitors, likely silver mica types. Somewhere I have a PA for 10-11m that I suspect has poor harmonic suppression so the 1kW rated filter would likely fit nicely in a system with that one - if it has sufficient linearity for SSB. OK, as I mainly want to use it for CW that is not so much of a problem. FSK digital modes will also work nicely.

The other option would be using this filter with an old IC-M710 that can deliver 150W continuously.

I would hesitate to use this filter with my 1kW power amplifier, even if I use it extremely rarely.

Given that I paid <$100 for the two filters, including the 1kW one, as well as the not fully functional PM2B, I consider this trade as excellent.

I picked up more at that rally, more about that later, as it is a different story.

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.

Mini Project #4a: 16 element Flexa Yagi for 23cm.

A while ago I purchased a front-mast mounted yagi antenna for 23cm.

This is a 16 element yagi with a  stated gain of 14dBd. We shall see, but it is much better than no antenna at all ;)

Today I got that one assembled.

Next: a corresponding 70cm antenna for front mast mounting.

Mini Project #4. 4 El. Yagi For 2m.

 A while ago I purchased the Flexa Yagi 4 element antenna for 2m. 

At the time I purchased it I did not have sufficient strength in the fingers, and  the precision to do the job, due to having chemo therapy. That is now much less of a problem, though there are some side effects of that left over. Yes, I did not ask for assistance, as I like to do most of my stuff myself.

This one is designed for being mounted in front of the mast, so the mast would be behind the reflector. This allows the antenna to be mounted for horizontal or in the vertical polarization.

Another advantage is that this antenna has very thin steel elements, so only the boom is clearly visible from the ground. This is part of my low-visibility antenna system.

For my use I have mounted the mast clamp between the reflector and the feed element.

The FX 205V has a claimed gain of 7.6dBd. That may be a bit on the high side, but let us estimate the gain to be above 6dBd, and I will be satisfied.

I have used a "Big Wheel" or "Clover leaf" omnidirectional antenna for a while. It has been mounted right in the to of an apple tree, and I did make a bit of DX on 2m with that one. Ukraine was one of them.

In order to get the full benefit of this antenna I need to mount it on a rotator. That will not happen until the weather is much better, some time in the spring. When that happens, the small Yagi will likely be mounted 2-3m higher than the clover leaf antenna, and due to the height difference and the fact that the Yagi will be in the clear, I would expect signals to improve significantly on 2m, probably in the order of 10dB.

What next?

Maybe the 23cm Flexa Yagi I have had lying in the box for quite a while Then it will be ready, even if I cannot mount it yet.

PM2B and Documentation, Mini Project #3 Goes on Hold.

Having seen the receiver working, if not very sensitive, and the transmitter part with no output at all,

I am putting the mini project on hold.

First of all because I have no proper documentation, no service manual, no circuit diagram and not even a user manual. If the set would have been in proper working order I would have found out how to use it, no problem.

Second, the transceiver is so old and primitive that I find the operation too cumbersome to my kind of CW operation:

1) The receiver preselector has to be readjusted when tuning through the band, and especially if changing band.

2) The transmitter needs 2 extra adjustments after tuning over the band, or at band switching.

3) The VFO tuning ranges are too large for my use. For CW I use about 100kHz at the bottom of each band. This model covers 3.5-4.0 MHz, 7.0-7.4 MHz and 14.0-14.8MHz. On 20m the useful tuning range of 100kHz takes up very little space on the dial.

4) I have not found any way of making an offset between receive and transmit frequencies, meaning that tuning to a proper receive tone offsets the transmitter frequency. Not practical on crowded bands. Modification necessary for this alone.

5) The audio output can only drive high impedance headphones (>1kOhm). Not very practical, as I do not have those any more, though I could use a piezoelectric earphone for tests, but I would not use it regularly. In order to use the set with ordinary modern headphones or earphones, or a speaker an additional audio amplifier is necessary. This already means that  another modification is needed in any case.

For these reasons I do not find the time to restore this radio to its original state a good use of my time.

So what to do now?

Modifications are needed in any case, if I should want to use the transceiver

The casing, with some shielding at the sides will still be useful. I can build my (partly) own construction in there, and make myself a multiband CW transceiver. This is no longer a mini project, but a much larger one.

I may try to find a replacement for the PA transistor, maybe the driver if necessary, so the transmitter can be shown as operational, but that is all. Apart from that, the PM2B mini project is on hold.

I do not have any lack of mini- or smaller projects, so life goes on.

Mini(?) Project #3. Ten-Tec PM2B.

After finishing the IC910 mod, here is the next mini project. This may be more than just a small one.

For a very low price I purchased two low pass filters (30MHz) and a non-tested Ten-Tec PM2B, so I do expect to have some activity before it is fully functional.

This is an old CW only QRP transceiver, officially with 1 or 2W out, and with a direct conversion receiver. The rig covers the 80, 40 and 20m bands

After cleaning the AF potentiometer and some slide switches I got it to draw about 30mA from a 14V power supply. The headphone output showed some noise, variable with the pot. It looks like the headphone output is high impedance. It does use banana plugs, not even a mini jack connector. Yes, this is very old.

With an external SSB receiver I found that the local oscillator is working and can be tuned correctly.

No external signal received yet.

No transmit output detected.

Also I have no documentation, not even a circuit diagram

It does indeed look like there is more work to do with this one

Looking into the casing I was not impressed with the build quality, with long flimsy wires running around, and it looks like it has been messed up somewhat.

This might end up being a larger project, essentially building a modernized version of a direct conversion CW transceiver with a digital VFO, and maybe with additional bands. We shall see what I do with this one.

If I do a total make-over I may add some shielding to the sides of the transceiver, as they are totally non-shielded.

Mini Project #2 (IC910) finished.

 The addition of the 23cm band to the IC910 is now complete.

After disassembling, checking the (flat) cables etc the fault was still there.

A complete reset of the CPU, losing all memory channels, cured the problem. The radio has been running all evening without trouble.

This concludes mini project #2.

I still need to set up an antenna or two for 23cm, but that is for later.

Quick Update. Mini Project #2a. IC910

Messing around inside the IC910 did get me improvements, but it developed a fault.

When setting a frequency, after a short while the dial moves the frequency without any action.

Initially I suspected that the switches in the microphone had got faulty, but this happens even with the microphone disconnected.

Then there are two more obvious possibilities:

a) Dust has entered into the the rotary encoder, or

b) A flat cable has a poor connection.

So tomorrow the radio goes on the lab desk again, let us see if we can get rid of that annoying fault.

Yes, beware when you mess around inside an older radio.

MIni-project #2: 23cm etc on the IC910.

 The second mini-project of the year is almost complete.

Two things had to happen with the IC-910: 

1) The original reference oscillator needed to be replaced with a high-stability oscillator. This was necessary, because temperature drift cannot keep the IC910 on frequency, especially when operating at high power levels.

I got the new oscillator mounted on the PLL board, and then the adjustment started. Initially I adjusted the output signal while transmitting low power FM on 70cm. Yes using lots of attenuation. I was using my microwave capable spectrum analyzer with a 10MHz GPSDO as reference. The trimmer in the oscillator was a bit fiddly to work with, but I got the initial 70cm frequency adjusted within 150Hz of the set frequency. After some warm up it looked a bit better.

Time to mount the shield for the PLL and the 23cm module. This is a rather easy add-on.

Set the main band to 23cm and test on 1296.000MHz. The frequency was less than 250Hz, and after warm-up it was within about 150Hz.

Now the radio is re-assembled with all the covers, and tomorrow I will make another test of frequencies with the radio fully assembled, and after a good warm-up period.

I do not expect any significant change, but I do need to check, so I know the offset.

Small Update on Solar Power.

My modest system has not had a lot of juice in the deep of winter.

Right now the only radio connected to solar is the IC705, and it is running a few hours every day.

While the days are clearly getting longer here at this time of the year it is still very short days with the sun very low over the horizon. On top of that we have had a lot of cloudy time.

If the day is clouded right now, with the panels available the system is just generating a tiny bit less than the IC705 uses. With full sunshine, and we had a bit of it today, I can run the IC705 for many hours a day. The battery voltage, as I use the radio, keeps the voltage of the LiFePo4 battery at around 12.8 - 13.3V. I consider that acceptable. 

This year I will need to mount more panels when the weather permits, and also get a bigger battery up and running.

With this setup I should be able to run full station activity for about 8 months of the year - except for high power amplifiers. The remaining part of the year I estimate that I will still have to run parts of the activities on mains power. 

One more thing: Before next winter I should make a "backup plan", so I can charge batteries when the price of mains power is lowest. This may be semi-manual, or I may find a way to automate the process using data downloaded from the internet.

Then there is the use of low power monitoring receivers. Yes, I need to build some of them, and we shall see how much I will build before next winter. There are still possibilities with some older receivers that I can put into service for parts of this. I do not have to build everything.

Higher and Higher. Solar Flux.

The solar flux rose again, this time to 228 SFI. This is almost as high as the highest SFI of the previous cycle. That happened on January 7th, 2014, and it reached 237 SFI.

It looks like the trend is still upwards for this cycle, so will we see a higher peak than in cycle 24?

I like to think so, but we shall see.

Solar Flux.

 The sun keeps on giving.

Today's SFI (21cm solar flux) is 212. I think this is the first time in this cycle the SFI has been above 200.

With a few more days of this high flux I would not be surprised to see 6m opening with F2 propagation.

Exciting times!

Mini Project #1.

Before the NanoVNAs became widely available it was tricky to find low cost test equipment for testing SWR or return loss in the low GHz range. 

At the time I did find one possibility: The transverter-store in Ukraine sold some low cost impedance bridge PCBs, so I got myself one.

The PCB bridge circuitry looks like this:

Looking at a Youtube video I found that the PCB has a fault. The bridge has 2 50Ohm resistances, made up by two 50Ohm resistors that should be connected in parallel. On the PCB he tested, and on mine, this is not the case. No connection between 2x two islands on one side of each pair.

Now, this is not difficult to correct. A short piece of wire  mounted at the junctions between the resistor pairs solve this.

A quick test using my NanoVNA 2 showed a shortcoming of the NanoVNA output level (too low), but also gave an indication of the functioning of the bridge.

With a 6dB attenuator as the DUT (Device Under Test) the return loss showed close to 12dB, as it should.

Testing a 10dB attenuator the same way showed that the return loss went down into the noise of the NanoVNA. Close enough to 20dB, so I accept the reading as correct, and that the bridge is working properly.

That is the end of mini project #1 of this year.

Will I use this bridge a lot? Not really, but I did want it to be in working order. It is now going into the test PCB pile as a working unit.

The NanoVNAs that came out after this are much easier yo use, and much more versatile. The cost is not prohibitive, so in the lab I will be using a NanoVNA F (I think is the designation) for frequencies up to 1GHz, and a NanoVNA v2 for up to 4GHz.

The Sun Is at it Again. X2 Flare.

 Some "new" (actually old, but recurring) sunspot groups just rotated into view of Earth.

3 days ago one of them fired a flare of magnitude X1, and minutes ago the sun fired again. This time X2 - well strictly speaking X1.98, but I made the rounding-up. This is bound to create a sudden Ionospheric Disturbance (short wave fade-out) on the day side of Earth, and it will likely las a little less than an hour.

Also the 21cm solar flux is at 184 today. If this continues for several days more I suspect that there is a good possibility of F2 openings on 6m. 

I will be aware and monitor the situation.

Mini Projects for This Year.

I have an idea for an addition to the challenge/wish list for 2023.

In my shack, and in the lab there are a ton of small projects that will improve the ability to make larger projects. 

This could be an extremely simple repair or modification of some existing equipment or a PCB module.

The intention is to make a small blog entry for each of mini projects.

There should be one mini project per month as an average, so 12 of them this year.

Why?

Sometimes I get the impression that I do not doo anything, even when I do. So this is to show me that I do, in actual fact do some stuff, even if not as much as I want to do.

This is, of course in addition to doing a few larger projects.

Last year's large project was making a minimum of 365 QSOs with 5W output, so I suspect this year I will make fewer QSOs, as I have some practical building projects I want to get done.

Let us see how that goes.

What Is This All About?

We have entered a new year, 2023. Let us take a look at what may or may not accomplish this year. 

I have been writing on this blog for a while now.

Some may wonder why I do it. So I write this reminder. 

Here we go:

I write here as a reminder of things I have done with ham radio, and also a a notebook of ideas.

If any of my writing is useful to you or anyone else, that is perfect. That is some of my contribution to ham radio.

I will continue to write about what I find fun or interesting about it. Good experiences. Great ones. Some experiments. Some challenges, Some projects. Ideas.

All a mixture of what you will find here.

I may even expand the content of the blog. We shall see. To me the main point is that it has to be fun, or at the least interesting.

Be seeing you a bit later this year, and more.

73 and Happy New Year, de Jan, OZ9QV