Solid Improvement on 1296MHz.

A little while ago I found a power amplifier for my 1296MHz setup.

This is essentially a W6PQL design with improvements and control/safety circuits by OZ2ELA.

A group had built this as a project, and one of the participants lost interest and sold the unit.

A test showed a solid output of 80 - 90W, enough for my purpose.

Controlling the mast preamplifier through the coax was not available, so I got myself 2 high power bias-tees for 1296MHz, capable of handling 600W.

Now I can bypass the DC control voltage from the radio to the preamplifier, and still use the PA as TX amplifier. This works well, and I am now running 50W on 1296 most of the time, with a drive of 3W from the transceiver.

I do have some cable loss, so often I could hear people who did not use mast preamplifiers at the antenna, but they could not hear me. With the amplifier, now there is a better balance between the local (FM) stations and my station.

There is still a lot to optimize here, mostly with respect to antennas and cable loss, and now the spring is coming, I can get started with that.

At the moment I am using a vertical monoband 1296MHz antenna. 

Some yagi or other directional antenna is in the planning for use with DX (SSB/CW/DIGI modes, or even FM), and I do have some decent cable available for this purpose.

Update Linton LT9100 Handheld.

Some of the others have received the LT9100 and have similar results.

One measured about 50uW (yes fifty microwatts), -13dBm.

It's not that difficult to amplify to a reasonable level, with modules I have. The trouble is that I have to modify the transceiver internally to access the PTT function. it will not be a handheld radio any more, but it will fall into my definition of (partly) home made, as a major operation is required.

It's possible to make a transceiver with low cost and low standby power, e.e. for use with the local repeater. For the price of the HT and the modules I already have, this is a reasonable project.

Handheld Transeiver Linton LT9100 on 23cm?

 A few weeks ago, in a weekly microwave video chat someone mentioned  getting the Linton LT9100 handheld transceiver. It claims to work up to 1300MHz with 5W (Chinese watts?)

A few of us ordered one, and I got mine today, and made a quick check.

When I use it in the house with the IC-9700, it actually does transmit and receive.

Here is the catch. When connected to an antenna normally used for running the local repeater with 1W, this happened:

In TX no signal through the repeater.

In RX, transmitting with the IC-9700, no reception whatsoever.

In other words, transmit power is certainly below 1W, and the receiver is deaf.

Given that the chip in this transceiver is not specified, and filters may be off, I am not so surprised.

Okay, let's try with a 30dB attenuator between radio and a spectrum analyzer, just to be safe.

Oops! Hardly any visible output on 1296. Let's just say that some amplification is needed. A lot of amplification, the output is in the uW (yes, microwatts) range. 

I still need to check receiver sensitivity, I do have a signal generator for the frequency, I need to check if I can modulate it with FM.

That is for another day.

The radio can be easily programmed for the repeater (and other 23cm) frequencies, so the question is, can it be used as a separate transceiver, with a bit of filtering and a good deal of amplification in both transmit and receive mode?

Possibly. There is no connector for external microphone (or speaker) so it will have to be dismantled and modified, so the PTT can be controlled externally.

I will also wait to see the results from other people in the group, and what they think about it.

So, first impressions, maybe not good for 1296. We shall see.

More Solar and Battery Power.

Last year I got a couple of 24V/100Ah LiFePO4 batteries and the plan was to use them as power supply for 24 - 28V power amplifiers, and as extra capacity for my two older 12V/100Ah batteries.

The 12V system has been used with 3x 100W solar panels, and has supplied a few radios with power in the period from mid February until beginning of November last year. In the dark months I needed to help charging from the mains power, but now the same radios can be supplied with solar power again. It's likely that I will add more panels and an extra charge controller or two to the 12V system.

The total capacity of the 12V system is about 2.5kWh, and I have used it with my power hungry IC-9700 and a bit of other radios. It's possible that I will add a bigger 12V battery later, for a capacity of about 6kWh.

Enter the 24V system. The plan is to add the capacity, so I will have a total of about 7 (or 9) kWh at the radios, using a simple DC/DC charger from 24V to 14V, with constant voltage/current setting and some switching control.

Some more solar panels need be added to th 24V system. I have some already, but I need to get them mounted.

I have found some reasonably priced 450W panels, and I will likely add a few of those to the system.

I have a small and a larger power station(s) that will likely be added to the system. Also, I have some LiFePO4 cells, so I can make a 12V, 24V and possibly a 48V system for the workshop upstairs.

A tiny system for lights and audio in the bedroom is also under construction. Yes, there are many smaller and a few larger projects to build here, along with the radio experiments.

Tidying and Birthday Present.

 As the house is a total mess, a massive task of tidying has been started. It will likely last the whole year, or longer. 

The first task was getting down to the surface of the work desk, test bench.

I found most of the test bench surface ;).

Then I had my birthday recently, and I decided to get myself a present.

I have started doing a bit of microwave activity, and I got myself a TinySA a while ago. This measures up to about 6GHz and has a generator for the same frequency range.

It looks like the generator can show harmonic output well over the 10GHz range. Interesting.

So I decided that I should be able to check filters and amplifiers up to the 6GHz range, and purchased the corresponding NanoVNA, got it calibrated with the calibration set that came with the VNA. 

I have created a few presets, and saved them into the VNA:

350 - 550MHz

2 - 3 GHz and 

5 - 6GHz. 

There is space fro a few more, so I will likely add a range for the 3.4GHz band, the 1296MHz band and maybe one other.

The initial test today showed pretty realistic results, so I consider it a success.

Now I can do a bit of experimentation again. There is a plethora of small and big projects for all frequencies, from 472kHz up to 10GHz, at least. The experimentation may be slow, but it's possible.

Small Transceivers and Low Power.

I now have a rather good collection of small, low power transceivers (and receivers)

Some are low cost Chinese builds, some are small kits assembled by me over time.

Some years ago I purchased some "single frequency" (crystal controlled) transceivers (from Ukraine) tuned to the old frequencies used for the JT65 mode. When FT8 took over, the use of JT65 ceased, because the over all efficiency of FT8 is much better, especially because the transmit sequence is 4 times faster, compensating for the lower sensitivity. and the frequency was moved 2kHz up. 

Usually the crystal frequencies can be tuned down fairly easily, tuning upwards is more limited, so I don't know if I can tune the local oscillator (yes, those are superhet transceivers). If I can, I will try that and use them for FT8.

This would make for a very nice, low power (1W) single frequency transceiver on the 40, 20 or 15m bands. Yes I have those three.

Then there are some simple single frequency kits, (Pixie, Rockmite, and others).

I do have some crystals for the 40, 30 and 20m bands for reception of FT8 and WSPR/QRSS frequencies, and I might use those for monitoring those frequencies.

All this is part of an ongoing (open) challenge of making QSOs on as many bands as possible with my own equipment, and expand this with using home built equipment, too.

Until now I have made QSOs with my own erquipment on all available (in Denmark) bands from 160m to 13cm The equipment can do 6cm and 3cm, too, but no contacts done yet.

Contacts with home made equipment has been done on 80, 40, 30 and 20m on HF, and 2m on VHF.

When I use the expression "home made" I include modified equipment intended for non amateur use, and partly home made equipment, like using a home made 2m transverter with my HF transceiver.

Somewhere I have a Pluto SDR "transceiver" that can be used for all bands from 70MHz to 6GHz, albeit with extremely low power, so that one is a candidate for home made equipment on 70, 144, 432, 1296, 2400, 3400 and 5760MHz, with added front ends for the different bands.

I wish I had more time to do all those experiments. (Don't we all?)

1296 Tropo.

 I am reorganising my station, so the activity level is not so high.

Yesterday, however, 1296MHz was open up to a few hundred km.

I didn't make QSOs, but with my omnidirectional vertical monoband antenna I could hear 9 beacons during the day and evening:

OZ7IGY (of course, it's local at 26km, and always audible) - Everyting else is over about 200km

SR1KOL at about 270km

OZ1UHF at 222km

DB0XY at 438km

SK6MHJ at 229km

SK6UHG at 261km

SK1UHG at 416km

LB2SHF at 369km

LA3SHF at 372km

I am pretty sure I would have heard more beacons with a horizontal antenna, but this tells me that propagation was very good.

Yes, a horizontal antenna system is in the planning, probably for spring next year.