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?)

Raspberry Pi as Shack Computer.

 The fan in the 8GB Raspi is failing. The SD card for the 8GB Raspi has veen re-located to a 4GB one in a casing with passive cooling. Some web browser tabs have been closed, so for now the 4GB is running as shack computer with reduced memory.

Casing(s) with passive cooling has(have) been ordered for the 8GB. The "old" SD card from the passively cooled 4GB Raspi has been re-located into the Raspi400. That SD card was set up as SDR, so I can monitor the QO100 satellite again.

I may be able to find a usable fan to replace the defective one, at least until the new casings arrive. 

When that happens I will have the following Raspberry Pi 4/400s available:

1x Raspi 4 8GB, should be the shack computer for browsing and logging, maybe back-end for VNC

2x Raspi 4 4GB for SDR and/or digimodes

1x Raspi 400 (4GB) Probably digimodes, some (circuit) and/or antenna design software.

Apart from that, I have a couple of Raspi 2s, usable for digimodes and/or QRSS monitoring, likely running a VNC (or other remote) server, so they can be remotely operated.

Batteries for Portable and Fixed Use.

Today I brought my hand held VX-5 on my walk. Yes, I am trying to work myself up to a daily walk of at least 2km. I thought the battery was well charged, and all was fine just operating in stand-by. Having a local chat with the highest power level ... oops! Battery died. Maybe this is because the battery is fairly old. I am now going to check the state of the battery (Li-Ion type, 7.2V)

I may have to purchase a couple of spares, because it is a nice little radio. The standard battery is rated to 1100mAh.

For now, I am thinking of making a battery pack with 3 18650 Li-Ion cells and a cord/connector, just to be sure to have some spare capacity. This way I have can always have a fully charged battery, and I can change the cells when it goes too low. The cells are used, but tested cells with more than 2000mAh, so even with full power (5W) I should have enough juice for some local chatting. I **could** use lead acid batteries, but I don't want a hole in my pocket or rucksack after all those batteries are heavy as lead ;)

I have a good supply of Li-Ion cells and battery cassettes, so I expect to use those for several portable experiments, including going to local hills with the 10GHz WBFM experiments.

In China I found 2 solar chargers with a 3-cell (18650) battery casing, and including a BMS system, possibly fine for portable work.

At home I am slowly building some battery supply, charged mostly by solar panels, but in winter time it is probably necessary to add some juice from the mains power.

Initially this is intended for very low power equipment, such as a 28200 simple beacon receiver and some other simple monitor receivers that should run 24/7, and preferably also when mains supply fails, even if that does not happen often here.

For some of the computing the plan is to use some Raspberry Pi boards. The idea is using this for both WSPR/FT8 propagation monitoring and QRSS. 

As usual, ideas a-plenty, now it is about making time to do something with them.

My "Home Made" Challenge.

I have been thinking of challenging myself with respect to (partly, at least) home made transmit and receive equipment used for making minimum one contact or received signal on as many bands, and in as many modes, as I can possibly do.

First my definition on "home made". it can  be a few different things, all involving some thinking or building activity, for example:

- use of equipment not designed for amateur radio, e.g. using a satellite TV LNB for receiving 10GHz amateur radio signals.

- use of modified (possibly surplus) equipment, e.g. using a HB-100 Doppler radar module for transmitting wideband FM or ATV on 10GHz, a home made (or modified) modulator is needed.

- using a kit I built/assembled (maybe modified) myself, e.g. the very simple Pixie transceiver kit.

- building transmitter and/or receiver circuits in non-kit form.

All of this can be arranged in stages, for example:

- building a transmitter and using an available receiver (kit or no kit).

- building a receiver (in addition) (kit or no kit).

- full transceiver (modified, built, kit or no kit).

Right now the status for the "home made" challenge is as follows, for the OZ9QV callsign:

80m: CW TRX, the single frequency - band modified - Pixie kit. - one QSO

60m: CW TRX, the single frequency - band modified - Pixie kit. - one QSO

40m: CW TRX, the single frequency -      unmodified - Pixie kit. - one QSO

This is a long term challenge that I intend to work on, slowly increasing the scope of bands, modes etc. Modes should include CW, Phone (DSB/SSB/AM/FM - DIGI-voice?), Digital modes (e.g. FT8).

Simple monitoring RXs should be included in the challenge, too.

This will involve using many kinds of home made equipment, all the way from simple CW TX,RX to SSB TX,RX.

More than enough projects to keep me busy!

Another part of the challenge is attempting to work 100 contacts, QRO or QRP with home made TX&RX, then 100 DXCC entities, just on a single band.

Challenges not including home made stuff could be 100 contacts or 100 DXCCs with QRP on as many bands as possible.

I could probably dream up other challenges, but let us see what I manage to get done. 

Idea Box: QRSS With Simple Home Made Equipment.

Some years ago, while living in the Netherlands, I made a few experiments in receiving QRSS (very slow morse) with a receiver and a computer running the SpectrumLab software under Wine in Linux.

Despite living in an apartment I had some success, but when I moved everything was dismantled.

I have still been following the developments in the QRSS activity, and I should like to get going again. Running a so-called Grabber (QRSS receiver does not take too much time out for other activities, because the spectrograms are simply up-loaded to a website for all to see.
QRSS provides a quite good weak signal performance, so it is usable for propagation monitoring, provided that there are some QRSS transmitters active.

Last time I was running a QRSS Grabber was before the time of the low cost Raspberry Pi single board computer, but these days it is an excellent candidate for running grabber software.

Now, what about receivers ? I was thinking of running a very simple, low cost receiver to begin with, e.g. a modifies Pixie kit.
The Pixie is an extremely simple 40m single frequency CW transceiver, mostly supplied with a 7023kHz crystal. On 40m it just might be capable of running a grabber on 7040kHz. The "IF" will be 17kHz, that should be within the capabilities of spectrum analysis programs for the Raspberry Pi. Alternatively, a different crystal, say 7030, 7035 or even 7038kHz crystal could be used, substantially bringing the "IF" down. If the missing image selectivity becomes a problem, a simple, single crystal filter with a 7040kHz crystal filter could be used.

To be fair, the Pixie is very low cost, a kit can be had for less than $5, so it is an excellent candidate for experiments. The design, however, is probably quite reliable, but certainly not high performance.

In the coming year I hope to have room for some experiments with QRSS, but a higher priority is getting a signal through the QO100 satellite.