Some Thoughts on 10m Propagation Monitoring.

It is no secret that one of my favourite bands (especially on HF) is 10m, and I want to be able to make the best possible use of that band. 

At the moment several receivers are used for monitoring the 10m band:

- the FRG-100 for 28200 "International Beacon Project" (IBP), current draw 500mA

- The IC-703 for 10m FM, 500mA

- The AR-8200 for 10m FT8, 200mA

All in all 1.2A of current consumption, just for monitoring 10m propagation using existing (older) equipment. Even using IC-705s for all it would be less. But for monitoring this could be considerably reduced by using simple home made receivers:

- Polyakov DCRX for FT8, using a (pulled) 14.04MHz Xtal as LO, 20mA?

- Polyakov DCRX for WSPR/QRSS, using a (pulled) 14.06MHz Xtal as LO, 20mA?

- Simple DCRX or superhet w/AGC for monitoring 27.555 (20-50mA?)

- simple FM RX with FM-IC for 29.6 FM likely 25mA

- simple superhet w/AGC for 28.200 IBP, likely 25-50mA

- the box could incorporate a Raspberry Pi 2 for decoding WSPR/QRSS and/or FT8, ???mA

Some LO signals could be made with an Arduino controlled Si5351 synth board.

A modular build of this is feasible, and could start with the 28.200 IBP TX.

After this the priority would be like:

- FT8 RX

- 29.6 FM RX

- 27.555 DXB RX

Signals from all could be mixed/matched into a stereo amplifier for "placing the audio", e.g.

28.200 in the centre, the 29.6 in the left channel and 27.555 in the right channel. If more audio monitoring, the 29.6 FM channel (squelched) could be shared with another (SSB or CW) channel audio.

A start would be a simple superhet for 28.200, using a 19.2MHz crystal oscillator (probably originally used for some GSM base station) as the local oscillator, followed by a simple 9MHz "IF receiver" with an audio filter. I do have 9MHz crystals, so if I can place the frequency correctly, a simple crystal ladder filter can be used. Alternative is using a simple audio filter. A limiter for audio (probably a combined clipper/AGC) should be used for reducing the shock value if a strong signal comes up on the frequency.

It should be possible to limit the total current consumption to about 50mA for all, including the audio output amplifier, replacing a receiver using about 500mA.

It should be possible to keep the total current consumption for all those receivers, including audio amplifiers, below 300mA. This should provide a considerable power saving when used with the solar power supply, compared to the present setup, and with more functionality when finished.

Considering that at least some of this should run 24/7, the solar budget looks considerably better.