21 Aug 2014

10m - closed now?

It is now 1857z and there has been no Es here now for over an hour. In the periods I was monitoring 10m, no F2 propagation was spotted. No GDX seen either in the last few hours.

I will QSY to 472kHz shortly I think.

I was thinking of buying a dedicated 10m rig, but unless my voice rapidly soon improves  (SSB, FM and AM are hard work for me because of my stroke) this is probably a waste of money at the moment. For now I shall stick with 2-5W on digital modes, which I can manage with the FT817 rig. JT65 and JT9-1 are my best bets. PSK31 is quite hard as it requires (near) real-time keyboard skills. I rather dislike PSK31 with macros -  you can usually tell when someone is using macros - I much prefer real QSOs. At least JT65 and JT9-1 use very formulaic formats for minimal data QSOs. QSOs are very very basic, but for me this helps at the moment. One reason I enjoy WSPR is it tells you about conditions on a given band and once set up, it just runs with minimal intervention. Some will (rightly) say it is computers talking to computers. At the moment, this is close to what I need. JT65 and JT9-1 are proper 2-way modes.
at 19:59
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5 comments:

Martin G7MRV said...

Roger, a quick query if I may about your 10m wispy receiver design - What is the max output audio level and impedance (roughly)? In other words, other than a PC soundcard, what should I use to listen, crystal earpiece/medium Z headphones etc?

Im still having no luck with my Wispy's Rx so have decided to come at it from another angle, starting with proving the audio stages

Cheers

Thu Aug 21, 09:35:00 pm GMT+1
Roger G3XBM said...

I have only used it with the PC sound card if I recall Martin, but a crystal earpiece would be suitable. Expect sub 1uV sensitivity at 28MHz. Still puzzled why it is so problematic. Have you tried as a dedicated RX only circuit, as this is what I used? Sounds like there is insufficient LO injection which is at half frequency. The audio circuit is very conventional and the whole circuit is pretty basic.

Thu Aug 21, 10:00:00 pm GMT+1
Roger G3XBM said...

In the limit you could use separate LOs for TX and RX. I would have expected the RX to be less problematic than the TX as the LO goes straight into the mixer. Are you using germanium diodes?

Thu Aug 21, 10:03:00 pm GMT+1
Martin G7MRV said...

Hi Roger,

Ive used both Ge (1N34) and Si (1N4148) diodes.

Ive had a thought tonight that part of the issue might be how Im trying to hear the test signal, which is via the Marconi 2955's 'scope/speaker, and I suspect its not sufficient. This is why I asked about how you listened. Im making a separate mockup of the AF strip so I can try some ideas out, and will dig out the crystal earpiece!

I'll also try it into the Laptop, something I havent yet done.

I suspect its something either ive done wrong and cant see, or an issue with how im testing!

Cheers

Thu Aug 21, 10:47:00 pm GMT+1
Martin G7MRV said...

Well Roger, It looks like It was me all along!

I rebuilt the AF stage and tested it to a crystal earpiece with an audio input signal - I could make that out down to 4uV!

I havent tested the Wispy design yet, but I tried it on my alternative mock-up which is based around an SBL-1, and could discern the received tone down easily to at least -120dBm, and using on/off comparisons to at least -125dBm

So again, as with the Tx side, it turns out to be my understanding of the expected levels that was the problem!

Hopefully back on track now! Just a shame that by the time I have this working the propagations probably gone!

Fri Aug 22, 05:08:00 pm GMT+1

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