DSB10 - more progress

I have now breadboarded the 10m DC receiver for this rig using a single balanced mixer with 2 diodes followed by two stages of audio. It works well and was pulling in plenty of stations in the IOTA contest this weekend on both SSB and CW without any sign of AM breakthrough. I think the secret is plenty of LO injection to switch the well balanced diodes hard.

10m DSB Rig - started at last

For some time I have been toying with the idea of building a simple but effective 1-2W DSB transceiver for 28MHz. Well, this weekend I made a start by breadboarding the transmitter up to, but not yet including the final PA stage. The 2N3904 has been used throughout plus a couple of 1N4148 diodes (which seemed well matched) for the TX balanced mixer. Output from the balanced mixer was sub milliwatt so a couple of linear stages lift the output to around 50-100mW pep. With a single 2N3866 PA stage this should take me up to the 1-2W pep level.

Next stage to breadboard is a mixer-VFO. I am thinking of a 20MHz xtal oscillator (because I have a crystal) and an 8MHz VFO. Ideally I'd like a higher xtal oscillator so the VFO is lower in frequency and more stable.

The RX was breadboarded last week and uses a single balanced diode mixer followed by 2 stages of audio. This works really well with no sign of AM breakthrough at all.

Pipit20 rig on air

This last week I have been building again. Not much, just another DC transceiver built ugly style. The rig covers 14048-14070 VXO controlled and puts out about 500mW using the OXO design. It uses an SBL1 mixer on RX followed by 3 stages of AF gain. Only station worked so far is M0BXT but hoping for some Europeans maybe at the weekend. It suffers a bit from AM breakthrough and the 2N3904 transistors used in the AF sections are too noisy really. This is really not a perfect radio, more a work in progress.

Why the name? The Pipit was a similar (better!) radio design I put in SPRAT many years back for 15m.
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Micro80 4-transistor transceiver QSO

After some time without use, I resurrected the little Micro80 4 transistor transceiver for 80m last weekend. To increase the power a bit I've now got provision to run it from an external gell cell battery at 12v, so giving me about 2dB more RF out compared with the 9V internal pack. Using it with the bench PSU was impossible because of 50Hz hum pick-up. I also managed to improve the AM breakthrough by around 10dB at least by putting a 4n7 cap across the base-emitter junction of the first stage of the darlington in the RX AF. This makes it a usable radio on 80m at night now as it is not obliterated by the BC stations around 4MHz. Success soon followed with a solid QSO with G3XIZ in Biggleswade around 30 miles away late Sunday afternoon.

Wet square on 6m

Just beat the pile-up to work UT1FG/MM on 6m SSB in IN38 square out in the Atlantic. Obviously I have not worked this square ever before!

501kHz listening

Having re-erected my end-fed wire antenna I am able to listen to 501kHz again. First station heard recently was G3XIZ on CW at 579. I have an NoV to transmit on the band so really must make an effort to get some sort of TX together.

6m DX QSL card from K1TOL

This is the QSL card confirming the June 25th 2007 6m QSO with Lefty, K1TOL. I was using 2.5w ERP at the time to a small vertical! Magic band? You bet!

Lefty has a big 6m antenna farm and runs 1kW, but I much appreciated him hearing my tiny signal and giving me the RST519 report that night. It was one of the best contacts I have ever had in 40 years on the bands.

Real 6m DX at last

Earlier this week 6m bucked up a bit allowing W5OZI in EM00 square to be heard hear at around 8000kms! Also heard were N3DB, 4X4DK and 4Z5LA. This was a few days ago now and I've not heard any further "super" DX since when I have listened. It is amazing what can be heard on just a small vertical antenna fed to the FT817 via about 40 feet of RG58 coax!

Also this week I received the QSL card from K1TOL for our 6m transatlantic QSO last summer - my best ever 6m QSO with just 2.5w ERP.

Canary Is and Cape Verde Is on 6m

6m opened up nicely this evening allowing two QRP SSB contacts into EA8 (EA8YT and EA8CQW) both in IL18 square. Also heard the D4C/B beacon in Cape Verde Is for the first time just hovering at the noise level for me at best.

Still below average on 6m

Just one EA worked on 6m QRP yesterday and still no further transatlantic stations heard. Conditions definitely not up to last season.