A 160m AM local natter rig

Further to my post a few days ago about possible bands to use for a very local "natter link" over a 3km path between G6ALB and here, my thoughts are turning to 160m, partly for nostalgic reasons. This is where I first started my ham radio operating with a small 400mW AM transmitter from Practical Wireless (Dec 67 I think).

Although 160m is VERY noisy now, especially at night, I figure that 100mW AM will be enough to kill the QRM/QRN over such a short distance. So, I am gathering ideas for something incredibly simple to build.

For the TX the most sensible rig would be a crystal oscillator (or ceramic oscillator) followed by a buffer and series modulated PA using the modulation circuit from the 2m AM Fredbox. On receive, either a regen receiver (operating just out of oscillation) or even an MK484 (like the ZN414) single chip receiver are worth a try.

This would be no DX rig, just a very basic transceiver to get me into the next village and not much further. I'll keep you posted. Incidentally I am unable to do much building right now as my house is in the middle of some redecoration. I can't find anything!

More Sixboxes and Fredboxes

Joe Milbourn has a nice photo of his version of my Sixbox QRP 6m AM transceiver. It looks he's made some changes including the addition of a beefier audio stage on receive, perhaps to drive a loudspeaker.  It also looks like he has added a mic pre-amp. Click the link for Joe's original size image. Incidentally, there are some great photos on Joe's picture site.

Then I noticed a version of my 2m AM Fredbox on a Romanian website. See http://www.garajuluimike.ro/electrice/emitator-receptor-144mhz.htm . This version also uses an LM386 audio amp to drive a loudspeaker.

Another 10m Chirpy

Martin Spreemann (callsign not known) in Berlin has sent me a picture of his version of Chirpy, the minimal component transceiver for 28MHz CW. I wonder what results people who have made this (rather chirpy) transceiver have obtained? Please let me know if you have built and used one. Remember the design uses a fundamental crystal for 28MHz, not a 3rd overtone. The design should work equally well on 24MHz (slightly less chirp too) and 21MHz, although I suspect broadcast breakthough will start to become more of an issue.

2 transistor transceiver kit

The Four State QRP Group is offering the new "HamCan" transceiver kit for sale at just $30.  It is a 2 transistor crystal-controlled CW transceiver, delivering 0.5-1W TX power with enough sensitivity and selectivity to receive plenty of signals. They claim it is a minimalist yet good performance transceiver. The kit features a high quality PCB, low parts count and fast and easy building. It is claimed to be an excellent kit for first time builders. It has been selected as one of the ARRL Midwest Convention's Buildathon kits. 

More information at http://www.wa0itp.com/hamcan.html .

More work on the 10m DSB rig

Today I continued breadboarding the TX strip of the 10m DSB transceiver changing the single balanced mixer to a broadband design and adding/changing stages in the driver and PA. After the mixer, the driver/PA design now has 2 transistors and 1 FET PA with an output of around 1W pep. This is not enough. My aim remains at least 2W pep either from this line-up (with an IRF510 PA) or with a different PA.

Incidentally, I need a name for this rig. I used the name "Tenner" for my 10m CW transceiver, so what shall I call this one? Please give me some ideas! DSB10? Sidebander10? 10phone?

HF transceiver ideas site

Vanyi Istvan Vanyi YO5OFJ has an excellent website with links to a whole list of HF transceiver designs from around the world. Most are QRP designs with links to the originating sites.

Fivehead QRP SSB transceiver kit

This afternoon Ted G4NUA came around to test the receiver section of his Fivehead 20m SSB transceiver kit from Walford kits in Somerset. I was surprised how small the transceiver was. We checked the RX with a signal generator and re-did the alignment. We then tried it on an external antenna and it was about the same sensitivity as the FT817 and was copying plenty of stations on 20m SSB. Ted has still to finish the TX part. When done it should put out about 1.5W pep.

XBM80-2 video and PCB (draft)

A short video about the XBM80-2 80m CW micro-transceiver. This is built "ugly style" on a piece of copper clad board. It will get put in a box soon! I've also been having a go at a PCB (just 1 inch square - 25mm x 25mm).

The Pixie Files

The Pixie and Micro80 are  well known simple transceivers for any HF bands. I've built both in the past and they do work well considering their lack of complexity. The main limitation is the receiver which uses the TX PA as a simple mixer. For those wanting more information on the Pixie and its derivatives check out The Pixie Files which is a collection of articles from SPRAT.

Some QRP operating

This is a picture of me in my shack. I had just completed some homebrewing and was having an SSB QSO. See next post for details of the homebrew experimental transceiver I had been working on.

Gnat 1 transceiver - anyone made/used one?

Has anyone here built and used a Gnat-1 single transistor transceiver? This was in SPRAT earlier this year and it was designed by Chris Trask N7ZWY. Although I've seen a few pages with photos of copies, I've not heard how well it works and what anyone has worked with one. The picture on the right is from LY3LP's website and shows his version for 20m.

YO5OFJ's pages with everything

Vanyi's Homemade/homebrew HF transceivers page is a collection of lots and lots of circuit ideas showing transceivers from 160m - 10m created by various people over the years. It is a good place to look for ideas when thinking about new projects.

Anyone built the Gnat-1 micro-transceiver?

Has anyone reading this blog built the neat little GNAT-1 transceiver featured in SPRAT 138 (Spring 2009) by Chris Trask N7ZWY? This looks a very elegant design making good use of the small number of parts needed. I must have a go. Unlike the FETer and similar micro-transceivers it doesn't need complex switching and it produces a decent RF output.

Chris tells me he hasn't actually air-tested the circuit (surprisingly), so I'd like to hear how people get on. It is important to keep the key leads short Chris advises.

GQRP Club and SPRAT

Attached is the 6V6 valve transceiver by Geoff, G3YVF, from SPRAT magazine number 137 (Winter 2008/9). It uses 19 parts in all.

Join the GQRP club and receive the excellent SPRAT magazine every 3 months. The fee is only £6 per year (or equivalent in other currencies) which is excellent value. See: http://www.gqrp.org/join.htm for details on how to join. You can now pay with Paypal too if you prefer. BTW, if times got hard and all other radio mags had to go then SPRAT would be the one I'd keep.

Every quarter SPRAT is packed with circuits, ideas and news of interest to those who enjoy QRP. Back issues of editions 1-132 are also available on a GQRP club CD for just £5 if you are a club member.

AA1TJ's 1 transistor transceiver

Take a look at Mike's neat 1 transistor VXO controlled 80m 80mW transceiver, The Reggie, which uses a passive RX with the VXO acting as LO for a heterodyne mixer. He's worked some decent distances with this modest little rig. Mike has a great website with plenty of other fine ideas. The little Reggie circuit continues to evolve so keep checking back to his site.

http://mjrainey.googlepages.com/reggie

Update 19/1/09: Mike tells me he has measured the MDS as -87dBm (using a sig gen and a stepped attenuator/20dB pad) which is pretty remarkable for essentially a passive RX using a switching mixer. It implies Mike can hear around -90dBm clearly in his ST3 headphones.