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G7CKF’s Fourbox

Jenny, G7CKF  has now taken the 2m Fredbox design and created a 4m version called the “Fourbox”.

Hi Roger,

    I feel I should drop you a line with my thanks and the link below, I’ve used your QRP AM transceivers as the basis for a 4M transceiver and published it on my blog. I’ve come back to amateur radio after a 20 year absence and since construction was always my main interest in the hobby I reached for the soldering iron.
http://thekeywordgeek.blogspot.co.uk/2015/05/a-transceiver-for-not-lot.html
There is no sparkling new insight to be had from it as it’s pretty much your fredbox with slightly bigger coils. There is no crystal because I am cheating and using a Raspberry Pi clock generator to make my 70.260MHz.
My QTH is IO91lw, between Bicester and Buckingham and rather low lying. Very little 4M activity hereabouts, sadly, so the chances of my actually working anyone with it are slim. But that’s not really the point of building, is it.
Anyway, hope you find it of interest, and thanks again for sharing your designs.

Jenny, G7CKF

Many years ago I designed and made the 2m AM Fredbox 2m AM transceiver. At the time it was the smallest 2m transceiver I’d ever seen or used.  Several close copies were made.  It worked some impressive DX including several 60 mile handheld contacts and one over 100 miles to Brittany from the South Devon coast.  All these were with whip antennas on the rig and not beams. Most QSOs were with locals. The power was only 10mW AM. It was ideal for contacts around Cambridge where I lived at that time.

Some years ago, I rebuilt the transceiver and had some decent QSOs yet again.

As with the Sixbox, I would suggest the design is taken as a springboard for your own version. It is certainly ripe for further development.

See https://sites.google.com/site/g3xbmqrp3/vuhf/fredbox .

Since my original Fredbox 2m AM design, a number of derivatives have been designed and built around the world. This is what our hobby is all about. Although the original Fredbox worked well and its results surprised me, it was always ripe for further developments, which is healthy. My Sixbox was a 6m version and at some point, when fitter, I’d like to make a simple 10m AM version for local natters.

See https://sites.google.com/site/g3xbmqrp3/vuhf/fredbox for the original Fredbox. Click on the schematic to enlarge. Other derivative ideas are on my website www.g3xbm.co.uk.   By the way, it got its name from Fred G8BWI who was a disabled local in the Cambridge area back in the 1970s. Fred was a regular contact and he could talk for hours and hours and hours and hours zzzzzzzzzzz. RIP Fred.

Fredbox 2m AM transceiver

The Fredbox was my design for a 10mW AM transceiver for 2m use back in the 1970s. It was rebuilt a few years ago and a 6m version was spun off. The same basic approach would work on 10m and 4m too, but I have not completed versions for these bands.

Even 2m 10mW AM was enough to work across the English Channel handheld on 2m and the 2m Fredbox made several 60 mile handheld QSOs . For quite a while it was used to natter across town in Cambridge. The Fredbox was named in honour of local Fred G8BWI back in the 1970s.

The Fredbox and Sixbox have appeared in G-QRP SPRAT and in Practical Wireless mags. The schematics also appeared in several foreign language magazines too. The circuits are basic and certainly capable of being improved.

See https://sites.google.com/site/g3xbmqrp3/vuhf/fredbox.
See https://sites.google.com/site/g3xbmqrp3/vuhf/sixbox .