SixBox (6m) and FredBox (2m) - /P tests

This evening I managed 16kms contacts with both the SixBox 6m 40mW AM transceiver and with the Fredbox 2m 10mW AM transceiver. QSOs were from Aldreth, Cambs, to Swaffham Prior.

Signals from the SixBox were copied by Andrew G6ALB when I was TXing with a 6m 1/4 wave antenna on a magmount on the car roof. On the superregen RX there was solid copy of G6ALB's 6m AM signal. Andrew uses a Diamond V2000 vertical, which recent discussions have confirmed are NOT as effective as a true 1/2 wave vertical on 6m. Clearly if Andrew had even a 2 el beam the QSO would have been a very decent one.

After finishing on 6m QRP, we moved to 2m AM to try some tests with the 2m Fredbox. A solid QSO was quickly achieved with the 10mW Fredbox using the 6m 1/4 wave antenna on the car magmount. This acts as a 3/4 wave antenna on 2m. I then tried the same antenna on the Fredbox handheld. Again, a solid 2-way QSO at 16kms distance. Switching over to a 1/4 wave whip on the handheld Fredbox resulted in a weaker, but just usable signal and QSO (same signal level as on the 6m SixBox). Finally, I tried the Fredbox handheld with a small helical antenna. Although Andrew could just detect this, no real QSO was possible.

So, with the V2000 in use at the far end of the contact, 40mW AM on 6m was not as strong as 10mW AM on 2m. Notheless, it was fun to give both rigs a portable outing and make some contacts.

The picture shows me during the Fredbox QSO using the 3/4 wave whip on the Fredbox.

VHF AM Yahoo group

This is a picture of G4BYE's version of my own Fredbox 2m AM transceiver design - a neat unit his is complete with proper PCB.

Many blog readers are already members of the Yahoo VHFam group. To join visit http://groups.yahoo.com/group/VHFam/ and follow the joining instructions.

At last VHF AM operation has got a mention in the latest UK VHF bandplans with the agreed "centre of AM activity" being notified in the footnotes as 144.55MHz. This spot in the European all-modes area is also used by some other users - I hear SSTV here sometimes - so it is NOT an exclusive spot, rather somewhere to look for 2m AM activity in the first instance. There's some AM activity on 145.8 still in Scotland but it would be good if users there would move to 144.55 so this became a UK-wide spot on which AM activity is likely to be found. Users can also be found on 70.26MHz on 4m.

VHF AM gear can be very simple to make and AM is an ideal mode for QRP building and experimenting. There's plenty of ex-PMR AM gear still to be found for next to nothing, ripe for use on 2m/4m AM.