17 Feb 2012

Simple local ragchewing rigs

The Sixbox 40mW AM transceiver for 6m. Maybe a Fourbox will follow?
The experiments last week by G6ALB and I confirm that to talk over a few kilometres, very little power is needed. Indeed, below 1mW is all that would be needed on any mode, at least on 144MHz. Andrew and I are now thinking about rigs that we can use to simply keep in touch whilst we get on with other QRP tests on bands from VLF to light. One idea is a 4m version of my Fredbox/Sixbox QRP AM transceivers to be called the Fourbox. This would be extremely simple to build and ideal for communication between a couple of stations in adjacent villages. Activity levels on 4m are not that great so we would be unlikely to suffer much interference issues if a super-regen receiver was used as on the original designs. A simple wire dipole in the loft would be fine for an antenna at each end. At 6m I was able to use T37-6 toroids, but at 70MHz I think these would be just beyond their intended design limits. Small airwound coils would probably be OK.

1 comment:

Anonymous said...

Hello Roger

I have been thinking of making something simple for 70 MHz rag chewing. Keeping it simple with 50-100mW output power. AM would be the desired mode with a sensitive superregen RX. Coils could be aircore or Torids wound on nylon washers. I do have a synthasized sig gen that that works up to 80MHz just need to-build a 1watt PA and modulate it with an LM380 or apply AF to the external mod input for FM & AM. I have heard of hams working through repeaters using signal gens with ext mod applied