20 Nov 2012

10m local range?

With the 10m AM Tenbox design coming along nicely I'm reminded of the fun we had in the early 1980s with 10m FM using converted CB rigs here in the UK. Using a converted CB radio with 4W FM into a vertical half wave antenna I was usually able to make contact with similarly equipped stations up to around 25-30 miles away pretty regularly. Certainly within a 5 mile radius signals were fully quietened, even to mobiles.

So, I am wondering how I'll get on with 0.5W of 29MHz AM? My expectation is that with a similar antenna (1/2 wave vertical - I currently use a horizontal halo) I should be able to cover 3-5 miles without too much problem. I'm wondering what sort of ranges people achieve with AM CB radios (WITHOUT add-on PAs!) where this mode is legal?  Running a few dB more power is no problem if required of the Tenbox design.

When 10m is wide open it is possible to work thousands of miles on FM but I always found that the competition was too great and therefore the mode is not well suited to DXing. The aim of the 29MHz AM Tenbox is just for very local communications and definitely not for DX working. In my mind I see the Tenbox being a modern version of the old Heath HW19 (the Tener) rig - see the image and data on the Rigpix page


TiƩgui said...

Hello Roger,
when I was 14 I had a CB radio (still have the same). I'm still having fun with that sometimes. You should listen to AM US stations they are really strong on 27.025 MHz !

My radio is just 4 W AM and when I was in Bordeaux, with a poor antenna location (very close to a wall) I was able to copy 10-15 km stations. Sometimes, I don't know why I could even make QSO with stations in Arcachon, around 50-60 km south to Bordeaux.

One day I made a dipole, it was in summer and there was Es propagation. There was a Spanish station from Andalusia coming really strong (he was singing a typical song from there with his guitar) and I made a QSO with him (just 4 W). But after I had to remove the dipole because people around was not happy to see it attached on trees...

73, from Thierry.

Tim said...

Hi Roger,

I run about 12W on AM on 29MHz from the car. It easily covers about 15 miles on ground wave - I'm sure further with the right topography.

73, Tim G4VXE