Thursday, 17 December 2009

4 metres

I've now got a better antenna at home for the 70Mhz band. I've got a
vertical Half wave in the loft, with a Philips FM1000 ex-pmr mobile. The half wave is a centre-fed coaxial dipole as described by G4CJZ. We found that the measurements given were slightly too long, but trimming the ends of the antenna only brought the SWR down from about 1.5 to 1.3:1. The inner matching section might need shortening too but for now, it seems OK.
The picture doesn't show very much (it was dark so couldn't tell what I was pointing the camera at), what you can see is the lower half of the dipole.
Here are some SWR and impedance plots for the 4m antenna:

These graphs were recorded using my RigExpert AA-500

I've installed WinWarbler 4.5 for PSK31, and I like that best because it can automatically list all the stations received, across the whole audio bandwidth. So I can just leave it going and when I come back to the PC, I've got a receiving log filled in. Callsigns it hears only once are deleted after a certain time as they are probably errors, and it detects who is calling who (only the callsign after 'de' is logged).
Here are a few on 20 metres this Friday morning:
2E0GHQ (Southport)
9A6ZT
OM7OM
SV7CUD
ZB3R (Gibraltar)

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