Quoting Steve Raas sraas@optonline.net:
As I prepare for getting on the birds.. I decided to test out this AG-25
Steve:
(Once again, it has to be said that I'm new at this stuff, too, and I'd be happy for the folks on this list who have taught me over the last two years to correct any errors.)
What you describe in your letter would, I believe, correspond to the situation in which the noise figure of your preamp is not much better than the noise figure of the front end of your receiver and there is not very much loss between the preamp and the radio (i.e., not very long a run of cable). Is it possible that you hooked it up with a short run of cable in the shack, shorter than you usually use for terrestrial work? Perhaps your receiver nf has improved. If the preamp and the front end have the same noise figure and there is significant loss in the cable, however, you will win with this setup.
From my experience, if your cable is low loss, a 145 preamp isn't as
necessary as a 435 one because thermal noise is higher and the cable won't ding you as much. My preamp went funny and it wasn't a complete tragedy. Who knows, maybe *my* 145 preamp is the pits, too :-) Those ICOM units are a bit dodgy, though: they don't seem to specify their noise figures very well.
I think all would agree that 435 MHz is the band that *really* needs a preamp. You want one that has a 1 dB noise figure or less for the usual 15 + dB of gain. Advanced Receiver Research and SSB USA are known to be fine. My in-shack ARR preamp is *amazing*. (I have a short run of heliax between antennas and preamp.) Be sure to get one that switches on xmit.
As far as setting up a station, I'd try building something minimal to start so that you can observe the improvement each added element brings. Use a female-female N connector in place of a preamp on 145 at first and observe the helpful always-on beacon on VO-52. How high above the horizon does it need to be before you can hear it over the noise? before it starts to move the S-meter? (Don't try this with AO-7; it's too weak.) Even on 435, you'll hear *something* without a preamp if you have an antenna with some directionality. (And, as I've mentioned in the previous letter, even a 1/4w vertical will bring in LO-19 and others.)
73, Bruce VE9QRP