Hi Leigh,
I run a homebrew preamp using a BF988 Mosfet, driving into a double-tuned circuit very loosely coupled together. -3 dB BW is from 156-162 MHz, with max gain of +15 dB. Tests at home with a signal generator and sound card showed about a 5 or 6 dB improvement in the receiver FM limiting threshold. From memory it went from -122 dBm (~ 0.18 uV) to ~ -128 dBm (~0.09uV) all +/-.
I doubt if I would hear anything otherwise.
You say on the website, you run a Garex Marine band preamp, how do you find that?
The signals I heard at work sounded pretty clear, with a recent model commercial handheld on a external dipole antenna.
At home I am hearing quite a reasonable number of AIS data bursts, so just need a few more dB to pull them out of the noise. With the FM threshold effect a 1 dB or 2 improvement at RF may make considerably more improvement at AF, until the knee flattens out.
A friend of mine has offered his 1.8m hockey stick, which will help with getting the antenna up.
The other solution of course is to buy a house on top of a large hill, which will help immensely...
Many decades ago I lived in the UK and spent many evening on 2M from what would be described as a "bath-tub" location in South Oxfordshire, but I persevered and worked reasonable DX. Others worked much further of course, but I probably learnt more...
During the day, I worked for one of the Racal Communications companies and learnt a lot over the 10 years I worked for them.
I better stop waffling...
Hi Allan,
What frequency is the paging over there? Over here it is just below 158 MHz, in the middle of the marine frequencies. I guess if I retuned the preamp so that it covered 162 to 168 MHz I could get some rejection of the pagers, but it doesnt affect me.
The line input to the external soundcard, definitely made a big difference to decoding errors on signals
Nice antenna. The antenna currently is a 1/2 wave ground independent whip antenna, which appears to be ok, but will see what is needed later.
Kevin
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