Thread: 2-meter Preamp?
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Old October 23rd 07, 09:29 AM posted to rec.radio.amateur.antenna
Jeff Jeff is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 158
Default 2-meter Preamp?

I am looking for ways to improve my receive for 2-meter SSB weak signal
work. I am running an Icom 706 MkIIG and a M2 5WL yagi. I understand mast
mounted preamps bring the signal up significantly.
Doe any one here use one for 2M SSB? What are your experiences?

Thanks
Russ



There are 3 factors that determine if a preamp will help: does the radio
have poor sensitivity to start with, do you have significant feeder loss,and
how high is your ambient noise floor.

Taking the first and last together; no matter how good a pre-amp you use it
will be of no help if you have a high ambient noise floor to start with.
This is governed by where you live, quite country locations are obviously
much better than cities. As a quick check, see on ssb if your noise floor
drops significantly when you disconnect your aerial.
If it does then it is worth doing a better check where you compare the noise
between the aerial and a good dummy load. If the noise still drops
significantly then you are limited by the external ambient noise and all a
preamp will do is amplify this noise. If is does not change then you either
have a quite location or a noisy receiver.

If you are not limited by external noise then a preamp may help if you have
a lot of feeder loss, but the pre-amp must be at the antenna end, and not
the radio end, to improve things (unless you have a very very deaf
receiver).

In any case keep the gain of the preamp as low as possible that is still
consistent with improving the noise floor in order to limit problems with
receiver overload.

73
Jeff