I got a couple of cheap and nasty BFR91 pre-amp boards from out local electronics store.
I built one and the gain was equal or worse. It had two sets of components for VHF and UHF.
So I took a gamble and put in the VHF parts instead.
Bingo S1 to S9 improvement.
Ok, so lets cascade them.
Sure enough the front end of my radio on 144 MHz overloaded with other signals.
It has bought up GO32 from S1 to S9
GENSAT is S4 from S nothing.
Now this is just before the radio.
I am now keen to throw it in a box and up at the antenna.
Having fun, also building a Power Break out box with meters and switches.
Cheers
---------------------------------------------------------------------------- Andrew Rich VK4TEC vk4tec@people.net.au http://www.tech-software.net
At 11:38 AM 12/23/2007, Andrew Rich wrote:
So I took a gamble and put in the VHF parts instead.
Bingo S1 to S9 improvement.
OK, but the important thing is what is the improvement in S/N? If the preamp has too high a noise figure, all you'll end up doing is moving the S meter a bit more... What you're aiming to do is improve the S/N of the received signal.
If the S/N doesn't change, you will still gain an improvement by siting the preamp at the masthead. If it does improve with the preamp at the radio, the improvement will be even more with the amplifier correctly installed at the antenna.
73 de VK3JED http://vkradio.com
Hi All, Here is a link to a noise figure meter project. Even if it is not calibrated it can be used for comparitive measurments. http://www.ham-radio.com/sbms/sd/nfsource.htm
Happy Holidays, Art , KC6UQH
----- Original Message ----- From: "Tony Langdon" vk3jed@gmail.com To: vk4tec@people.net.au; "Amsat-Bb@Amsat. Org" amsat-bb@amsat.org Sent: Saturday, December 22, 2007 5:56 PM Subject: [amsat-bb] Re: Pre-amps
At 11:38 AM 12/23/2007, Andrew Rich wrote:
So I took a gamble and put in the VHF parts instead.
Bingo S1 to S9 improvement.
OK, but the important thing is what is the improvement in S/N? If the preamp has too high a noise figure, all you'll end up doing is moving the S meter a bit more... What you're aiming to do is improve the S/N of the received signal.
If the S/N doesn't change, you will still gain an improvement by siting the preamp at the masthead. If it does improve with the preamp at the radio, the improvement will be even more with the amplifier correctly installed at the antenna.
73 de VK3JED http://vkradio.com
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participants (3)
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Andrew Rich -
kc6uqh -
Tony Langdon