Hi,
I am in the process of getting the ARR SP432VDG preamp for my mobile setup (and just to have around), and I have read that the closer to antenna you mount the preamp, the lower noise figure you will have. My question is, what is close to the antenna – 1ft., 5ft., 10ft.? Ideally, I would probably mount it about 5-6ft. from the antenna (1/4 wave) – would this be acceptable?
Any additional advice would be appreciated!
Zack KD8KSN
Why do you need a preamp in the mobile? Most new rigs are great at sensitivity. You must also remember that if you are mobile, Intermod is just around the corner at these high sensitivity preamps. Preamps, as a rule, should be as close to the antenna as mechanically possible. Good Luck, 73, Dee, NB2F
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Zachary Beougher Sent: Wednesday, March 30, 2011 10:24 AM To: amsat-bb@amsat.org Subject: [amsat-bb] Preamp Distance from Antenna
Hi,
I am in the process of getting the ARR SP432VDG preamp for my mobile setup (and just to have around), and I have read that the closer to antenna you mount the preamp, the lower noise figure you will have. My question is, what is close to the antenna - 1ft., 5ft., 10ft.? Ideally, I would probably mount it about 5-6ft. from the antenna (1/4 wave) - would this be acceptable?
Any additional advice would be appreciated!
Zack KD8KSN _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi Dee,
I have tried monitoring passes with the FTM-350AR, and it is just about impossible to hear anything. Granted, I was using a 5/8 wave, but I have used a 1/4 wave several times before with a different radio and experienced similar results. I will probably try it again just to make sure, but I would still like to get something to take the edge off and increase my hearing time a bit.
I know a few of you here have used the ARR preamps in your mobile (or while mobile) setups - does anyone have issues with intermod?
Zack KD8KSN
-----Original Message----- From: Dee Sent: Wednesday, March 30, 2011 10:53 AM To: 'Zachary Beougher' Cc: Amsat BB Subject: RE: [amsat-bb] Preamp Distance from Antenna
Why do you need a preamp in the mobile? Most new rigs are great at sensitivity. You must also remember that if you are mobile, Intermod is just around the corner at these high sensitivity preamps. Preamps, as a rule, should be as close to the antenna as mechanically possible. Good Luck, 73, Dee, NB2F
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Zachary Beougher Sent: Wednesday, March 30, 2011 10:24 AM To: amsat-bb@amsat.org Subject: [amsat-bb] Preamp Distance from Antenna
Hi,
I am in the process of getting the ARR SP432VDG preamp for my mobile setup (and just to have around), and I have read that the closer to antenna you mount the preamp, the lower noise figure you will have. My question is, what is close to the antenna - 1ft., 5ft., 10ft.? Ideally, I would probably mount it about 5-6ft. from the antenna (1/4 wave) - would this be acceptable?
Any additional advice would be appreciated!
Zack KD8KSN _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi Zack, KD8KSN
The loss in dB of the coax cable from the antenna to your preamplifier adds directly to the Noise Figure NF of your preamplifier. As an example if the loss of the coax cable is say 0.7 dB and the Noise Figure of the preamplifier is 0.55 dB as specified by the manufacturer then the overall Noise Figure of the system antenna plus preamplifier is 0.7+0.55=1.25 dB
This is why to reduce the overall Noise Figure of any receiving system it is necessary to install the preamplifier as close as possible to the antenna connector.
By the way the gain of a ARR SP432VDG preamplifier is 16 dB and as connected in front of your 70 cm receiver you will see an increase of noise level of about 3 S-units in your S meter but the overall Noise Figure of your receiving system will be much lover than the Noise Figure of the 70 cm receiver alone.
In this condition using a preamplifier the 70 cm receiving system will be more sensitive but it will be more susceptible to intermodulation and overloading when you transmit to a satellite in the 2 meters band.
If you suffer with intermod the only cure is to add a 6 dB attenuator from the preamplifier output to the 70 cm receiver input but if you use a 70 cm tranceiver don't forget to remove the attenuator before to transmit in 70 cm
I hope this helps.
73" de
i8CVS Domenico
----- Original Message ----- From: "Zachary Beougher" zack.kd8ksn@hotmail.com To: amsat-bb@amsat.org Sent: Wednesday, March 30, 2011 4:24 PM Subject: [amsat-bb] Preamp Distance from Antenna
Hi,
I am in the process of getting the ARR SP432VDG preamp for my mobile setup
(and just to have around), and I have read that the closer to antenna you mount the preamp, the lower noise figure you will have. My question is, what is close to the antenna – 1ft., 5ft., 10ft.? Ideally, I would probably mount it about 5-6ft. from the antenna (1/4 wave) – would this be acceptable?
Any additional advice would be appreciated!
Zack KD8KSN _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
participants (3)
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Dee -
i8cvs -
Zachary Beougher