GaFET Preamp for XV144 transverter

[Edmund Wright]

I have recently finished aligned and tested an Elecraft XV144 Transverter.  I have an Advanced Receiver Research SP144VDG GasFet 2 meter preamplifier.  Its specs are as follows:

    Noise Figure  < 0,55 dB
    Gain 24 dB
    Compression +12 dBm
    Transceiver Power  <25 watts

Should I use my preamplifier between my Isopole 144 MHz vertical antenna and my XV144 transverter antenna connector?  I will have about 25 feet of coaxial cable between the preamplifier mounted on the antenna and the XV144 transverter.

I will appreciate any comments or suggestions

Ed Wright
AA6LZ
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[Evert Bakker (PA2KW)]

Hello Ed,

I do not know the NF of the XV144, but I guess it's somewhere around 1 dB.
If you want me to calculate how much there is to win, give me the NF of the
XV144 and your cable loss.
It makes only sense (practically in most cases) if you place the preamp at
the antenne side.
But gaining 0,2 db in NF by placing the preamp at the antenne side isn't
worth the trouble unless you go for EME (not the case here I guess looking
at the antenne type)

73's Evert PA2KW


-----Oorspronkelijk bericht-----
Van: [hidden email]
[mailto:[hidden email]] Namens Edmund Wright
Verzonden: vrijdag 14 maart 2014 0:25
Aan: [hidden email]
Onderwerp: [Elecraft] GaFET Preamp for XV144 transverter

I have recently finished aligned and tested an Elecraft XV144 Transverter.
I have an Advanced Receiver Research SP144VDG GasFet 2 meter preamplifier.
Its specs are as follows:

    Noise Figure  < 0,55 dB
    Gain 24 dB
    Compression +12 dBm
    Transceiver Power  <25 watts

Should I use my preamplifier between my Isopole 144 MHz vertical antenna and
my XV144 transverter antenna connector?  I will have about 25 feet of
coaxial cable between the preamplifier mounted on the antenna and the XV144
transverter.

I will appreciate any comments or suggestions

Ed Wright
AA6LZ
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[Don Wilhelm-4]

Ed,

I can't answer your question directly because "it all depends".

Your preamp has a very low noise figure.  If mounted at the antenna, it
will swamp out any losses in the feedline (as opposed to mounting it in
the shack).  However, with good low loss feedline, the loss in 25 feet
of coax may not be significant.  If you had 200 feet of coax, then you
would likely want to put the preamp at the antenna.

If you do add the preamp at the antenna:
With 24 dB of gain, you may find that the dynamic range of your
receiving system is reduced.  That can be increased by reducing the
front end gain of the XV144 - it involves removing the MAR6 amplifier in
the XV144.  The instructions are in the XV Owner's Manual.

If you do not currently have the preamp mounted at the antenna, I would
suggest trying the stock XV144 to see if that meets your operating
needs.  Should you find that weak signals are difficult to copy, then
add the preamp at the antenna for improved noise figure of the entire
system.

If you add the preamp, it may be beneficial to run a separate RX coax
from the preamp to the XV144 (split RX and TX at 144 MHz) which entails
removing a relay and adding a jumper.

If you are not into extremely weak signal reception (such as EME), then
the XV144 without the preamp may be more than adequate.  The typical
XV144 will receive a signal less than -140 dBm above the receiver noise
floor with no difficulty.

73,
Don W3FPR

On 3/13/2014 7:24 PM, Edmund Wright wrote:

> I have recently finished aligned and tested an Elecraft XV144 Transverter.  I have an Advanced Receiver Research SP144VDG GasFet 2 meter preamplifier.  Its specs are as follows:
>
>      Noise Figure  < 0,55 dB
>      Gain 24 dB
>      Compression +12 dBm
>      Transceiver Power  <25 watts
>
> Should I use my preamplifier between my Isopole 144 MHz vertical antenna and my XV144 transverter antenna connector?  I will have about 25 feet of coaxial cable between the preamplifier mounted on the antenna and the XV144 transverter.
>
> I will appreciate any comments or suggestions
>
>

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