[amsat-bb] Re: Preamp advice, pse

[Edward Cole]

At 02:45 PM 11/3/2008, ANTHONY JAPHA wrote:
>Bird Lovers,
>Pse let me have advice on which of the following ARR 2 mtr preamps I 
>should get: P144VDA: 1.0db nf, 15 db gain; or P144VDG: 0.5db nf, 24db gain.
>
>The preamp will be used primarily for AO-7.  I operate only portable 
>in a high noise environment here in Manhattan.  I doubt the nf 
>difference is at all meaningful in my use.  The large difference in 
>gain between the 2 preamps may not be impt. either, that is the real 
>question.  My XCVR is the FT-817.  Another 817 is used to transmit, 
>running abt 15-20 watts into a small amp. with an Arrow split 
>between 2 booms on 2 tripods only abt. 1 ft. from each other.
>
>So what's the verdict?
>
>Tnx and 73,
>Tony, N2UN

Hard to advise you since I live in rural Alaska....but:

I have used both preamps in a slightly different use (eme).  The 
GasFet P144VDG is really nice to get the NF down and has sufficient 
gain to be used at the antenna with a long run of RG-58 to the 
radio.  But in the RF contaminated environ of Manhattan the P144VDA 
may work as well (or better due to the high noise floor).

I use the P144VDA as my second preamp in my 2m-eme system to increase 
the gain of my mgf-1801 preamp since it has 16.8 dB gain and I need a 
minimum of 22 dB gain before the FT-847.  The result is = 16.8 + 15 - 
1.8 - 0.5 = 29.5 dB.   The last two items are my Rx line loss of 
150-feet of LMR-400 and line filter loss.

The P144VDA uses a 3SK48 MOSFet which is quite tolerant of high 
levels of RF and that makes it a fine second preamp.

So I would say if your line loss were under 2-dB the P144VDA will be 
OK.  The P144VDG will work great if it is not subject to high out of band RFI.


***********************************************************
73, Ed - KL7UW              BP40iq, 6m - 3cm
144-EME: FT-847, mgf-1801, 4x-xp20, 185w
1296-EME: DEMI-Xvtr, 0.30 dBNF, 4.9m dish, 60W
http://www.kl7uw.com       AK VHF-Up Group
NA Rep. for DUBUS: dubususa at hotmail.com
***********************************************************