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@hotmail.com ***********************************************************