The problem is hams expect things to cost near nothing and prices never to increase.
ARR Gasfet preamps* sold for years at $79.xx yet cost of material are rising. Last I checked they still use the mgf-1302 yet where is one able to find one? The mgf-1302 provides a reliable 0.5 dBNF and about 22 to 25 dB gain.
PGA-103+ appears to get 0.6 dB gain with about 15-18 dB gain
If you are a small mfr you do not get the volume parts discounts so materials represent 80% or more of your price and return on labor does not justify working. When I built DEMI transverter kits for $100 in labor I made $100/16 = $6.25 per hour. I finally quit as I thought about doing something else in my retirement.
WA2ODO has quit the preamp business (age & health). For $85-110 you don't make much for your time once the cost of materials is paid.
*non RF switched versions
Spend $95 each for two coax relays and add to $79 and see how cheap you can make a switched one for yourself. Yes, some pcb relays can be used if you can figure out how to eliminate inherent inductance/capacitance. RF-sensed switching preamps are still "hot switched": RF arcs across the contacts as the relay closes. Only with a switched preamp under sequenced dc control is the device truly safe.
73, Ed - KL7UW http://www.kl7uw.com Dubus-NA Business mail: dubususa@gmail.com
On 2019-11-08 17:17, Edward R Cole via AMSAT-BB wrote:
ARR Gasfet preamps* sold for years at $79.xx yet cost of material are rising. Last I checked they still use the mgf-1302 yet where is one able to find one? The mgf-1302 provides a reliable 0.5 dBNF and about 22 to 25 dB gain.
PGA-103+ appears to get 0.6 dB gain with about 15-18 dB gain
For those home-brewers among us:
If you just want something to fix the inherently high noise figure of a FM HT, you might try using, for 70cm and 33cm, the MAX2640. It can be obtained for ~$3.75 in qty 1 on Digikey.
Here's an application note[1] which matches it for 433MHz, close enough for the satellite band. They claim 1.17dB NF, which is not EME class but works great for the Fox satellites.
I have built up this circuit and can attest to its effectiveness in front of my Alinco DJ-580T. No picture of this setup, but I can post it later.
I've also used a classic U310 (J310, MMBT310) design on 2m to great success. It's not the neatest layout[2], but it seems to work fine.
--- Zach N0ZGO
[1] https://www.maximintegrated.com/en/design/technical-documents/app-notes/1/17...
participants (2)
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Edward R Cole
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Zach Metzinger