Hi Tom, Beko Elektronik, represented by Island Amplifiers has your answer(s) with a complete remote 440mhz preamp with internal T/R by-pass relay.      https://islandamplifier.com/

https://www.beko-elektronik.de

Another source is Down East Microwave          https://www.downeastmicrowave.com/ Best of knowledge, neither had a 1296 (23cm) complete remote pre-amp with internal T/R by-pass relay.With my engineering background, I made a 600 watt model.  Works great on the weak signal / tropo scatter.

Thanks n 73,JamesKI5DQ On Monday, December 26, 2022 at 11:04:54 PM CST, Zach Metzinger via AMSAT-BB amsat-bb@amsat.org wrote:

On 12/26/22 22:31, tjschuessler--- via AMSAT-BB wrote:

I do have a question for Yaesu FT847 users.  With that radio, you can   power a Preamp via the built in Bia- T power inserter, And assume that when this mode is turned on, it cuts the inserted DC to the preamp as the tranciever goes into transmit.  Does this work fast enough to protect, even RF switched preamps?  That might be a good safety measure as I have traditionally used external DC to power my preamps.

I have a homebrew UHF LNA that initially suffered the same fate as yours before it was modified with protective PIN diodes on the output.

I am powering the relays which switch from "inline" (during RX) to "bypass" (during TX) with the FT-847's bias-tee function. I found that the relays might not be quite fast enough to avoid getting a significant RF pulse back into the LNA output. This was most pronounced with CW, while SSB was tolerated better -- probably because I waited a moment to speak after pressing the PTT.

In a previous posting, I wrote:

http://www.n0zgo.net/lna/70cm/max2640/70cm_lna_max2640_annotated.jpg

(The BAR64 PIN diodes were added to protect the MAR3-SM+ output gain block when transmitting. Without those, the MAR3 was dead within a few minutes of use at >10W TX.)

You might try putting some of those PIN diodes into your unit. It might just keep it from going up in smoke.

--- Zach N0ZGO

-----------------------------------------------------------

Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/

View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/amsat-bb@amsat.org To unsubscribe send an email to amsat-bb-leave(a)amsat.org Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org