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. 


Another source is Down East Microwave

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,
On Monday, December 26, 2022 at 11:04:54 PM CST, Zach Metzinger via AMSAT-BB <[email protected]> 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


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