Fred,

I would guess most use RF sense switched mast-head preamps since they are using radios with a single antenna connector. But some folks modify the radio so the Rx has an independent antenna input isolated from the Tx so they can run a separate coax line to a simple preamp and use a coax relay on the antenna side of the preamp. This requires a separate coax run to the Tx output.

This second approach is not uncommon approach for those involved in serious weak-signal VHF+ operating (which includes eme). I have both approaches at my station. I have several DEMI transverters that provide separate Tx and Rx antenna connection so a simple remote located preamp with TR relay can be used.

But I also have a FT-736R (unmodified) which can use a yagi with Rf sense-switched preamp and only requires one coax run. I do have external switching control line to that preamp which will require adding ext. PTT from the FT-736R. I originally used preamps for 144 & 432 with separate TR relays for my AO-40 era satellite set up and will be restoring that this summer. This will require modifying my FT-736R.

I use a station control panel with integrated sequencer, but that was done for eme and other weak-signal operation (not specifically for satellite). My satellite control ckts will utilize the sequencer (which provides extra protection to the preamps - but not normally used by satellite stations.

73, Ed - KL7UW

From: Fred Castello fredcastello@gmail.com To: "amsat-bb@amsat.org" amsat-bb@amsat.org Subject: [amsat-bb] RF Sensing Preamps, Sequencer, or both? Message-ID: 579fe396.e928c80a.c54fd.4af3@mx.google.com Content-Type: text/plain; charset="utf-8"

Hi folks,

I am in the process of trying to set up a station here and have been researching equipment. While I suspect there will be a fair amount of variety, I am curious to the responses to my question:

Do you use the relatively less expensive ?indoor? NON RF switching preamps in an enclosure near the antennas (on the tower) with RF relays and with a sequencer in the shack (do the preamps holdup up on the tower even if protected?) OR

Do you use RF sensing preamps mounted at the tower OR

Both (for those that are extra careful)? I suspect operators that do other VHF/UHF low signal work tend toward sequencers (one for 2 meters and one for 440), i.e. moon bounce, meteor scatter, etc.

Also, I am curious what type/brand/model of RF relays folks use?

As usual, I really appreciate your time. Best, Fred Castello, KF4FC

73, Ed - KL7UW http://www.kl7uw.com "Kits made by KL7UW" Dubus Mag business: dubususa@gmail.com