[NLRS] Sequencer Question

[Glen Overby]

Dr. Gerald N. Johnson wrote:
> The high power IF transverters protect the mixer by receiving through
> that same transmit attenuator and including extra receive path gain. So
> long as that gain stage never gets driven to clipping by incoming
> signals it works, but it can lead to more intermod on receive.

I'm curious which ones do this?

My DEMI 902 and up transverters have an Omron G8Y relay to switch the common
IF port.  The 50-ohm load is only on the transmit side.  For the past few
years they'be been shipping a pair of 1N4148 diodes to put on the RX side to
attenuate transmit before the relay gets switched.  There's a MAR-6 on the RX
path to provide addional gain, and a small adjustable attenuator (I haven't
calculated how many db) to offset the gain.  I'm sure the MAR-6 does a lot to
protect the mixer as well.

The DEMI 222 is an older design and is quite a bit different.  It uses PIN
diodes for T/R switching, but I believe the load is still only switched in on
TX.

Glen, KC0IYT