Antenna mute

w9mdb
Posts: 59
Joined: Sun Apr 09, 2017 5:53 pm

Antenna mute

Postby w9mdb » Wed Aug 29, 2018 6:17 pm

I'm reading the instructions on my Pixel Pro 1B since I will be increasing my potential transmit power up to 250W.
I found the Pixel gives me a 7dB increase in sensitivity over my dipole.
It says it can output up to 1.3 watts into the rig when it is saturated.
I can run a PTT line to the Pixel Pro to shut it up during transmit but would prefer not to do that.

I have an ANAN-100 so am wondering if 1.3W is too much into the antenna jacks or if there is some sort of antenna disconnect on transmit I should enable in PowerSDR.

de Mike W9MDB
User avatar
w-u-2-o
Posts: 1223
Joined: Fri Mar 10, 2017 1:47 pm

Re: Antenna mute

Postby w-u-2-o » Wed Aug 29, 2018 8:28 pm

Damn! Over +30dBm? :o That's a ton! You definitely don't want to let that impinge on anything on the Hermes board. However, assuming the switching on your PA/RF board doesn't fail in some horrible way, you would probably be OK to set it up for TX on ANT1 and RX on ANT2, and the Pixel is on ANT2. During TX the ANT2 relay will be disconnected and life should be good.

Refer to: https://apache-labs.com/community/viewtopic.php?f=35&t=2336 and see if you agree.
w9mdb
Posts: 59
Joined: Sun Apr 09, 2017 5:53 pm

Re: Antenna mute

Postby w9mdb » Wed Aug 29, 2018 8:35 pm

27dB gain but quite possible when your tx antenna is real close.

I assume ANT3 is also disconnected during Tx? So in any combinatin all non-transmitting antennas are disconnected?

de Mike W9MDB
w9mdb
Posts: 59
Joined: Sun Apr 09, 2017 5:53 pm

Re: Antenna mute

Postby w9mdb » Wed Aug 29, 2018 8:41 pm

I just tried transmitting on ANT2 and receiving on ANT1 using WSJT-X instances.
I still got decodes from ANT1 during the transmit so ANT1 did NOT disconnect.

de Mike W9MDB
User avatar
w-u-2-o
Posts: 1223
Joined: Fri Mar 10, 2017 1:47 pm

Re: Antenna mute

Postby w-u-2-o » Thu Aug 30, 2018 1:01 pm

w9mdb wrote:I just tried transmitting on ANT2 and receiving on ANT1 using WSJT-X instances.
I still got decodes from ANT1 during the transmit so ANT1 did NOT disconnect.

Mike,

I am skeptical that ANT1 did not disconnect. If so, if both the ANT1 and ANT2 relays were connected during TX, surely you would have damaged your receive antenna by now.

It would not be unusual to receive decodes of a weak signal mode that was sufficiently strong to overcome the isolation of one of the antenna selection relays.

I can't say for certain what your test procedure was, of course, but I'd suggest trying the following: with no antennas connected to ANT2 or ANT3, receive some larger signals, at least S9, regular SSB or CW, on ANT1 and make note of the signal levels. Then switch RX to ANT2 or ANT3 and see if you are still receiving those same signals and at what signal level. This will show you what kind of isolation you are obtaining through the relay. My guess is that it is something like 30dB. If so, then that should be sufficient to protect your receiver during TX.

73,

Scott

Return to “Everything Else: Antennas, Relays, Switches, Power, Grounding, Cooling, etc.”