Using AG8x2 Port B for RX only

KI5RLR

Is there any way to set Port B on the AG8x2 to stay on one antenna all the time, EXCEPT when I transmit on Port A? I have a WebSDR (KiwiSDR) which stays on 24/7, connected to a wire antenna. I would like for the AG to 'rest' on port B, with the RX antenna selected, feeding the KiwiSDR. Then, when I use Port A to transmit, I would like port B to shut off during the Port A transmit period, and automatically return to port B... or something like that. I am not sure if that is possible or not. Any help/suggestions would be appreciated.

Thank you!

KD0RC

I think that what you are really looking for is an SDR TR switch that protects the SDR when you transmit. I have seen them advertised on Amazon, Ali, and eBay.

KI5RLR

Something triggered by the PTT signal into the transmitter, that then disconnects the SDR input coax during transmission?

If I have the SDR TR switch in place, can I set the AG8x2 to keep Port B connected to a certain antenna all the time, even when I transmit on Port A?

Thanks!

KD0RC

Yes. Some T/R switches detect RF to do the switching and some use the PTT signal.

Second question is also yes. If you never want to switch the RX only antenna, it might be better to connect it to the RX input on the Flex.

KI5RLR

I did not word my last question correctly. Let me try again.

My 8x2 switch is connected to 4 antennas, all of which I use to transmit at some point. Assuming my 2nd SDR (KiwiSDR) is protected when I transmit, how can I accomplish the following task.

Manually set Port B to any of the four antennas and have it stay that way until I manually switch Port B to another antenna.

Port A would run in the 'Flex' mode which selects the last antenna I used on each band, unless of course that antenna is the one I have manually selected for Port B. If I need the antenna on Port B for transmitting, I will have to manually switch that antenna 'away' from Port B (KiwiSDR) and 'assign' a new antenna.

A) Can I set it up that way?

B) Is it possible to damage the switch itself that way?

Thanks again!

KD0RC

A) Yes

B) No

When you select the antenna away from the kiwi, you can leave the kiwi disconnected, or you can connect it to a different antenna depending on what you are trying to do.

If you connect it to a different antenna, you just need to be sure that the amount of signal on the kiwi antenna does not exceed the max level that it can handle.

In any event, the Antenna Genius itself is not in any danger.

KI5RLR

Great! 😀

My plan is to use a coax disconnect actuator made by Paradan. It will disconnect the coax to the KiwiSDR (coming from Port B) when PTT is enabled on any radio in the shack. I might put a front end protector in-line, right before the KiwiSDR, as well.

A few other questions out of curiosity.

Can the switch be damaged (with RF, not a hammer) if the same antenna is on PortA and PortB simultaneously while transmitting, without some sort of special filters in place? Is that what the 'in band' setting permits on the AG menu?

Thanks again for taking the time answer my questions!!

73, Clif - K5IUC

KD0RC

Hi Clif, I don't think that you can have one antenna on two ports simultaneously. That would defeat much of the purpose of the switch.

David Decoons, wo2x

hi Cliff,

The Paradin probably will not be fast enough to disconnect the antenna from the Kiwi.

The Inband feature of AG allows you to have both port A and B on two different antennas on the same band simultaneously. This is used in contesting where you have a run station and a second station looking for multipliers on the same band. NOTE - YOU MUST HAVE PROPER ISOLATION BETWEEN ANTENNAS TO PREVENT RISK OF DAMAGE TO RECEIVERS DUE TO RF OVERLOAD.

The best solution is to use something like a Dow Key relay from antenna port of Kiwi to antenna or antenna switch (depending on your configuration). Use one of the Flex TX lines (1, 2 , or 3) to control the relay. Watch keying voltage and current requirements of the relay. A relay buffer may be needed. Common side of relay to Kiwi, RX side to antenna/antenna switch, and TX side put a sorted connector so the Kiwi antenna port is grounded when Flex is transmitting.

You will need to set Flex TX delay to appropriate value to ensure antenna disconnected from Kiwi before you transmit RF.

73

Dave wo2x

David Decoons, wo2x

Cliff

Re-reading your initial question, use a dedicated RX antenna to Kiwi and relay as described to ground Kiwi antenna port when Flex transmits. No need for Antenna Genius (unless you have a 6700/6600/8600 and want the Flex to receive two different bands on two different antennas simultaneously)

73 Dave wo2x