Question about the FLEX-8400ATU / FLEX-8600ATU receive RF path

ea4fw

I have a technical question before purchasing a FLEX-8400ATU or FLEX-8600ATU.

I intend to use a non-resonant HF antenna and it is important for my application that the internal ATU also be in the receive RF path.

When the internal ATU is enabled (not bypassed), does the received RF from ANT1/ANT2 pass through the ATU matching network before reaching the receiver?

Or is the ATU switched into the RF path only during transmit?

In other words, when receiving with the ATU enabled, is the matching network physically inserted in the receive signal path?

I am looking for the actual RF hardware architecture, not just the operating procedure.

Thank you very much.

Erik Carling EI4KF

Tim Ellison of Flex, in reply to the same question in another Thread, stated:

It is in the signal path if the RX antenna is the same as the TX.  For RX-A/RX-B is is not.

Mike-VA3MW

I had to go check on this with engineering (K1KP):

The ATU is only in the TX path on the 6000, 8000, and Aurora radios. Not in the RX path.

The practical effect is that matching is only done for TX. If the antennas have moderate SWR it would make little difference. If the SWR is very high, matching on RX would improve the noise figure. Still, noise figure is not much of an issue on HF due to high atmospheric and man-made noise.

Trucker

The above is one of the reasons I use a external, manual tuner. Besides the wider matching ability, it improves reception on a single antenna ( 130' open wire fed dipole in my case) as well as providing a good match between the radio and antenna. There is a noticeable difference as the system becomes resonate with a external tuner. Not everyone can have multiple antennas for different bands. This solution, in my case, works. And it protects the radio as well.

James

WD5GWY

ea4fw

Hi to everybody, and thanks for the answers.

I also opened a ticket in FlexRadio Helpdesk. I attached the answers of Ken Wells(NM9P), from FlexRadio Inc.:

"Jorge,

Thank you for using the HelpDesk. Let's get started addressing your issue.

From the techs I have consulted, it does NOT appear that for the 8000 Series the ATU is active in the receive signal path...

Since this issue has been addressed, we are closing this support ticket.

If you have any further questions or concerns regarding this support incident, please don’t hesitate to reach out. You can re-open the ticket at any time simply by replying to this message, and we’ll be happy to continue working with you.

Thank you for using the FlexRadio HelpDesk.

73"

So is clear to me that unfortunately, the Flex 8000 series does not insert the ATU in the receive path.

73s.