Confused over RXA / LoopA difference

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  • Updated 4 years ago
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Okay, I admit I'm still confused. I've read and re-read the SSDR documentation pertaining to RXA / LoopA & RXB / LoopB.

I understand LoopA is physically connected to RXA but is logically different from it, but I don't understand in what way.

If I have a pan adapter or "Slice A". receive ant set to LoopA, does that mean there is DC power inserted in order to power a pre-amp that isn't there if I use it as RXA?

[obvious similar question for RXB / LoopB].

- Bob, W1RE
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W1RE

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Posted 5 years ago

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Ken - NM9P, Elmer

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This is the one part of the manual that I think could use some clarification.

If you look on your back panel, There are 2 connectors, RXA IN and RXA OUT.
The LoopA sends the antenna signal from ANT A out of RXA OUT so you can loop to a preamp, preselector, attenuator, or other processing unit, and then back IN to the Slice Receiver.

It is like an effects send and return on audio equipment, where they can send a channel on the mixer board OUT to an effects processor like an echo, compressor, flanger, etc, and then back IN to the audio chain...

So in other words:

LOOP sends it out the LOOP and back

RXA just uses the RXA IN as a separate receive antenna.

If you want to test it, you can put a Coax loop with BNC connectors between RXA OUT and IN and you will be listening on the antenna connected to ANT1.

Hope this helps.
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Ernest - W4EG

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I am happy to see your answer. I could not make head or tail on the explanation given in the manual. Thanks Ken and Bob for asking the question!
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Michael Engstrom

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I'm new to Flex and am enjoying the 6700. Why not include a simple schematic for this very  simple concept in the Hardware Manual? The paragraph quoted above is good and way better than 7.17 through 7.20 in new hardware manual (Ver 1.3 Aug, 2014.) Thank you Ken. One schematic is all that is necessary! What's the saying... "one picture is worth 1000 (confusing) words!"
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Bob Wright, N7ZO

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Hi Michael,

Check section 11 "Antenna Considerations" in the version 1.3 hardware manual.  The block diagram covers the various antenna connections.
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Michael Engstrom

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Thank you, Should have kept reading!
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W1RE

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So that's what the manual was trying to get across Makes perfect sense now, Thanks Ken!

Basically it's a way to selectively add external processing on the ANTx signal by looping out and back in on RXx.
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W5XZ - dan

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http://smartsdr.flexradio.com/FLEX-60...

page 30, sure helped me out, FWIW 73
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Robert -- N5IKD, Elmer

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It would be cool to have this diagram animated in SSDR indicating the actual settings thus showing visually the RF path associated with each audio slice.
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Reggie-k6xr

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I was extemely confused by it all. I sat here trying to figure it out and got nowhere! thanks
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Ken - NM9P, Elmer

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Thanks Dan,
...This passage from page 31 in the Hardware Manual is also helpful...

===
*ANT1 and ANT2 can be used for transceive operation. RX ANT-A (and RX ANT-B on FLEX-6700) are for receive only but can be paired with ANT1 or ANT2 for split
antenna operation. The XVTR port can be used for transverter operation or as an
additional receive antenna port.

* Signals from ANT1 and ANT2 can be “looped” through external filters and preamplifiers for additional system flexibility. THE ANT1/2 incoming signal is routed
to the RX ANT-A OUT port then to the remote device. The modified signal is
returned to the radio via the RX ANT-A IN port then to SCU-A. For the FLEX-6700,
the RX ANT-B “loop” is available also.
===

I hadn't read that part of the Hardware Manual, yet. This section is very well written.
My comments above were about the User Manual, which is otherwise VERY well written, except it wasn't very clear about Loop A / Loop B.
Though I understood the concept myself, (having a lot of experience with Live Audio systems), I thought that section of the User Manual could have had an additional sentence or two describing the function.

Or perhaps a sentence at the beginning of the section in the User Manual that describes the different antenna selections that says "See p. 31 of the Hardware Manual for detailed descriptions of the various Antenna settings."

If I had seen that page before my previous answer, I would have just copied & pasted it. It said it better than I did!
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K1UO - Larry

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yes Ken, Mayby releasing the manuals a few days early to the "preview" group before official release might have helped with some of the definitions. Overall though it looks very good for a first release Document. Like everything SDR..It just gets better.
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Ken - NM9P, Elmer

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I do a lot of writing in my job, and have only found one or two places in the manual that I thought needed improvement. Overall it is a very nice job. Kudos to the team.

But then again, this rig is so simple and intuitive to operate overall, that I figured out 90-95% of it just by playing! the rest I got by participating in this Support Community. This also is very well done.

Somewhere down the pike, I may blog a few simple tutorials for simple things, such as:

1) Flex-Quality Audio for multiple situation -- How to properly adjust your mike levels, EQ, bandwidth & Compression.
2) The Flex Control Knob - Secrets to Success.
3) Coaxing more signals out of your receiver -- using DSP, AGC, RX EQ, and more.

Any interest in this?
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K1UO - Larry

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I for one would be very interested.. Im an SDR Newbie so to speak... A little exposure in a way via my Elecraft K3 but learning and setting up interface ports etc etc for the 6700 is going to be my downfall I suppose.
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Robert -- N5IKD, Elmer

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Has anyone used the DX Engineering RPA-1 pre-amplifier?

http://goo.gl/pJtaAR
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W5XZ - dan

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yup....drop me a note at w5xz@att.net...73
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W5XZ - dan

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it''s a push-pull Norton with 2n5179's as i recall; i have one...
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K4EAR

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I have a Clifton labs preamp and took it out of the RXb loop, as the 6700 seemed better as I only needed it for 6M, jacking the internal preamp gain up. On the 5000 it was a different story.
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Reg

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Ken: The tutorials sound like a great idea. Go for it.