Question for Flex 6300 owners

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FLEX SAYS: "The FLEX-6300, FLEX-6500 and FLEX-6700 all have the option of receiving from the
XVTR port. The XVTR port is not recommended as a receive antenna port if an external preamp is used on its antenna. Transmission on the XVTR port could put up to +10 dBm of reverse power into the connected preamp."

 Many people I know, including myself, use a variety of preamps as needed on their extensive receive antennas.  My Hi-Z array has 8 preamps with one at each 24ft tall rx antenna and I have another two available inside the shack as well as the DXE preamp at the array center (over 800ft away).  Isnt there a way to inhibit the TX side of that same bnc connector so up to +10dbm of power doesn't fry the preamps?   I know I am ok with the 6700 as I have dedicated RX inputs but what about the users of a 6300?   I sent my 6700 in for a tuneup so currently I cant open the GUI to check if indeed the Xvtr port can be inhibited from TX only. (and of course I cant remember) .

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K1UO - Larry

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Posted 5 years ago

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Steve - N5AC, VP Engineering / CTO

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Official Response
First, during the PowerSDR era, placing an extra checkbox on a form to enable a feature for a set of users was less of a concern.  But we learned that the more of these kinds of things we add, the greater number of instantaneous modes the radio could be in and the higher likelihood that the operator will get confused about the "mode" of the radio and have difficulty operating it.  Our GUI designer now jokes that every time we request a checkbox option "an angel loses it's wings."  It's a tongue-on-cheek expression, but the point is valid: lots of options add lots of complexity.

Second, from our perspective, the more options like this that are added, the higher the support load becomes because operators can casually check a box like this and then totally forget the box ever existed.  Later when they are trying to transmit, we end up fielding a call from an upset customer that has spent several hours taking apart their station trying to find a problem, and believe their radio is broken.  Although the resolution might be quick, it's no fun for our customer to have this kind of experience.  This can also be embarrassing for a customer when in reality it's our fault for making something complex, really.

Third, I am a microwave guy and so my entire lash-up consists of a cascade of amplifiers, preamps, power supplies, etc. all depending on one another.  Most microwaves will tell you that if you build a hardware system than can blow up if it weren't for a software setting, that what you have is a ticking time bomb.  In other words, if you can break something with a setting in software, you eventually will.  Knowing that your system can never achieve an over-power, over-current, over-voltage, etc. condition if you do something wrong in the operation of the station brings a certain comfort.  It's nice to be able to tell a fellow ham "sure, try it out -- you're not going to hurt anything."  I've operated stations before where I've been given very strict instructions that ended with "and if you do ___________ you will destroy _________ which will cost me _________."  It's a lot less fun to operate given that set of conditions.

Fourth, as I suggested before, I think it is likely that this level of RF wouldn't hurt most devices anyway.  In the HF world, we're all used to thinking that transmit power kills anything but antennas, amplifiers, coax and relays, but this is a very low level of power.  If it's not a problem let's not fix it.

For these reasons, I'm going to resist doing something like this.  But if it is shown that this is a necessary thing to do, of course we'll go do it.  I'm just asking that before we complicate things for everyone, let's make sure it has to be done.

Steve
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Robert Farmer

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Steve, thanks for the robust and logical feedback.  I'm all for employing the KISS principle where applicable.

I sent a note to Lee, K7TJR, the Hi-Z designer who warned of inserting rf into the JFET's in the preamps.  I asked him to comment on the 10mW that you say is the limit of TX power that could be applied accidently.

If/when I get a response, I will relay.

Bob W9BF
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Lee, Elmer

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In theory and philosophy your reply is logical but there are other aspects of this radio to consider.  Certainly the more degrees of freedom you provide the more perverse permutations you will reap, and the harder the system will become to control and trouble shoot.  I understand that but some things are frivolous and some add robustness to a system.  Absolutely defining the nature of a port reduces your degrees of freedom when it comes to making a mistake (desirable) but it may increase the # of phone calls.  Those phone calls over time also increase the robustness however because your owners become smarter, and smart satisfied owners are your best salesmen.  I love discussing the things I like about my new radio with potential customers.   

The way you make a transverter tx mistake is you make a wrong choice or you forget or some piece of software, even SSDR chooses for you.  I have never had the radio come up in transverter mode but I have had it come up in TX and RX ant 2 on some bands quite often.  I never use ant 2.  There is nothing connected to ant 2.  It's not hard to spot because when the panadapter is reading -140 dBm I say "OH this must be in ant 2".  If it comes up in TX ant 2 then I have to trouble shoot why my SWR is 100:1.  It's either some state instability in the software (like it was preceded by some kind of funky shutdown) or old Hiram Percy is playing a trick on me.  Either way it makes me nervous.  

Your radio's code is not exclusively developed by you (Flex).  You have an API that allows others to control the radio through their own software development.  The 6300 has a transverter port which doubles as a receive port.  It is a major selling point of the radio.  I've had some email that indicates that one point, a external rx port, makes or breaks the sale.  I don't see any reason to not have the software tell that port exactly how to behave as part of the API and the setup form instead of relying on fail safes.  If you stuffed a cocked and loaded .45 in your pocket would you not lock the safety or would you rely on the hope that a misfire probably won't hit someone?  There is a syndrome called Glock leg.  It happens when someone pulls their Glock after doing a 3lb trigger job on the gun and that silly button they call a safety somehow gets defeated and you wind up shot in the ass.  (this is my appeal to the Texan in you)

I've been thinking about getting one of those $500 Pixel antennas Greg uses at the hamfests.  Maybe you guys could shoot some RF into that thing for me and see if it blows up.   

73  W9OY
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Steve B.

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Would recommend the addition of transmit inhibit on ANT1, ANT2, and XVTR ports. 

Method:  On setup screens: Add a LOV (drop down) for each of ANT1, ANT2 and XVTR with values:  TX/RX, RX, Inhibit.

Our GUI designer now jokes that every time we request a checkbox option "an angel loses it's wings."  It's a tongue-on-cheek expression, but the point is valid: lots of options add lots of complexity.  - Steve N5AC
Agreed - 100 % unless there is a strong case, see blow.

Later when they are trying to transmit, we end up fielding a call from an upset customer that has spent several hours taking apart their station trying to find a problem, and believe their radio is broken
To the GUI, add alt text over the field with the following values:

where RX - 'Transmit (TX) disabled in the Antenna Setup Page'
where Inhibit - 'Transmit (TX) and Receive disabled in the Antenna Setup Page'
Most microwaves will tell you that if you build a hardware system than can blow up if it weren't for a software setting, that what you have is a ticking time bomb.  In other words, if you can break something with a setting in software, you eventually will.
Understood, however - when I listened to your TAPAR presentation in Seattle on the 6000 series and the introduction of the 6300 (the reason I bought one) .. you focused on wanting to deliver a better user experience, support bringing new folks into SDR realm (and the hobby).

I just ordered a Pixel Mag Loop receive antenna, to add a fast acting relay on the feedline to protect me from myself (sending RF down the feedline by accident), it would be considerable expense effort and more infrastructure to maintain.  As this is a hobby, I work in Product Development at Oracle during the day .. I am often operating with a sleep deficiency. If the contesters do come, as I suspect they will after listening to your talk - they too will be operating sleep deprived and subject to making a mistake.  Switching an antenna port to no load/ant, TX on receive antenna.

If I blew the LNA on my receive antenna or the finals on my 6300 (as I had no ANT connected to a port, in error -- 
While it would be self inflicted, some part of me would be upset my 6300/SmartSDR and Flex Radio .. as I would know that it would have been possible to add a feature that would protect my infrastructure. 

The Alt text is in the context of the control.  When I tried to click on the grayed out TX control, I would get one on the two messages, right there in context -- and I would know how and why.  This should offset your concern about support calls.

Steve, please reconsider the request.

Warm Regards,

Steve Buchan
VE7ORA