Date   

Re: QCX mini: RF output BNC or SMA #poll-notice

Shane Justice
 

All,

The life cycle mating on SMA is for the full frequncy range, plus mechanical wear aspects. At HF frequencies, the wear cycles should be greater than for the microwave frequencies. 

That said, SMA is not the most rugged connector for field use, even though there are many used in HTs. If you look how the sma base antennas are constructed for HTs, they have a wider base of plastic that physically.mates with the body of the radio to reduce torque that the SMA will experience if the radio is dropped and lands on the antenna, or experience other torques from the radio being grabbed by the antenna, for example. Motorola even made some of their radios with the SMA in reverse, so the recepticle was mounted within the chassis, and the antenna had the protruding  threaded SMA as part of the antenna. If the SMA were to fail, it would be easier to replace the antenna. Think about what cable you might use with the SMA- will you have PL259s on the cable? Do you plan to use a threaded adapter? You may lose a few dB with that adapter.

BNCs are subject to wear and toque issues as well- I've seen more than a few failures in rugged environments. Again, what size cable will you use? RG8x? 

TNCs are probably much more rugged than BNCs or SMAs, but I saw one soldier radio where that rugged connector had the outer rim of the jack side crimped inward, with tailtale signs of jaw marks from heavy duty pliers across the folded-in part of the connector. It was clear that some gorilla thought he'd prove that connected could be damaged. This was a brand new Soldier Radio, on its initial field trial. First day with the troops.

If we assume that we hams will treat our equipment much more carefully, then we can proceed with a slightly different tack- reasonable use, and attempt to accommodate some of the more likely accidents that can occur; people tripping over the cable between antenna and operating position, wind gusts causing the tree to "yank" on the antenna and a taut coaxial cable, an antenna/tower falling and launching the radio trebuchet - style, as examples.

In these scenarios, whatever torques experienced by the connector should be stopped at the case and not permitted to transfer the load to the PCB. In other words, it should be bulkhead mounted.

Now, let's say the connector is damaged. Which connector, in bulkhead form, is most likely to be available? 

I have used services that provide 1 week turnaround after receipt of order for connectorized SMA-TNC cables of any length under 12 inches for $6-7, including shipping. You could order spares to your specification ahead of time and carry one and the tools necessary to replace it in your pack, but that is adding weight.

If you want the most rugged connector, the TNC is really hard to beat. I am using them for my telemetry link to my high power rockets, where an approximately one foot long spring steel (measuring tape) radial is being buffeted by 110 feet per second winds on descent (thats a little over 60MPH if my mental math holds) for at least one minute, as the 35 pound rocket descends from apogee to the main parachute opening height of 1300 feet. The TNC is a bulkhead mounted connector and seems no worse for wear. All that said, I have only launched this rocket once, as there are logistics issues with getting to a suitable launch location with FAA clearance, so no long history of many flights to stand upon here.

The fact that the TNC is the treaded cousin to the BNC makes it a more rugged connector  that will stay tight at finger torque levels and has a purchase you won't get with either an SMA or BNC plug end, making it easier to connect/disconnect with cold or gloved hands in the Winter, or sweaty hands in the Summer. It's slightly larger than a BNC, but smaller than a SO239.

Speaking of SO239s, while they are big, have you ever heard of someone needing to replace one? I certainly don't recall one. They are ubiquitous, and almost any coaxial cable made has a PL259 that can accommodate it. They are heavier than the other connectors considered.

How much weight is too.much to carry on a SOTA expedition? I am unlikely to attempt a SOTA due to my age and medical issues, so I leave this to those who will be making this adventures.

In conclusion, whatever connector is ultimately used, it should be ridgedly mounted to the metal case, not to the PCB, to prevent damage to the PCB, and prevent mission impact.


73,
Shane
KE7TR


On Aug 6, 2020 at 06:34, Hans Summers <hans.summers@...> wrote:

Hi Russ

I have to admit to a preference for BNC. 

What kind of issues have they seen? 

73 Hans G0UPL
http://qrp-labs.com

On Thu, Aug 6, 2020 at 4:28 PM Russ@va3rr via groups.io <va3rr=yahoo.ca@groups.io> wrote:
The NanoVNA group has been seeing some issues with SMA connectors.

It's too bad TNC connectors aren't more prevalent in amateur equipment.  I have some LMR cables with TNC connectors and they really are quite robust...




Re: Deliveries for QCX+

ke9uw
 

Cosmic ring...where can I order?


Re: QCX mini: RF output BNC or SMA #poll-notice

George Korper
 

I like that idea! 


On Thu, Aug 6, 2020 at 12:43 PM Alan de G1FXB <g1fxb.groups@...> wrote:
I fully expect I'm in a group of one.
But especially as the QCX was first requested and now being offered as field optimised.......

Imagine the gods gave were kind hearing the rarest of rare DX station,
when you trip over the feeder and it pulls out the back of your radio, or the patch lead that was OK when you packed it away you find is no longer.......
I know I don't want to be fudging with SMA connectors and mini coax with minimal hand and soldering tools on a hill top or worse still atop a ski jump.
SMA's were not "invented" to be a regularly disconnectable connector, then add to it some dust & dirt "grinding paste" and who knows how durable it will be on the trails.

At least some  BNC's styles are available as "Solderless" that will suffice for field repairs to get you out of trouble, even then cable preparation can be a faff when you discover at the most inconvenient time you have a bad cable.
 in the past either by luck or by design the  QRP labs enclosures for the U3 has allowed for substitution and the drilling out & fitting of a female shielded Banana Plug receptacle, more commonly known as a SO239
Assembled PL259 can be reclaimed easily enough on hill tops, although solderless and non-crimp also exist, the cable can be remade without the need of a soldering iron for field day repairs if need be if I have forgotten to pack a few spares......


We all have a favourite "Shack Standard" RF Connector and like all good standards, they are far from it......


If the QCX enclosure had what ever the preferred end up being  "RF Out" suitably separated from the next connector then we all could pick & choose "our own" favourite SMA, TNC, SMB, BNC Chassis socket. Or whatever........?


Alan

On 06/08/2020 14:49, Jim Mcilroy via groups.io wrote:

At one stage in my professional life I worked in a components factory which made SMA, TNC, SMB, BNC and you name it. We also made semi-rigid and flexible cable assemblies for space and general aviation applications.

The network analysers we used had SMA on the ports as we measured up to 26GHz in the day. They were good for more than 50 mate/demate cycles but they were of high quality.

I agree that TNC is a resilient connector and would like to see it used more.

If a connector fault was reported or something sent back we would measure what we could and if in doubt pot the connector and section it to see how the assembly materials fared. I did see one example of a faulty SMA where some metal of the inner connector dislodged, made its way through the dielectric to the outer core and short circuited.

Jim

PS BNC connectors are OK up to 4GHz


On 06/08/2020 14:39, Dave wrote:
The SMA is only rated for 50 mate/demate cycles, and that is for the real gold plated versions. Quite a nice connector for applications that call for a very few disconnects, like inside equipment.

There is a reason why the BNC is found on scopes and signal generators, etc.

The TNC is a close relative of the BNC, without the vibration induced connection noise.

Dave


On Aug 6, 2020, at 09:34, Hans Summers <hans.summers@...> wrote:


Hi Russ

I have to admit to a preference for BNC. 

What kind of issues have they seen? 

73 Hans G0UPL
http://qrp-labs.com

On Thu, Aug 6, 2020 at 4:28 PM Russ@va3rr via groups.io <va3rr=yahoo.ca@groups.io> wrote:
The NanoVNA group has been seeing some issues with SMA connectors.

It's too bad TNC connectors aren't more prevalent in amateur equipment.  I have some LMR cables with TNC connectors and they really are quite robust...




Re: QCX mini: RF output BNC or SMA #poll-notice

Alan de G1FXB
 

I fully expect I'm in a group of one.
But especially as the QCX was first requested and now being offered as field optimised.......

Imagine the gods gave were kind hearing the rarest of rare DX station,
when you trip over the feeder and it pulls out the back of your radio, or the patch lead that was OK when you packed it away you find is no longer.......
I know I don't want to be fudging with SMA connectors and mini coax with minimal hand and soldering tools on a hill top or worse still atop a ski jump.
SMA's were not "invented" to be a regularly disconnectable connector, then add to it some dust & dirt "grinding paste" and who knows how durable it will be on the trails.

At least some  BNC's styles are available as "Solderless" that will suffice for field repairs to get you out of trouble, even then cable preparation can be a faff when you discover at the most inconvenient time you have a bad cable.
 in the past either by luck or by design the  QRP labs enclosures for the U3 has allowed for substitution and the drilling out & fitting of a female shielded Banana Plug receptacle, more commonly known as a SO239
Assembled PL259 can be reclaimed easily enough on hill tops, although solderless and non-crimp also exist, the cable can be remade without the need of a soldering iron for field day repairs if need be if I have forgotten to pack a few spares......


We all have a favourite "Shack Standard" RF Connector and like all good standards, they are far from it......


If the QCX enclosure had what ever the preferred end up being  "RF Out" suitably separated from the next connector then we all could pick & choose "our own" favourite SMA, TNC, SMB, BNC Chassis socket. Or whatever........?


Alan

On 06/08/2020 14:49, Jim Mcilroy via groups.io wrote:

At one stage in my professional life I worked in a components factory which made SMA, TNC, SMB, BNC and you name it. We also made semi-rigid and flexible cable assemblies for space and general aviation applications.

The network analysers we used had SMA on the ports as we measured up to 26GHz in the day. They were good for more than 50 mate/demate cycles but they were of high quality.

I agree that TNC is a resilient connector and would like to see it used more.

If a connector fault was reported or something sent back we would measure what we could and if in doubt pot the connector and section it to see how the assembly materials fared. I did see one example of a faulty SMA where some metal of the inner connector dislodged, made its way through the dielectric to the outer core and short circuited.

Jim

PS BNC connectors are OK up to 4GHz


On 06/08/2020 14:39, Dave wrote:
The SMA is only rated for 50 mate/demate cycles, and that is for the real gold plated versions. Quite a nice connector for applications that call for a very few disconnects, like inside equipment.

There is a reason why the BNC is found on scopes and signal generators, etc.

The TNC is a close relative of the BNC, without the vibration induced connection noise.

Dave


On Aug 6, 2020, at 09:34, Hans Summers <hans.summers@...> wrote:


Hi Russ

I have to admit to a preference for BNC. 

What kind of issues have they seen? 

73 Hans G0UPL
http://qrp-labs.com

On Thu, Aug 6, 2020 at 4:28 PM Russ@va3rr via groups.io <va3rr=yahoo.ca@groups.io> wrote:
The NanoVNA group has been seeing some issues with SMA connectors.

It's too bad TNC connectors aren't more prevalent in amateur equipment.  I have some LMR cables with TNC connectors and they really are quite robust...




Re: QCX mini: RF output BNC or SMA #poll-notice

jmh6@...
 

Hi All,

I have had long term reliability problems with BNC connectors. So much so that I have converted most stuff to either real screw terminals or simple soldered connections. Clamp type 'screw' terminals seem to have the same problems as BNC over time.

What is needed is a 'gas tight' connection of whatever type.

BNC is great for lab stuff, but when whatever 'should' keep working week in week out, BNC doesn't cut it at least for me.

Lots of fun :).

John

On Thu, 6 Aug 2020, Skip Davis via groups.io wrote:

SMA connectors are nice and cute on small rigs but BNC are far easier to use with fat fingers. Also how many have actually ever made up SMA cables and adapter cables? It?s pretty tough and much harder than BNC. Most people will hang a SMA/BNC adapter off that SMA which defeats the purpose of the choice of the smaller connector.
Just my thoughts on this YMMV.

Skip NC9O



Re: How about an ultra-portable "QCX mini" version? #qcx

Hans Summers
 

Hi Kees

It's the same extrusion used on the 50W PA kit http://qrp-labs.com/50wpabox.html but cut to a shorter length, and with the top and sides mutilated in different ways. So yes, all drilled and cut and printed. Printing is laser etch though, not silkscreen. Laser etch is a higher quality finish and more durable, higher resolution. 

73 Hans G0UPL
http://qrp-labs.com

On Thu, Aug 6, 2020 at 5:47 PM Kees T <windy10605@...> wrote:
Hans,

9.1 cuin ....with a 2x16 display, and DIP ATMega328.....WOW. .....with all the SMT premounted, that's cool.

I think 92mm x 25mm x 63mm is one of the "standard" aluminum clamshell enclosures like on the QCX+.  Drilled and Silkscreened ?

73 Kees K5BCQ


Re: QCX mini: RF output BNC or SMA #poll-notice

George Korper
 

OK. I am thinking the longer BNC with the threads could be substituted with one that is shorter
and needs no nut and lock washer. Democracy is all about arriving at the best solutions...hee hee. 
It may be fractionally cheaper too. 

OH let Hans decide, the topic is exhausted. 

On Thu, Aug 6, 2020 at 12:00 PM ajparent1/KB1GMX <kb1gmx@...> wrote:
Shorter BNC is the same.  How reliable they are for its connection to
the board is unknown as all the systems used a variant that locked
to the chassis. for mechanical support.

I do not see the problem being lifetime in use.  More like user friendliness.
Small connectors are harder to handle both in use (that 5/16th nut on SMA)
and also making cables. 

For every socket connector wear out on gear I've had cables fail in use many
many times over and that applies to C, N, BNC, TNC, PL259, SMA, SMB. 
Some connectors however provide better support for the cable and generally
SMA [and SMB] do not.

Allison
-------------------------------
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Re: QCX mini: RF output BNC or SMA #poll-notice

Skip Davis
 

SMA connectors are nice and cute on small rigs but BNC are far easier to use with fat fingers. Also how many have actually ever made up SMA cables and adapter cables? It’s pretty tough and much harder than BNC. Most people will hang a SMA/BNC adapter off that SMA which defeats the purpose of the choice of the smaller connector.
Just my thoughts on this YMMV.

Skip NC9O


Re: 500 times for the SMA

George Korper
 

Good low profile solution, and they work fine for me. Used on SotaBeam tuners. 


On Thu, Aug 6, 2020 at 12:02 PM <g3vgr@...> wrote:
I never understood why hf qrp rigs have BNC sockets. They're totally unnecessary at HF, difficult to use with RG174 and breakages in the field are impossible to easily repair.
For portable operation, I've always used phono plugs on coax feeder and a phono/BNC adapter on the BNC socket. Much easier
73, Dave G3VGR


Re: Who needs feet for their builds?

Jim Netwal
 

Mark,

Can you attach a picture with them installed please?

73, Jim W9UUM


Re: 500 times for the SMA

g3vgr@...
 

I never understood why hf qrp rigs have BNC sockets. They're totally unnecessary at HF, difficult to use with RG174 and breakages in the field are impossible to easily repair.
For portable operation, I've always used phono plugs on coax feeder and a phono/BNC adapter on the BNC socket. Much easier
73, Dave G3VGR


Re: QCX mini: RF output BNC or SMA #poll-notice

ajparent1/KB1GMX
 

Shorter BNC is the same.  How reliable they are for its connection to
the board is unknown as all the systems used a variant that locked
to the chassis. for mechanical support.

I do not see the problem being lifetime in use.  More like user friendliness.
Small connectors are harder to handle both in use (that 5/16th nut on SMA)
and also making cables. 

For every socket connector wear out on gear I've had cables fail in use many
many times over and that applies to C, N, BNC, TNC, PL259, SMA, SMB. 
Some connectors however provide better support for the cable and generally
SMA [and SMB] do not.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting


Re: QCX mini: RF output BNC or SMA #poll-notice

Giuseppe Marullo
 

Maybe something like these are a little better/sturdier:

https://www.knjn.com/ShopFlashyWidyAccessories.html (don't know Jean source tough)


Definitely SMA are not the best if you need many connect/disconnect cycles. They are not even nice to handle compared to BNC, let's admit it, size ok but why suffer?

They change characteristics based on the torque applied (yes, both ways, more or less torque do both affect the measure), I have a MiniVNA Pro and it is nasty when performing calibration, you just need the exact range of torque else the graph will be funny. Not nice.

I ended up using a SMA saver(m/f) on each connector to limit the wear (SMAs are a PITA to substitute on the MiniVNA),sadly it won't do much on the torque issue.

Giuseppe Marullo
IW2JWW - JN45RQ

On 8/6/2020 4:38 PM, Shirley Dulcey KE1L wrote:
BNC connectors without the plastic housing exist. I have a mini oscilloscope, a DSO138, that has one.

Here are links to examples:
https://www.digikey.com/product-detail/en/molex/0731000105/WM5524-ND/1465146
https://www.digikey.com/product-detail/en/te-connectivity-amp-connectors/5414373-1/A32274-ND/811172

On Thu, Aug 6, 2020 at 10:26 AM Kees T <windy10605@... <mailto:windy10605@...>> wrote:

I would say prefer board mount BNC .....but find one which does
not have the plastic housing (I believe they have those). If you
are really an industrious builder with all 5 fingers on each hand,
cut the plastic off and solder the two locator pins to the bare
BNC barrel for mechanical rigidity. they are not connected to
anything anyway on the ones I have dissected. There is also the
"locate off board" option ....not preferred.

Having the two footprints on top of each other (BNC/SMA) would
allow the option.

73 Kees K5BCQ


Re: QCX mini: RF output BNC or SMA #poll-notice

George Korper
 

Agree with Allison. The extra length of the plastic gets snaggy when putting a radio in a bag. 
If you look at a QCX the long BNC is ridiculous. So I ask Allison if the shorter BNC is reliable. 

On Thu, Aug 6, 2020 at 11:42 AM ajparent1/KB1GMX <kb1gmx@...> wrote:
SMA for size. 
BNC for durability and less fiddly when up on a hill with cold hands.

Note some of the PCB edge mount BNC may provide a lower profile.

Allison
-------------------------------
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Re: 500 times for the SMA

George Korper
 

Well actually, I only object to the length of the current BNC.
I was trying to match the "MountainTopper" and a short BNC is used on that I think. 
So I would like to see Han's comment on
reducing the length. The size really needs to include that. 

On Thu, Aug 6, 2020 at 11:40 AM ajparent1/KB1GMX <kb1gmx@...> wrote:
Worn out dozens over the years.  I'd add 500 is optimistic.
Failure mode is center socket looses flex and fails.
Second most common the center pin of cable breaks loose
from the internal wire.

Best are the stainless steel steel types, the gold ones are eye candy
and generally fail faster though are easier to solder.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting


Re: QCX mini: RF output BNC or SMA #poll-notice

ajparent1/KB1GMX
 

SMA for size. 
BNC for durability and less fiddly when up on a hill with cold hands.

Note some of the PCB edge mount BNC may provide a lower profile.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting


Re: 500 times for the SMA

ajparent1/KB1GMX
 

Worn out dozens over the years.  I'd add 500 is optimistic.
Failure mode is center socket looses flex and fails.
Second most common the center pin of cable breaks loose
from the internal wire.

Best are the stainless steel steel types, the gold ones are eye candy
and generally fail faster though are easier to solder.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting


500 times for the SMA

George Korper
 

We should live so long! 


Re: QCX mini: RF output BNC or SMA #poll-notice

jjpurdum
 

Regardless of the connector used, I would likely not mount it on the PCB even if the board provides for it. Off-board mounting, to me, gives me more flexibility in the case I might use. My problem is that I tend to "snag" things, often breaking them off. I originally voted for the SMA for that reason, but when I started reading about the SMA problems that some have, I changed my vote. I can put the connector off board, too, and will factor that into my nexts case. For my next QCX case, I am 3D printing a case with an "recessed box" in it. The box will be open by removing a two-screw panel that covers the box. On the front will be the (alas, discontinued) mini paddle that QRPGuys used to sell:

Inline image
I plan to mold brass nuts into the case front and will use brass thumb screws to attach the dit paddles to the circuit inside. A molded center contact point is the ground. When I'm done operating, I'll detach the paddle and store it with the screws in the "recessed box". That way, no heavy set of paddles to drag along and I can't snap them off when packing it for travel. All this is easier for me if the connectors are "off board".

Jack, W8TEE

On Thursday, August 6, 2020, 10:59:09 AM EDT, Al Holt <grovekid2@...> wrote:


I admit I voted for SMA, mainly on the basis of my experience with those threaded plastic BNC connectors, UGH!
I'm more in favor of a bulkhead mounted connector with a jumper to the board. If the the mini design is going to hold up out in the field, it's better not to depend on a board mounted connector, BNC or SMA.

With SMA connectors able to work into the GHz range, it's no wonder a manufacturer would want to limit the number of reconnections to stay in spec.

--Al
WD4AH


Re: QCX+ 30 done! Low power.

Ronald Taylor
 

James, if you are getting that much power out, then everything else is probably good, so OK to play with the lowpass filter. 

Ron