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


Hans Summers
 

On the proposed QCX-mini, do you prefer a BNC connector like on QCX, or an SMA connector? 

Thank you for voting.



Scott McDonald
 

Hans, any chance the connector location on the board could be etched to support both?  A bnc -sized hole should work for SMA, other than for weather sealing perhaps.

Keep up the good work :)

Thanks, Scott ka9p


-----Original Message-----
From: Hans Summers <hans.summers@...>
To: QRPLabs@groups.io
Sent: Thu, Aug 6, 2020 7:44 am
Subject: [QRPLabs] QCX mini: RF output BNC or SMA #poll-notice

A new poll has been created:
On the proposed QCX-mini, do you prefer a BNC connector like on QCX, or an SMA connector? 
1. BNC
2. SMA
Do not reply to this message to vote in the poll. You can vote in polls only through the group's website.


Russ@va3rr
 

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...


Hans Summers
 

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...




Dave
 

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...




Russ@va3rr
 

Mostly just torque issues - both over and under-torqueing. One gentleman broke the fingers that connect the SMA connector to the circuit board using too much torque.

Even when a torque wrench is used, one member of the group advised that SMA connectors are rated for a limited number of connection cycles...


Hans Summers
 

Then I say "VOTE BNC!"

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

On Thu, Aug 6, 2020 at 4:39 PM Dave <VE3GSO@...> 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...




Jim Mcilroy
 

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...




Ben
 

Searching online mating cycles seems to be between 100 and 500 times. To reach the max number of mating cycles, you would need to clean the SMA connector and use a torque wrench...

I still prefer BNC. I think SMA would be a bit fiddly in the field, or I would need to always have a BNC adapter connected. So my vote goes to BNC.


Graham, VE3GTC
 

SMA connectors have a limited life span measured in only 100's of mating cycles. Check the data sheets for Ampehnol, Pasternack, (etc) parts. The inexpensive SMA's from Asia quite likely are even less robust. I have seen some pretty poorly made SMA connectors which instead of fighting with just end up in the trash.

Also, to be used properly and to spec, SMA connectors need to be installed to a specified torque setting ( see the data sheets ). For general use this is not likely much of an issue until the connectors start to wear but on test and GHZ equipment it can be an issue.

SMA's being tiny are also subject to large forces when longish cables are attached ( think of Archimedes ) and moved around. Cheap SMA's and those not well secured are all the more likely to suffer in this scenario.  Mini and micro size USB connectors also suffer for this same reason.

TNC are an excellent choice but never really became as popular as other types - about BNC size but with the added connection security of being screwed on. 

Given the choice of SMA or BNC / TNC  or something else on portable equipment, I would choose BNC.

On equipment that has SMA connectors, I often use a SMA to BNC adapter / converter such as this:

image.png

I place a washer between the adapter and the equipment that allows the adapter to be screwed down securely without any space between the equipement and the adapter in order to provide security and strain relief ( think of Archimedes again ).

cheers, Graham ve3gtc


On Thu, Aug 6, 2020 at 1:28 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...




Per - LA9XKA
 

True, but Tyco Electronics also specifies only 50 cycles for their gold plated center pin BNC connectors. https://docs.rs-online.com/616e/0900766b81409ff0.pdf

73 de LA9XKA - Per


On Thu, Aug 6, 2020 at 03:39 PM, 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...




Kees T
 

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


Shirley Dulcey KE1L
 

BNC connectors without the plastic housing exist. I have a mini oscilloscope, a DSO138, that has one.

Here are links to examples:


On Thu, Aug 6, 2020 at 10:26 AM Kees T <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


Scott McDonald
 

I'm not pro or con on this but it is interesting to note that Elecraft uses SMA connectors on their 2/4 meter transverter for the KX3.

I'm well past 50 cycles with no trouble on mine but now sufficiently paranoid about it :)

Scott ka9p


-----Original Message-----
From: Russ@va3rr via groups.io <va3rr@...>
To: QRPLabs@groups.io
Sent: Thu, Aug 6, 2020 8:40 am
Subject: Re: [QRPLabs] QCX mini: RF output BNC or SMA

Mostly just torque issues - both over and under-torqueing.  One gentleman broke the fingers that connect the SMA connector to the circuit board using too much torque.

Even when a torque wrench is used, one member of the group advised that SMA connectors are rated for a limited number of connection cycles...



Al Holt
 

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


Dave VE3LHO
 

Supporting both SMA and BNC footprints makes a lot of sense to me.

Use right angle, PCB mount connectors. Not the edge mount SMA's like those used on the nano. I'd expect that having the connectors break off the PCB would be a bigger issue then having the connector wearout from use when we're talking about people using this in a portable environment. In both SMA and BNC you can get right angle connectors which have mounting nuts that allow fairly rigid mounting to a case.


On Thu, Aug 6, 2020 at 06:09 AM, Scott McDonald wrote:
Hans, any chance the connector location on the board could be etched to support both?  A bnc -sized hole should work for SMA, other than for weather sealing perhaps.
 
Keep up the good work :)
 
Thanks, Scott ka9p


-----Original Message-----
From: Hans Summers <hans.summers@...>
To: QRPLabs@groups.io
Sent: Thu, Aug 6, 2020 7:44 am
Subject: [QRPLabs] QCX mini: RF output BNC or SMA #poll-notice

A new poll has been created:
On the proposed QCX-mini, do you prefer a BNC connector like on QCX, or an SMA connector? 
1. BNC
2. SMA
Do not reply to this message to vote in the poll. You can vote in polls only through the group's website.


Phil/K3UT (ex W3HZZ)
 

What about RCA connectors?


Shirley Dulcey KE1L
 

Please, no. Those give me nightmares. Too many cases of them either not staying in or refusing to come out.


On Thu, Aug 6, 2020 at 11:11 AM Phil/K3UT (ex W3HZZ) <pgraitcer@...> wrote:
What about RCA connectors?


Bill Cromwell
 

Hi,

I have a nanoVNA with SMA fittings. The early deterioration most likely affects their performance in the microwaves. I use mine at HF and may use it some day a time or two on two meters but probably not. I take reasonable care to not wear or damage the connectors soldered into the unit and I don't expect a lot of trouble from them.

For my radios I like the BNC and UHF (PL-259) connectors. I have used RCA, SMC, C, and N connectors.

bark less - wag more

On 8/6/20 10:59 AM, Al Holt 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


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