Author Topic: Pomona BNC boxes  (Read 11850 times)

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Offline KenGalerTopic starter

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Pomona BNC boxes
« on: December 11, 2016, 06:27:24 pm »
Anybody know of an alternate to these Pomona boxes?  My butt hurts just thinking about $30 each.

If there are no other good choices, does anybody make proto pcbs for them?

Tx
Ken

Online Fraser

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Re: Pomona BNC boxes
« Reply #1 on: December 20, 2016, 07:24:38 pm »
I have used even bitter BNC project boxes that came from Radio Spares in the UK. Sadly I think they cost about the same as the Pomona offering though. These boxes have always been a tad pricey. For small projects I had to drill the BNC holes in Hammond/Eddystone diecast boxes and fit panel mount connectors. In terms of the time it takes, a commercial project would likely buy the Pomona 'ready to use' product.

Sorry I cannot help. I would be interested in alternatives also.

Fraser
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Offline SingedFingers

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Re: Pomona BNC boxes
« Reply #2 on: December 20, 2016, 07:53:24 pm »
I managed to pick up a couple of these, used (just attenuator networks in them) in a box of assorted junk on eBay. £5 for two in the end. Plus some old OC81D transistors that went back on ebay for a small fortune. Couldn't believe my luck.

However they're really "not all that". I'd be annoyed if I bought a new one come to think of it. You can do the same with a couple of bulkhead mount BNC connectors and a die cast aluminium box with a few holes drilled. Plus I usually need a switch or something as well which hurts if you have to blow a hole in a Pomona one.

I haven't used a prototype board in mine. Just wired rat's nest.
« Last Edit: December 20, 2016, 07:59:52 pm by SingedFingers »
 

Online Fraser

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Re: Pomona BNC boxes
« Reply #3 on: December 20, 2016, 08:15:30 pm »
I agree. The Pomona boxes are not that great.

The RS BNC project boxes used two large square flange connectors and a rectangular two piece shell  between them. This gave great access to what was being constructed within. Nice quality construction and very solid in use. I have used dozens of these during my career in RF. Modern kit often uses SMA connectors which was not available in that particular case range. There were N type and PL/SO239 versions. I see that RS no longer sells them. I have five or so in my project stock though.

Regarding NOS Germanium transistors...... I almost binned a bag of OC and AC series last week. I shall have to place them on eBay 😄

Fraser
« Last Edit: December 20, 2016, 09:35:32 pm by Fraser »
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Offline Gyro

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Re: Pomona BNC boxes
« Reply #4 on: December 20, 2016, 08:58:36 pm »
I think this is the one you mean Fraser. I used my only one recently avter having it for about 20 years. A shame to hear that they don't sell them any more (I hate using my last one of anything!).

Best Regards, Chris
 

Online Fraser

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Re: Pomona BNC boxes
« Reply #5 on: December 20, 2016, 09:05:03 pm »
@Gyro,

Yes that is one of the versions I have. There is also a slightly different version that I have which has 'L' shaped side panels that lock together and long threaded rods slide through them to secure everything together. I will did one out and photograph it later.

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Online Fraser

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Re: Pomona BNC boxes
« Reply #6 on: December 20, 2016, 09:18:32 pm »
OK, I found a few of the RS type boxes on the shelf in my lab. I have several more squirreled away somewhere !

Sadly I do not know who actually manufactured these boxes as they may still be in production somewhere.

The last time I bought one of these it was £15 +VAT so they were never cheap. That was about 10 years ago.

RS datasheet attached

Fraser
« Last Edit: December 20, 2016, 09:23:23 pm by Fraser »
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Online Fraser

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Re: Pomona BNC boxes
« Reply #7 on: December 20, 2016, 09:28:40 pm »
The original RS boxes were made by TYCO Electronics and have now been replaced with a cylindrical version found here

http://uk.rs-online.com/web/p/rf-coaxial-adapters/3950447/

Datasheet of the new version attached.

I prefer a flat face box for when buttons or sockets need to be fitted into the shell.

Fraser
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Offline Gyro

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Re: Pomona BNC boxes
« Reply #8 on: December 20, 2016, 09:49:53 pm »
Quote
Datasheet of the new version attached.

They could have given some indication of how much space there is inside.  :palm: Being RS own brand I don't know how you'd find out any more. Only available in 75R too.

Presumably that screw on the side allows the thin walled cylinder to slide off. The countersunk screws at the ends look quite meaty so it might be tight in there!

It's about time someone in China started running off those extrusions.
Best Regards, Chris
 

Offline SingedFingers

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Re: Pomona BNC boxes
« Reply #9 on: December 20, 2016, 10:03:55 pm »
Not sure I like cylindrical ones. It's much easier to screw up and not be able to get the cover on. The old RS ones look nice: will keep an eBay eye peeled for some.

Gyro: nice idea for a prescaler BTW assuming that is what it is. Need to build one of them myself when I get time as my counter is only good to 22MHz which sucks (disclaimer: homebrew thing mistakenly built on stripboard in the 1990s)

Fraser: some crazy person paid £13 each for some OC81Ds. Even had some American guy almost have a nervous breakdown because I wouldn't ship outside UK. Find the lowest price ones in the UK and undercut them with a buy it now by only £0.01. Easy money.
« Last Edit: December 20, 2016, 10:06:49 pm by SingedFingers »
 

Offline Gyro

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Re: Pomona BNC boxes
« Reply #10 on: December 20, 2016, 10:22:36 pm »
Quote
Gyro: nice idea for a prescaler BTW assuming that is what it is. Need to build one of them myself when I get time as my counter is only good to 22MHz which sucks (disclaimer: homebrew thing mistakenly built on stripboard in the 1990s)

Project link if it helps... https://www.eevblog.com/forum/projects/my-600mhz-prescaler-(from-the-scrap-box)/msg1074092/#msg1074092

Manhattan beats stripboard every time.  ;)
Best Regards, Chris
 

Offline SingedFingers

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Re: Pomona BNC boxes
« Reply #11 on: December 20, 2016, 11:22:43 pm »
Thanks for the link. Will read :)
 

Offline karoru

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Re: Pomona BNC boxes
« Reply #12 on: December 21, 2016, 05:35:15 pm »
They could have given some indication of how much space there is inside.  :palm: Being RS own brand I don't know how you'd find out any more. Only available in 75R too.

Really, there should be some award for the guy that made this technical drawing and didn't notice that there's something "kind of" important missing:)
 

Online Fraser

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Re: Pomona BNC boxes
« Reply #13 on: December 21, 2016, 05:50:25 pm »
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Offline KJDS

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Re: Pomona BNC boxes
« Reply #14 on: December 21, 2016, 09:29:57 pm »
I'll have to have a root through my old drawers to see what germanium parts I have.

For boxes, I've often just cut up some double sided board and soldered it together.

Offline cdev

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Re: Pomona BNC boxes
« Reply #15 on: December 22, 2016, 04:43:55 pm »
You likely can also use a short length of thin copper pipe for some project boxes. If the PCB can be cut to fit in it and the RF connector isn't too big.

For an inline trap or band pass filter, for example, if its small, that might make a lot of sense. It certainly would be a lot cheaper than those die cast aluminum boxes and also copper is a better conductor.
"What the large print giveth, the small print taketh away."
 

Online Fraser

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Re: Pomona BNC boxes
« Reply #16 on: December 22, 2016, 05:29:54 pm »
I just managed to buy 14 of these nice RS format rectangular in line boxes with nice black cases. Brand new and unused. They are a nice mix of good quality N type and BNC type connectors plus two lengths of case, 65mm and 75mm. The cost? £43  :)
These will keep me going for a while 🙂

Sadly that was all of the chaps stock or I would provide his details.

Fraser
« Last Edit: December 22, 2016, 05:42:25 pm by Fraser »
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Offline SingedFingers

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Re: Pomona BNC boxes
« Reply #17 on: December 22, 2016, 06:00:59 pm »
Good price!
 

Online Fraser

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Re: Pomona BNC boxes
« Reply #18 on: December 22, 2016, 06:07:16 pm »
I thought so, hence buying his entire stock  :)

Fraser
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Offline Gyro

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Re: Pomona BNC boxes
« Reply #19 on: December 22, 2016, 06:26:18 pm »
We need an emoticon for 'Green with envy'.  :)

The China extrusion boxes would be good if you could get the original large flange BNC connectors (presumably they are the same flange size as N type).
« Last Edit: December 22, 2016, 06:30:40 pm by Gyro »
Best Regards, Chris
 

Offline GreyWoolfe

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Re: Pomona BNC boxes
« Reply #20 on: December 23, 2016, 03:20:55 pm »
We need an emoticon for 'Green with envy'.  :)
Quote

Here ya go.
"Heaven has been described as the place that once you get there all the dogs you ever loved run up to greet you."
 
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Offline KenGalerTopic starter

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Re: Pomona BNC boxes
« Reply #21 on: December 23, 2016, 04:53:34 pm »
I've been looking at those boxes from ebay also.  This one for instance.

http://tinyurl.com/hqmhmm9

I'm considering using these but with PCB end plates.  It wouldn't be difficult to design a family of PCBs in a small panel that would consist of:

- Two end plates for each of BNC, SMA, and N connectors.  These connectors could be the type that edge connects to the internal PCB.  This is a good example:

http://tinyurl.com/glq2kms
http://tinyurl.com/z5nweoj
http://tinyurl.com/hrwsjdv

- And internal boards with a 50 or 75 ohm stripline connecting the connectors.  The line can be cut to add series parts. 

This kit of break-off PCBs along with the $2 enclosure would be useful and a LOT cheaper than the Pomona boxes.

It's hard to describe.  Do you know what I mean?

Ken




Offline SingedFingers

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Re: Pomona BNC boxes
« Reply #22 on: December 23, 2016, 05:06:25 pm »
Good idea with PCB based ends. Cheap and easy then!
 

Offline cncjerry

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Re: Pomona BNC boxes
« Reply #23 on: December 26, 2016, 05:54:28 pm »
Those cylindrical boxes changed my builds for sure.  Having tons of pipe and a CNC metal lathe, I can know them out quickly.  The only issue is mounting the PCB, but if you make it a snug diametrical fit, the likelihood of the parts grounding is mitigated.  I've been using the little bud boxes but having to cut a D in the end (and sides for reflection bridges) was a pain and I never had the right size.  Now looking at the cylindrical boxes, I can use even metal pipe for more shielding and I picked up a ton of end cap sized cutoffs for free a while back.  Also, being cylindrical, they give a better look to in-line filters, etc.
 

Offline cdev

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Re: Pomona BNC boxes
« Reply #24 on: December 26, 2016, 07:56:01 pm »
For using small boxes.. this kind of SMA connector is useful in grounding to both sides of both ends of the PCB and the box effectively, and not just one or the other.

Edit:  You can buy these with a nut and lock washer, thats what I meant, (the pictured one doesn't have them). These are useful with the small die-cast Pomona boxes (the ones that don't come with coax connectors pre- attached) too.
« Last Edit: December 26, 2016, 08:00:36 pm by cdev »
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