SMB Adaptor (again)


Stephen
 

After searching the archives, I didn’t find the answer to my question. So here it is.
I found these on Fleebay. It’s supposedly an SMB to BNC female adaptor. However, they don’t look like they’re gonna fit the male SMB connectors on my DC505. What am I missing...?
Should I just change the connectors on the DC505, or is there another alternative?

https://www.ebay.fr/itm/193549663301


Stephen Hanselman
 

If they are SMB they should BUT, repeat BUT at $1.34 each I wouldn’t touch them. Adapters that work properly and don’t inject their own silliness cost money. Save the hassle and buy one from Mouser or Pasternack.

Regards,

Stephen Hanselman
Datagate Systems, LLC

On Mar 12, 2021, at 08:32, Stephen <stephen.nabet@gmail.com> wrote:

After searching the archives, I didn’t find the answer to my question. So here it is.
I found these on Fleebay. It’s supposedly an SMB to BNC female adaptor. However, they don’t look like they’re gonna fit the male SMB connectors on my DC505. What am I missing...?
Should I just change the connectors on the DC505, or is there another alternative?

https://www.ebay.fr/itm/193549663301





Jean-Paul
 

agree 100% the Chinese connectors are junk and can damage the instrument.

Get a real USA made, search "used" on ebay

Jon


Ed Breya
 

I think they would work just fine performance-wise, but going direct to BNC will be a bit awkward - try just holding a BNC cable end in front of the DC505 and imagine working it while in place. I'd recommend using a thin SMB to BNC cable instead, so it stays small and less obtrusive near the front panel.

Ed


 

I have some 1m cables with an SMB female plug on one side and a BNC male plug on the other. I find them more convenient in cramped places like in the DC505. I'm mainly using them on a 7D15 counter.
The greater length of converter plugs creates a greater risk of damaging the SMB socket on the DC505.
These are not critical HF applications and Chinese cables probably work just fine.

Raymond


Stephen
 

Thank you all for your always and again good pieces of advice.

Ed, you’re right... It is awkward.
Raymond, would you happen to know a good source for these in Europe?

Yes, these Chinese ones are probably pretty cheap as far as the quality, but I was not particularly interested in this actual item. All the other more expensive ones look the same. I was just wondering if they were the right ones because they don’t seem like they would fit. But it’s probably just an optical effect.


 

Stephen,

I just ordered several SMB-BNC cables from Amazon (I hope I got the polarity correct, I ordered SMB-K Female to BNC-J Male, and the SMB connector looked like it would work with my DC505). The were only $10 US, which I thought was pretty inexpensive for a speciality part (are these SMB connectors common? I've never seen them anywhere but a couple of Tek instruments).

-- Jeff Dutky


 

On Sat, Mar 13, 2021 at 11:36 PM, Stephen wrote:


Raymond, would you happen to know a good source for these in Europe?
Hi Stephen,
Unfortunately, I don't know a source for affordable cables of this type. Mine I bought together with some other partly NOS stuff. Brands are Amphenol and Radiall (the latter being even better quality).

Haven't seen them offered recently but will keep an eye open.

Raymond


Tom Lee
 

SMBs are relatively common. Anywhere you want quick disconnect and reasonable rf performance in a small form factor, the SMB stands out. Quick disconnect is not just for lazy folks, btw. If you have a board with dozens of cables, you can see how the need to unscrew each one soon loses its charm.

Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 3/13/2021 14:42, Jeff Dutky wrote:
Stephen,

I just ordered several SMB-BNC cables from Amazon (I hope I got the polarity correct, I ordered SMB-K Female to BNC-J Male, and the SMB connector looked like it would work with my DC505). The were only $10 US, which I thought was pretty inexpensive for a speciality part (are these SMB connectors common? I've never seen them anywhere but a couple of Tek instruments).

-- Jeff Dutky




 

Tom,

Clearly my complete unfamiliarity with RF equipment of any kind betrays me.

They're awfully cute little connectors. I'm a bit surprised that they weren't used more frequently on the various plug-in families: space is quite limited on those front panels.

My main exposure to RF connectors is the tiny, right angle coax connectors used on modern laptops for the WiFi antennas. I expect that they are not rated for a large number of connect/disconnect cycles.

-- Jeff Dutky


n4buq
 

The mini-BNC (MBNC) connectors are cuter.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Jeff Dutky" <jeff.dutky@gmail.com>
To: TekScopes@groups.io
Sent: Saturday, March 13, 2021 6:27:08 PM
Subject: Re: [TekScopes] SMB Adaptor (again)

Tom,

Clearly my complete unfamiliarity with RF equipment of any kind betrays me.

They're awfully cute little connectors. I'm a bit surprised that they weren't
used more frequently on the various plug-in families: space is quite limited
on those front panels.

My main exposure to RF connectors is the tiny, right angle coax connectors
used on modern laptops for the WiFi antennas. I expect that they are not
rated for a large number of connect/disconnect cycles.

-- Jeff Dutky






Tom Lee
 

They are pretty cute, but I've not seen 50 ohm versions. Do they exist? And if they exist, do they mate with their 75 ohm cousins? (That may be illegal in some states)

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 3/13/2021 17:24, n4buq wrote:
The mini-BNC (MBNC) connectors are cuter.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Jeff Dutky" <jeff.dutky@gmail.com>
To: TekScopes@groups.io
Sent: Saturday, March 13, 2021 6:27:08 PM
Subject: Re: [TekScopes] SMB Adaptor (again)

Tom,

Clearly my complete unfamiliarity with RF equipment of any kind betrays me.

They're awfully cute little connectors. I'm a bit surprised that they weren't
used more frequently on the various plug-in families: space is quite limited
on those front panels.

My main exposure to RF connectors is the tiny, right angle coax connectors
used on modern laptops for the WiFi antennas. I expect that they are not
rated for a large number of connect/disconnect cycles.

-- Jeff Dutky







n4buq
 

I've only seen them in the Collins R390/R390A and Collins aircraft radios. I don't know whether those are 50-ohm or 75-ohm.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: TekScopes@groups.io
Sent: Saturday, March 13, 2021 7:58:48 PM
Subject: Re: [TekScopes] SMB Adaptor (again)

They are pretty cute, but I've not seen 50 ohm versions. Do they exist?
And if they exist, do they mate with their 75 ohm cousins? (That may be
illegal in some states)

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 3/13/2021 17:24, n4buq wrote:
The mini-BNC (MBNC) connectors are cuter.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Jeff Dutky" <jeff.dutky@gmail.com>
To: TekScopes@groups.io
Sent: Saturday, March 13, 2021 6:27:08 PM
Subject: Re: [TekScopes] SMB Adaptor (again)

Tom,

Clearly my complete unfamiliarity with RF equipment of any kind betrays
me.

They're awfully cute little connectors. I'm a bit surprised that they
weren't
used more frequently on the various plug-in families: space is quite
limited
on those front panels.

My main exposure to RF connectors is the tiny, right angle coax connectors
used on modern laptops for the WiFi antennas. I expect that they are not
rated for a large number of connect/disconnect cycles.

-- Jeff Dutky













Joseph Strickland
 

My experience when I worked at Collins Radio in Richardson was that there were two types of BNC connectors. In the 50 ohm case there was a white nylon or Delrin plastic protection sleeve around the female center contact of the connector. The 50 ohm male pin that interfaces with the female contact is physically a little larger than the male pin in the 75 ohm mating BNC connectors. The 75 ohm BNC connectors with the female contacts have exposed contacts not surrounded by the white plastic seen in the 50 ohm connectors. That makes them more subject to damage from mating connectors pushed on to them at a slight angle. That is why you often see 50 ohm BNC connectors used on 75 ohm cables and their mating connectors on test equipment. In true 75 ohm connectors both the female and male contacts are exposed in the center of the connector and somewhat thinner than their 50 ohm family equivalents. When 50 ohm connectors are used in 75 ohm applications the main difference seen is that there is a slight reduction in return loss when compared to true 75 ohm connectors. Typical BNC connectors cause about 1/2 dB of signal loss whether 50 ohm or 75 ohm.

When it came to coaxial cables, the best quality ones specified in Collins/Rockwell telecommunication equipment used double shielded 1% 30dB or better return loss specified cables made by Times Cable Co. I don't know if it was a standard practice of Times Cable for their 75 ohm coaxial cable of the 1% return loss type or not, but they usually came with a violet stripe along the length of the coaxial cable. The high return loss (30dB or higher) had to be checked against 50 ohm or 75 ohm high accuracy loads in order to verify the true quality of the coaxial cable. Times Cables always were consistently best in that measure. 50 versus 75 ohm impedance connectors become more important the higher the signal frequencies are that are being handled by the equipment being tested or verified.

Collins often used variable trimmer capacitors on both baseband and RF circuits that required best impedance match to the highest expected frequency to be handled. They were adjusted with unit under test equipment having its normal cables within the equipment already connected while using a swept input signal covering the full range of signal frequencies to be handled by the equipment. The trimmer capacitors were adjusted for the best return loss over the full range of the signals being handled. Typically Selective Volt Meters of high accuracy by HP, Tektronix or Wandel & Goltermann were used for those checks and adjustment verification. Test equipment had to be verified against industry calibration standards on a regular schedule. Most of the analog equipment had to have good return loss at baseband frequencies from near DC to at least 30mHz. All the systems and unit test technicians I worked with insisted upon the very best performance that could be obtained with state of the art products.

Joe KC5LY


Stephen
 

Thanks Jeff.


snapdiode
 

On Sat, Mar 13, 2021 at 05:24 PM, n4buq wrote:

The mini-BNC (MBNC) connectors are cuter.

They are, but are they as cute as the BSM connectors on certain S heads?


 

The BSM connector for my 3S2 trigger output is cute, but I traded cuteness for "connectability"... I replaced it with an SMA since I couldn't find a BSM to BNC cable anywhere, Tek original or aftermarket.


 

The SMB-BNC cables I ordered from Amazon arrived and they do fit my DC505, but they are very tight, almost impossible to disconnect using just my fingers. Where/are the outputs on the DC505 infrequently used?

The specific cables that I bought (KNARCO) seem to be out of stock now, but I see another (even less expensive) listing from LIVISN. The odd company names (and the price) make me suspect that these are Chinese sellers, but I have no proof of that. The cables I ordered came somewhat inexplicably triple bagged: first a small bubble wrap bag, enclosed in a sealed anti-static bag, and finally in a blue and white ziplock bag.

-- Jeff Dutky


Stephen
 

The SMA are much larger then the SMB, aren’t they??


Stephen
 

Thanks Jeff,

I haven’t ordered anything yet. I’m waiting for my list of needed stuff to get a bit bigger and order everything at the same time. I’ll keep that in mind though. Thank you.