Tektronix 11801C - Page 1
Forum section: electronics / testgear

author: EVlab
author_rank: Contributor
timestamp: November 01, 2014, 08:40:40 am
content: Hello!I recently acquired a used Tek 11801C and now have some trouble by finding the right interface connectors. Maybe someone can help out.The sampling heads of this scope have "precision SMA 3.5mm" inputs. And here starts my problem: I don't know what kind of cable and/or adapter I should buy.I don't need the RF - performance of the precision SMA connectors. For my application, standard SMA would be fine. As they are mechanically compatible with the precision ones, one could say: okay, just screw them in ... But I'm afraid to damage the sampling head inputs.My fist though was, to use some kind of adapter: precision SMA <-> SMABut I was not able to find one (eBay). Next, I thought to by a precision SMA cable (e.g. SUHNER Sucoflex 100), and then rip of one connector and replace that with a normal SMA to get some kind of adapter kabel for daily work ... but I'm unsure, if I'm able to mount a standard SMA onto an air-insulated cable ?!Can someone give me a hint?How can I build a "connector saver" cable for daily work?What kind of adapters / cables you are using?Best, Simon

author: Lukas
author_rank: Frequent Contributor
timestamp: November 02, 2014, 10:42:48 pm
content: These are 3.5mm inputs. They're the same as SMA, except that they use air instead of PTFE for insulation. For daily work, I recommend putting on a 3.5mm-3.5mm adapter on (Minicircuits 35F-35M50+ for example). 3.5mm and SMA mate just fine. Of course, you shouldn't connect the cheapest SMA cable to this one as well... Also consider watching this video:

author: EVlab
author_rank: Contributor
timestamp: November 05, 2014, 08:13:54 am
content: Finally, I found a „3.5mm precision to SMA“ adapter on eBay. Combined with a SMA torque wrench, I will be fine for connection my standard SMA cables without damaging the scope connector.Can someone tell, which are good and low cost cable with precision 3.5mm connectors? I’m not familiar with these, the only one I found, that is made by a known manufacturer, was the “SUHNER Sucoflex 100”. But it is also quiet pricy (e.g. 250EUR) when new.To my understanding, “precision” and “used on eBay” are two things that will not work: When do these cables show up on eBay? -> when they are worn out … but often description and pictures of the items are poor, so one cannot tell …

author: TerraHertz
author_rank: Super Contributor
timestamp: November 05, 2014, 10:54:14 am
content: Can't help with the connectors, but just in case you are not aware of a trap related to that +-3V yellow warning symbol, I'll post this:I have a HP 54121T scope, which have similar 3.5mm connectors and voltage range inputs. The manual cautions related to these go on for pages. In essence the +-3V is serious, and it's referring to static discharge as well as continuous signal levels.Even a few nanoseconds of higher voltage will destroy the GaAs input sampler.So you must:* Keep a shorting or 50R terminator cap on the input when not in use.* Observe rigorous anti-static procedures when using the scope, and anything connected to it.* In particular, any piece of coax you are about to connect to the input, you MUST short the center conductor to the shield BEFORE connecting it to the scope input. And of course your hands and the cable shield must be at scope ground, via wrist strap, etc. The center conductor of coax if left floating can carry a charge that will be fatal to the scope input.This goes for anything else you are about to connect to the cable too.With these highly static-prone input instruments it's a totally different experience to a standard scope. You can't just turn it on, connect it up and start poking at circuits. You really have to carefully plan exactly what you are going to do, and the static/over-voltage risks involved, before touching the thing.

author: Marco
author_rank: Super Contributor
timestamp: November 05, 2014, 12:34:02 pm
content: Looking around 2.92mm cables actually seem to be cheaper than 3.5mm.If 18GHz is enough stick to sma for 10x less money.

author: EVlab
author_rank: Contributor
timestamp: November 13, 2014, 09:24:19 am
content: Another question: Can someone help out with two knobs?There are two knobs missing on one sample plugin.The part number is 366-0673-00 (KNOB:O.096 ID X 0.24 OD X 0.299H)I would be pleased if someone could help out …