low MHz connector design consultant

I was gonna say ... it all looks very professional, and then this DB-9 :-)

You got one of these things to check them out with?

I wonder how long the sales guys would lend one for... might be fun.

If you tell him it's for a 20MHz connector design, hopefully he'll think you misspoke and meant 20GHz... :-)

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Well, at least he's using the same hardware everywhere. I hate it when one side of something is screwed in using a straight blade, and the other side a Phillips!!

You should have seen some of the stuff I built as a kid. When I ran out of screws I occasionally used a chunk from a nail, stuck it through and flattened it using a punch. But only if I was fairly sure that I never needed to swap things because that would have required my dad's electric drill.

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Hello Mook,

When you have already a company that knows mechanical design and reliability issues, you only need the EM-field guy. When you can keep the mechanical guys and the EM-field guy in one room, this should converge to a solution fast.

One familiar with the concept of characteristic impedance, complex propagation constant (contains both complex epsilon and permeability) and know how to measure the material constants can do the job.

What about: required Return Loss, characteristic impedance, Insertion loss, propagation delay, size, cross section, (coaxial, square, symmetrical, etc), peak and average power, etc?

Kind regards,

Wim PA3DJS

You mean DE-9?

If I actually wanted to be technically correct, yep, that's what I would mean. :-)

On a sunny day (Fri, 30 Apr 2010 13:09:44 -0700) it happened "Joel Koltner" wrote in :

Yes, some are, that one has been replaced by a USB-to-serial 9 Euro adaptor. Need to stock up on both shells and adaptors...

On a sunny day (Fri, 30 Apr 2010 12:58:48 -0700) it happened John Larkin wrote in :

I have never used those, I use SMA, BNC. That is a very nice board, but I do not like those IC sockets, I prefer the turned ones. I have had plenty of bad contacts with that sort of IC sockets. Oxides I suppose, my old Epson R460 inkjet as example.

The main problem with the "UHF" PL-259 connector is that moisture will enter quite easily into the cable. With standard BNC/TNC/N connectors, this is not so much an issue.

With UHF connectors, the reflection coefficient is reasonable in the whole VHF range and even partially in the lower end of the UHF range.

No, I'm using an old 11802/SD24 TDR rig. But we do have a 40 GHz sampling head for it, 1 THz equivalent-time sample rate, so I'm still theoretically ahead of the $200K Agilent monster. And my scope doesn't run Windows!

Hey, the rental rate on the Agilent, with a couple of probes, would run about $25K a month. I can buy a nice 11801 and an SD24 for a tenth of that, and get TDR for free.

John

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Then again, many coaxes used with PL-259's aren't rated for outdoor use in the first place!

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I have a question for you:

Do you believe that the characteristic impedance is dependent on the length of the coax? (For the ratio of transverse electric field to transverse magnetic field launched on a transmission line of infinite length.)

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Actually I used RG-8 and RG-58 outdoors extensively, all with PL-259 connectors. But I applied the regular precautions like trying to seal stuff and preferably not running a cable in a way that rain water would creep towards the connector. I never had any coax go bad. Ok, one, but that was my own fault for not watching the SWR meter and running full bore into an antenna that had just burned out ... *PHOOMP*

Well, it does date back to W.W.II which is the 'Model T' days for connectors. It was a simple design that could be assembled with few tools, and repaired quickly in the field by soldiers with little training. Those RG- coax numbers were military, as well. RG = "Radio Guide".

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Trust me on this: Many RG-type jackets are indeed water permeable. I know this as the former Vice President of Engineering for Pinnacle Towers (Now Crown Castle). We had over 10,000 tower sites and rooftops in inventory at one point (pre Ch-11), mostly in the US, but some in Canada and the UK as well. I'm pretty certain I've seen everything imaginable when it comes to coaxes and antennas.

And the "fun" doesn't stop there: I've even seen the occasional dual Motorola Mitrek mobiles placed back to back to make a UHF repeater. For that matter, I once ran across a Motorola T1414 used as a crossband repeater with a GE Master Exec II 35-watt mobile. I've seen 9" continuous coax run 3 Class-C FM's (New Orleans). Pressurized with Freon, and then later, sodium hexaflouride (when Freon became unobtanium) I helped engineer the first ever 3-FM and 1 Full Power Analog TV (later DTV) on a single coax. (Fountain, FL) I was involved with the original HDTV tests in Charlotte (Ch-6, WCNC-36) and Washington DC (Ch-4, WRC) Then there's the 8 Class-C FM's (each 100kW, H&V) on a dual stack Harris panel antenna (St. Louis). Note: That later blew up (badly!) when they tried to add C-3 station #9. (I had since moved on.) More terrestrial microwave & uplink/downlink than I can remember. (Typically with quad-shield RG-6 - also not waterproof jacket)

...and more leaky RG-type cables, and even Andrew SuperFlex (both RF and water intrusion) than you can imagine. I've seen a few instances where the fire department had to be called to put out the transmitter, and cellular monopoles that collapsed (or bent badly), or caught on fire during tower re-strengthening attempts (i.e., welding structural sleeve or plate reinforcements.) Generally speaking, it is never a good day when the Fire Dept arrives.

I think the worst installation I EVER came across - the Grandaddy of them all - was an AM station using (and I am NOT KIDDING!), sawed-off metal garden shovel parts used as their main AC power / genset disconnect!

And believe it or not, this baby was a close tie for the entire town of Bayou Sale, LA. (Don't ever go there!!!)

You are free to form your own opinions of course about the survivability (including UV protection) of RG-type cables. From direct experience over the course of many years, I probably can't be easily swayed. Even if the datasheets say otherwise.

-mpm

"infinite length" "independent of length"

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Oops - obviously meant so say "Sulpher Hexafloride" Probably got solar power on my mind... :)