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Hi Jim/Dave, I too have used these mini-circuits limiters, mostly the
ones in a higher range 20/30MHz to 3000 and 6000MHz on commercial SA's observing multiple 6MHz wide QAM carrier systems with 10 to >100 carriers. Haven't observed any excessive third order IM (IP3). Of course you have to be aware of the total power produced by the sum of the carrier powers. Referencing the data sheet (attached) for this particular limiter, the VSWR is pretty good with highs of 1.44 at 0.2MHz and 1.4 at 3K with mostly less than 1.1 between those extremities. The packaging is great, hardly larger that a normal SMA attenuator, and at $49/ea ordered direct from mini-circuits, it won't break the bank. Might be a good solution for those who would prefer not to do surgery on their NanoVNA/TinySA circuit boards. -----------------------------------------From: "Jim Lux" To: [email protected] Cc: Sent: Friday February 4 2022 3:50:39PM Subject: Re: [nanovna-users] Is there a known ch0 input protection mod? #problem #nanovna On 2/4/22 2:00 PM, W0LEV wrote: > Device from MiniCircuits: VLM-33W-2W-S+ > > URL: /> > > Rated from 0.200 through 3000 MHz in a 50-ohm system. It's marketed as a > spectrum analyzer protector. > > Dave - W?LEV That looks like the ticket. One thing to check - if you put two signals in (with the sum of signals being < limiting threshold) is there any IMD. For NanoVNA, which is single frequency at a time, this would be ok, but for a spectrum analyzer or receiver protector, maybe not. I suspect that this has one of the TVS parts we're talking about inside, but just in case it's just a diode or something, you want to check. (It is sold for protecting SAs, so it's probably not going to introduce IMD, but...) > On Fri, Feb 4, 2022 at 8:19 PM Roy J. Tellason, Sr. > wrote: > >> On Friday 04 February 2022 07:43:31 am Michael wrote: >>> Search on "How not to damage your NanoVNA when measuring SWR" in >>> Youtube. Good video basically TVS + Back to Back diodes, series resistor >>> and good description of functions. Also applies to TinySA. >>> >>> Michael (GW7BBY/GB2MOP) >> Good video, that. I wonder, though, how necessary that protection >> network is if you make it a point to ground the cable to the antenna to >> discharge static buildup, and you don't plan to leave the Nano connected? >> >> >> -- >> Member of the toughest, meanest, deadliest, most unrelenting -- and >> ablest -- form of life in this section of space, a critter that can >> be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters" >> - >> Information is more dangerous than cannon to a society ruled by lies. >> --James >> M Dakin >> >> >> >> >> >> Links: ------ [1] /g/nanovna-users/files [2] /g/nanovna-users/leave/8706519/4866111/1865567994/xyzzy |
