[Elecraft] loss of RX sensitivity

[riese-k3djc at juno.com]

https://www.eham.net/ehamforum/smf/index.php?topic=34680.0;wap2

Bob K3DJC



On Tue, 18 Sep 2018 16:53:01 -0400 (EDT) donovanf at starpower.net writes:
> Hi Wes, 
> 
> 
> Thanks for forwarding the information about DG5MK's new FA-VA5 
> VNA. What is its current selling price? 
> 
> 
> If you use many BNC connectors, you'll notice a distinct difference 
> in 
> connector quality especially above 100 MHz. Avoid using BNC male 
> connectors with weak tension when you turn the bayonette 
> to engage the connector. If the bayonette turns too easily it 
> doesn't 
> maintain sufficient engagement force to keep the RF connections 
> in proper alignment. 
> 
> 
> 73 
> Frank 
> W3LPL 
> 
> 
> 
> 
> ----- Original Message -----
> 
> From: "Wes Stewart" <wes_n7ws at triconet.org> 
> To: elecraft at mailman.qth.net 
> Sent: Tuesday, September 18, 2018 5:51:45 PM 
> Subject: Re: [Elecraft] loss of RX sensitivity 
> 
> It's difficult to argue with Frank's experience and expertise. That 
> said, fools 
> rush in... 
> 
> I own some network analyzers, 1) an N2PK which I built with type N 
> connectors, 
> 2) a DG8SAQ VNWA-3, supplied with SMA connectors and 3) a RigExpert 
> AA-55 Zoom 
> with a SO239. Professionally, I've used analyzers with type N, 3.5mm 
> (beadless 
> SMA) and K connectors. With the exception of the AA-55, which only 
> goes to 55 
> MHz, all of these can be calibrated with "precision" calibration 
> kits that can 
> cost thousands of dollars. So far, Frank is right, not a BNC in the 
> bunch. 
> 
> But that has changed with the introduction of the DG5MK's FA-VA5, 
> one-port 
> vector analyzer. I am on the reserve list to buy one of these. The 
> thing to 
> note is that it is supplied with a BNC connector. There has been a 
> lot of 
> anguish, heartburn, etc about this on the VNWA Yahoo group but the 
> consensus is 
> that it will be fine and BNC calibration kit has been developed and 
> tested 
> without issue. https://www.youtube.com/watch?v=X8Z7veGV57o 
> 
> There are tens of thousands of BNCs on oscilloscopes and other 
> instruments and 
> I've seldom had an issue with them in 30+ years of lab work. For 
> quick 
> disconnect I also use short jumper cables with BNCs to break the 
> connections 
> between the hardline running to the tower and the cable entrance to 
> the shack 
> during lightning season. Admittedly, I'm only running 500 W. When I 
> can leave 
> them more permanently connected I revert to type N. 
> 
> Wes N7WS 
> 
> On 9/17/2018 5:04 PM, donovanf at starpower.net wrote: 
> > If you have a vector network analyzer you'll discover that BNC 
> > connectors aren't all that great at VHF and above, l oss and 
> > impedance vary with connector axial alignment because the bayonnet 
> 
> > shell doesn't support aligh the connector body very well. Strain 
> relief 
> > is extremely important with BNC connectors. TNC connectors are 
> > far superior but not widely used. 
> > 
> > 
> > While professionally installed N connectors have superb RF 
> > characteristics, all too often they're improperly installed -- 
> even by 
> > professionals -- leading to damaged connectors if the male pin is 
> 
> > misaligned, or unreliable contact if the pin or socket depth is 
> just a 
> > few millimeters less than the manufacturers specification. I use 
> > only captive pin male N connectors, avoiding the most severe 
> > problems. I never use female N connectors on cables, the N sockets 
> 
> > are much too fragile. 
> > 
> > 
> > Its hard to beat high quality silver plated UHF connectors at HF 
> and 
> > 6 meters. But its important to use a tool to tighten them. That's 
> a 
> > small price to pay for a very reliable connector. 
> > 
> > 
> > 73 
> > Frank 
> > W3LPL 
> > 
> 
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