[Elecraft] loss of RX sensitivity

Tue Sep 18 16:53:01 EDT 2018

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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