[Elecraft] P3 Hash

[Fred Townsend]

BNCs are known as constant impedance connectors but what impedance? Usually
it's 50 ohms but there are 75 ohm out there particularly in the video world.
They do have different dimensions but you are not likely to detect the
difference with the naked eye. Jack you are absolutely correct that at least
one Chinese connector company markets both 50 and 75 ohm but with identical
dimensions. These connectors actually measure out at about 62 ohms, a
compromise dimension. The worst part is the oversized parts can damage the
mating connector. Correspondingly some connectors may use soft metal so once
they are spread they are forever sloppy. Caveat Emptor. Buy quality American
or UK connectors and save the headache.  
73
Fred, AE6QL

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jack Smith
Sent: Friday, August 17, 2012 11:03 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] P3 Hash

Some Chinese BNC male connectors don't properly mate with a dimensionally
correct BNC female.

Not sure where the dimensional problem is, but I've run into the problem
more than once.

Jack K8ZOA

On 8/17/2012 1:15 PM, Rowland R Johnson wrote:
> I had the same problem. Replacing the BNC coax cable (between the P3 
> and
> K3) with one I had lying around fixed it. Howard at Elecraft tech 
> support then sent a new cable that arrived 36 hours after I talked to 
> him. This new cable from Elecraft worked fine, for a while, but then 
> started having the same kinds of problems. I put my old cable that I 
> had lying around back on and it's worked for several months now.
>
> I haven't pursued getting a second replacement from Elecraft because 
> it hardly seems worthwhile. In addition, it's not 100% clear to me 
> that the problem is the cable. With the 2 Elecraft cables I've noticed 
> some difficulty in connecting the BNC plug to the BNC receptacle on 
> the back of the P3. Not so with my old cable. The supposition being 
> that the physical dimensions of BNC receptacle on the P3 aren't quite
right.
> Whereas the new cables have a problem fitting, my old cable may be 
> worn enough that it fits anyway.
>
>
> On 8/17/2012 9:00 AM, Gene Trasti wrote:
>>> P3 with svga
>>>
>>> I have a considerable amount of "hash" on my panadapter screen.  It
tracks the same spot on all bands.  All my equipment is very well grounded.
I have measured my shack for RFI-it is very clean.  I swapped out my
switching power supply for a highly filtered one.  I even purchased a pretty
expensive ac terminal strip with isolation transformers.  I have been
through the house and have virtually switched off and unplugged
everything-nothing seems to help.  This hash takes up a pretty healthy
portion of the bandwidth.  Any sugestions would be appreciated.  Is it
possible that this could be a problem with the P3 or K3 they are both
factory built-although I added the svga board using a wrist ground..
>>>
>>>
>>> Gene. W6jmp
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