[time-nuts] Don't use cheap cables -- a cautionary tale (Bob Camp)

David Kirkby david.kirkby at onetel.net
Tue Mar 5 13:16:54 EST 2013

On 5 March 2013 17:08, Gregory Muir <engineering at mt.net> wrote:
> When I compare the typical easily-obtained "Jameco"
> or "Marlin P Jones" type of connector to a better made product such as a
> true MIL item on a network analyzer, one can see a noticeable difference
> between the impedance and VSWR characteristics. It has been long known that
> the simple nickel-plate connector can cause problems over time in an
> installation from changing contact resistance and such.  The manufacturer
> "RF Industries" still uses silver & gold plating on their types of RF
> connectors as compared to the cheaper nickel-plated types and I have found
> these to be very reliable with a cost slightly higher than the cheaper
> nickel plated types.

I've recently been playing with some N adapters from various
manufacturers. I was particularly keen to find a decent male to male
adapter to include with a low-cost N calibration and verification kit
I am sellling.


If you read the specs on that, I state if the male to male adapter is
used, it limits performance. I've tried various makes, from the cheap
to fairly expensive (Huber and Suhner), although I am not considering
metrology grade devices, given the price I am selling the kit for.

I don't have all the data in front of me, but certain things stick in my mind.

1) The Huber and Suhner female-female N barrel was the most expensive
of any I tried. The qualtiy of the threads was excellent. But when I
stuck it on the VNA, the performance was really poor. I was intending
to phone H+S to ask what was wrong, but before doing so I looked at
the specification sheet. The spec was indeed poor, and the one I had
met it.

2) Someone recently sent me a couple of RF Industries male to male N
barrel adapters. RF performance was higher than I had seen on any
connector of its type with the exception of metrology grade devices.
However, it felt as though there was sand between the threads when
tightening these up.

3) I found some pretty decent female-female Ns that were really cheap
(< $5). RF performance was good, mechanically well made. They did not
have the best RF performance of those I found, but they were cheap.

For a male-male adapter in that cal kit, I have settled on the Radiall
component for now, but I'd like to find a better one. The RF
Industries unit would do, as long as I supply a lubricant to make
screwing the things on better.

So to me, there does not appear to much correlation between cost and
performance. I've seen poor expensive items and fairly decent very
cheap items.


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