On Mon, 20 Jan 2014 16:13:00 -0500, Phil Hobbs
wrote:
On 01/20/2014 12:49 PM, Jeff Liebermann wrote:
On Mon, 20 Jan 2014 11:10:46 -0500, Phil Hobbs
wrote:
On 01/20/2014 08:46 AM, dave wrote:
Use Snap-N-Seal type F-connectors. They are moisture proof and
positively crimp correctly.
I don't have TV at home, and there's no way I'd use F connectors for
anything but entertainment.
Cheers
Phil Hobbs
Ok, I'll bite. What's wrong with F-connectors? There are zillions
installed on indoor and outdoor CATV installations with no failures or
issues. Certainly there are connectors with better specifications,
but for the intended purpose and cost ($0.30/ea), F-connectors are
more than adequate. The only real problem I've found is the wide
variety of cables claiming to be RG-6/u. Making a connector that will
fit all these RG-6/u mutations is tricky, but T&B has done a decent
job with their "red" SNS1P6U Snap-N-Seal connectors:
http://www.ebay.com/itm/221344116756
So, what's wrong with F-connectors and what would you recommend the
CATV industry use instead?
If the CATV industry likes them, well, I'm happy they're happy.
The CATV industry is never happy. If it were happy, innovation would
cease and the status quo would become permanent.
Instrument use is quite a different regime. F connectors use the centre
conductor of the coax as the contact, and are very susceptible to damage
with repeated mating cycles. The ones I've seen are also fairly far
from constant-impedance.
I believe that I mumbled something about "for the intended purpose". I
don't think anyone uses F-connectors for precision test equipment.
They're not really good enough. Looking at the pile, most of my CATV
specific test equipment uses BNC connectors. However, that's not
because the F-connector is in some way electrically inferior. It's
because the F-connector receptacles were not designed to survive
repeated insertion/removal cycles. The few that have built in
F-connectors allow for easy replacement, such as my Wavetek SAM-1000
which uses a panel mounted F barrel adapter.
The F-connector is certainly not constant impedance. On a TDR, the
bump is rather obvious. Yet, some cable and connector combinations
are rated and tested to 4.5GHz:
http://www.tselectronic.com/shop/product/1694A-Belden-4.5GHz-RG6-U-Precision-Video-Cable-for-Analog-and-Digital-Applications/1026
The recommended connectors are T&B SNS1P6 or FSNS6U compression
F-connectors.
I partly agree with you about center conductor problems. I assume
that you're referring to the copper plated steel center conductor,
found in most cheap RG-6/u cables, which is not intended for repeated
insertion/extraction cycles. Still, the rating is 500
insertion/extraction cycles minimum. The copper will eventually
scrape off. However, solid copper center conductor RG-6/u (such as
Belden 1694A) works quite nicely, without any damage. I couldn't find
a spec for insertion/extraction cycles for 1694A.
BNCs and SMAs for me.
Crimp or compression plugs, in quantities of 100 on eBay:
F-connector $0.30/ea
SMA male $0.70/ea
BNC male $1.00/ea
For test equipment, the price difference is not enough to justify
using the cheapest. For CATV, which consumes connectors by the
millions, every penny counts.
Thanks.
Cheers
Phil Hobbs
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558