[TowerTalk] Ameritron Remote Controlled Switches

Ian White, G3SEK G3SEK@ifwtech.demon.co.uk
Tue, 10 Nov 1998 20:51:57 +0000


Steve Gehring, KL7DC wrote:
>
>Hi Tom and Ian,
>
>Thank you for the information on the N vs. UHF series.  Ian and you
>diminished my respect for the N connector quite a bit.  These points are
>well taken.  I realize the center pins and their connections are fragile,
>but my expertise at properly building the clamped and crimped N is far
>better than that of the UHF series.  I also diligently check N plugs and
>sockets for out of place pins or bent tines, replacing them when suspect.
>My PL-259 building has progressed over the last 15 years, but I'm never
>quite satisfied with the results, even after using silver/Teflon connectors
>and pre-soldering the braid before screwing on the PL-259.  
>
>Now, let’s go to legal limit levels, and below.  This is where I reside.
>I've run 1 to 2 KW (intermittent SSB and data) into N's without incident at
>HF freqs in the federal and industrial arenas for over 15 years.  So, with
>my diligence in connector assembly and inspection, what are the chances of
>running into problems if I continue to use N's at legal limit and below?
>Have I been taking chances at HF?  

Given your expertise and diligence with assembling N connectors, you
probably haven't been taking many chances, especially at HF.
 
>What are the safe power levels for these
>N's at VHF and UHF?  
>
Perfect N connectors will handle 1.5kW ICAS at 432MHz (Reference: K1FO
in the ARRL UHF/Microwave projects book. Sorry I can't give you an exact
quotation, someone else has the book at the moment.) I can confirm this
at 900-1000W ICAS. The kind of "ICAS" we mean is EME contest service,
slow Morse code for 2.5min on, 2.5min off, for 6-10 hours.

However, with IMperfect N connectors it's anybody's guess! That's why I
only use brand-new, top-quality N connectors for QRO on 432MHz. There
aren't many connectors involved, so the peace of mind is well worth the
money. 

>Besides the UHF connector, is there another alternative to the N that is
>about the same size, but better at power handling, ease of installation,
>and ruggedness?  For example, use of the C or HN series?
>
C and HN are good, but sometimes hard to find. C connectors are like a
giant BNC so are quick to connect and have good power handling; but like
BNC they use a rubber gasket as a spring, which becomes slack with age
and allows the whole connector to spin. HN are like N but bigger -
though still not as big a center pin as a PL259. 

For UHF QRO I'm gradually trying to change to 7/16 DIN, which are
seriously large connectors good for several kW at UHF. They originated
in Germany but are being increasingly used in cellular base stations
world-wide, because they give reliably better connections with lower
inter-channel IMD than N. They're gradually emerging onto the surplus
market over here, but would be major overkill at HF!


>Here's perplexing question.  Why is the N rated for 1500V and the BNC rated
>for 500V, with their dielectrics of air/TFE and TFE respectively (excluding
>mating junctions)?  Could it be center pin size again?  Could the designers
>have limited the current capacity through the voltage rating, referenced to
>50 ohms with the BNC?  

Dunno, beats me Guv...

>Wanting to stay away from clunky, labor intensive UHF connectors...
>
With my background, I just can't bring myself to call them "UHF" at all.


73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)
                           http://www.ifwtech.demon.co.uk/g3sek

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