Date: Mon, 25 Apr 2011 18:00:07 -0400
From: "Roger (sub1)" <sub1@rogerhalstead.com>
Subject: Re: [Amps] DIN vs N
>> What's the advantage / disadvantages of the DIN ?
> At HF, zero. An N and RG-213 will handle many times the legal limit. The DIN
> is popular with the 20-40KW and up CB crowd and the hams running that level.
Maybe if you don't try to cover all of 75 or 160, but I've blown out N
connectors (Amphenols no less) running no more than the legal limit on
75 a number of times. I use a tuner so I can cover all of both bands and
have not had good luck with N connectors on either of those two bands.
On 40 I not only can use N connectors, but RG8X, and CNT240 at the legal
limit.
73
Roger (K8RI)
## here's how I got around the high swr problem on 75m. Years ago, I bought
a new F-12, EF-180B 80m rotary dipole.
It's 68' long, 4.8 sq foot, and has -.2db gain. [42 lbs] The 2:1 points are
only 31 khz apart. It used alumo-weld wires for the combo linear loading+
truss support. The stock set-up used relays and small coils..[ at the
feedpoint] to add 8 x 62 khz segments.
## after mech beefing it up in a few places, I also dumped the LL
altogether, and replaced the LL with a single dacron rope truss. I added
17.5' long
capacity hats..[ "T-bars"] part way out on each ele half....where the former
LL wires terminated. The balance of the loading is done via a
motor driven compressible coil setup at the feed-point. Mike Kelly, at seco
systems in W6 land, built me a custom modified version of his infamous 80-D
drive. This features a pair of compressible, plastic coated, 1/4" copper
tubing coils, both driven by a 12 vdc, reversible motor. The motor rotates a
threaded
delrin rod that goes down the inside of the coils. A simple 1/4-3/8" 5-turn
hairpin coil+ choke balun, across the feedpoint steps the Z up to 50 ohms.
The assy also outputs a digital pulse signal, to drive the mating Ameritron
SDC-102 screwdriver control box in the shack. The SDC-102 box contains a
4 x digit, digital turns counter + 10 x pre-sets. SWR is dead flat from 3200
khz - 4100 khz. At 3500 khz, there is an air gap between turns, which of
course
increases, as uh goes down, and freq goes up. The SDC-102 control box also has
over-current motor protection circuit built into it, and also a... 'park mode'.
In 'park mode', it fully compress's both coils and re-sets the digital turns
counter to 'zero'. Paralleled, pvc coated 'flex weave' wire and 1/4-20
hardware is
used to terminate the connections to both ends of both coils. OK, now it
can't be blown up with YC-156++ power levels. The parallel flex weaves act
like litz wire,
and doubles the RF current rating to the ends of the coils.
## The point here is, even with a simple dpst relay + 2 x small 12 ga coils,
in a small box, you can flatten the swr BW on any simple, wire dipole. There is
no need to be operating
with sky high swr on the low bands, including verticals. Also, just a spst
relay and one coil, inserted either leg of a dipole, will work the same. Yeah,
I know, Carl can stuff 2.5 kw
into anything on any band with a 5:1 swr. I haven't had much success going
that route.
later.... Jim VE7RF
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