[Elecraft] Antennas for K1 Field Use

[David Y.]

David and all,

The phasing system we used is described in most recent issues of the ARRL 
Antenna Handbook.  In the 20th edition of that book, it is on page 8-31, 
under the sub-heading "Directional Switching of Arrays".

Some pruning and trimming is necessary, but basically, two 1/4 wavelength 
verticals are spaced 1/2 wave apart.  We elevated our verticals about 5 or 6 
feet.  The phasing lines were made using RG-6 (75 ohm coax), and one 
vertical is fed with an approx. 3/4 wavelength section, and the other with 
an approx. 1/4 wavelength section.  The two sections of coax are joined 
together with a T-connector.  50 ohm coax is used to feed the system to the 
rig.

The configuration described above gives you "end-firing".  If you want to 
switch to fire broadside, an approx. 1/2 wave length of RG-6 is added to the 
already attached 1/4 wavelength section.  The use of RG-6 for the phasing 
line more or less matches the antenna array to 50 ohms at the "T".  The 
verticals themselves are something like 35 ohms at the base, so the 75 ohm 
coax doubles as sort of a tuning stub.  At least I think that's what it 
does.

We used aluminum elements for the verticals, but wire could be used I would 
think.  It's usually better to use larger diameter material if possible. 
I've seen all sorts of material used for verticals like this.  One method 
that worked pretty well was to use coax for the vertical element (like 
RG-8), and just use the shield as the actual element.  You can suspend the 
coax from tree limbs, or whatever.

Our radials were sloping downward, but still raised slightly off the ground. 
It probably would have been better if they were elevated even more, but info 
I have read in "white papers" like the ones written by K6KL tells me that 
even a little bit off the ground is good.

We manually switched the phasing from end fire to broadside, but you could 
set up a relay system to do that.

Hope this gives you some idea of how we did it.

Dave W7AQK

----- Original Message ----- 
From: <d.cutter at ntlworld.com>
To: <elecraft at mailman.qth.net>; "Mike Morrow" <kk5f at arrl.net>; "David Y." 
<w7aqk at cox.net>
Cc: <kd8fip at gmail.com>
Sent: Monday, July 13, 2009 2:38 AM
Subject: Re: [Elecraft] Antennas for K1 Field Use


> Dave
>
> I agree about verticals elevated off the ground with raised radials.
>
> Could you describe your phasing method, was it passive, ie a reflector?
>
> Did you use fishing poles to hold up your wires?
>
> David
> G3UNA
>
>
>>
>> Here in the desert, verticals are often the best choice.  Some ham 
>> friends
>> of mine and I go out frequently on camping trips, and unless we go to 
>> high
>> ground, trees are pretty much non-existent.  A couple of these guys have
>> fabricated vertical installations that are very good performers.  A 20 
>> meter
>> vertical we used was elevated about 6 feet, and 30 radials were staked 
>> out
>> around it.  The whole job only took about an hour to erect.  A 40 meter
>> vertical is in the works.  Performance on the 20 meter vertical was
>> excellent, so we then did two of them and phased them.  Of course, 
>> results
>> were even better.
>>
>> >
>> If circumstances allow you to put up a dipole, that's probably what you
>> should do.  But don't think a vertical system is not an effective option.
>> You certainly don't have to suffer the 30 db or so deficiency that Mike
>> suggests, or anything close to it.  With just a little extra effort you 
>> can
>> be within an S unit or so of a dipole, and you might even sound better to 
>> a
>> DX station.
>>
>> Dave W7AQK
>> .