[TowerTalk] Fwd: Tower and antenna decisions

[Gene Fuller]

A simple "line flattener", and some hardline, pretty near moves a station 
located "tuner" to the antenna, giving probably as much or more radiated 
power and a lot more convenience. Exceptions of course for  VHF and higher.
Gene / W2LU

----- Original Message ----- 
From: "Roger (K8RI) on TT" <K8RI-on-TowerTalk at tm.net>
To: <towertalk at contesting.com>
Sent: Sunday, October 27, 2013 1:25 PM
Subject: Re: [TowerTalk] Fwd: Tower and antenna decisions


> On 10/27/2013 10:10 AM, Jim Lux wrote:
>> On 10/26/13 8:15 PM, Hans Hammarquist wrote:
>>> All these "modern", solid state, PA have the same problem, they are 
>>> "protected" and the "protection" rolls back the power as soon as they 
>>> detect reflected power. Little depending on make and design they roll 
>>> back more or less. That's why the manufacturer offer built in tuners. 
>>> The "old days" with a pi-filter on the output could be tuned to most 
>>> anything below SWR of 1:3 or even more, and they didn't have (needed 
>>> maybe) the "protection". As long as you didn't kill the final tubes by 
>>> overheating them, you were OK. Do we like to have the "old" tube final 
>>> back? Maybe.
>>>
>>
>> I would rather have "smart antennas" with the finals *at the antenna* and 
>> the matching done there.
>
> This gets back to what I want to do...sorta.
> Particularly on 160 you don't have a lot of room to make frequency 
> excursions and that is to put the tuner "at the antenna", but that comes 
> with a location that is hazardous to the tuner's health. Another is just 
> how good are the remote autotuners?  Will they take the SWR right down to 
> 1:1 which is important for SS amps, not because of power, but because of 
> deteriorating signal quality.
>
> With a remote tuner, I want to match the antenna impedance, not just move 
> the resonant point.  Yes, if I move the resonant point to cover the entire 
> band it does make life easier and I could take care of the rest in the 
> shack, but again I'd prefer to do this at the antenna so in most cases I 
> only need a small L network even for 160 if it's close to resonance.
>
> With the half sloper other than the difficult maintenance problem this 
> becomes rather easy although on 160 that makes for a lot of resonant 
> points.
>
> putting the matching network at the antenna for a center fed, half wave, 
> sloping dipole is not practical although a single band tuner at the tower 
> using open wire line might.  Ice storms are common here spring and fall, 
> although there are far fewer in the fall but the make open wire 
> problematic and to me, reliability/durability is important because I have 
> to impose on others to get things fixed.
>
>>
>> Sure, it's more complex than the historic Transmitter in 
>> Shack/Feedline/Fixed Antenna, but life moves on.
>>
>> For instance, I sketched out an interesting design for a form of Yagi 
>> with all driven elements, using an array of magnetic loops, rather than 
>> the traditional horizontal elements. The matching from low Z 
>> semiconductors to the low Z of the magnetic loop is actually kind of what 
>> you want.   And you're doing spatial combining, so with 5 elements, each 
>> driven with a 200W module, you don't have the losses in the power 
>> combiner you see in a "single output" SSPA.
>>
>>
>> Combine this with things like polar modulation, and you can get some very 
>> interesting designs. It's almost like having the entire rig at the top of 
>> the tower, and all you need is power and an ethernet link, which could be 
>> wireless.
>>
>> Sure, its nothing like ham radio in the past, but that's what ham radio 
>> is all about: try new things.
>
> I like the idea and to me it's far less different than a remote regular 
> station, controlled over the internet. You're just combining the rig with 
> the antenna. There might be issues with lightening, maintenance, and cost 
> though.  Could it be made to match the big mono band Yagi for performance?
>
> It's a radical design, but used much the same way as ham rigs have since 
> day one.
>
> 73
>
> Roger (K8RI)
>
>
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