[ARC5] ARC-5 antenna match

[Christopher Bowne]

Like I originally posted, it was origially presented in an early ER in Uniform column by Walt Hutchens KJ4KV in /around 1989 or early 1990s.  I can't easi;y get to my back issues fromthen at this point, if i could I would scan the schematic and post it here.  Perhaps someone else can dig it out of their back issues? 

Its really pretty simple

Start by envisioning a parallel L/C tuned circuit.

Both antenna shield and a lead to TX chassis run to "cold" end of coil, along with one side of the variable cap of the tuned circuit.  I used a 200pf wide spaced transmitting cap to avoid flash-over.  
Antenna coax center conductor tapped on coil about 6 turns above ground/cold end of coil.
ARC-5 transmitter connected to tap about 3 turns above cold end of coil
through a fixed 200 pf series cap.   I use a small transmitting type mica cap.
Other side of variable cap connects to top "hot" end of parallel circuit coil, nothing else connected there.

Operating instructions:

With transmitter keyed, resonate the L/C circuit for max output on a wattmeter connected between the matching network and the antenna.

Peak transmitter output indicated on the wattmeter by adjusting the transmitter's roller inductor for best power transfer through it and the 200pf fixed series cap.

Back off on the transmitter coupling coil, then advance it until you find a "sweet spot" or reach output saturation.  You will like go into saturation somewhere past 50% of full travel, vs never maxing out when feeding a nominla 50 ohm unbalanced load directly into the transmitter.

I am getting about 50 watts out of a totally stock dynamotor powered system.  (Actually it's ARC-5 transmitters lined up to a SCR-274N BC-456 screen modulator/dynamotor unit, with the final amplifier screen resistor changed to the SCR-274 transmitter value). The screen resistor difference is the only significant electrical difference between the two types of transmitters, most likely differ due to plate modulated ARC-5 and screen modulated SCR-274 sets.





________________________________
 From: D C _Mac_ Macdonald <k2gkk at hotmail.com>
To: W7EKB Ken Gordon <kgordon2006 at frontier.com>; ARC-5 Mail List <arc5 at mailman.qth.net> 
Sent: Monday, July 29, 2013 11:21 AM
Subject: Re: [ARC5] ARC-5 antenna match
 

A photo of the schematic with component values at a clickable URL link would be of great help to those of us who have trouble visuallizing things!


* * * * * * * * * * * 
* 73 - Mac, K2GKK/5 * 
* (Since 30 Nov 53) * 
* k2gkk at hotmail.com * 
* Oklahoma City, OK * 
* USAF & FAA (Ret.) * 
* * * * * * * * * * * 


> From: kgordon2006 at frontier.com
> To: neilb at ihug.co.nz
> Date: Mon, 29 Jul 2013 14:34:12 +0000
> CC: arc5 at mailman.qth.net
> Subject: Re: [ARC5] ARC-5 antenna match
> 
> On 29 Jul 2013 at 20:44, Neil wrote:
> 
> > Is this a high quality parallel tuned circuit, with the antenna coax
> > connected between ground (braid) and a tap on the coil, and the ARC-5
> > output connected between ground (chassis) and a lower tap? Sounds like
> > it could work well. 
> > 
> > 73 de Neil ZL1ANM
> 
> Yes...to both statements. 
> 
> Furthermore, as Chris pointed out, my "device" is exactly what he was talking about before I 
> "horned in". I had not read his post thoroughly before I posted mine.

                          
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