[Elecraft] O.T. Tuning a Counterpoise

[Vic Rosenthal]

I am thinking that if you make the wire more than 1/4 wavelength at the lowest frequency, all you would need to tune it would be a variable capacitor.

Vic 4X6GP

> On 16 Jul 2016, at 20:39, Ron D'Eau Claire <ron at cobi.biz> wrote:
> 
> One approach to reduce "RF in the shack" using an end-fed wire is to
> resonate the "counterpoise" for the band you are using. MFJ made just such a
> "tuner" (model 931 IIRC) but any tunable L-network will work. The idea is to
> adjust the "tuner" for maximum current flowing into the counterpoise
> (meaning the counterpoise is offering the lowest possible impedance to the
> equipment it is connected to.) I have successfully used that in a 2nd story
> apartment feeding an end-fed wire running outside. I know one Ham who bought
> the MFJ box and found it worked FB. 
> 
> For a homebrew "counterpoise tuner" you'll need an RF ammeter but a good
> cheap one is an incandescent flashlight bulb in series  where the
> counterpoise connects to the rig chassis. Tune for the counterpoise for
> maximum brightness with the rig running at the lowest power that will light
> the bulb, then short-circuit the bulb for higher power. Of course, the
> adjustments will interact with the tuner settings for the end-fed wire. But
> the "tuning" of the counterpoise is usually broad enough (low-Q) that noting
> the settings for each band you can return to them without doing the whole
> retuning thing again. (The MFJ box my buddy bought has an ammeter built in.)
> 
> 
> My "counterpoise" was a thin white wire run around the baseboard of the
> shack and down the hall - about 30 feet total. White wire + apartment white
> wall = invisible counterpoise. Worked FB 40 through 10 meters.  
> 
> While that will reduce the RF voltage on the rig itself, you will be sitting
> in a high-level RF field from the end fed wire, which limits your maximum
> power to meet radiation exposure limits, depending upon how far from you the
> antenna is located and the band you are using. 
> 
> 73, Ron AC7AC
> 
> 
> 
> 
> 
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Drew
> AF2Z
> Sent: Saturday, July 16, 2016 9:30 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] Power Supplies
> 
> I do have counterpoises: "decent" is another matter. If I had better
> shack/antenna choices I wouldn't be using an endfed wire to begin with. 
> So, the counterpoises, ferrites, ground loop isolators, equipment/cable
> arrangement are all part of the solution.
> 
> 73,
> Drew
> AF2Z
> 
> 
> 
>> On 07/16/16 12:04, Jim Brown wrote:
>> Drew,
>> 
>> Forget your field strength meter and 1) concentrate on providing a 
>> decent counterpoise for your antenna so that return current flows on 
>> that counterpoise rather than ground wiring inside your shack; and 2) 
>> on killing Pin One Problems in the equipment in your shack. You have 
>> high field strength in your shack because the antenna ends at your 
>> shack, and because it is working!
>> 
>> Study k9yc.com/RFI-Ham.pdf
>> 
>> 73, Jim K9YC
>> 
>>> On Sat,7/16/2016 8:26 AM, Drew AF2Z wrote:
>>> I have an endfed wire antenna for the low bands so there is RF in the 
>>> shack which needs to be managed. In such a case a field strength 
>>> meter is handy in figuring out how to arrange equipment, cables, 
>>> keyboards, etc and placing ferrite toroids and snap-ons for best 
>>> results. I use an old Simpson 37
> 
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