Re: [Elecraft] O.T. Tuning a Counterpoise

2016-07-16 Thread Drew AF2Z 
Tks, Ron- I'll keep that in mind. My counterpoises lie on a flat roof 
adjacent the shack. I've never tried to tune them other than initially 
cutting them to theoretical best length; I suppose they could be better...


73,
Drew
AF2Z



On 07/16/16 13:39, Ron D'Eau Claire 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

  






   




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Re: [Elecraft] O.T. Tuning a Counterpoise

2016-07-16 Thread Phil Wheeler 
Thanks, Ron. You just reminded me that I have an 
MFJ-934 (ATU with artificial ground) stashed 
somewhere.


No real need for it just now, but who knows?  Now 
I just need to find it!


73, Phil W7OX

On 7/16/16 10:39 AM, Ron D'Eau Claire 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


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Re: [Elecraft] O.T. Tuning a Counterpoise

2016-07-16 Thread 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  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-boun...@mailman.qth.net] On Behalf Of Drew
> AF2Z
> Sent: Saturday, July 16, 2016 9:30 AM
> To: elecraft@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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