[ARC5] Is better to half at least half of the Tx coil when loading
Jim Falls
radio-tuber at att.net
Fri Apr 21 00:47:15 EDT 2017
I'll try this with my TCS-8 and report back. I usually crank it to zero, tune the outboard VC for max output.
Cheers!
Jim K6FWT
> On Apr 20, 2017, at 14:34, Tom Bridgers <Tarheel6 at msn.com> wrote:
>
> Is better to half at least half of the Tx coil when loading an antenna
>
> with a series capacitor. The optimum settings, though, must be
>
> found with trial and error...
>
> -t
>
>
>
>
> From: ARC5 <arc5-bounces at mailman.qth.net> on behalf of arc5-request at mailman.qth.net <arc5-request at mailman.qth.net>
> Sent: Thursday, April 20, 2017 10:12 AM
> To: arc5 at mailman.qth.net
> Subject: ARC5 Digest, Vol 159, Issue 36
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> Today's Topics:
>
> 1. Re: Rollerductor setting (AKLDGUY .)
> 2. Re: Rollerductor setting (Dennis Monticelli)
> 3. Re: Rollerductor setting (J Mcvey)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 20 Apr 2017 17:11:55 +1200
> From: "AKLDGUY ." <neilb0627 at gmail.com>
> To: Dennis Monticelli <dennis.monticelli at gmail.com>, ARC-5 List
> <arc5 at mailman.qth.net>
> Subject: Re: [ARC5] Rollerductor setting
> Message-ID:
> <CAETC+7Mg_0AkmcZH2XnrRVkZduLBQFVdM7Ehc7SOiS1iJ3JhCA at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hi Dennis
>
> OK, so the rollerductor and the 150pF series cap interact? Is that it?
>
> So I should set the rollerductor arbitrarily to more than half the
> inductance and adjust the cap to suit?
>
> I like your harmonic reduction comment. It makes sense.
>
> 73 de Neil ZL1ANM
>
>
> On Thu, Apr 20, 2017 at 4:10 PM, Dennis Monticelli <
> dennis.monticelli at gmail.com> wrote:
>
> > Neil,
> >
> > Whether 80M or 40M, I like to adjust for at least half the rollerductor.
> > Too little inductance will compromise harmonic attenuation.
> >
> > Dennis AE6C
> >
> > On Wed, Apr 19, 2017 at 7:12 PM, AKLDGUY . <neilb0627 at gmail.com> wrote:
> >
> >> To match my T-19/ARC-5 (3-4 Mc/s) to 50 ohm coax, I'll be using a 150pF
> >> variable capacitor connected in series with the inner of the coax.
> >>
> >> This configuration worked very well with my BC-AO-230 with the cap at
> >> about half-mesh.
> >>
> >> What setting should I use for the ANT. INDUCTANCE?
> >> Frequency is 3.850 MHz for the ZL AM net.
> >>
> >> 73 de Neil ZL1ANM
> >>
> >> ______________________________________________________________
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> ------------------------------
>
> Message: 2
> Date: Wed, 19 Apr 2017 23:03:27 -0700
> From: Dennis Monticelli <dennis.monticelli at gmail.com>
> To: "AKLDGUY ." <neilb0627 at gmail.com>
> Cc: ARC-5 List <arc5 at mailman.qth.net>
> Subject: Re: [ARC5] Rollerductor setting
> Message-ID:
> <CADgAsST7ehh+rBy3up2d__cJ5pCG9=CnhGpKanWEqe+FCbQoZA at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Yes, there will be a series resonance with the variable capacitor. Sure,
> just set the rollerductor first and then adjust the capacitor. If that
> combo doesn't give you the loading you desire, try adjusting the
> rollerductor differently.
>
> Dennis AE6C
>
> On Wed, Apr 19, 2017 at 10:11 PM, AKLDGUY . <neilb0627 at gmail.com> wrote:
>
> > Hi Dennis
> >
> > OK, so the rollerductor and the 150pF series cap interact? Is that it?
> >
> > So I should set the rollerductor arbitrarily to more than half the
> > inductance and adjust the cap to suit?
> >
> > I like your harmonic reduction comment. It makes sense.
> >
> > 73 de Neil ZL1ANM
> >
> >
> > On Thu, Apr 20, 2017 at 4:10 PM, Dennis Monticelli <
> > dennis.monticelli at gmail.com> wrote:
> >
> >> Neil,
> >>
> >> Whether 80M or 40M, I like to adjust for at least half the rollerductor.
> >> Too little inductance will compromise harmonic attenuation.
> >>
> >> Dennis AE6C
> >>
> >> On Wed, Apr 19, 2017 at 7:12 PM, AKLDGUY . <neilb0627 at gmail.com> wrote:
> >>
> >>> To match my T-19/ARC-5 (3-4 Mc/s) to 50 ohm coax, I'll be using a 150pF
> >>> variable capacitor connected in series with the inner of the coax.
> >>>
> >>> This configuration worked very well with my BC-AO-230 with the cap at
> >>> about half-mesh.
> >>>
> >>> What setting should I use for the ANT. INDUCTANCE?
> >>> Frequency is 3.850 MHz for the ZL AM net.
> >>>
> >>> 73 de Neil ZL1ANM
> >>>
> >>> ______________________________________________________________
> >>> ARC5 mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/arc5
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:ARC5 at mailman.qth.net
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>>
> >>
> >>
> >
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> ------------------------------
>
> Message: 3
> Date: Thu, 20 Apr 2017 14:11:10 +0000 (UTC)
> From: J Mcvey <ac2eu at yahoo.com>
> To: Dennis Monticelli <dennis.monticelli at gmail.com>, "AKLDGUY ."
> <neilb0627 at gmail.com>
> Cc: ARC-5 List <arc5 at mailman.qth.net>
> Subject: Re: [ARC5] Rollerductor setting
> Message-ID: <1626905070.4905077.1492697471016 at mail.yahoo.com>
> Content-Type: text/plain; charset="utf-8"
>
> Here is my take on the matching:
> The ARC-5 and ARA/ATA were all designed to work with short, capacitve antennas as one might expect on an aircraft.The radiation resistance range is spec'ed at 5 to 12 ohms . The roller inductor was there to "tune out" the capactive reactance of the antenna.
> I have tested these units with sloping wires. They will load into amazingly short lnon resonant lengths.The official dummy load or phantom antenna (a-61-a)for this series consisted of a 5 ohm resistor in series with a 100 pf cap.This is an extremely reactive scenario. 5-j425 ohms!
>
> If we assume that the antenna load is actually 50 ohms ( and very few are) , a 4:1 unun with the high side to the antenna should provide
> a 12.5 resistance for the Tx to match into. Even If it were a perfect 50 ohms and no reactance you wouls still need to resonate the roller inductance with a capacitor to get the system to load properly.For best results, try to provide the transmitter with a load within it's published design parameters
> Since antennas are have variable characteristics, selecting the cap for a center position? while tuned in the center of the band will allow you to compensate for inductive or capactive reactance presented by the antenna as you tune up or down. (assuming the that the antenna is tuned to the band center) .
>
> I can tell you that a 100 to 150 pf/5kv transmit cap? in series with a 4:1 unun worked very well for me on 80 meters.That being said, your antenna may be be quite? a bit different due to construction , height above ground, proximity to other objects, etc.The best thing to do is to have someone with a an antenna analyzer map your antenna response over the BW. That's the only way you know for sure what to match. I found that mine had issues at the very low end of the band where the impedance was about 100-j75 which the the Tx didn't like at all.Fixing the antenna is another item on the "to do list"? and another reason to say "ASSUME NOTHING".
>
> I have never tried the series cap WITHOUT the unun? because I thought it would be too far out of the specified range.The variometer was designed for the lower impedance, so that may introduce inefficiencies.
> How many watts do you get in CW mode?
>
>
>
>
>
> On Thursday, April 20, 2017 2:03 AM, Dennis Monticelli <dennis.monticelli at gmail.com> wrote:
>
>
> Yes, there will be a series resonance with the variable capacitor.? Sure, just set the rollerductor first and then adjust the capacitor.? If that combo doesn't give you the loading you desire, try adjusting the rollerductor differently.
> Dennis AE6C
> On Wed, Apr 19, 2017 at 10:11 PM, AKLDGUY . <neilb0627 at gmail.com> wrote:
>
> Hi Dennis
> OK, so the rollerductor and the 150pF series cap?interact? Is that it?
> So I should set the rollerductor arbitrarily to more than half the inductance and adjust the cap to suit?
> I like your harmonic reduction comment. It makes sense.
> 73 de Neil ZL1ANM
>
> On Thu, Apr 20, 2017 at 4:10 PM, Dennis Monticelli <dennis.monticelli at gmail.com> wrote:
>
> Neil,
> Whether 80M or 40M, I like to adjust for at least half the rollerductor.? Too little inductance will compromise harmonic attenuation.
> Dennis AE6C
> On Wed, Apr 19, 2017 at 7:12 PM, AKLDGUY . <neilb0627 at gmail.com> wrote:
>
> To match my T-19/ARC-5 (3-4 Mc/s) to 50 ohm coax, I'll be using a 150pF variable capacitor connected in series with the inner of the coax.
> This configuration worked very well with my BC-AO-230 with the cap at about half-mesh.
> What setting should I use for?the?ANT. INDUCTANCE?Frequency is 3.850 MHz for the ZL AM net.
> 73 de Neil ZL1ANM
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