Elecraft

Strong recommendation: MFJ 18xx-series single-band whips for KX3, etc.

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wayne burdick

Re: Attaching a whip to the KX3, HT-style or table-top (right angle)

Administrator

If you use a mag-mount for an HF whip, be sure to use one with three magnets, not one. I tried a Hustler 17-m whip with a one-magnet mount, and it tipped over at freeway speeds.

I agree that the capacitance of a mag-mount is insufficient. The coax braid may actually be serving as the better part of the counterpoise.

I gave up on the mag-mount and now have a bracket on the spare tire mount. Works great.

On our KX3 web page you'll find a link to an application note about mobile installations. There are many subtleties.

73,
Wayne
N6KR

On Mar 31, 2016, at 10:33 AM, Jim Brown <[hidden email]> wrote:

> On Thu,3/31/2016 6:06 AM, [hidden email] wrote:
>> When you operate mobile, do you use some sort of magnetic mount to support the whip? Also does the metal of the vehicle take the place of a counter poise?
>
> I'm not Wayne, but I've studied this issue. Yes, the vehicle chassis needs to serve as the counterpoise for a mobile antenna, but I have yet to see a mag mount that does that effectively. VHF/UHF mag mounts are designed to do that by means of capacitance between the mount and the roof, but nearly all that I have seen have no contact between the coax shield and the enclosure of the mount!
>
> At HF, I see no practical way for any mag mount I've seen to have anywhere near enough capacitance to a roof to work as a counterpoise at HF.
>
> If you want to work mobile, you need to make a solid connection to the frame, AND it needs to be a part of the frame that is not insulated from the rest of the frame by PAINT. That isn't easy in most modern vehicles.
>
> Two examples. With a Volvo S80 I owned about 15 years ago, I used a license plate mount for Hamsticks. The license plate holder was insulated from the trunk roof, and the trunk roof was insulated from the rest of the body by the hinges, so I had to bond around both. That worked pretty well, but I suspect there were still pieces of the body that were insulated by paint.
>
> Second example. My current vehicle, a 2006 Toyuota Sequoia (big SUV) that I bought in Nov to move to CA from IL. It was winter in Chicago, so K9IKZ let me bring it into the loading dock of his biz, and we poked around to try to find good contact with the body. Lots of paint in the way -- I found bolts a few inches from each other with no continuity between them. I eventually mounted the antenna socket to the roof rack, and found a nearby bolt that did get to the body.
>
> That worked pretty well as an antenna, but the vehicle has really bad susceptibility to HF RF -- at 100W on 20M, the main computer that runs the vehicle goes into "limp home mode." I've never bothered to try to fix it -- I was in the process of moving when I learned that (on an isolated stretch of I-80 in the NV desert), so didn't have time to chase it down, and because it was RF on the body that was exciting vehicle wiring, I figured that it would have been pretty difficult to fix. :) And my only interest in HF mobile is for long trips without the XYL, which I no longer take after I finished moving. I've heard that other big SUVs are far better in this regard.
>
> 73, Jim K9YC

Elecraft mailing list

Re: Attaching a whip to the KX3, HT-style or table-top (right angle)

In reply to this post by Jim Brown-10

While I found a DC ground on the bed of my GMC, I had a beautiful match... Hint loss.. Put a 2" wide copper strap to the frame after grinding down to metal and using Penetrox to seal the connection. Had to change the match at the base, but performance was noticeably better. Less, loss.. I then went around an bonded ever piece of the body to the frame. I am happy now.

Mel, K6KBE

From: Jim Brown <[hidden email]>
To: [hidden email]
Sent: Thursday, March 31, 2016 10:33 AM
Subject: Re: [Elecraft] Attaching a whip to the KX3, HT-style or table-top (right angle)

On Thu,3/31/2016 6:06 AM, [hidden email] wrote:
> When you operate mobile, do you use some sort of magnetic mount to support the whip? Also does the metal of the vehicle take the place of a counter poise?

I'm not Wayne, but I've studied this issue. Yes, the vehicle chassis
needs to serve as the counterpoise for a mobile antenna, but I have yet
to see a mag mount that does that effectively. VHF/UHF mag mounts are
designed to do that by means of capacitance between the mount and the
roof, but nearly all that I have seen have no contact between the coax
shield and the enclosure of the mount!

At HF, I see no practical way for any mag mount I've seen to have
anywhere near enough capacitance to a roof to work as a counterpoise at HF.

If you want to work mobile, you need to make a solid connection to the
frame, AND it needs to be a part of the frame that is not insulated from
the rest of the frame by PAINT. That isn't easy in most modern vehicles.

Two examples. With a Volvo S80 I owned about 15 years ago, I used a
license plate mount for Hamsticks. The license plate holder was
insulated from the trunk roof, and the trunk roof was insulated from the
rest of the body by the hinges, so I had to bond around both. That
worked pretty well, but I suspect there were still pieces of the body
that were insulated by paint.

Second example. My current vehicle, a 2006 Toyuota Sequoia (big SUV)
that I bought in Nov to move to CA from IL. It was winter in Chicago, so
K9IKZ let me bring it into the loading dock of his biz, and we poked
around to try to find good contact with the body. Lots of paint in the
way -- I found bolts a few inches from each other with no continuity
between them. I eventually mounted the antenna socket to the roof rack,
and found a nearby bolt that did get to the body.

That worked pretty well as an antenna, but the vehicle has really bad
susceptibility to HF RF -- at 100W on 20M, the main computer that runs
the vehicle goes into "limp home mode." I've never bothered to try to
fix it -- I was in the process of moving when I learned that (on an
isolated stretch of I-80 in the NV desert), so didn't have time to chase
it down, and because it was RF on the body that was exciting vehicle
wiring, I figured that it would have been pretty difficult to fix. :)
And my only interest in HF mobile is for long trips without the XYL,
which I no longer take after I finished moving. I've heard that other
big SUVs are far better in this regard.

73, Jim K9YC
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N1EU

Re: Strong recommendation: MFJ 18xx-series single-band whips for KX3, etc.

In reply to this post by wayne burdick

If anyone else out there has an MFJ-1820T and also an antenna analyzer, I
wonder if you could please do me a favor. Please just connect the whip
directly to the analyzer and tell me what the SWR looks like across the 20M
and the 17M bands.

I swept my MFJ-1820T with my Rig Expert AA-30 and my MFJ-1820T is resonant
on 17M, not 20M. I'm wondering if I have a mislabeled MFJ-1817T.

Thanks & 73,
Barry N1EU

On Thu, Mar 24, 2016 at 2:12 AM, Wayne Burdick <[hidden email]> wrote:

> Hi all,
>
> I've been using an MFJ-1820T telescoping 20-meter whip for a few months.
> Considering its length (48"), results have been excellent. I typically use
> it with the KX3 on a picnic table at 15 W (with an external battery), or
> hand-held at 3 to 5 W (internal battery).
>
> During the ARRL DX contest I worked many countries in CW and RTTY modes,
> and have also had a number of longer QSOs on 20-meter SSB. Of course at
> these power levels, with an electrically short whip, good band conditions
> can't hurt.
>
> I prefer a 25' or so wire-in-a-tree antenna when there's time. But when I
> need a quick deployment antenna that weighs very little, I pull out the
> 1820T. Note that you *must* use at least one counterpose wire. More than
> one helps, but all of the QSOs I described were made with a single 13'-long
> wire laid out on the ground. With no ground wire, you'll be down some 15 to
> 20 dB in transmit mode.
>
> Since the 20-meter results were so good, I also bought the whips for 40,
> 17, 15, and 10 meters. 40 meters is a rough ride at 48", but I was still
> able to check into daytime SSB nets all over the west coast running 10 W.
> On the higher bands, results improve as you go higher in frequency. I
> worked a few JAs on 15 meter SSB running just 1 watt.
>
> A traditional problem with such antennas is that the the SWR can sometimes
> be unexpectedly high, requiring that you micro-adjust the telescoping
> length and/or adjust the length of the counterpoise wire. This is
> completely unnecessary if you have an auto-tuner available. In particular,
> the KX3's ATU can quickly match any of these whips over their full target
> band. In a pinch the ATU can also match a given whip on adjacent bands. In
> the DX contest mentioned I tuned up the 20-meter whip on 17 and 15 meters
> as well, and made a few Q's there, despite the losses due to off-resonance
> operation.
>
> These whips can handle a surprising amount of power. They're rated to 25
> W, but I ran 50 W through the 20-meter version for several minutes without
> damaging it. Some other compact whips I've tried overheated quickly even at
> 10 W, including some of the Maldol models. When this happens, the SWR goes
> up and stays up until the coil cools down.
>
> Caveat: Always use a full-size antenna when possible. But if you've just
> crested a new hill and only have a couple of minutes to see if the RF
> really is greener on the other side, this is an excellent choice.
>
> 73,
> Wayne
> N6KR
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

Don Butler

Re: Strong recommendation: MFJ 18xx-series single-band whips for KX3, etc.

You may be right Barry ... it may be mislabeled ... there can't be much
chance of a real 20M whip resonating on 17 ... .... FWIW I've had a full set
of the MFJ whips for several years and did SWR testing on each one when I
first got them .... but I did not connect them directly to my Rig Expert
analyzer ... I had built a stand alone aluminum base with a BNC connector
for the whips and wingnuts for attaching counterpoise wires so I did my
testing in that configuration

My 20 meter whip is resonant at 14.400 .... and runs from 1.2:1 at the top
of the band to 2.2:1 at 14.025

My 17 meter whip is even better ... resonant at 17.900 ... but tests at
1.2:1 all through the band

All of my high band whips are usable (10, 12, 15, 17, and 20) .... but my
30, 40 and 80 whips have never worked well ... the 80 resonates at 3.350
... and SWR is at infinity throughout the band .... my 40 resonates at 6.800
... and my 30 resonates at 9.700 ..... all my testing was done with the
whips fully extended .... I figure if I shorten them I will essentially be
turning them into non-radiating dummy loads..

I personally do not like to attach the whips directly to my KX3 ... it
feels to me that they're putting too much torque on the BNC connector and
the antenna seems like it weighs almost as much as the radio .... which is
why I made the aluminum base ...

But I later bought a CrankIR vertical which has become my "Go To" portable
antenna ... so the MFJ whips have been retired to a box in the shack...

Don, N5LZ

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Barry
N1EU
Sent: Saturday, April 02, 2016 6:15 PM
To: Elecraft Reflector; [hidden email]
Subject: Re: [Elecraft] Strong recommendation: MFJ 18xx-series single-band
whips for KX3, etc.

If anyone else out there has an MFJ-1820T and also an antenna analyzer, I
wonder if you could please do me a favor. Please just connect the whip
directly to the analyzer and tell me what the SWR looks like across the 20M
and the 17M bands.

I swept my MFJ-1820T with my Rig Expert AA-30 and my MFJ-1820T is resonant
on 17M, not 20M. I'm wondering if I have a mislabeled MFJ-1817T.

Thanks & 73,
Barry N1EU

On Thu, Mar 24, 2016 at 2:12 AM, Wayne Burdick <[hidden email]> wrote:

> Hi all,
>
> I've been using an MFJ-1820T telescoping 20-meter whip for a few months.
> Considering its length (48"), results have been excellent. I typically
> use it with the KX3 on a picnic table at 15 W (with an external
> battery), or hand-held at 3 to 5 W (internal battery).
>
> During the ARRL DX contest I worked many countries in CW and RTTY
> modes, and have also had a number of longer QSOs on 20-meter SSB. Of
> course at these power levels, with an electrically short whip, good
> band conditions can't hurt.
>
> I prefer a 25' or so wire-in-a-tree antenna when there's time. But
> when I need a quick deployment antenna that weighs very little, I pull
> out the 1820T. Note that you *must* use at least one counterpose wire.
> More than one helps, but all of the QSOs I described were made with a
> single 13'-long wire laid out on the ground. With no ground wire,
> you'll be down some 15 to
> 20 dB in transmit mode.
>
> Since the 20-meter results were so good, I also bought the whips for
> 40, 17, 15, and 10 meters. 40 meters is a rough ride at 48", but I was
> still able to check into daytime SSB nets all over the west coast running

10 W.

> On the higher bands, results improve as you go higher in frequency. I
> worked a few JAs on 15 meter SSB running just 1 watt.
>
> A traditional problem with such antennas is that the the SWR can
> sometimes be unexpectedly high, requiring that you micro-adjust the
> telescoping length and/or adjust the length of the counterpoise wire.
> This is completely unnecessary if you have an auto-tuner available. In
> particular, the KX3's ATU can quickly match any of these whips over
> their full target band. In a pinch the ATU can also match a given whip
> on adjacent bands. In the DX contest mentioned I tuned up the 20-meter
> whip on 17 and 15 meters as well, and made a few Q's there, despite
> the losses due to off-resonance operation.
>
> These whips can handle a surprising amount of power. They're rated to
> 25 W, but I ran 50 W through the 20-meter version for several minutes
> without damaging it. Some other compact whips I've tried overheated
> quickly even at
> 10 W, including some of the Maldol models. When this happens, the SWR
> goes up and stays up until the coil cools down.
>
> Caveat: Always use a full-size antenna when possible. But if you've
> just crested a new hill and only have a couple of minutes to see if
> the RF really is greener on the other side, this is an excellent choice.
>
> 73,
> Wayne
> N6KR
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net Please help support this email
> list: http://www.qsl.net/donate.html Message delivered to
> [hidden email]
>

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Bruce Nourish

Re: Strong recommendation: MFJ 18xx-series single-band whips for KX3, etc.

In reply to this post by N1EU

Did you have a counterpoise when you swept the antenna? If not, you're only
looking at half your antenna, especially as the RigExpert is almost all
plastic.

On Sun, Apr 3, 2016, 01:15 Barry N1EU <[hidden email]> wrote:

> If anyone else out there has an MFJ-1820T and also an antenna analyzer, I
> wonder if you could please do me a favor. Please just connect the whip
> directly to the analyzer and tell me what the SWR looks like across the 20M
> and the 17M bands.
>
> I swept my MFJ-1820T with my Rig Expert AA-30 and my MFJ-1820T is resonant
> on 17M, not 20M. I'm wondering if I have a mislabeled MFJ-1817T.
>
> Thanks & 73,
> Barry N1EU
>
> On Thu, Mar 24, 2016 at 2:12 AM, Wayne Burdick <[hidden email]> wrote:
>
> > Hi all,
> >
> > I've been using an MFJ-1820T telescoping 20-meter whip for a few months.
> > Considering its length (48"), results have been excellent. I typically
> use
> > it with the KX3 on a picnic table at 15 W (with an external battery), or
> > hand-held at 3 to 5 W (internal battery).
> >
> > During the ARRL DX contest I worked many countries in CW and RTTY modes,
> > and have also had a number of longer QSOs on 20-meter SSB. Of course at
> > these power levels, with an electrically short whip, good band conditions
> > can't hurt.
> >
> > I prefer a 25' or so wire-in-a-tree antenna when there's time. But when I
> > need a quick deployment antenna that weighs very little, I pull out the
> > 1820T. Note that you *must* use at least one counterpose wire. More than
> > one helps, but all of the QSOs I described were made with a single
> 13'-long
> > wire laid out on the ground. With no ground wire, you'll be down some 15
> to
> > 20 dB in transmit mode.
> >
> > Since the 20-meter results were so good, I also bought the whips for 40,
> > 17, 15, and 10 meters. 40 meters is a rough ride at 48", but I was still
> > able to check into daytime SSB nets all over the west coast running 10 W.
> > On the higher bands, results improve as you go higher in frequency. I
> > worked a few JAs on 15 meter SSB running just 1 watt.
> >
> > A traditional problem with such antennas is that the the SWR can
> sometimes
> > be unexpectedly high, requiring that you micro-adjust the telescoping
> > length and/or adjust the length of the counterpoise wire. This is
> > completely unnecessary if you have an auto-tuner available. In
> particular,
> > the KX3's ATU can quickly match any of these whips over their full target
> > band. In a pinch the ATU can also match a given whip on adjacent bands.
> In
> > the DX contest mentioned I tuned up the 20-meter whip on 17 and 15 meters
> > as well, and made a few Q's there, despite the losses due to
> off-resonance
> > operation.
> >
> > These whips can handle a surprising amount of power. They're rated to 25
> > W, but I ran 50 W through the 20-meter version for several minutes
> without
> > damaging it. Some other compact whips I've tried overheated quickly even
> at
> > 10 W, including some of the Maldol models. When this happens, the SWR
> goes
> > up and stays up until the coil cools down.
> >
> > Caveat: Always use a full-size antenna when possible. But if you've just
> > crested a new hill and only have a couple of minutes to see if the RF
> > really is greener on the other side, this is an excellent choice.
> >
> > 73,
> > Wayne
> > N6KR
> >
> >
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> > Message delivered to [hidden email]
> >
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

N1EU

Re: Strong recommendation: MFJ 18xx-series single-band whips for KX3, etc.

Thanks for all the responses. Don, your comments are much appreciated and
I planned on building a bracket just as you describe and mounting my
whip/counterpoise to the top of a trekking pole..

Again, I'm not asking about antenna performance. I will add the
counterpoise in actual operation. I'm asking if anyone out there who
actually owns the MFJ-1820T can please connect it directly to a antenna
analyzer and check 20M performance. Yes, I believe these antennas actually
DO resonate just as they are. I believe mine is 17M (mislabeled), not 20M,
and just looking to confirm that.

Thanks & 73,
Barry N1EU

On Sun, Apr 3, 2016 at 9:34 AM, Bruce Nourish <[hidden email]> wrote:

> Did you have a counterpoise when you swept the antenna? If not, you're
> only looking at half your antenna, especially as the RigExpert is almost
> all plastic.
>
> On Sun, Apr 3, 2016, 01:15 Barry N1EU <[hidden email]> wrote:
>
>> If anyone else out there has an MFJ-1820T and also an antenna analyzer, I
>> wonder if you could please do me a favor. Please just connect the whip
>> directly to the analyzer and tell me what the SWR looks like across the
>> 20M
>> and the 17M bands.
>>
>> I swept my MFJ-1820T with my Rig Expert AA-30 and my MFJ-1820T is resonant
>> on 17M, not 20M. I'm wondering if I have a mislabeled MFJ-1817T.
>>
>> Thanks & 73,
>> Barry N1EU
>>
>>

Don Butler

Re: Strong recommendation: MFJ 18xx-series single-band whips for KX3, etc.

Barry . I just tested my 20 meter and 17 meter whips by fully extending them
and connecting them directly to a Rig Expert AA-230 Pro outside in the open
yard ... With NO Counterpoise wire ... this is the first time I've tried
this ..

And after doing so I'm not so sure that it's reliable.

1. The fully extended 20 meter whip, mounted directly to the analyzer
dips to 2.6:1 at 17.860 Mhz .. ( when mounted on an aluminum base with
counterpoise wires it ran from 1.2:1 to 2.2:1 through the 20 meter band).

2. The fully extended 17 meter whip, mounted directly to the analyzer
dips to 2.7:1 at 21.940 Mhz ... (when mounted on the aluminum base with
counterpoise wires it ran around 1.2:1 from 18.100 to 18.200)

Based upon my testing, and what you previously reported, I'd say that you
probably do have a stock 20 meter whip that is correctly labeled.

I have photos of my homemade aluminum base ... but am not sure if I can post
it to the reflector so will not attempt that ... but if anyone would like to
see them contact me offlist and I'll be happy to share them.

Don, N5LZ

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Barry
N1EU
Sent: Sunday, April 03, 2016 4:38 AM
To: Elecraft Reflector; [hidden email]
Subject: Re: [Elecraft] Strong recommendation: MFJ 18xx-series single-band
whips for KX3, etc.

Thanks for all the responses. Don, your comments are much appreciated and I
planned on building a bracket just as you describe and mounting my
whip/counterpoise to the top of a trekking pole..

Again, I'm not asking about antenna performance. I will add the
counterpoise in actual operation. I'm asking if anyone out there who
actually owns the MFJ-1820T can please connect it directly to a antenna
analyzer and check 20M performance. Yes, I believe these antennas actually
DO resonate just as they are. I believe mine is 17M (mislabeled), not 20M,
and just looking to confirm that.

Thanks & 73,
Barry N1EU

On Sun, Apr 3, 2016 at 9:34 AM, Bruce Nourish <[hidden email]> wrote:

> Did you have a counterpoise when you swept the antenna? If not, you're
> only looking at half your antenna, especially as the RigExpert is
> almost all plastic.
>
> On Sun, Apr 3, 2016, 01:15 Barry N1EU <[hidden email]> wrote:
>
>> If anyone else out there has an MFJ-1820T and also an antenna
>> analyzer, I wonder if you could please do me a favor. Please just
>> connect the whip directly to the analyzer and tell me what the SWR
>> looks like across the 20M and the 17M bands.
>>
>> I swept my MFJ-1820T with my Rig Expert AA-30 and my MFJ-1820T is
>> resonant on 17M, not 20M. I'm wondering if I have a mislabeled

MFJ-1817T.
>>
>> Thanks & 73,
>> Barry N1EU
>>
>>
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wayne burdick

Whips and counterpoise wires

Administrator

This probably goes without saying, but... always use a counterpoise (at least one wire) if you're actually trying to make QSOs. Without one, the whip not be resonant on its target band, and you'll lose 15-20 dB of signal at the receiving station. Even with the counterpoise, I always use the internal ATU in the KX3 to improve the SWR.

For listening only, I'll sometimes use the whip without a counterpoise wire. I still use the ATU in the KX3 in this case (you can't hurt it, since this is done at 2 W). This resonates the whip for RX purposes.

Wayne
N6KR

Don Butler <[hidden email]> wrote:

> Barry . I just tested my 20 meter and 17 meter whips by fully extending them
> and connecting them directly to a Rig Expert AA-230 Pro outside in the open
> yard ... With NO Counterpoise wire ... this is the first time I've tried
> this ..
>
> And after doing so I'm not so sure that it's reliable.
>
> 1. The fully extended 20 meter whip, mounted directly to the analyzer
> dips to 2.6:1 at 17.860 Mhz .. ( when mounted on an aluminum base with
> counterpoise wires it ran from 1.2:1 to 2.2:1 through the 20 meter band).
>
> 2. The fully extended 17 meter whip, mounted directly to the analyzer
> dips to 2.7:1 at 21.940 Mhz ... (when mounted on the aluminum base with
> counterpoise wires it ran around 1.2:1 from 18.100 to 18.200)
>
> Based upon my testing, and what you previously reported, I'd say that you
> probably do have a stock 20 meter whip that is correctly labeled.
>
> I have photos of my homemade aluminum base ... but am not sure if I can post
> it to the reflector so will not attempt that ... but if anyone would like to
> see them contact me offlist and I'll be happy to share them.
>
> Don, N5LZ

Jim Brown-10

Re: Strong recommendation: MFJ 18xx-series single-band whips for KX3, etc.

In reply to this post by Don Butler

On Sun,4/3/2016 8:33 AM, Don Butler wrote:
> Barry . I just tested my 20 meter and 17 meter whips by fully extending them
> and connecting them directly to a Rig Expert AA-230 Pro outside in the open
> yard ... With NO Counterpoise wire ... this is the first time I've tried
> this ..

Good that you've never done that -- as W0MBT noted, omitting the
counterpoise leaves out half of the antenna! The counterpoise provides
a RETURN for antenna current. Without that return, the chassis of
whatever box it's connected to (and whatever the chassis is connected
to) serves as the return.

Let's get something straight. Current flows in LOOPS, whether it's DC,
audio, or RF. If current flows out on one wire (in this case, the whip),
it MUST flow in on something else connected to the transmitter. In the
case of the whip, it's whatever is connected to the chassis of the
transmitter. We call that a counterpoise. An antenna creates an
electromagnetic field, which space couples between the two pieces of the
antenna (the whip and the counterpoise), so around the antenna space is
part of that loop.

Without that counterpoise, the antenna doesn't work as well. First, it
is less efficient, because the return path for the feed current and the
field is poor. Second, because it is part of the antenna, a missing or
shortened counterpoise causes the antenna to resonate at a higher
frequency.

Radials are a more ideal form of counterpoise -- they SHIELD the antenna
from the lossy earth (which burns TX power before it can be radiated);
instead, return current flows in low resistance radials, making the
antenna more efficient (and our signal louder at the other end).

On Sun,4/3/2016 9:17 AM, Wayne Burdick wrote:
> This probably goes without saying, but... always use a counterpoise (at least one wire) if you're actually trying to make QSOs. Without one, the whip not be resonant on its target band, and you'll lose 15-20 dB of signal at the receiving station.

Exactly.

> Even with the counterpoise, I always use the internal ATU in the KX3 to improve the SWR.

Poor choice of words. An antenna tuner does NOT "improve the SWR" -- SWR
is a property of a TRANSMISSION LINE, and it is determined ENTIRELY by
the match between the antenna and the transmission line. Rather, an
antenna tuner transforms the Z of the antenna to the load impedance that
the output stage of the rig wants to see as a load, in most cases, 50
Ohms resistive. This does two things -- it prevents protection circuitry
from "folding back" the output stage (reducing drive to the output
stage, thus reducing its power) to protect it, and it reduces distortion
in the output stage.

> For listening only, I'll sometimes use the whip without a counterpoise wire. I still use the ATU in the KX3 in this case (you can't hurt it, since this is done at 2 W). This resonates the whip for RX purposes.

In this context, the counterpoise (and the tuner) do two things -- they
make the antenna more efficient (by providing a better return for
current), AND increase the current at the input of the RX. With TX, we
care about efficiency of the antenna (how much RF field does it create)
because it makes our signal stronger. With RX, we don't care much, or
don't care at all, because we have more than enough sensitivity in the
RX to hear weaker signals. SO -- a counterpoise is far less important
for listening.

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