K3: 160m SWR issue

9 messages

K3: 160m SWR issue

Reply Threaded

I'm feeding a "double L" antenna on 160m (visualize a vertical dipole with
the top and bottom legs bent to form something like a capital "C" and fed in
the middle of the vertical leg). The SWR bridge on the K3 shows 1:1 SWR, but
when I fire up my Alpha 91B, I see significant reflected power.

I recently saw a post on the topband reflector from another K3 owner whose
160m output power is being reduced from 100W to 50W by the K3 even though
the SWR reads 1:1 on the K3's internal SWR bridge.

Has anyone else seen this or have an explanation for it?

--
73 -- Brian -- K1LI
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Don Wilhelm-4

Re: K3: 160m SWR issue

Reply Threaded

Brian,

Is the higher reflected power indicated on the K3 or is it the reading
on a meter in the line between the amp and the antenna?

If it is read on an external meter --
Is there any possibility that something is arcing over at high power -
check your antenna system for that condition.

If the indication is on the K3, then the problem is in the input circuit
for the amp (giving a non-50 ohm resistive load to the K3).

73,
Don W3FPR

Brian Machesney wrote:

> I'm feeding a "double L" antenna on 160m (visualize a vertical dipole with
> the top and bottom legs bent to form something like a capital "C" and fed in
> the middle of the vertical leg). The SWR bridge on the K3 shows 1:1 SWR, but
> when I fire up my Alpha 91B, I see significant reflected power.
>
> I recently saw a post on the topband reflector from another K3 owner whose
> 160m output power is being reduced from 100W to 50W by the K3 even though
> the SWR reads 1:1 on the K3's internal SWR bridge.
>
> Has anyone else seen this or have an explanation for it?
>
>

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hb9ari

Re: K3: 160m SWR issue

Reply Threaded

Hi Brian,

Just an "idiot" question: are you using the K3 ATU?

73, Rudolf HB9ARI

Don Wilhelm wrote:

> Brian,
>
> Is the higher reflected power indicated on the K3 or is it the reading
> on a meter in the line between the amp and the antenna?
>
> If it is read on an external meter --
> Is there any possibility that something is arcing over at high power -
> check your antenna system for that condition.
>
> If the indication is on the K3, then the problem is in the input circuit
> for the amp (giving a non-50 ohm resistive load to the K3).
>
> 73,
> Don W3FPR
>
> Brian Machesney wrote:
>
>> I'm feeding a "double L" antenna on 160m (visualize a vertical dipole with
>> the top and bottom legs bent to form something like a capital "C" and fed in
>> the middle of the vertical leg). The SWR bridge on the K3 shows 1:1 SWR, but
>> when I fire up my Alpha 91B, I see significant reflected power.
>>
>> I recently saw a post on the topband reflector from another K3 owner whose
>> 160m output power is being reduced from 100W to 50W by the K3 even though
>> the SWR reads 1:1 on the K3's internal SWR bridge.
>>
>> Has anyone else seen this or have an explanation for it?
>>
>>
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>
>

Brian Machesney

Re: K3: 160m SWR issue

Reply Threaded

Good question, Rudolf, but no the ATU is not engaged.

On Tue, Nov 3, 2009 at 2:56 PM, hb9ari <[hidden email]> wrote:

> Hi Brian,
>
> Just an "idiot" question: are you using the K3 ATU?
>
> 73, Rudolf HB9ARI
>
> Don Wilhelm wrote:
> > Brian,
> >
> > Is the higher reflected power indicated on the K3 or is it the reading
> > on a meter in the line between the amp and the antenna?
> >
> > If it is read on an external meter --
> > Is there any possibility that something is arcing over at high power -
> > check your antenna system for that condition.
> >
> > If the indication is on the K3, then the problem is in the input circuit
> > for the amp (giving a non-50 ohm resistive load to the K3).
> >
> > 73,
> > Don W3FPR
> >
> > Brian Machesney wrote:
> >
> >> I'm feeding a "double L" antenna on 160m (visualize a vertical dipole
> with
> >> the top and bottom legs bent to form something like a capital "C" and
> fed in
> >> the middle of the vertical leg). The SWR bridge on the K3 shows 1:1 SWR,
> but
> >> when I fire up my Alpha 91B, I see significant reflected power.
> >>
> >> I recently saw a post on the topband reflector from another K3 owner
> whose
> >> 160m output power is being reduced from 100W to 50W by the K3 even
> though
> >> the SWR reads 1:1 on the K3's internal SWR bridge.
> >>
> >> Has anyone else seen this or have an explanation for it?
> >>
> >>
> >>
> > ______________________________________________________________
> > 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
> >
> >
> ______________________________________________________________
> 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
>

--
73 -- Brian -- K1LI
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Guy, K2AV

Re: K3: 160m SWR issue

Reply Threaded

In reply to this post by Brian Machesney

When the alpha 91 is in line, the K3 meter will report the SWR of the 91B
input circuitry. The apparent SWR of the 91b input can change with
different drive levels. You did not report what "significant reflected
power" was.

73, Guy.

On Tue, Nov 3, 2009 at 2:18 PM, Brian Machesney <[hidden email]> wrote:

> I'm feeding a "double L" antenna on 160m (visualize a vertical dipole with
> the top and bottom legs bent to form something like a capital "C" and fed
> in
> the middle of the vertical leg). The SWR bridge on the K3 shows 1:1 SWR,
> but
> when I fire up my Alpha 91B, I see significant reflected power.
>
> I recently saw a post on the topband reflector from another K3 owner whose
> 160m output power is being reduced from 100W to 50W by the K3 even though
> the SWR reads 1:1 on the K3's internal SWR bridge.
>
> Has anyone else seen this or have an explanation for it?
>
> --
> 73 -- Brian -- K1LI
> ______________________________________________________________
> 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
>

rkayakr

Re: K3: 160m SWR issue

Reply Threaded

In reply to this post by Brian Machesney

Brian
I also use a "C" antenna on 160 m with my K3 and I have not seen any problems with power reduction. I also have an ALS-600 Amp which is far more sensitive to SWR than the K3 on all bands.
Bob
KD8CGH

hb9ari

Re: K3: 160m SWR issue

Reply Threaded

In reply to this post by Brian Machesney

Ok, Brian!
No other idea
Good luck for solving this problem!
73, Rudolf

Brian Machesney wrote:

> Good question, Rudolf, but no the ATU is not engaged.
>
> On Tue, Nov 3, 2009 at 2:56 PM, hb9ari <[hidden email]
> <mailto:[hidden email]>> wrote:
>
> Hi Brian,
>
> Just an "idiot" question: are you using the K3 ATU?
>
> 73, Rudolf HB9ARI
>
> Don Wilhelm wrote:
> > Brian,
> >
> > Is the higher reflected power indicated on the K3 or is it the
> reading
> > on a meter in the line between the amp and the antenna?
> >
> > If it is read on an external meter --
> > Is there any possibility that something is arcing over at high
> power -
> > check your antenna system for that condition.
> >
> > If the indication is on the K3, then the problem is in the input
> circuit
> > for the amp (giving a non-50 ohm resistive load to the K3).
> >
> > 73,
> > Don W3FPR
> >
> > Brian Machesney wrote:
> >
> >> I'm feeding a "double L" antenna on 160m (visualize a vertical
> dipole with
> >> the top and bottom legs bent to form something like a capital
> "C" and fed in
> >> the middle of the vertical leg). The SWR bridge on the K3 shows
> 1:1 SWR, but
> >> when I fire up my Alpha 91B, I see significant reflected power.
> >>
> >> I recently saw a post on the topband reflector from another K3
> owner whose
> >> 160m output power is being reduced from 100W to 50W by the K3
> even though
> >> the SWR reads 1:1 on the K3's internal SWR bridge.
> >>
> >> Has anyone else seen this or have an explanation for it?
> >>
> >>
> >>
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> <mailto:[hidden email]>
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
> >
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
> <mailto:[hidden email]>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
>
>
> --
> 73 -- Brian -- K1LI

Julius Fazekas n2wn

Re: K3: 160m SWR issue

Reply Threaded

In reply to this post by Brian Machesney

Hi Brian,

The TopBand query that you reference had a situation that may or may not apply to your setup. He only had 15' of feedline between the Tx and the antenna. Weird things can happen.

Phil's situation was somewhat remedied by adding a longer run of coax.

I've had my share of issues on 160 as well, even without running an amp, because the base of my antenna is VERY close to the transmitter (>30').

Several things cleared up my issues including better matching at the antenna, and isolation style 1:1 current choke and partially buried feedline.

You can't count on the K3 (or K2) SWR reading 1:1 or some other low value. You really need to see what the impedance of the antenna is in real and imaginary terms. Several antenna measuring devices and the LP-100 will tell you this and you can better match the antenna. You're not lost if you don't have access to such tools, often a good choke balun will moderate some of the problem, if not eliminate it altogether. See Jim, K9YC, RFI and choke tutorials.

160 presents some interesting technical challenges, but they aren't are draconian as some would like you to believe.

Hope this helps.

73,
Julius

Brian Machesney wrote:

I'm feeding a "double L" antenna on 160m (visualize a vertical dipole with
the top and bottom legs bent to form something like a capital "C" and fed in
the middle of the vertical leg). The SWR bridge on the K3 shows 1:1 SWR, but
when I fire up my Alpha 91B, I see significant reflected power.

I recently saw a post on the topband reflector from another K3 owner whose
160m output power is being reduced from 100W to 50W by the K3 even though
the SWR reads 1:1 on the K3's internal SWR bridge.

Has anyone else seen this or have an explanation for it?

--
73 -- Brian -- K1LI
______________________________________________________________
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Julius Fazekas
N2WN

Tennessee Contest Group
http://www.k4ro.net/tcg/index.html

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http://www.tnqp.org/

Elecraft K2/100 #4455
Elecraft K3/100 #366
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Brian Machesney

Re: K3: 160m SWR issue

Reply Threaded

The issue(s) that I'm facing are being dealt with fully in the "other"
thread re: K3 SWR accuracy. I would like to abandon this thread.

73 -- Brian -- K1LI
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