Re: [Elecraft] Product Suggestion - 500W Dummy Load

[ae4pb]

Forgive me in advance if this is a stupid question. 

Is there any reason you have to tune at full power? It seems to me that
tuning can be accomplished easily with much lower power. The same thing goes
for the ATU to the antenna. I don't see why we need more than a few MW at
most for the ATU to Antenna link. 



Rightly or wrongly when I was in the hobby the first time I ran a TS-850
into an SB-220 to an MFJ roller tuner connected to an antenna switch
feeding: 80m inverted V, 30m/40m rotatable dipoles, and a triband beam.
Whenever I tuned on the inverted V or outer band limits of where my antennas
where tuned I ended up putting labels on the ATU on cap position and a
number/clock combo that represented a roller inductor position for each band
area I cared about. It ended up I rarely had to tune up anything one the air
because I knew where the antenna tuning was using just the Rig and ATU;
tuned the APM into a paintcan MFJ load then switch it inline. I was all set
and never had issues when I needed to kick in the horses. 

Now my debate is 500w vs 800w... there's a larger difference between 500w
and 800w than between 800w and 2.5kw signal wise if I understand
correctly... 


Jerry Moore
AE4PB, K3S - S.N. 010324



-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Edward
R Cole
Sent: Friday, September 18, 2015 2:00 PM
To: Elecraft@mailman.qth.net
Subject: Re: [Elecraft] Product Suggestion - 500W Dummy Load

Don't have much to say:

Had a Cantenna from Heath in the 60's - knocked over; spilt mineral oil on
the floor, threw can away!

I have acquired "dry" loads over the years rated into UHF and sometimes to
mw at flea markets and swaps.  My highest power load is 500w Sierra with
power meter and switch for 150 or 500w (probably good to 1000-MHz).  Have a
couple Bird terminations rated 50w.  Most can handled double their rating
for short duration.

The hardest duty on my loads is when optimizing the output of a new unit
where I'm keyed up longer than I should.

But I do have a question on how adjusting a tuner into a 50-ohm load saves
one from transmitting a signal once the tuner is connected to an antenna
that may not be 50-ohms.  On 600m my inverted-L is Z = 0.8 
+j680.  Tuning into a 50-ohm load does nothing to help match the
antenna.  The amplifier is solid state with input and output transformers
(no adjustment).

I think, unless you use a high power tetrode or triode, that no one tunes
amplifiers anymore.  Solid state amps are broadband and need LP filters to
keep from amplifying harmonics.  BTW my 2m-8877 is capable of 2000w* RF
output so pretty hard to find a dummy load to take that.  Fortunately the
amp does not change much so very little tuning is ever needed (of course I
am on a small segment of one band about 200-KHz wide).  Of course the answer
is to tune antenna at lower power and hope the High Power amp will always be
looking at 50-ohms.

I do not have a QRO 2m antenna tuner but the antenna SWR < 1.25 so only the
anode tuning needs a light adjustment occasionally (loading has not be
adjusted for 8 years).  My "dummy load" has 19.2 dBd gain and radiates well.

*I operate at 1365w CW which allows for about 9% variance in meter accuracy
to stay legal.

73, Ed - KL7UW
http://www.kl7uw.com
 "Kits made by KL7UW"
Dubus Mag business:
 dubus...@gmail.com

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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[mfsj]

Very true my main HF amps are like that both Alphas an 87A and a 9500. Other 
amps like my KPA500, Yaesu 1000 series SS units are fine to tune at low power.
Fred  N0AZZ


Sent via the Samsung Galaxy S6 edge+, an AT 4G LTE smartphone 
Original message From: Edward R Cole <kl...@acsalaska.net> Date: 
09/18/2015  6:14 PM  (GMT-06:00) To: ae...@carolinaheli.com, 
Elecraft@mailman.qth.net Subject: Re: [Elecraft] Product Suggestion - 500W 
Dummy Load 
Jerry,

Certainly its appropriate to tune your antenna tuner at low power.  I 
have an "ancient" Drake MN-2000 which is rated for 2000w PEP but I 
can tune it with 10w from my K3/10 with my linear off.  Then I turn 
on my station control panel which enables PTT to the amp.  Lately 
been using my AN-762 140w amp from CCI which I drive to about 120w with 5.6w.
http://www.communication-concepts.com/140-watt/

I set the tuner on the 200w range to measure fwd and ref 
power.  Sometimes I will touch up the tuner with the amp online as 
the amp and K3 are separated by 8-foot of coax and that appears to 
affect tuning (a little).  But that only takes a couple seconds.

Marking down cap settings for favorite frequencies is a good idea.

But tuning a high-power tube amp at greatly lowered output does not 
work.  Because the internal impedance of the tube shifts as anode 
current rises.  My 8877 is about 5500-ohms at 1400w so you need to 
adjust it at working voltage and current.  Input impedance changes 
radically from 100w to 1300w.

So, unless you run high-power tube amps, you probably can get away 
with tuning the antenna on low power.

Situation changes if you are using a sspa instead of tubes.

73, Ed - KL7UW

At 10:16 AM 9/18/2015, ae...@carolinaheli.com wrote:
>Forgive me in advance if this is a stupid question.
>
>Is there any reason you have to tune at full power? It seems to me that
>tuning can be accomplished easily with much lower power. The same thing goes
>for the ATU to the antenna. I don't see why we need more than a few MW at
>most for the ATU to Antenna link.
>
>
>
>Rightly or wrongly when I was in the hobby the first time I ran a TS-850
>into an SB-220 to an MFJ roller tuner connected to an antenna switch
>feeding: 80m inverted V, 30m/40m rotatable dipoles, and a triband beam.
>Whenever I tuned on the inverted V or outer band limits of where my antennas
>where tuned I ended up putting labels on the ATU on cap position and a
>number/clock combo that represented a roller inductor position for each band
>area I cared about. It ended up I rarely had to tune up anything one the air
>because I knew where the antenna tuning was using just the Rig and ATU;
>tuned the APM into a paintcan MFJ load then switch it inline. I was all set
>and never had issues when I needed to kick in the horses.
>
>Now my debate is 500w vs 800w... there's a larger difference between 500w
>and 800w than between 800w and 2.5kw signal wise if I understand
>correctly...
>
>
>Jerry Moore
>AE4PB, K3S - S.N. 010324
>
>
>
>-Original Message-
>From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Edward
>R Cole
>Sent: Friday, September 18, 2015 2:00 PM
>To: Elecraft@mailman.qth.net
>Subject: Re: [Elecraft] Product Suggestion - 500W Dummy Load
>
>Don't have much to say:
>
>Had a Cantenna from Heath in the 60's - knocked over; spilt mineral oil on
>the floor, threw can away!
>
>I have acquired "dry" loads over the years rated into UHF and sometimes to
>mw at flea markets and swaps.  My highest power load is 500w Sierra with
>power meter and switch for 150 or 500w (probably good to 1000-MHz).  Have a
>couple Bird terminations rated 50w.  Most can handled double their rating
>for short duration.
>
>The hardest duty on my loads is when optimizing the output of a new unit
>where I'm keyed up longer than I should.
>
>But I do have a question on how adjusting a tuner into a 50-ohm load saves
>one from transmitting a signal once the tuner is connected to an antenna
>that may not be 50-ohms.  On 600m my inverted-L is Z = 0.8
>+j680.  Tuning into a 50-ohm load does nothing to help match the
>antenna.  The amplifier is solid state with input and output transformers
>(no adjustment).
>
>I think, unless you use a high power tetrode or triode, that no one tunes
>amplifiers anymore.  Solid state amps are broadband and need LP filters to
>keep from amplifying harmonics.  BTW my 2m-8877 is capable of 2000w* RF
>output so pretty hard to find a dummy load to take that.  Fortunately the
>amp does not change much so very little tuning is ever needed (of course I
>am on a small segment of one band about 200-KHz wide).  Of course the answer
>is to tune antenna at lower power and hope the High Power amp will always be
>looking at 50-ohms.
>
>I do not 

Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Wes (N7WS)]

I tested my amp (http://sadxa.org/n7ws.html#amp) with 150' of RG8 into a 
Cantenna (almost) submerged in a bucket of water.  Wasn't CCS but okay for my 
purposes.  Using the loss in coax for an attenuator isn't unheard of.


When I was still in the work force I once had to test some cables with 100 Watts 
applied at elevated temperature (+85C) and VSWR = 3:1 @10GHz.  For a load I used 
about four feet of 0.085" semi-rigid coax (3 dB loss) shorted at the end (6 dB 
return loss) coiled up in a can of water for a load.  An amazing tribute to the 
Hughes TWTA (and its circulator) that ran for over a hundred hours during this test.


Wes  N7WS

On 9/18/2015 11:00 AM, Edward R Cole wrote:
BTW my 2m-8877 is capable of 2000w* RF output so pretty hard to find a dummy 
load to take that.


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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[mfsj]

I can tell you this there is a world of difference between 800w and 2.5k or 
even 1.5k for that matter. I am in 0 land and very hard to break the coasts on 
a good day at times so a little extra helps break those pile ups.
Fred  N0AZZ


Sent via the Samsung Galaxy S6 edge+, an AT 4G LTE smartphone 
Original message From: ae...@carolinaheli.com Date: 09/18/2015  1:16 PM 
 (GMT-06:00) To: 'Edward R Cole' <kl...@acsalaska.net>, 
Elecraft@mailman.qth.net Subject: Re: [Elecraft] Product Suggestion - 500W 
Dummy Load 
Forgive me in advance if this is a stupid question. 

Is there any reason you have to tune at full power? It seems to me that
tuning can be accomplished easily with much lower power. The same thing goes
for the ATU to the antenna. I don't see why we need more than a few MW at
most for the ATU to Antenna link. 



Rightly or wrongly when I was in the hobby the first time I ran a TS-850
into an SB-220 to an MFJ roller tuner connected to an antenna switch
feeding: 80m inverted V, 30m/40m rotatable dipoles, and a triband beam.
Whenever I tuned on the inverted V or outer band limits of where my antennas
where tuned I ended up putting labels on the ATU on cap position and a
number/clock combo that represented a roller inductor position for each band
area I cared about. It ended up I rarely had to tune up anything one the air
because I knew where the antenna tuning was using just the Rig and ATU;
tuned the APM into a paintcan MFJ load then switch it inline. I was all set
and never had issues when I needed to kick in the horses. 

Now my debate is 500w vs 800w... there's a larger difference between 500w
and 800w than between 800w and 2.5kw signal wise if I understand
correctly... 


Jerry Moore
AE4PB, K3S - S.N. 010324



-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Edward
R Cole
Sent: Friday, September 18, 2015 2:00 PM
To: Elecraft@mailman.qth.net
Subject: Re: [Elecraft] Product Suggestion - 500W Dummy Load

Don't have much to say:

Had a Cantenna from Heath in the 60's - knocked over; spilt mineral oil on
the floor, threw can away!

I have acquired "dry" loads over the years rated into UHF and sometimes to
mw at flea markets and swaps.  My highest power load is 500w Sierra with
power meter and switch for 150 or 500w (probably good to 1000-MHz).  Have a
couple Bird terminations rated 50w.  Most can handled double their rating
for short duration.

The hardest duty on my loads is when optimizing the output of a new unit
where I'm keyed up longer than I should.

But I do have a question on how adjusting a tuner into a 50-ohm load saves
one from transmitting a signal once the tuner is connected to an antenna
that may not be 50-ohms.  On 600m my inverted-L is Z = 0.8 
+j680.  Tuning into a 50-ohm load does nothing to help match the
antenna.  The amplifier is solid state with input and output transformers
(no adjustment).

I think, unless you use a high power tetrode or triode, that no one tunes
amplifiers anymore.  Solid state amps are broadband and need LP filters to
keep from amplifying harmonics.  BTW my 2m-8877 is capable of 2000w* RF
output so pretty hard to find a dummy load to take that.  Fortunately the
amp does not change much so very little tuning is ever needed (of course I
am on a small segment of one band about 200-KHz wide).  Of course the answer
is to tune antenna at lower power and hope the High Power amp will always be
looking at 50-ohms.

I do not have a QRO 2m antenna tuner but the antenna SWR < 1.25 so only the
anode tuning needs a light adjustment occasionally (loading has not be
adjusted for 8 years).  My "dummy load" has 19.2 dBd gain and radiates well.

*I operate at 1365w CW which allows for about 9% variance in meter accuracy
to stay legal.

73, Ed - KL7UW
http://www.kl7uw.com
 "Kits made by KL7UW"
Dubus Mag business:
 dubus...@gmail.com

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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[mcduffie]

On Fri, 18 Sep 2015 14:16:43 -0500, Grant Youngman wrote:

> The difference better 800W and 500W is about 2 dB. Barely noticeable. 

Two db is quite noticeable when you are in the noise.

Gary
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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Bob McGraw - K4TAX]

There is no need, in fact it is considered objectionable, to adjust a 
tuner at full power.  It is also very hard on the components. As to an 
amp, the only way I know to adjust one is working it up to full power 
and than reducing drive to the power value you desire to operate.


For manual tuners and amps, a written "tuning chart" really comes in handy.

73
Bob, K4TAX
K3S s/n 10,163

On 9/18/2015 1:16 PM, ae...@carolinaheli.com wrote:

Forgive me in advance if this is a stupid question.

Is there any reason you have to tune at full power? It seems to me that
tuning can be accomplished easily with much lower power. The same thing goes
for the ATU to the antenna. I don't see why we need more than a few MW at
most for the ATU to Antenna link.



Rightly or wrongly when I was in the hobby the first time I ran a TS-850
into an SB-220 to an MFJ roller tuner connected to an antenna switch
feeding: 80m inverted V, 30m/40m rotatable dipoles, and a triband beam.
Whenever I tuned on the inverted V or outer band limits of where my antennas
where tuned I ended up putting labels on the ATU on cap position and a
number/clock combo that represented a roller inductor position for each band
area I cared about. It ended up I rarely had to tune up anything one the air
because I knew where the antenna tuning was using just the Rig and ATU;
tuned the APM into a paintcan MFJ load then switch it inline. I was all set
and never had issues when I needed to kick in the horses.

Now my debate is 500w vs 800w... there's a larger difference between 500w
and 800w than between 800w and 2.5kw signal wise if I understand
correctly...


Jerry Moore
AE4PB, K3S - S.N. 010324



-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Edward
R Cole
Sent: Friday, September 18, 2015 2:00 PM
To: Elecraft@mailman.qth.net
Subject: Re: [Elecraft] Product Suggestion - 500W Dummy Load

Don't have much to say:

Had a Cantenna from Heath in the 60's - knocked over; spilt mineral oil on
the floor, threw can away!

I have acquired "dry" loads over the years rated into UHF and sometimes to
mw at flea markets and swaps.  My highest power load is 500w Sierra with
power meter and switch for 150 or 500w (probably good to 1000-MHz).  Have a
couple Bird terminations rated 50w.  Most can handled double their rating
for short duration.

The hardest duty on my loads is when optimizing the output of a new unit
where I'm keyed up longer than I should.

But I do have a question on how adjusting a tuner into a 50-ohm load saves
one from transmitting a signal once the tuner is connected to an antenna
that may not be 50-ohms.  On 600m my inverted-L is Z = 0.8
+j680.  Tuning into a 50-ohm load does nothing to help match the
antenna.  The amplifier is solid state with input and output transformers
(no adjustment).

I think, unless you use a high power tetrode or triode, that no one tunes
amplifiers anymore.  Solid state amps are broadband and need LP filters to
keep from amplifying harmonics.  BTW my 2m-8877 is capable of 2000w* RF
output so pretty hard to find a dummy load to take that.  Fortunately the
amp does not change much so very little tuning is ever needed (of course I
am on a small segment of one band about 200-KHz wide).  Of course the answer
is to tune antenna at lower power and hope the High Power amp will always be
looking at 50-ohms.

I do not have a QRO 2m antenna tuner but the antenna SWR < 1.25 so only the
anode tuning needs a light adjustment occasionally (loading has not be
adjusted for 8 years).  My "dummy load" has 19.2 dBd gain and radiates well.

*I operate at 1365w CW which allows for about 9% variance in meter accuracy
to stay legal.

73, Ed - KL7UW
http://www.kl7uw.com
  "Kits made by KL7UW"
Dubus Mag business:
  dubus...@gmail.com

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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Tim]

Hi All,
My Cantenna has sat in a bucket since I built it many many years ago.  
No seen it as yet from our house move last month, but have not seem any 
oil stains as yet.  I am sure the boss would have told me!

73
Tim
gm4lm
On 18/09/2015 19:00, Edward R Cole wrote:

Don't have much to say:

Had a Cantenna from Heath in the 60's - knocked over; spilt mineral 
oil on the floor, threw can away!


I have acquired "dry" loads over the years rated into UHF and 
sometimes to mw at flea markets and swaps.  My highest power load is 
500w Sierra with power meter and switch for 150 or 500w (probably good 
to 1000-MHz).  Have a couple Bird terminations rated 50w.  Most can 
handled double their rating for short duration.


The hardest duty on my loads is when optimizing the output of a new 
unit where I'm keyed up longer than I should.


But I do have a question on how adjusting a tuner into a 50-ohm load 
saves one from transmitting a signal once the tuner is connected to an 
antenna that may not be 50-ohms.  On 600m my inverted-L is Z = 0.8 
+j680.  Tuning into a 50-ohm load does nothing to help match the 
antenna.  The amplifier is solid state with input and output 
transformers (no adjustment).


I think, unless you use a high power tetrode or triode, that no one 
tunes amplifiers anymore.  Solid state amps are broadband and need LP 
filters to keep from amplifying harmonics.  BTW my 2m-8877 is capable 
of 2000w* RF output so pretty hard to find a dummy load to take that.  
Fortunately the amp does not change much so very little tuning is ever 
needed (of course I am on a small segment of one band about 200-KHz 
wide).  Of course the answer is to tune antenna at lower power and 
hope the High Power amp will always be looking at 50-ohms.


I do not have a QRO 2m antenna tuner but the antenna SWR < 1.25 so 
only the anode tuning needs a light adjustment occasionally (loading 
has not be adjusted for 8 years).  My "dummy load" has 19.2 dBd gain 
and radiates well.


*I operate at 1365w CW which allows for about 9% variance in meter 
accuracy to stay legal.


73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
dubus...@gmail.com

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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Wes (N7WS)]

Actually, it you are talking about tube amps---typically the ones that need 
tuning---then although it may seem objectionable, tuning into the actual load, 
at the power level you are going to run is the appropriate thing to do.



On 9/18/2015 12:57 PM, Bob McGraw - K4TAX wrote:
There is no need, in fact it is considered objectionable, to adjust a tuner at 
full power.  It is also very hard on the components. As to an amp, the only 
way I know to adjust one is working it up to full power and than reducing 
drive to the power value you desire to operate.


For manual tuners and amps, a written "tuning chart" really comes in handy.

73
Bob, K4TAX
K3S s/n 10,163


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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Edward R Cole]

Don't have much to say:

Had a Cantenna from Heath in the 60's - knocked over; spilt mineral 
oil on the floor, threw can away!


I have acquired "dry" loads over the years rated into UHF and 
sometimes to mw at flea markets and swaps.  My highest power load is 
500w Sierra with power meter and switch for 150 or 500w (probably 
good to 1000-MHz).  Have a couple Bird terminations rated 50w.  Most 
can handled double their rating for short duration.


The hardest duty on my loads is when optimizing the output of a new 
unit where I'm keyed up longer than I should.


But I do have a question on how adjusting a tuner into a 50-ohm load 
saves one from transmitting a signal once the tuner is connected to 
an antenna that may not be 50-ohms.  On 600m my inverted-L is Z = 0.8 
+j680.  Tuning into a 50-ohm load does nothing to help match the 
antenna.  The amplifier is solid state with input and output 
transformers (no adjustment).


I think, unless you use a high power tetrode or triode, that no one 
tunes amplifiers anymore.  Solid state amps are broadband and need LP 
filters to keep from amplifying harmonics.  BTW my 2m-8877 is capable 
of 2000w* RF output so pretty hard to find a dummy load to take 
that.  Fortunately the amp does not change much so very little tuning 
is ever needed (of course I am on a small segment of one band about 
200-KHz wide).  Of course the answer is to tune antenna at lower 
power and hope the High Power amp will always be looking at 50-ohms.


I do not have a QRO 2m antenna tuner but the antenna SWR < 1.25 so 
only the anode tuning needs a light adjustment occasionally (loading 
has not be adjusted for 8 years).  My "dummy load" has 19.2 dBd gain 
and radiates well.


*I operate at 1365w CW which allows for about 9% variance in meter 
accuracy to stay legal.


73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
dubus...@gmail.com

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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Wes (N7WS)]

The power limit for most hams and ham bands is 1.5 KW PEP output. The rules 
don't state where the output is measured.  I assume it's at the antenna since 
the transmission line is part of my transmitter's matching system.  With lossy 
lines, 2.5 KW at the line input doesn't seem unreasonable.


On 9/18/2015 1:10 PM, Bob McGraw - K4TAX wrote:

Who runs 2.5K ?   Uh, isn't that just a wee bit over the legal limit?

73
Bob, K4TAX
K3S s/n 10,163

On 9/18/2015 1:54 PM, mfsj wrote:
I can tell you this there is a world of difference between 800w and 2.5k or 
even 1.5k for that matter. I am in 0 land and very hard to break the coasts 
on a good day at times so a little extra helps break those pile ups.

Fred  N0AZZ


Sent via the Samsung Galaxy S6 edge+, an AT 4G LTE smartphone 
Original message From: ae...@carolinaheli.com Date: 09/18/2015  1:16 
PM  (GMT-06:00) To: 'Edward R Cole' <kl...@acsalaska.net>, 
Elecraft@mailman.qth.net Subject: Re: [Elecraft] Product Suggestion - 500W 
Dummy Load

Forgive me in advance if this is a stupid question.

Is there any reason you have to tune at full power? It seems to me that
tuning can be accomplished easily with much lower power. The same thing goes
for the ATU to the antenna. I don't see why we need more than a few MW at
most for the ATU to Antenna link.



Rightly or wrongly when I was in the hobby the first time I ran a TS-850
into an SB-220 to an MFJ roller tuner connected to an antenna switch
feeding: 80m inverted V, 30m/40m rotatable dipoles, and a triband beam.
Whenever I tuned on the inverted V or outer band limits of where my antennas
where tuned I ended up putting labels on the ATU on cap position and a
number/clock combo that represented a roller inductor position for each band
area I cared about. It ended up I rarely had to tune up anything one the air
because I knew where the antenna tuning was using just the Rig and ATU;
tuned the APM into a paintcan MFJ load then switch it inline. I was all set
and never had issues when I needed to kick in the horses.

Now my debate is 500w vs 800w... there's a larger difference between 500w
and 800w than between 800w and 2.5kw signal wise if I understand
correctly...


Jerry Moore
AE4PB, K3S - S.N. 010324



-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Edward
R Cole
Sent: Friday, September 18, 2015 2:00 PM
To: Elecraft@mailman.qth.net
Subject: Re: [Elecraft] Product Suggestion - 500W Dummy Load

Don't have much to say:

Had a Cantenna from Heath in the 60's - knocked over; spilt mineral oil on
the floor, threw can away!

I have acquired "dry" loads over the years rated into UHF and sometimes to
mw at flea markets and swaps.  My highest power load is 500w Sierra with
power meter and switch for 150 or 500w (probably good to 1000-MHz).  Have a
couple Bird terminations rated 50w.  Most can handled double their rating
for short duration.

The hardest duty on my loads is when optimizing the output of a new unit
where I'm keyed up longer than I should.

But I do have a question on how adjusting a tuner into a 50-ohm load saves
one from transmitting a signal once the tuner is connected to an antenna
that may not be 50-ohms.  On 600m my inverted-L is Z = 0.8
+j680.  Tuning into a 50-ohm load does nothing to help match the
antenna.  The amplifier is solid state with input and output transformers
(no adjustment).

I think, unless you use a high power tetrode or triode, that no one tunes
amplifiers anymore.  Solid state amps are broadband and need LP filters to
keep from amplifying harmonics.  BTW my 2m-8877 is capable of 2000w* RF
output so pretty hard to find a dummy load to take that. Fortunately the
amp does not change much so very little tuning is ever needed (of course I
am on a small segment of one band about 200-KHz wide).  Of course the answer
is to tune antenna at lower power and hope the High Power amp will always be
looking at 50-ohms.

I do not have a QRO 2m antenna tuner but the antenna SWR < 1.25 so only the
anode tuning needs a light adjustment occasionally (loading has not be
adjusted for 8 years).  My "dummy load" has 19.2 dBd gain and radiates well.

*I operate at 1365w CW which allows for about 9% variance in meter accuracy
to stay legal.

73, Ed - KL7UW
http://www.kl7uw.com
  "Kits made by KL7UW"
Dubus Mag business:
  dubus...@gmail.com



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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Grant Youngman]

The difference better 800W and 500W is about 2 dB. Barely noticeable. 

The difference between 2500W and 800W is about 5dB. About an S-unit. 

Grant NQ5T

Sent from my iPhone

> 
> Now my debate is 500w vs 800w... there's a larger difference between 500w
> and 800w than between 800w and 2.5kw signal wise if I understand
> 
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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Bob McGraw - K4TAX]

Who runs 2.5K ?   Uh, isn't that just a wee bit over the legal limit?

73
Bob, K4TAX
K3S s/n 10,163

On 9/18/2015 1:54 PM, mfsj wrote:

I can tell you this there is a world of difference between 800w and 2.5k or 
even 1.5k for that matter. I am in 0 land and very hard to break the coasts on 
a good day at times so a little extra helps break those pile ups.
Fred  N0AZZ


Sent via the Samsung Galaxy S6 edge+, an AT 4G LTE smartphone Original 
message From: ae...@carolinaheli.com Date: 09/18/2015  1:16 PM  (GMT-06:00) To: 
'Edward R Cole' <kl...@acsalaska.net>, Elecraft@mailman.qth.net Subject: Re: 
[Elecraft] Product Suggestion - 500W Dummy Load
Forgive me in advance if this is a stupid question.

Is there any reason you have to tune at full power? It seems to me that
tuning can be accomplished easily with much lower power. The same thing goes
for the ATU to the antenna. I don't see why we need more than a few MW at
most for the ATU to Antenna link.



Rightly or wrongly when I was in the hobby the first time I ran a TS-850
into an SB-220 to an MFJ roller tuner connected to an antenna switch
feeding: 80m inverted V, 30m/40m rotatable dipoles, and a triband beam.
Whenever I tuned on the inverted V or outer band limits of where my antennas
where tuned I ended up putting labels on the ATU on cap position and a
number/clock combo that represented a roller inductor position for each band
area I cared about. It ended up I rarely had to tune up anything one the air
because I knew where the antenna tuning was using just the Rig and ATU;
tuned the APM into a paintcan MFJ load then switch it inline. I was all set
and never had issues when I needed to kick in the horses.

Now my debate is 500w vs 800w... there's a larger difference between 500w
and 800w than between 800w and 2.5kw signal wise if I understand
correctly...


Jerry Moore
AE4PB, K3S - S.N. 010324



-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Edward
R Cole
Sent: Friday, September 18, 2015 2:00 PM
To: Elecraft@mailman.qth.net
Subject: Re: [Elecraft] Product Suggestion - 500W Dummy Load

Don't have much to say:

Had a Cantenna from Heath in the 60's - knocked over; spilt mineral oil on
the floor, threw can away!

I have acquired "dry" loads over the years rated into UHF and sometimes to
mw at flea markets and swaps.  My highest power load is 500w Sierra with
power meter and switch for 150 or 500w (probably good to 1000-MHz).  Have a
couple Bird terminations rated 50w.  Most can handled double their rating
for short duration.

The hardest duty on my loads is when optimizing the output of a new unit
where I'm keyed up longer than I should.

But I do have a question on how adjusting a tuner into a 50-ohm load saves
one from transmitting a signal once the tuner is connected to an antenna
that may not be 50-ohms.  On 600m my inverted-L is Z = 0.8
+j680.  Tuning into a 50-ohm load does nothing to help match the
antenna.  The amplifier is solid state with input and output transformers
(no adjustment).

I think, unless you use a high power tetrode or triode, that no one tunes
amplifiers anymore.  Solid state amps are broadband and need LP filters to
keep from amplifying harmonics.  BTW my 2m-8877 is capable of 2000w* RF
output so pretty hard to find a dummy load to take that.  Fortunately the
amp does not change much so very little tuning is ever needed (of course I
am on a small segment of one band about 200-KHz wide).  Of course the answer
is to tune antenna at lower power and hope the High Power amp will always be
looking at 50-ohms.

I do not have a QRO 2m antenna tuner but the antenna SWR < 1.25 so only the
anode tuning needs a light adjustment occasionally (loading has not be
adjusted for 8 years).  My "dummy load" has 19.2 dBd gain and radiates well.

*I operate at 1365w CW which allows for about 9% variance in meter accuracy
to stay legal.

73, Ed - KL7UW
http://www.kl7uw.com
  "Kits made by KL7UW"
Dubus Mag business:
  dubus...@gmail.com

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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Eric Swartz - WA6HHQ, Elecraft]

End of thread. We've well surpassed the list posting limit per hr on this one..

73,

Eric
Modulator
elecraft.com
_..._

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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Bob McGraw - K4TAX]

Well ...it seems pretty clear.

Part 97.3 states: "(6) PEP (peak envelope power). The average power 
supplied to the antenna transmission line by a transmitter during one RF 
cycle at the crest of the modulation envelope taken under normal 
operating conditions."


Part 97. 313 states "(b) No station may transmit with a transmitter 
power exceeding 1.5 kW PEP" There are specific lower power limits as 
applied to certain bands, i.e. 30M and 60M etc.


73
Bob, K4TAX
K3S s/n 10,163

On 9/18/2015 3:36 PM, Wes (N7WS) wrote:
The power limit for most hams and ham bands is 1.5 KW PEP output. The 
rules don't state where the output is measured.  I assume it's at the 
antenna since the transmission line is part of my transmitter's 
matching system.  With lossy lines, 2.5 KW at the line input doesn't 
seem unreasonable.


On 9/18/2015 1:10 PM, Bob McGraw - K4TAX wrote:

Who runs 2.5K ?   Uh, isn't that just a wee bit over the legal limit?

73
Bob, K4TAX
K3S s/n 10,163

On 9/18/2015 1:54 PM, mfsj wrote:
I can tell you this there is a world of difference between 800w and 
2.5k or even 1.5k for that matter. I am in 0 land and very hard to 
break the coasts on a good day at times so a little extra helps 
break those pile ups.

Fred  N0AZZ


Sent via the Samsung Galaxy S6 edge+, an AT 4G LTE 
smartphone Original message From: 
ae...@carolinaheli.com Date: 09/18/2015  1:16 PM  (GMT-06:00) To: 
'Edward R Cole' <kl...@acsalaska.net>, Elecraft@mailman.qth.net 
Subject: Re: [Elecraft] Product Suggestion - 500W Dummy Load

Forgive me in advance if this is a stupid question.

Is there any reason you have to tune at full power? It seems to me that
tuning can be accomplished easily with much lower power. The same 
thing goes
for the ATU to the antenna. I don't see why we need more than a few 
MW at

most for the ATU to Antenna link.



Rightly or wrongly when I was in the hobby the first time I ran a 
TS-850

into an SB-220 to an MFJ roller tuner connected to an antenna switch
feeding: 80m inverted V, 30m/40m rotatable dipoles, and a triband beam.
Whenever I tuned on the inverted V or outer band limits of where my 
antennas

where tuned I ended up putting labels on the ATU on cap position and a
number/clock combo that represented a roller inductor position for 
each band
area I cared about. It ended up I rarely had to tune up anything one 
the air

because I knew where the antenna tuning was using just the Rig and ATU;
tuned the APM into a paintcan MFJ load then switch it inline. I was 
all set

and never had issues when I needed to kick in the horses.

Now my debate is 500w vs 800w... there's a larger difference between 
500w

and 800w than between 800w and 2.5kw signal wise if I understand
correctly...


Jerry Moore
AE4PB, K3S - S.N. 010324



-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf 
Of Edward

R Cole
Sent: Friday, September 18, 2015 2:00 PM
To: Elecraft@mailman.qth.net
Subject: Re: [Elecraft] Product Suggestion - 500W Dummy Load

Don't have much to say:

Had a Cantenna from Heath in the 60's - knocked over; spilt mineral 
oil on

the floor, threw can away!

I have acquired "dry" loads over the years rated into UHF and 
sometimes to
mw at flea markets and swaps.  My highest power load is 500w Sierra 
with
power meter and switch for 150 or 500w (probably good to 1000-MHz).  
Have a
couple Bird terminations rated 50w.  Most can handled double their 
rating

for short duration.

The hardest duty on my loads is when optimizing the output of a new 
unit

where I'm keyed up longer than I should.

But I do have a question on how adjusting a tuner into a 50-ohm load 
saves
one from transmitting a signal once the tuner is connected to an 
antenna

that may not be 50-ohms.  On 600m my inverted-L is Z = 0.8
+j680.  Tuning into a 50-ohm load does nothing to help match the
antenna.  The amplifier is solid state with input and output 
transformers

(no adjustment).

I think, unless you use a high power tetrode or triode, that no one 
tunes
amplifiers anymore.  Solid state amps are broadband and need LP 
filters to

keep from amplifying harmonics.  BTW my 2m-8877 is capable of 2000w* RF
output so pretty hard to find a dummy load to take that. Fortunately 
the
amp does not change much so very little tuning is ever needed (of 
course I
am on a small segment of one band about 200-KHz wide).  Of course 
the answer
is to tune antenna at lower power and hope the High Power amp will 
always be

looking at 50-ohms.

I do not have a QRO 2m antenna tuner but the antenna SWR < 1.25 so 
only the

anode tuning needs a light adjustment occasionally (loading has not be
adjusted for 8 years).  My "dummy load" has 19.2 dBd gain and 
radiates well.


*I operate at 1365w CW which allows for about 9% variance in meter 
accuracy

to stay legal.

73, Ed - KL7UW
http://www.kl7uw.com
  "Kits made 

Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Jim Brown]

On Fri,9/18/2015 1:42 PM, Wes (N7WS) wrote:
Actually, it you are talking about tube amps---typically the ones that 
need tuning---then although it may seem objectionable, tuning into the 
actual load, at the power level you are going to run is the 
appropriate thing to do. 


Absolutely. The dynamic impedance of the tube varies with power level. 
Tube amps should ALWAYS be tuned at full power AND with the actual load 
attached. K6XX has observed that the distortion rises when the load is 
not matched to the amplifier. To do that without overstressing the tube, 
I always tune with dits.


I never tune with a dummy load except when testing a radio or amp. 
Instead, I have created a "cheat sheet" of amplifier tuning settings for 
every band and every antenna, so that when I start tuning, I'm close. I 
always find a clear frequency, send my dits, and get out of the way 
fast. :)


73, Jim K9YC
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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Edward R Cole]

Jerry,

Certainly its appropriate to tune your antenna tuner at low power.  I 
have an "ancient" Drake MN-2000 which is rated for 2000w PEP but I 
can tune it with 10w from my K3/10 with my linear off.  Then I turn 
on my station control panel which enables PTT to the amp.  Lately 
been using my AN-762 140w amp from CCI which I drive to about 120w with 5.6w.

http://www.communication-concepts.com/140-watt/

I set the tuner on the 200w range to measure fwd and ref 
power.  Sometimes I will touch up the tuner with the amp online as 
the amp and K3 are separated by 8-foot of coax and that appears to 
affect tuning (a little).  But that only takes a couple seconds.


Marking down cap settings for favorite frequencies is a good idea.

But tuning a high-power tube amp at greatly lowered output does not 
work.  Because the internal impedance of the tube shifts as anode 
current rises.  My 8877 is about 5500-ohms at 1400w so you need to 
adjust it at working voltage and current.  Input impedance changes 
radically from 100w to 1300w.


So, unless you run high-power tube amps, you probably can get away 
with tuning the antenna on low power.


Situation changes if you are using a sspa instead of tubes.

73, Ed - KL7UW

At 10:16 AM 9/18/2015, ae...@carolinaheli.com wrote:

Forgive me in advance if this is a stupid question.

Is there any reason you have to tune at full power? It seems to me that
tuning can be accomplished easily with much lower power. The same thing goes
for the ATU to the antenna. I don't see why we need more than a few MW at
most for the ATU to Antenna link.



Rightly or wrongly when I was in the hobby the first time I ran a TS-850
into an SB-220 to an MFJ roller tuner connected to an antenna switch
feeding: 80m inverted V, 30m/40m rotatable dipoles, and a triband beam.
Whenever I tuned on the inverted V or outer band limits of where my antennas
where tuned I ended up putting labels on the ATU on cap position and a
number/clock combo that represented a roller inductor position for each band
area I cared about. It ended up I rarely had to tune up anything one the air
because I knew where the antenna tuning was using just the Rig and ATU;
tuned the APM into a paintcan MFJ load then switch it inline. I was all set
and never had issues when I needed to kick in the horses.

Now my debate is 500w vs 800w... there's a larger difference between 500w
and 800w than between 800w and 2.5kw signal wise if I understand
correctly...


Jerry Moore
AE4PB, K3S - S.N. 010324



-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Edward
R Cole
Sent: Friday, September 18, 2015 2:00 PM
To: Elecraft@mailman.qth.net
Subject: Re: [Elecraft] Product Suggestion - 500W Dummy Load

Don't have much to say:

Had a Cantenna from Heath in the 60's - knocked over; spilt mineral oil on
the floor, threw can away!

I have acquired "dry" loads over the years rated into UHF and sometimes to
mw at flea markets and swaps.  My highest power load is 500w Sierra with
power meter and switch for 150 or 500w (probably good to 1000-MHz).  Have a
couple Bird terminations rated 50w.  Most can handled double their rating
for short duration.

The hardest duty on my loads is when optimizing the output of a new unit
where I'm keyed up longer than I should.

But I do have a question on how adjusting a tuner into a 50-ohm load saves
one from transmitting a signal once the tuner is connected to an antenna
that may not be 50-ohms.  On 600m my inverted-L is Z = 0.8
+j680.  Tuning into a 50-ohm load does nothing to help match the
antenna.  The amplifier is solid state with input and output transformers
(no adjustment).

I think, unless you use a high power tetrode or triode, that no one tunes
amplifiers anymore.  Solid state amps are broadband and need LP filters to
keep from amplifying harmonics.  BTW my 2m-8877 is capable of 2000w* RF
output so pretty hard to find a dummy load to take that.  Fortunately the
amp does not change much so very little tuning is ever needed (of course I
am on a small segment of one band about 200-KHz wide).  Of course the answer
is to tune antenna at lower power and hope the High Power amp will always be
looking at 50-ohms.

I do not have a QRO 2m antenna tuner but the antenna SWR < 1.25 so only the
anode tuning needs a light adjustment occasionally (loading has not be
adjusted for 8 years).  My "dummy load" has 19.2 dBd gain and radiates well.

*I operate at 1365w CW which allows for about 9% variance in meter accuracy
to stay legal.

73, Ed - KL7UW
http://www.kl7uw.com
 "Kits made by KL7UW"
Dubus Mag business:
 dubus...@gmail.com

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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Don Wilhelm]

While a dummy load that has a power rating greater than your maximum 
transmit power is a worthwhile addition to any hamshack - at higher 
power levels, I do not see them being used as precision measurement 
devices, but only as a temporary load for the purposes of "tuning up" or 
operating into a dummy load for test purposes.


While the "Tune Up" situation has been largely eliminated for "No Tune" 
amplifiers, there is still the question of how to do a TUNE into an 
antenna when you have a tuner such as the KAT500 in line - but that 
tunes into the antenna at reduced power with the Elecraft K-line, and 
the tune cycle is relatively short.


The net that I see of all that is one does not need a precision dummy 
load for high power levels.
At the 100 watt level, I do find a need for precision dummy loads which 
can be used for lab measurement devices, bu at higher power levels in 
the normal hamshack, I do not understand a need for a precise 50 ohm 
non-inductive load (as long as you do not stray too far from that 50 ohm 
point.


In other words, the gallon size "cantenna" dummy loads should suffice 
for most purposes in the ham shack that I can conceive of - primarily 
providing a suitable load for a high power transmitter for routine test 
purposes.


Those who do precision measurements at high power levels will have to 
invest in precision dummy loads, but for typical ham use, I don't think 
that level of precision is necessary.  Such precision comes at a cost.


73,
Don W3FPR

On 9/17/2015 8:19 PM, Byron Peebles wrote:

I'd love to find Elecraft offering a 500W dummy load to match the K-Line.
No one even makes a sturdy paint can anymore.

73, Byron
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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[GRANT YOUNGMAN]

> On 9/17/2015 8:19 PM, Byron Peebles wrote:
>> I'd love to find Elecraft offering a 500W dummy load to match the K-Line.
>> No one even makes a sturdy paint can anymore.
>> 

Actually, Ameritron still makes a “Cantenna" style dummy load.  I’ve had the 
same one sitting under my desk for 20+ years. 

Grant NQ5T

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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Matthew Cook]

http://www.ebay.com.au/itm/DUMMY-LOAD-RESISTOR-HYBRID-TERMINATION-800W-50OHM-DC-1GHZ-17-0376-DICONEX-/191284146241?hash=item2c896c7041

Heatsink, length of coax and a plug... finished !

73

Matthew
VK5ZM

On 18 September 2015 at 09:49, Byron Peebles  wrote:

> I'd love to find Elecraft offering a 500W dummy load to match the K-Line.
> No one even makes a sturdy paint can anymore.
>
> 73, Byron
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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Bob McGraw - K4TAX]

Don, et al:

I do agree that we typically do not need a precision load nor do we 
likely need a "full legal limit CCS" load.   Most loads have a power vs. 
time de-rating curve.  Just following that practice will save on lots of 
$$ and space.


Yes the Cantenna loads are generally suitable.  I find the Z to be 50 
ohms +/- 10% or so.  They will handle legal limit power for 2 or3 
minutes and 100 to 300 watt power for almost CCS times.  As a rule, they 
are good for HF and become a bit less so suitable for VHF.


I prefer dry loads as they are less "messy" where one uses an oil filled 
load it seems they all want to weep a bit.  Oh my gosh should on kick 
one over and the lid separate.  As a suggestion, solder the lid in place 
at 3 or 4 locations around the edge.


It would do well for folks to consider switching and tuning methods so 
as not to put a signal on the air.  Although this typically can't be 
done with automatic type tuners,  with manual tuners, using an antenna 
bridge will allow one to adjust the tuner for a proper match and not put 
a signal on the air.Then with older amps, tuning those into a dummy 
load again will not put a signal on the air. When the amp is switched to 
the tuner then all is well and no QRM has been generated.


73 Bob, K4TAX

K3S s/n 10,163


On 9/17/2015 8:37 PM, Don Wilhelm wrote:
While a dummy load that has a power rating greater than your maximum 
transmit power is a worthwhile addition to any hamshack - at higher 
power levels, I do not see them being used as precision measurement 
devices, but only as a temporary load for the purposes of "tuning up" 
or operating into a dummy load for test purposes.


While the "Tune Up" situation has been largely eliminated for "No 
Tune" amplifiers, there is still the question of how to do a TUNE into 
an antenna when you have a tuner such as the KAT500 in line - but that 
tunes into the antenna at reduced power with the Elecraft K-line, and 
the tune cycle is relatively short.


The net that I see of all that is one does not need a precision dummy 
load for high power levels.
At the 100 watt level, I do find a need for precision dummy loads 
which can be used for lab measurement devices, bu at higher power 
levels in the normal hamshack, I do not understand a need for a 
precise 50 ohm non-inductive load (as long as you do not stray too far 
from that 50 ohm point.


In other words, the gallon size "cantenna" dummy loads should suffice 
for most purposes in the ham shack that I can conceive of - primarily 
providing a suitable load for a high power transmitter for routine 
test purposes.


Those who do precision measurements at high power levels will have to 
invest in precision dummy loads, but for typical ham use, I don't 
think that level of precision is necessary.  Such precision comes at a 
cost.


73,
Don W3FPR

On 9/17/2015 8:19 PM, Byron Peebles wrote:
I'd love to find Elecraft offering a 500W dummy load to match the 
K-Line.

No one even makes a sturdy paint can anymore.

73, Byron
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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Bob McGraw - K4TAX]

Don't forget to add a BIG heat sink to the materials list along with 
some thermal compound.


73
Bob, K4TAX
K3S s/n 10,163

On 9/17/2015 9:15 PM, Matthew Cook wrote:

http://www.ebay.com.au/itm/DUMMY-LOAD-RESISTOR-HYBRID-TERMINATION-800W-50OHM-DC-1GHZ-17-0376-DICONEX-/191284146241?hash=item2c896c7041

Heatsink, length of coax and a plug... finished !

73

Matthew
VK5ZM

On 18 September 2015 at 09:49, Byron Peebles  wrote:


I'd love to find Elecraft offering a 500W dummy load to match the K-Line.
No one even makes a sturdy paint can anymore.

73, Byron
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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Fred Jensen]

Strangely, these non-inductive resistors do not last forever.  When I 
came home from SE Asia to Houston in 67, I filled my Heath  with mineral 
oil [interesting story on a Sunday], and it measured 51 ohms DC.  Today, 
it measures 74 ohms DC.


73,

Fred K6DGW
- Northern California Contest Club
- CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
- www.cqp.org


On 9/17/2015 7:12 PM, GRANT YOUNGMAN wrote:



On 9/17/2015 8:19 PM, Byron Peebles wrote:

I'd love to find Elecraft offering a 500W dummy load to match the K-Line.
No one even makes a sturdy paint can anymore.



Actually, Ameritron still makes a “Cantenna" style dummy load.  I’ve had the 
same one sitting under my desk for 20+ years.

Grant NQ5T


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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Cliff Frescura]

Maybe the dummy load could be an option for the speaker /s

73,

Cliff K3LL

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Fred 
Jensen
Sent: Thursday, September 17, 2015 7:36 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Product Suggestion - 500W Dummy Load

Strangely, these non-inductive resistors do not last forever.  When I came home 
from SE Asia to Houston in 67, I filled my Heath  with mineral oil [interesting 
story on a Sunday], and it measured 51 ohms DC.  Today, it measures 74 ohms DC.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
- www.cqp.org


On 9/17/2015 7:12 PM, GRANT YOUNGMAN wrote:
>
>> On 9/17/2015 8:19 PM, Byron Peebles wrote:
>>> I'd love to find Elecraft offering a 500W dummy load to match the K-Line.
>>> No one even makes a sturdy paint can anymore.
>>>
>
> Actually, Ameritron still makes a “Cantenna" style dummy load.  I’ve had the 
> same one sitting under my desk for 20+ years.
>
> Grant NQ5T

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[Elecraft] Product Suggestion - 500W Dummy Load

[Byron Peebles]

I'd love to find Elecraft offering a 500W dummy load to match the K-Line.
No one even makes a sturdy paint can anymore.

73, Byron
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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Bob McGraw - K4TAX]

Here you can find some nice 500 watt CCS Bird loads for $250 or so.

http://www.nm3e.com/loadSampler.htm#LoadSampler

Otherwise, it is Ameritron and MFJ  that have the gallon bucket loads 
with oil for under $100.


73
Bob, K4TAX
K3S s/n 10,163

On 9/17/2015 7:19 PM, Byron Peebles wrote:

I'd love to find Elecraft offering a 500W dummy load to match the K-Line.
No one even makes a sturdy paint can anymore.

73, Byron
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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Don Wilhelm]

My "gallon size" dummy load is not a Heath, but that was inspiration for 
mine.  I came across a bunch of 620 ohm 20 watt carbon resistors a long 
time ago.
I wired 12 of them in parallel and put them into a gallon can of mineral 
oil.  That dummy load still measures 51 ohms over the bands from 80 thru 
10 meters with a minimal amount of inductance - and it is over 40 years 
after I first built it.


I figure since it will do 240 watts in open air, in the oil, it should 
take the legal limit for relatively short periods, but I have not 
subjected it to more than 500 watts.


Yes, I have heard stories about how the Heath resistors changed value, 
but my 'substitute' has not changed over the years.


73,
Don W3FPR

On 9/17/2015 10:36 PM, Fred Jensen wrote:
Strangely, these non-inductive resistors do not last forever.  When I 
came home from SE Asia to Houston in 67, I filled my Heath  with 
mineral oil [interesting story on a Sunday], and it measured 51 ohms 
DC.  Today, it measures 74 ohms DC.




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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Walter Underwood]

Some non-inductive resistors do not have the coating that protects from the 
oil. Those will rise in resistance over time. 

This article has more than you ever wanted to know about the Cantenna and 
modern equivalents.

http://www.orcadxcc.org/content/cantenna_va7jw.pdf 


wunder
K6WRU
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Sep 17, 2015, at 8:15 PM, Don Wilhelm  wrote:
> 
> My "gallon size" dummy load is not a Heath, but that was inspiration for 
> mine.  I came across a bunch of 620 ohm 20 watt carbon resistors a long time 
> ago.
> I wired 12 of them in parallel and put them into a gallon can of mineral oil. 
>  That dummy load still measures 51 ohms over the bands from 80 thru 10 meters 
> with a minimal amount of inductance - and it is over 40 years after I first 
> built it.
> 
> I figure since it will do 240 watts in open air, in the oil, it should take 
> the legal limit for relatively short periods, but I have not subjected it to 
> more than 500 watts.
> 
> Yes, I have heard stories about how the Heath resistors changed value, but my 
> 'substitute' has not changed over the years.
> 
> 73,
> Don W3FPR
> 
> On 9/17/2015 10:36 PM, Fred Jensen wrote:
>> Strangely, these non-inductive resistors do not last forever.  When I came 
>> home from SE Asia to Houston in 67, I filled my Heath  with mineral oil 
>> [interesting story on a Sunday], and it measured 51 ohms DC.  Today, it 
>> measures 74 ohms DC.
>> 
> 
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Re: [Elecraft] Product Suggestion - 500W Dummy Load

[Jim Brown]

On Thu,9/17/2015 6:37 PM, Don Wilhelm wrote:
While a dummy load that has a power rating greater than your maximum 
transmit power is a worthwhile addition to any hamshack - at higher 
power levels, I do not see them being used as precision measurement 
devices, but only as a temporary load for the purposes of "tuning up" 
or operating into a dummy load for test purposes. 


Remember also that dummy load ratings include a duty cycle. The cheap 
stuff has a very short duty cycle -- one might be rated 100W for 1 
minute. :) It's all about heat -- do you get hot enough to damage it?


Duty cycle can be interpreted two ways. One is to use a series of dits 
to tune up, which gets you to full power but half the time. That's what 
I do. I just sold a nice little keyer-pulser that W2VJN used to make. 
Its duty cycle could be adjusted as low as 20%.


Another way to interpret it is how LONG you transmit into it. My big 
professional oil filled dummy load is rated 500W for a long time (don't 
remember the spec). I transmit dits (and even RTTY) into it at legal 
limit for a minute or so, and it doesn't overheat. And then I let it 
cool off.


73, Jim K9YC




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