Elecraft

Product Suggestion - 500W Dummy Load

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Wes (N7WS)

Re: Product Suggestion - 500W Dummy Load

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&T 4G LTE smartphone--------
>> Original message --------From: [hidden email] Date: 09/18/2015 1:16
>> PM (GMT-06:00) To: 'Edward R Cole' <[hidden email]>,
>> [hidden email] 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:[hidden email]] On Behalf Of Edward
>> R Cole
>> Sent: Friday, September 18, 2015 2:00 PM
>> To: [hidden email]
>> 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:
>> [hidden email]
>>

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Wes (N7WS)

Re: Product Suggestion - 500W Dummy Load

In reply to this post by Bob McGraw - K4TAX

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

Bob McGraw - K4TAX

Re: Product Suggestion - 500W Dummy Load

In reply to this post by Wes (N7WS)

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&T 4G LTE
>>> smartphone-------- Original message --------From:
>>> [hidden email] Date: 09/18/2015 1:16 PM (GMT-06:00) To:
>>> 'Edward R Cole' <[hidden email]>, [hidden email]
>>> 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:[hidden email]] On Behalf
>>> Of Edward
>>> R Cole
>>> Sent: Friday, September 18, 2015 2:00 PM
>>> To: [hidden email]
>>> 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:
>>> [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]
>
>
>

Jim Brown-10

Re: Product Suggestion - 500W Dummy Load

In reply to this post by Wes (N7WS)

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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Edward R Cole

Re: Product Suggestion - 500W Dummy Load

In reply to this post by ae4pb

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, [hidden email] 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:[hidden email]] On Behalf Of Edward
>R Cole
>Sent: Friday, September 18, 2015 2:00 PM
>To: [hidden email]
>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:
> [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]

Fred Smith-2

Re: Product Suggestion - 500W Dummy Load

In reply to this post by Byron Peebles

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&T 4G LTE smartphone-------- Original message --------From: Edward R Cole <[hidden email]> Date: 09/18/2015 6:14 PM (GMT-06:00) To: [hidden email], [hidden email] 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, [hidden email] wrote:

73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[hidden email]

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Eric Swartz - WA6HHQ

Re: Product Suggestion - 500W Dummy Load

Administrator

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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