Re: [AMRadio] Frequency Response

[Donald Chester]

By 'tilt' I mean the observable tilting of the top and bottom of a
square wave (or resulting modulated envelope) caused by low frequency
roll off and non constant group delay through the transmitter in
question.


That's why the transmitter frequency response, including transformers, 
should be essentially flat at least one octave above and one octave below 
the actual range of frequencies you plan to transmit.


For example, if you intended to limit your audio response to 150-4000~, the 
audio chain should test flat from 75 to 8000~.


Don k4kyv

Re: [AMRadio] WTB SB-220

[Jim Candela]

Hmmm, the boys on 3878 are running 1500 watts pep plus
on USB, and there is  a 100 watt AM'er calling CQ on
3880. How much of an antenna would the AM'er need to
overcome the S/N ratio? I think Astabula Bill, W8VYZ
says it all:
 
http://www.amwindow.org/audio/mov/w8vyz.mov
 
Ever hear Bill running 100 watts? When Bill and Less
K6HQI (sk) were regulars on 14286 they had to run
heavy iron to hold the frequency. A 100 watt rig was
seldom heard whereas a 500 watt rig (that 6db again)
was often armchair copy, and sometimes often drive the
QRM away.

Regards,
Jim

RJ Mattson <[EMAIL PROTECTED]> wrote:
If you can't get out consistantly with a Viking II,
you need an antenna -
not an amp.
bob...w2ami
www.qrz.com/callsign/w2ami


- Original Message - 
From: "Gary Blau" 
To: "Discussion of AM Radio" 
Sent: Sunday, September 26, 2004 9:22 PM
Subject: Re: [AMRadio] WTB SB-220


> I've always found more RF power, at least in
significant iterations of
> ~100watts, can make a big difference on the air in
cutting thru noise
> and band conditions. But what's more important is
full modulation.
>
> One potential benefit of running a -modified- Viking
or Ranger, etc.
> into an amp like the SB220 is you can then
concentrate on improving the
> modulation performance of the exciter xmtr. This can
in turn deliver a
> more effectively modulated signal thru the entire
system and thereby on
> the air.
> Add that to the increased power ability of running a
fully modulated
> ~400 watts carrier, and a case can be made that this
is one of the
> easiest ways to get a big AM signal on the air.
> The easiest is to use a rice box for an exciter, but
that's another fist
> fight.
>
> The Viking would have to be modified a good bit to
optimize this
> approach. The first problem being reducing the RF
output to the 10-25
> watt level that the SB220 will want to see. I've
never had a VikingII,
> so I can't say for sure, but my first thought is to
try a variable PA
> screen voltage scheme. (I did this to good effect in
my Ranger.) You'd
> probably have to remove one of the 6146's in the
Viking, and make other
> changes as well, but the idea is that not only will
you be able to vary
> the drive to the amp, but it will also give the huge
benefit of much
> higher positive peak modulation capability. Positive
peaks can easily
> go way beyond 100% as the PA now is operating well
below its peak
> dissipation point. Even if you're not a believer in
hugely asymmetrical
> 'supermodulation', having an xmtr that can easily
handle it will still
> be a big improvement over the 'stock' Viking.
>
> Loudness is where it's at to get thru on a noisy
band, but having an
> extra 100-200watts as well makes a potent combo.
>
> g
>
>
> [EMAIL PROTECTED] wrote:
> >
> > << I am looking for a Heathkit SB-220 to run about
300 watts on AM using
the
> > Viking II to drive it. >>
> >
> > Hi,
> >
> > If you are getting the full output from the V II
into a good well
matched
> > antenna, a couple of hundred more watts is not
going to make any
significant
> > difference on the receive end and will only serve
to heat up the shack
and run up
> > your power bill.
> >
> > 73,
> >
> > John, W4AWM
>
>
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http://mailman.qth.net/mailman/listinfo/amradio
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Re: [AMRadio] WTB SB-220

[Gary Blau]

No argument there.

g

RJ Mattson wrote:
> 
> If you can't get out consistantly with a Viking II, you need an antenna -
> not an amp.
> bob...w2ami

Re: [AMRadio] Frequency Response

[Gary Blau]

By 'tilt' I mean the observable tilting of the top and bottom of a
square wave (or resulting modulated envelope) caused by low frequency
roll off and non constant group delay through the transmitter in
question.
Ideally what you want is waveform fidelity, what goes in should come
out.
The closer you can get to this ideal the better.
Square wave tests are very useful as they will tell you a lot of info in
one picture, and many hams have function generators available, (and if
you operate AM you should already have a scope).   

This tilt will increase the peak voltage of the incoming waveform.  This
in turn will force you to reduce your average modulation level to keep
the increased peak level from overmodulating the transmitter.
The same result happens from any ringing or overshoot the system may
have.

Where this becomes a significant issue is if you try to drive this poor
performing xmtr with waveforms that have flattop components, typically
produced by audio clipping.  You end up fighting yourself as you just
increased your average level with the clipping, but are then forced to
turn it down again to some extent by the inability of the xmtr to pass
the waveshape.  Since some degree of peak control is necessary to
prevent negative overmodulation (and the resulting splatter and
unneighborly excessive occupied bandwidth), this all conspires against
you to produce a less than fully modulated signal.  There are some low
level audio gimmicks that can be applied to partially compensate for
this, but it's always best to go after the root cause and improve that
first.  

Granted this is only ham radio and it's not a big deal if everything
isn't optimized.  But it's interesting to look at all this and try to
improve things, and it gives us something else to talk about on the air
other than politics!  

I'm looking for some helpful pictures for you but haven't located any at
hand.  
FWIW, you might look at Fig. 2-9 on page 2-22, and Fig. 2-10 on page
2-24 of the operating manual for the Orban AM Optimod 9100B, which is on
their FTP site here:

ftp://ftp.orban.com/9100B/9100B_Manual_Section_2.pdf

That may help make it more clear.

g


Byron Lichtenwalner wrote:
> 
> Gary
> I have read several of your writings that refers to "tilt".  What is it, or
> where can I go to learn more about it?
> Byron W3WKR

Re: [AMRadio] WTB SB-220

[RJ Mattson]

If you can't get out consistantly with a Viking II, you need an antenna -
not an amp.
bob...w2ami
www.qrz.com/callsign/w2ami


- Original Message - 
From: "Gary Blau" <[EMAIL PROTECTED]>
To: "Discussion of AM Radio" 
Sent: Sunday, September 26, 2004 9:22 PM
Subject: Re: [AMRadio] WTB SB-220


> I've always found more RF power, at least in significant iterations of
> ~100watts, can make a big difference on the air in cutting thru noise
> and band conditions.  But what's more important is full modulation.
>
> One potential benefit of running a -modified- Viking or Ranger, etc.
> into an amp like the SB220 is you can then concentrate on improving the
> modulation performance of the exciter xmtr.  This can in turn deliver a
> more effectively modulated signal thru the entire system and thereby on
> the air.
> Add that to the increased power ability of running a fully modulated
> ~400 watts carrier, and a case can be made that this is one of the
> easiest ways to get a big AM signal on the air.
> The easiest is to use a rice box for an exciter, but that's another fist
> fight.
>
> The Viking would have to be modified a good bit to optimize this
> approach.  The first problem being reducing the RF output to the 10-25
> watt level that the SB220 will want to see.  I've never had a VikingII,
> so I can't say for sure, but my first thought is to try a variable PA
> screen voltage scheme.  (I did this to good effect in my Ranger.)  You'd
> probably have to remove one of the 6146's in the Viking, and make other
> changes as well, but the idea is that not only will you be able to vary
> the drive to the amp, but it will also give the huge benefit of much
> higher positive peak modulation capability.  Positive peaks can easily
> go way beyond 100% as the PA now is operating well below its peak
> dissipation point.  Even if you're not a believer in hugely asymmetrical
> 'supermodulation', having an xmtr that can easily handle it will still
> be a big improvement over the 'stock' Viking.
>
> Loudness is where it's at to get thru on a noisy band, but having an
> extra 100-200watts as well makes a potent combo.
>
> g
>
>
> [EMAIL PROTECTED] wrote:
> >
> > << I am looking for a Heathkit SB-220 to run about 300 watts on AM using
the
> > Viking II to drive it. >>
> >
> > Hi,
> >
> > If you are getting the full output from the V II into a good well
matched
> > antenna, a couple of hundred more watts is not going to make any
significant
> > difference on the receive end and will only serve to heat up the shack
and run up
> > your power bill.
> >
> > 73,
> >
> > John,  W4AWM
>
> __
> AMRadio mailing list
> Home: http://mailman.qth.net/mailman/listinfo/amradio
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:AMRadio@mailman.qth.net
>

Re: [AMRadio] WTB SB-220

[Gary Blau]

I've always found more RF power, at least in significant iterations of
~100watts, can make a big difference on the air in cutting thru noise
and band conditions.  But what's more important is full modulation.

One potential benefit of running a -modified- Viking or Ranger, etc.
into an amp like the SB220 is you can then concentrate on improving the
modulation performance of the exciter xmtr.  This can in turn deliver a
more effectively modulated signal thru the entire system and thereby on
the air.  
Add that to the increased power ability of running a fully modulated
~400 watts carrier, and a case can be made that this is one of the
easiest ways to get a big AM signal on the air.  
The easiest is to use a rice box for an exciter, but that's another fist
fight.

The Viking would have to be modified a good bit to optimize this
approach.  The first problem being reducing the RF output to the 10-25
watt level that the SB220 will want to see.  I've never had a VikingII,
so I can't say for sure, but my first thought is to try a variable PA
screen voltage scheme.  (I did this to good effect in my Ranger.)  You'd
probably have to remove one of the 6146's in the Viking, and make other
changes as well, but the idea is that not only will you be able to vary
the drive to the amp, but it will also give the huge benefit of much
higher positive peak modulation capability.  Positive peaks can easily
go way beyond 100% as the PA now is operating well below its peak
dissipation point.  Even if you're not a believer in hugely asymmetrical
'supermodulation', having an xmtr that can easily handle it will still
be a big improvement over the 'stock' Viking.  

Loudness is where it's at to get thru on a noisy band, but having an
extra 100-200watts as well makes a potent combo.

g


[EMAIL PROTECTED] wrote:
> 
> << I am looking for a Heathkit SB-220 to run about 300 watts on AM using the
> Viking II to drive it. >>
> 
> Hi,
> 
> If you are getting the full output from the V II into a good well matched
> antenna, a couple of hundred more watts is not going to make any significant
> difference on the receive end and will only serve to heat up the shack and 
> run up
> your power bill.
> 
> 73,
> 
> John,  W4AWM

Re: [AMRadio] WTB SB-220

[Jim Candela]

Bob,  
 
It seems that the plate modulator type hams look down at those running AM 
Linears! It would be interesting to run the numbers to look at heat radiated 
into the hamshack for say a globe king 500 pumping out  350 watts carrier, and 
a SB-220 putting out the same, and driven from something like a Heath DX-60 
with the carrier control removed. We all know both would heat the shack 
considerably. How much more though from one over the other?? I'm talking about 
total heat dissipated including filament power, bleeder resistors, plate 
dissipation, etc.
 
Now for that 6 DB that is not detectable. When listening to a signal under 
marginal conditions at the threshold of being copyable, that extra S unit or 
about 6 DB is huge.
I'd say let Cory run his amplifier, and maybe chip in a suggestion or two on 
how to maximize the linearity, and stability of the setup. For example a audio 
feedback loop from the SB-220 RF out (add a detector circuit) to the modulator 
audio chain to straighten out the trapezoidal pattern as seen on a scope. The 
linear won't be perfectly linear, so this technique if done well can really 
help clean up the signal and reduce bandwidth by reducing the distortion 
products.
 
   BTW on my QRO 20A project I am doing just that to linearize the single EL-34 
output tube which runs AM linear AB1 mode to provide 10 watts RF carrier 
output. A 6DB reduction in audio gain from the feedback has a considerable 
effect on the modulated envelope (matches the low level waveform much closer) 
and increases the maximum PEP power some for a given amount of gain compression.
 
Regards,
Jim
WD5JKO

RJ Mattson <[EMAIL PROTECTED]> wrote:
If your Viking II runs 100 watts, 400 watts will give you about 1 s-unit
gain. Not even detectable unless you look at the meter.
Could be helpful during the winter months as a supplemental room heater.

bob...w2ami

- Original Message - 
From: "Cory Hine" 
To: 
Sent: Sunday, September 26, 2004 2:13 PM
Subject: [AMRadio] WTB SB-220


> Hey gang,
>
> I am looking for a Heathkit SB-220 to run about 300 watts on AM using the
Viking II to drive it. Does anyone have a decent amp that they want to sell?
I would like pics if possible.
>
> Thanks,
>
> Cory/AD5QP


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Re: [AMRadio] WTB SB-220

[RJ Mattson]

If your Viking II runs 100 watts, 400 watts will give you about 1 s-unit
gain. Not even detectable unless you look at the meter.
Could be helpful during the winter months as a supplemental room heater.

bob...w2ami

- Original Message - 
From: "Cory Hine" <[EMAIL PROTECTED]>
To: 
Sent: Sunday, September 26, 2004 2:13 PM
Subject: [AMRadio] WTB SB-220


> Hey gang,
>
> I am looking for a Heathkit SB-220 to run about 300 watts on AM using the
Viking II to drive it. Does anyone have a decent amp that they want to sell?
I would like pics if possible.
>
> Thanks,
>
> Cory/AD5QP

Re: [AMRadio] Frequency Response

[Edward B Richards]

Hi Don;

Thanks for your input. A discussion of bandwidth is meaningless unless
you tie it to how far down from peak voltage. The standard is 1/2 voltage
or -6 dB down. However, as I remember, the 9 kc the FCC is talking about
is further down. -26 dB if I remember right. We cannot compare apples to
oranges. That may be 6 kc at -6 dB. The Canadian regulation is probably
at the standard -6 db. So they may be the same. I think the implication
is 6 kc @ -6 db and I am going to comply with that.

73, Ed Richards K6UUZ


On Sun, 26 Sep 2004 18:02:32 + "Donald Chester" <[EMAIL PROTECTED]>
writes:
> 
> >What about bandwidth? +/- 5kc would be a 10 kc band width. I 
> thought we
> >were supposed to limit our band width to 6kc. Please correct me if 
> I am
> >wrong.
> >
> 
> That is a popular urban myth.  There is NOTHING in the US 
> regulations that 
> specifically limits bandwidth.  The regulations specify "good 
> engineering 
> and amateur practice", and deliberately leaves the specific 
> bandwidth  
> vague.  In Canada, there is a rule on the books limiting bandwidth 
> to 6 kHz, 
> but I have never heard of them enforcing it against AM signals that 
> may 
> exceed that figure.  Besides, accurate measurement of bandwidth 
> would 
> require a visit to the station with test instruments.  Over-the-air 
> measurement leaves too many possibilities for error due to 
> propagation, QRM, 
> QSB, etc.
> 
> The US regulations  could be interpreted to mean a reasonable 
> bandwidth for 
> the mode being used, considering band occupancy .  If you had a cw 
> signal 
> with so much noise, hum or FM on the carrier that it was 3 kHz wide, 
> the FCC 
> probably could interpret that as a violation of good engineering 
> practice.  
> If the band is empty, as for example, 10 m. most of the time 
> nowadays, or 
> 160m in the middle of the day, you could run hi-fi AM with audio all 
> the way 
> up to 15  kHz and that would probably be ok as long as you made sure 
> you 
> were not causing any harmful interference to anyone.  On the othre 
> hand if 
> you were limiting the audio response to 3000~ and generating the 
> same wide 
> bandwidth due to splatter (overmodulation or distortion), that would 
> be 
> considered not to be "good engineering practice."  If you operated 
> the full 
> hi-fi audio at high power on 75m at night when the band was crowded, 
> that 
> could be interpreted as violation of good amateur practice.
> 
> The bottom line seems to be, use common sense and adjust bandwidth 
> according 
> to conditions, and make sure your transmitter's spurious distortion 
> products 
> fall within the FCC's specifications, which are listed in the rules.
> 
> There was a flare-up regarding bandwidth a year or so ago, with 
> "hi-fi SSB". 
>   This resulted in petitions to specifically limit bandwidth.  The 
> FCC 
> apparently turned them down.  Now the ARRL is proposing to change 
> the 
> definitions of subbands to be defined by bandwidth instead of 
> emission mode, 
> to promote "digital" experimentation.  The proposed bandwidth limit 
> for AM 
> is 9 khz.  The League has received so much mail questioning the 
> wisdom of 
> such a change, that the League seems to be rethinking the idea.  
> They still 
> have an open invitiation to the amateur community to send them 
> comments and 
> opinions on this subject.
> 
> Don K4KYV
> 
> 
> __
> AMRadio mailing list
> Home: http://mailman.qth.net/mailman/listinfo/amradio
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:AMRadio@mailman.qth.net
> 

RE: [AMRadio] WTB SB-220

[Jim candela]

Cory,

I have a Gonset GSB201 linear amplifier (GG 4-572B) where I use it on 75
/ 40 meters as an AM Linear. My GSB-201 only puts out about 800 - 900 watts
key down depending on drive and line voltage. I use an AM exciter that can
produce a clean 10 watt carrier, and this carrier if any stronger would over
drive the linear on AM. I get a clean 150 watts carrier output with this
setup with room for lots of upward modulation.

I never had a SB-220 but these are nice rigs with lots of upgraded
circuitry available from various places. Now consider my situation where
much above 10 watts drive results in non-linearity as seen from a trapezoid
pattern when 100% modulating the drive on AM. I'd bet that with a SB-220 all
you need is 20 to 25 watts drive for 375 watts output. The Viking II cannot
run down there unless you modify it so that the final amp, and modulator run
off the low B+ (might be pretty extensive modification to make work right),
or run at about 80-100 watts output, and insert a 6 DB pad between the
Viking II output and SB-220 input. That might do the trick.

Now for efficiency sake, AM linear is poor in that regard, but is
capable of being extremely effective, and linear. You can also run the legal
limit on AM and not worry about a big heavy modulation transformer. As a
bonus winter is coming, and a little air moving past those 3-500Z's will
certainly heat the shack!

Regards,
Jim

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Cory Hine
Sent: Sunday, September 26, 2004 1:14 PM
To: amradio@mailman.qth.net
Subject: [AMRadio] WTB SB-220


Hey gang,

I am looking for a Heathkit SB-220 to run about 300 watts on AM using the
Viking II to drive it. Does anyone have a decent amp that they want to sell?
I would like pics if possible.

Thanks,

Cory/AD5QP


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Re: [AMRadio] Frequency Response

[Vince Wesa Werber]

Thank you Don... this needs to be repeated every so often because these 'Urban 
Myths'  seem to never die in spite of the facts...

The way I've got it figured is the FCC doesn't want to do much of anything to 
limit bandwidth...  not so much for the sake of AM but to leave the doors 
open for other yet unknown modes...

I mean, and this is a silly comparison but...,  Just how 'wide' is a spread 
spectrum signal???  and for giggles run an check on some of the DAT modes...  
intermodulation distortion is a bug in even some of the best equipment and 
that brings us back to 'good enginneering practices'...

Bad example I admit but when you think about it...

tnx agn Don...
73
vince
ka1iic



On Sunday 26 September 2004 06:02 pm, Donald Chester wrote:

> That is a popular urban myth.  There is NOTHING in the US regulations that
> specifically limits bandwidth.  The regulations specify "good engineering

[AMRadio] WTB SB-220

[Cory Hine]

Hey gang,
 
I am looking for a Heathkit SB-220 to run about 300 watts on AM using the 
Viking II to drive it. Does anyone have a decent amp that they want to sell? I 
would like pics if possible. 
 
Thanks,
 
Cory/AD5QP


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<< I am looking for a Heathkit SB-220 to run about 300 watts on AM using the 
Viking II to drive it. >>

Hi,

If you are getting the full output from the V II into a good well matched 
antenna, a couple of hundred more watts is not going to make any significant 
difference on the receive end and will only serve to heat up the shack and run 
up 
your power bill.

73,

John,  W4AWM

Re: [AMRadio] Frequency Response

[Donald Chester]

What about bandwidth? +/- 5kc would be a 10 kc band width. I thought we
were supposed to limit our band width to 6kc. Please correct me if I am
wrong.



That is a popular urban myth.  There is NOTHING in the US regulations that 
specifically limits bandwidth.  The regulations specify "good engineering 
and amateur practice", and deliberately leaves the specific bandwidth  
vague.  In Canada, there is a rule on the books limiting bandwidth to 6 kHz, 
but I have never heard of them enforcing it against AM signals that may 
exceed that figure.  Besides, accurate measurement of bandwidth would 
require a visit to the station with test instruments.  Over-the-air 
measurement leaves too many possibilities for error due to propagation, QRM, 
QSB, etc.


The US regulations  could be interpreted to mean a reasonable bandwidth for 
the mode being used, considering band occupancy .  If you had a cw signal 
with so much noise, hum or FM on the carrier that it was 3 kHz wide, the FCC 
probably could interpret that as a violation of good engineering practice.  
If the band is empty, as for example, 10 m. most of the time nowadays, or 
160m in the middle of the day, you could run hi-fi AM with audio all the way 
up to 15  kHz and that would probably be ok as long as you made sure you 
were not causing any harmful interference to anyone.  On the othre hand if 
you were limiting the audio response to 3000~ and generating the same wide 
bandwidth due to splatter (overmodulation or distortion), that would be 
considered not to be "good engineering practice."  If you operated the full 
hi-fi audio at high power on 75m at night when the band was crowded, that 
could be interpreted as violation of good amateur practice.


The bottom line seems to be, use common sense and adjust bandwidth according 
to conditions, and make sure your transmitter's spurious distortion products 
fall within the FCC's specifications, which are listed in the rules.


There was a flare-up regarding bandwidth a year or so ago, with "hi-fi SSB". 
 This resulted in petitions to specifically limit bandwidth.  The FCC 
apparently turned them down.  Now the ARRL is proposing to change the 
definitions of subbands to be defined by bandwidth instead of emission mode, 
to promote "digital" experimentation.  The proposed bandwidth limit for AM 
is 9 khz.  The League has received so much mail questioning the wisdom of 
such a change, that the League seems to be rethinking the idea.  They still 
have an open invitiation to the amateur community to send them comments and 
opinions on this subject.


Don K4KYV

RE: [AMRadio] Frequency Response

[Donald Chester]

I have always admired what Don has done with his modulation system. That 
3400 hertz brick wall filter is a rarity unless one uses high technology 
active circuitry such as active op-amps, switched capacitor filters, dsp, 
etc.  I believe Don has a passive module that does a great job. I wonder 
where he got it?


It is a passive module.  I picked it up in Washington, DC back in 1972 when 
I had stopped over there to visit a friend.  We went to a little 
hole-in-the-wall military surplus outlet.  I paid $5 for it.  It is potted, 
about 1 1/2" X 1 3/4" X 2 ".  It has an octal plug on the bottom.  The 
impedance in/out is 10,000 ohms.  I wasn't sure about it when I purchased 
it, but when I tried it out with a signal generator after returning home, I 
wished I had bought every one they had.  It is flat up to about 3300~, and 
at 3500~ the signal is so far down as to be undetectable on the scope.  You 
can simulate the envelope pattern of a cw signal by swishing the test 
oscillator about 100~!


The only thing like that I have ever seen at a hamfest was physically and 
electrically identical but had a useless cutoff frequency of 2000~.


Don K4KYV