[K3] Tunijng the Radio

classic Classic list List threaded Threaded
13 messages Options
Reply | Threaded
Open this post in threaded view
|

[K3] Tunijng the Radio

David Guernsey
If I tune my K3 to 14.225 MHz will I be in the General Class portion
of the 20 meter band, or do I have to allow for the width of my USB
signal when I transmit?

 
73 de Dave KJ6CBS
______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

Ian Kahn, KM4IK
You'll be in the General portion of 20m.  Your band spread will take you up
to 14.2278 (+2.8 khz) which will be fine on USB.

73,

Ian, KM4IK
On Jul 14, 2012 6:55 PM, "David Guernsey" <[hidden email]> wrote:

> If I tune my K3 to 14.225 MHz will I be in the General Class portion
> of the 20 meter band, or do I have to allow for the width of my USB
> signal when I transmit?
>
>
> 73 de Dave KJ6CBS
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

Dick Dievendorff
In reply to this post by David Guernsey
In general, you have to allow for the width of your signal.   As a rule of
thumb, I figure my USB/LSB signals occupy the range from the VFO suppressed
carrier frequency to 3 kHz away from the VFO frequency.  Maybe 4 if you have
ESSB selected.

If you tune to 14.225, the suppressed carrier frequency is 14.225, and your
USB signal will occupy the range roughly from 14.225 to 14.228, so you're
within the General section of the band.  The problem we all run into is the
high end of these bands.  If you set your VFO (the suppressed carrier
frequency) above 14.347, parts of your USB signal will spill off the end of
the band, 14.350.

On 40 meters, LSB, the situation is reversed.  If you tune your VFO to a
suppressed carrier frequency of 7.300 and the LSB signal will fall into the
range from 7.297 to 7.300.  However you can't crowd the bottom edge of the
40 meter band.  For a general, your lowest frequency is 7.175.  You
shouldn't tune below 7.178 to avoid putting any part of your LSB signal
below 7.175.

73 de Dick, K6KR


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of David Guernsey
Sent: Saturday, July 14, 2012 1:40 PM
To: Elecraft List
Subject: [Elecraft] [K3] Tunijng the Radio

If I tune my K3 to 14.225 MHz will I be in the General Class portion of the
20 meter band, or do I have to allow for the width of my USB signal when I
transmit?

 
73 de Dave KJ6CBS
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

Nr4c
In reply to this post by David Guernsey
Well, you'd be legal if your dial is accurate, but I prefer to move up a bit to allow for "Professor Murphy".  And don't forget to stop at least 3kHz below the top (14.347000).  Reverse is true for LSB.

...bill nr4c

Sent from my Verizon Wireless Droid

-----Original message-----
From: David Guernsey <[hidden email]>
To: Elecraft List <[hidden email]>
Sent: Sat, Jul 14, 2012 20:39:33 GMT+00:00
Subject: [Elecraft] [K3] Tunijng the Radio

If I tune my K3 to 14.225 MHz will I be in the General Class portion
of the 20 meter band, or do I have to allow for the width of my USB
signal when I transmit?

 
73 de Dave KJ6CBS
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

Don Wilhelm-4
In reply to this post by David Guernsey
Dave,

You have already received some correct answers, but let me try to inject
a bit of generalized information that should allow you to figure this
out in the future for any band and for either LSB or USB.

The K3 will display the (suppressed) carrier frequency.  That means that
USB signals will be higher in frequency than the carrier, so in the
specific case of your question, you will be in the band (assuming the K3
frequency is properly calibrated).  Similarly, LSB signals will be below
the carrier frequency, so if you are operating on 80 meters where your
lower band limit is 3800 kHz, you will be within the general portion of
the band if your VFO is set to 3804 kHz (to be safe).  If you are
absolutely certain your SSB width is 3 kHz or less, then you can go as
low as 3803 kHz.

73,
Don W3FPR

On 7/14/2012 4:39 PM, David Guernsey wrote:
> If I tune my K3 to 14.225 MHz will I be in the General Class portion
> of the 20 meter band, or do I have to allow for the width of my USB
> signal when I transmit?
>
>  
>

______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

Geoffrey Mackenzie-Kennedy-3
In reply to this post by David Guernsey
Dave,

To add to the replies which you have received, the width of your USB signal
should also include those intermodulation products which appear at
frequencies less than that of the suppressed carrier frequency, i.e. in the
LSB region.  If you tuned your K3 to 14.225 MHz, these IMD products would
fall outside of your General Class portion of the band and could create
interference.  To be safe I would suggest that you do not operate your K3 in
USB mode below 14.228 kHz.

In Europe the top end of our 80m allocation is 3.800 MHz, and some European
hams operate LSB on or very close to 3.800 MHz.  This practice has caused
some non-amateur users operating just above 3.800 MHz to complain about
interference from amateur IMD products.  Fortunately those complaints which
I have heard are still at the "muttering" stage.

73,
Geoff
LX2AO


On July 14, 2012 at 10:39 PM, David Guernsey wrote:


> If I tune my K3 to 14.225 MHz will I be in the General Class portion
> of the 20 meter band, or do I have to allow for the width of my USB
> signal when I transmit?



______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

ke9uw
In reply to this post by David Guernsey
http://www.contesting.com/articles/148

Chuck, KE9UW
aka Jack, BMW Motorcycles BMWMOA #224

________________________________________
From: [hidden email] [[hidden email]] on behalf of David Guernsey [[hidden email]]
Sent: Saturday, July 14, 2012 3:39 PM
To: Elecraft List
Subject: [Elecraft] [K3] Tunijng the Radio

If I tune my K3 to 14.225 MHz will I be in the General Class portion
of the 20 meter band, or do I have to allow for the width of my USB
signal when I transmit?


73 de Dave KJ6CBS
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Chuck, KE9UW
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

KD8NNU
In reply to this post by David Guernsey
Being a SDR there is really no suppressed carrier as the carrier is
never created only the sideband for the mode selected.   So unless you
have signficant splatter there should not be an IMD problem with a K3.

Again assuming no splatter and a properly functioning radio.

This is no analog radio and all TX is based on the DSP first and then
the TX filter last.

~73
Don
KD8NNU


On Sun, Jul 15, 2012 at 7:34 AM, Geoffrey Mackenzie-Kennedy wrote:

> Dave,
>
> To add to the replies which you have received, the width of your USB
> signal should also include those intermodulation products which appear
> at frequencies less than that of the suppressed carrier frequency,
> i.e. in the LSB region.  If you tuned your K3 to 14.225 MHz, these IMD
> products would fall outside of your General Class portion of the band
> and could create interference.  To be safe I would suggest that you do
> not operate your K3 in USB mode below 14.228 kHz.
>
> In Europe the top end of our 80m allocation is 3.800 MHz, and some
> European hams operate LSB on or very close to 3.800 MHz.  This
> practice has caused some non-amateur users operating just above 3.800
> MHz to complain about interference from amateur IMD products.
> Fortunately those complaints which I have heard are still at the
> "muttering" stage.
>
> 73,
> Geoff
> LX2AO
>
>
> On July 14, 2012 at 10:39 PM, David Guernsey wrote:
>
>
>> If I tune my K3 to 14.225 MHz will I be in the General Class portion
>> of the 20 meter band, or do I have to allow for the width of my USB
>> signal when I transmit?
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

Jack Smith-6
Don:

Not so at all - whilst the low level SSB generated by the K3's DSP may
be close to theoretically perfect, intermodulation products produced by
the K3's IPA and final amplifier stages are present in quantity and are
the limiting factor.

Jack K8ZOA


On 7/15/2012 8:02 AM, [hidden email] wrote:

> Being a SDR there is really no suppressed carrier as the carrier is
> never created only the sideband for the mode selected.   So unless you
> have signficant splatter there should not be an IMD problem with a K3.
>
> Again assuming no splatter and a properly functioning radio.
>
> This is no analog radio and all TX is based on the DSP first and then
> the TX filter last.
>
> ~73
> Don
> KD8NNU
>
>
> On Sun, Jul 15, 2012 at 7:34 AM, Geoffrey Mackenzie-Kennedy wrote:
>
>> Dave,
>>
>> To add to the replies which you have received, the width of your USB
>> signal should also include those intermodulation products which appear
>> at frequencies less than that of the suppressed carrier frequency,
>> i.e. in the LSB region.  If you tuned your K3 to 14.225 MHz, these IMD
>> products would fall outside of your General Class portion of the band
>> and could create interference.  To be safe I would suggest that you do
>> not operate your K3 in USB mode below 14.228 kHz.
>>
>> In Europe the top end of our 80m allocation is 3.800 MHz, and some
>> European hams operate LSB on or very close to 3.800 MHz.  This
>> practice has caused some non-amateur users operating just above 3.800
>> MHz to complain about interference from amateur IMD products.
>> Fortunately those complaints which I have heard are still at the
>> "muttering" stage.
>>
>> 73,
>> Geoff
>> LX2AO
>>
>>
>> On July 14, 2012 at 10:39 PM, David Guernsey wrote:
>>
>>
>>> If I tune my K3 to 14.225 MHz will I be in the General Class portion
>>> of the 20 meter band, or do I have to allow for the width of my USB
>>> signal when I transmit?
>>
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>


______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

KD8NNU
In reply to this post by David Guernsey
Hi Jack,

So I think what you are telling me is that the IPA is after the DSP and
that obvioulsy any inperfections in this circuit and the final amp are
what creates the IMD products.

Is that another reason that the tx filter is 2.7 or 2.8 wide at the
skirts to act as a wall to prevent this from getting out on the air
compared to using a 3.0 wide filter.

Thanks
Don

~73
Don
KD8NNU


On Sun, Jul 15, 2012 at 8:51 AM, Jack Smith wrote:

> Don:
>
> Not so at all - whilst the low level SSB generated by the K3's DSP may
> be close to theoretically perfect, intermodulation products produced
> by the K3's IPA and final amplifier stages are present in quantity and
> are the limiting factor.
>
> Jack K8ZOA
>
>
> On 7/15/2012 8:02 AM, [hidden email] wrote:
>> Being a SDR there is really no suppressed carrier as the carrier is
>> never created only the sideband for the mode selected.   So unless
>> you
>> have signficant splatter there should not be an IMD problem with a
>> K3.
>>
>> Again assuming no splatter and a properly functioning radio.
>>
>> This is no analog radio and all TX is based on the DSP first and then
>> the TX filter last.
>>
>> ~73
>> Don
>> KD8NNU
>>
>>
>> On Sun, Jul 15, 2012 at 7:34 AM, Geoffrey Mackenzie-Kennedy wrote:
>>
>>> Dave,
>>>
>>> To add to the replies which you have received, the width of your USB
>>> signal should also include those intermodulation products which
>>> appear
>>> at frequencies less than that of the suppressed carrier frequency,
>>> i.e. in the LSB region.  If you tuned your K3 to 14.225 MHz, these
>>> IMD
>>> products would fall outside of your General Class portion of the
>>> band
>>> and could create interference.  To be safe I would suggest that you
>>> do
>>> not operate your K3 in USB mode below 14.228 kHz.
>>>
>>> In Europe the top end of our 80m allocation is 3.800 MHz, and some
>>> European hams operate LSB on or very close to 3.800 MHz.  This
>>> practice has caused some non-amateur users operating just above
>>> 3.800
>>> MHz to complain about interference from amateur IMD products.
>>> Fortunately those complaints which I have heard are still at the
>>> "muttering" stage.
>>>
>>> 73,
>>> Geoff
>>> LX2AO
>>>
>>>
>>> On July 14, 2012 at 10:39 PM, David Guernsey wrote:
>>>
>>>
>>>> If I tune my K3 to 14.225 MHz will I be in the General Class
>>>> portion
>>>> of the 20 meter band, or do I have to allow for the width of my USB
>>>> signal when I transmit?
>>>
>>>
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

Geoffrey Mackenzie-Kennedy-3
In reply to this post by KD8NNU
Sorry Don, I was "offline" and I have just seen your comment, to which I see
Jack has responded. Thank you Jack!!

73,

Geoff
LX2AO


On July 15, 2012 at 2:02 PM, Don KD8NNU wrote:

> Being a SDR there is really no suppressed carrier as the carrier is
> never created only the sideband for the mode selected.   So unless you
> have signficant splatter there should not be an IMD problem with a K3.
>
> Again assuming no splatter and a properly functioning radio.
>
> This is no analog radio and all TX is based on the DSP first and then
> the TX filter last.
>
> ~73
> Don
> KD8NNU

______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

Jack Smith-6
In reply to this post by KD8NNU
Don:

The TX crystal filter is ahead of the IPA and HPA stages and while a
narrower filter may help a  bit, the real source of almost all
transmitted 3rd, 5th, 7th, 9th etc. order IMD products is  the power stages.

Jack K8ZOA

On 7/15/2012 9:12 AM, [hidden email] wrote:

> Hi Jack,
>
> So I think what you are telling me is that the IPA is after the DSP and
> that obvioulsy any inperfections in this circuit and the final amp are
> what creates the IMD products.
>
> Is that another reason that the tx filter is 2.7 or 2.8 wide at the
> skirts to act as a wall to prevent this from getting out on the air
> compared to using a 3.0 wide filter.
>
> Thanks
> Don
>
> ~73
> Don
> KD8NNU
>
>
> On Sun, Jul 15, 2012 at 8:51 AM, Jack Smith wrote:
>
>> Don:
>>
>> Not so at all - whilst the low level SSB generated by the K3's DSP may
>> be close to theoretically perfect, intermodulation products produced
>> by the K3's IPA and final amplifier stages are present in quantity and
>> are the limiting factor.
>>
>> Jack K8ZOA
>>
>>
>> On 7/15/2012 8:02 AM, [hidden email] wrote:
>>> Being a SDR there is really no suppressed carrier as the carrier is
>>> never created only the sideband for the mode selected.   So unless
>>> you
>>> have signficant splatter there should not be an IMD problem with a
>>> K3.
>>>
>>> Again assuming no splatter and a properly functioning radio.
>>>
>>> This is no analog radio and all TX is based on the DSP first and then
>>> the TX filter last.
>>>
>>> ~73
>>> Don
>>> KD8NNU
>>>
>>>
>>> On Sun, Jul 15, 2012 at 7:34 AM, Geoffrey Mackenzie-Kennedy wrote:
>>>
>>>> Dave,
>>>>
>>>> To add to the replies which you have received, the width of your USB
>>>> signal should also include those intermodulation products which
>>>> appear
>>>> at frequencies less than that of the suppressed carrier frequency,
>>>> i.e. in the LSB region.  If you tuned your K3 to 14.225 MHz, these
>>>> IMD
>>>> products would fall outside of your General Class portion of the
>>>> band
>>>> and could create interference.  To be safe I would suggest that you
>>>> do
>>>> not operate your K3 in USB mode below 14.228 kHz.
>>>>
>>>> In Europe the top end of our 80m allocation is 3.800 MHz, and some
>>>> European hams operate LSB on or very close to 3.800 MHz.  This
>>>> practice has caused some non-amateur users operating just above
>>>> 3.800
>>>> MHz to complain about interference from amateur IMD products.
>>>> Fortunately those complaints which I have heard are still at the
>>>> "muttering" stage.
>>>>
>>>> 73,
>>>> Geoff
>>>> LX2AO
>>>>
>>>>
>>>> On July 14, 2012 at 10:39 PM, David Guernsey wrote:
>>>>
>>>>
>>>>> If I tune my K3 to 14.225 MHz will I be in the General Class
>>>>> portion
>>>>> of the 20 meter band, or do I have to allow for the width of my USB
>>>>> signal when I transmit?
>>>>
>>>> ______________________________________________________________
>>>> Elecraft mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>> Post: mailto:[hidden email]
>>>>
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list: http://www.qsl.net/donate.html
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>


______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: [K3] Tunijng the Radio

Dick Dievendorff
In reply to this post by KD8NNU
Few filters have vertical skirts.  They roll off gradually; the slope of
that rolloff is one of the measures of filter quality.

The filter width is often (but not always) described as the 6 dB down point
on that rolloff curve,  A filter described as 2.8 kHz wide will pass some
energy through at frequencies outside its 2.8 kHz bandwidth.

Graphs of representative Elecraft K3 filters are available at
http://www.elecraft.com/K3/K3_filter_plots.htm

For example, the representative 2.8 kHz 8-pole filter is 2.888 kHz at 6 dB
down, and 4.488 kHz at 60 dB down.  The 2.7 kHz 5-pole filter is wider at
the 60 dB down point.

Some older radios depended on filtering to remove the unwanted sideband and
carrier.

Current generation radios generate just the desired SSB signal, without the
unwanted sideband and without the carrier.

There are a number of amplifiers after the SSB signal generation and
filtering that generate various levels of IMD products.

It's up to the radio manufacturer to provide equipment that meets the FCC
specified limits when the equipment is operated according to its owner-level
instructions.

It's up to us to operate the radio within these described limits in order to
keep the unwanted signals within the FCC-prescribed limits and good amateur
practice.
When the instruction manual says "4-5 bars", that doesn't mean "turn it up
as far as it will go".  

http://www.youtube.com/watch?v=XuzpsO4ErOQ

None of this is specific to the K3 except the details of the filters.

73 de Dick, K6KR

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of [hidden email]
Sent: Sunday, July 15, 2012 6:13 AM
To: [hidden email]
Subject: Re: [Elecraft] [K3] Tunijng the Radio

Hi Jack,

So I think what you are telling me is that the IPA is after the DSP and that
obvioulsy any inperfections in this circuit and the final amp are what
creates the IMD products.

Is that another reason that the tx filter is 2.7 or 2.8 wide at the skirts
to act as a wall to prevent this from getting out on the air compared to
using a 3.0 wide filter.

Thanks
Don

~73
Don
KD8NNU


On Sun, Jul 15, 2012 at 8:51 AM, Jack Smith wrote:

> Don:
>
> Not so at all - whilst the low level SSB generated by the K3's DSP may
> be close to theoretically perfect, intermodulation products produced
> by the K3's IPA and final amplifier stages are present in quantity and
> are the limiting factor.
>
> Jack K8ZOA
>
>
> On 7/15/2012 8:02 AM, [hidden email] wrote:
>> Being a SDR there is really no suppressed carrier as the carrier is
>> never created only the sideband for the mode selected.   So unless
>> you
>> have signficant splatter there should not be an IMD problem with a
>> K3.
>>
>> Again assuming no splatter and a properly functioning radio.
>>
>> This is no analog radio and all TX is based on the DSP first and then
>> the TX filter last.
>>
>> ~73
>> Don
>> KD8NNU
>>
>>
>> On Sun, Jul 15, 2012 at 7:34 AM, Geoffrey Mackenzie-Kennedy wrote:
>>
>>> Dave,
>>>
>>> To add to the replies which you have received, the width of your USB
>>> signal should also include those intermodulation products which
>>> appear at frequencies less than that of the suppressed carrier
>>> frequency, i.e. in the LSB region.  If you tuned your K3 to 14.225
>>> MHz, these IMD products would fall outside of your General Class
>>> portion of the band and could create interference.  To be safe I
>>> would suggest that you do not operate your K3 in USB mode below
>>> 14.228 kHz.
>>>
>>> In Europe the top end of our 80m allocation is 3.800 MHz, and some
>>> European hams operate LSB on or very close to 3.800 MHz.  This
>>> practice has caused some non-amateur users operating just above
>>> 3.800
>>> MHz to complain about interference from amateur IMD products.
>>> Fortunately those complaints which I have heard are still at the
>>> "muttering" stage.
>>>
>>> 73,
>>> Geoff
>>> LX2AO
>>>
>>>
>>> On July 14, 2012 at 10:39 PM, David Guernsey wrote:
>>>> If I tune my K3 to 14.225 MHz will I be in the General Class portion of
the 20 meter band, or do I have to allow for the width of my USB signal when
I transmit?

______________________________________________________________
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