[600MRG] FT Question Answered?
Alan Cooper
w7aln at netzero.com
Mon Jan 15 14:53:54 CST 2018
Hello All,
Ok on the caution for "linear vs non-linear" I think Linear and as clean
As possible important as well, so does that then rule out the use of the
"one local osc, through a double balanced mixer" design transverter?
There will be non-linear things happening in the mixer after all in order
To get a stable signal generated inside the 630m band. That question of
course does not even begin to address all of the mixers and mixing that
might be
found in any of the transceivers on the market at hf.
Just wondering?
Thanks
Alan
-----Original Message-----
From: 600MRG [mailto:600mrg-bounces at w7ekb.com] On Behalf Of
600mrg-request at w7ekb.com
Sent: Monday, January 15, 2018 10:00 AM
To: 600mrg at w7ekb.com
Subject: 600MRG Digest, Vol 81, Issue 16
Send 600MRG mailing list submissions to
600mrg at w7ekb.com
To subscribe or unsubscribe via the World Wide Web, visit
http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com
or, via email, send a message with subject or body 'help' to
600mrg-request at w7ekb.com
You can reach the person managing the list at
600mrg-owner at w7ekb.com
When replying, please edit your Subject line so it is more specific than
"Re: Contents of 600MRG digest..."
Today's Topics:
1. Re: FT Question Answered? (Bill Cromwell)
2. Re: FT Question Answered? (Roger Graves)
3. Re: FT Question Answered? (lstoskopf at cox.net lstoskopf at cox.net)
4. Re: FT Question Answered? (KL7AJ)
----------------------------------------------------------------------
Message: 1
Date: Sun, 14 Jan 2018 13:04:55 -0500
From: Bill Cromwell <wrcromwell at gmail.com>
To: Ben Gelb <ben.gelb at gmail.com>
Cc: 600MRG <600mrg at w7ekb.com>
Subject: Re: [600MRG] FT Question Answered?
Message-ID: <9a906c73-4149-0168-a081-aeaf82b95139 at gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Hi Ben,
I hope that my cautionary comments are taken as just that. We have to keep
an eye on those things. To do that we need to know what we are looking for.
Distortion in the system is detrimental whether we are using AFSK or FSK in
in the carrier oscillator. Historically the RF FSK has been more reliable. I
doubt whether 'modern' gear makes very much difference. Take a close look at
some of the 'digital' signals on the air. As always, some are pretty good.
Some should be cause for shame.
The OP asked about using nonlinear amplifiers. I think my reply is
appropriate. I use linear amplifiers even for conventional CW just to
promote a cleaner signal.
73,
Bill KU8H
On 01/14/2018 11:47 AM, Ben Gelb wrote:
> I think what you are describing is distortion in the audio chain. That
> seems like a problem even with linear amplification (though maybe
> nonlinear would make it worse) ... I don't know that your comments
> really apply to modern equipment and AFSK techniques, though... audio
> should be pretty clean (and needs to be in order to control occupied
> bandwidth).
>
> 73 de N1VF
>
> On Jan 14, 2018 7:07 AM, "Bill Cromwell" <wrcromwell at gmail.com
> <mailto:wrcromwell at gmail.com>> wrote:
>
> Hi John,
>
> Consider that Collins and others used a single audio tone to
> generate a CW signal in some of their SSB transmitters. In theory it
> is wonderful. It is less expensive. It actually seems to work as
> *theory* says it should. They dropped it because it did not
> *reliably* give a clean signal..even with 'linear' amplifier chains.
>
> I understand that the shift is small for the newfangled digital
> modes but shift they do. It is not a single tone and then later
> another single tone. Use caution if you are going to add nonlinear
> amplifiers into the mix.
>
> 73,
>
> Bill KU8H
>
> On 01/13/2018 03:45 PM, John Andrews wrote:
>
> Bill,
>
> What you say is correct for speech or any audio that has
> multiple tones
> <<at the same time>>. But FT8, WSPR, and the vast majority of
> sound-card
> generated modes only output one tone at a time. In that case,
> you can
> have non-linear amplifier stages after the SSB signal is
generated.
>
> Consider a properly run SSB generator in USB mode at 474.200
> kHz. The
> carrier frequency and the LSB are suppressed by maybe 50 dB. If
you
> apply a single 1500 Hz tone to the input, you will get a carrier
at
> 474.200 + 1.500 = 475.700 kHz and nothing else of significance. A
> non-linear amplifier will do no damage to a single frequency
> signal. No
> magic involved.
>
> So, as long as you avoid the use of simultaneous multi-tone or PSK
> modes, linearity is not required after the SSB generator. FT8
> and the
> other "K1JT" modes are all single-tone.
>
> John, W1TAG
>
> On 1/13/2018 1:47 PM, Bill Cromwell wrote:
>
> Hi Frank,
>
> That is what I was going to say in reply to your latest
> query. If you
> are using audio modulation in upper or lower sideband SSB
> non linear
> amps will ruinate and splaterate it.
>
> 73,
>
> Bill KU8H
>
> On 01/13/2018 10:47 AM, Frank Lotito wrote:
>
> I may have answered my question - We use AFSK not direct
> FSK to
> generate modulation modes such as FT8. AFSK as I recall
> requires
> "linearity" in the audio processing stages. But once in
> the RF
> domain we can use non-linear devices, such as heterodyne
> converters,
> Class E amps, etc. Did I get that correct? 73 Frank
> K3DZ / WH2XHA
>
> Get Outlook for Android<https://aka.ms/ghei36>
>
> _______________________________________________
> 600MRG mailing list
> 600MRG at w7ekb.com <mailto:600MRG at w7ekb.com>
> http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com
> <http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com>
>
>
>
> _______________________________________________
> 600MRG mailing list
> 600MRG at w7ekb.com <mailto:600MRG at w7ekb.com>
> http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com
> <http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com>
>
>
> --
> bark less - wag more
>
> _______________________________________________
> 600MRG mailing list
> 600MRG at w7ekb.com <mailto:600MRG at w7ekb.com>
> http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com
> <http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com>
>
--
bark less - wag more
------------------------------
Message: 2
Date: Sun, 14 Jan 2018 10:14:28 -0800
From: Roger Graves <ve7vv at shaw.ca>
To: 600mrg at w7ekb.com
Subject: Re: [600MRG] FT Question Answered?
Message-ID: <9961853F-15EA-4B48-B11D-D8A405836D87 at shaw.ca>
Content-Type: text/plain; charset=utf-8
Interesting that Collins tried using audio tones to generate CW. IDK how
they were generating the audio. Now we are using DAC?s. A major problem with
these is not that the main audio signal is not stable but that there is
wideband noise in addition to the pure tone. SM5BSZ has documented this well
and tested lots of soundcards. Some soundcards are so bad that they should
never be used for TX. In general, he advises running the TX soundcard at the
max bit depth (e.g. 24 bit) and max sampling rate (e.g. 96 kHz) to minimize
quantization noise and to run it at close to the maximum output level to
maximize the s/n ratio as some of the noise output is independent of the
main signal level (this requires using an attenuator or reducing the gain of
the transmitter audio input). Further, an audio low pass filter is advisable
to reduce the high frequency noise, which can be extreme above the sampling
freq in some soundcards. All that noise can be mixed into other frequencies
by nonlinear RF stages, so we need to have clean audio for both linear and
non-linear amplifiers.
------------------------------
Message: 3
Date: Sun, 14 Jan 2018 15:37:43 -0500 (EST)
From: "lstoskopf at cox.net lstoskopf at cox.net" <lstoskopf at cox.net>
To: Ben Gelb <ben.gelb at gmail.com>, Bill Cromwell
<wrcromwell at gmail.com>
Cc: 600MRG <600mrg at w7ekb.com>
Subject: Re: [600MRG] FT Question Answered?
Message-ID: <1813866484.6532.1515962263995 at myemail.cox.net>
Content-Type: text/plain; charset=UTF-8
May question again and again.....why don't we have software/hardware to
generate these signals directly so we don't have to use a sideband rig? Or
with 630M either a transverter of softrock? N0UU
------------------------------
Message: 4
Date: Sun, 14 Jan 2018 13:06:47 -0900
From: KL7AJ <kl7aj at acsalaska.net>
To: 600mrg at w7ekb.com
Subject: Re: [600MRG] FT Question Answered?
Message-ID: <a2169c14-a015-c59c-8be7-e21f5390f4bb at acsalaska.net>
Content-Type: text/plain; charset=utf-8; format=flowed
AlasKit Educational and Scientific Resources is developing a stand alone
transceiver for 630 and 2200 meters.? Stay tuned!
Eric
On 1/14/2018 11:37 AM, lstoskopf at cox.net lstoskopf at cox.net wrote:
> May question again and again.....why don't we have software/hardware to
generate these signals directly so we don't have to use a sideband rig? Or
with 630M either a transverter of softrock? N0UU
> _______________________________________________
> 600MRG mailing list
> 600MRG at w7ekb.com
> http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com
>
>
--
AlasKit Educational and Scientific Resources
P.O. Box 56235
3763 Lyle Avenue
North Pole, AK 99705
(907) 488-0483
(907) 371-7120
http://alaskit.co
kl7aj at arrl.net
------------------------------
Subject: Digest Footer
_______________________________________________
600MRG mailing list
600MRG at w7ekb.com
http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com
------------------------------
End of 600MRG Digest, Vol 81, Issue 16
**************************************
____________________________________________________________
After Weeks Of Rumors, Joanna Gaines Comes Clean
risingstarnewspaper.com
http://thirdpartyoffers.netzero.net/TGL3241/5a5d14d91607e14d81687st01vuc
More information about the 600MRG
mailing list